{"gene":"SCAP","run_date":"2026-06-10T07:46:29","timeline":{"discoveries":[{"year":2002,"finding":"INSIG-1 is an ER protein that binds the sterol-sensing domain of SCAP in a sterol-dependent manner, retaining the SCAP/SREBP complex in the ER and preventing SREBP transport to the Golgi for proteolytic processing. Mutant SCAP(Y298C) fails to bind INSIG-1 and is resistant to sterol-mediated ER retention.","method":"Coimmunoprecipitation, tandem mass spectrometry, blue native-PAGE, mutant SCAP analysis","journal":"Cell","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — reciprocal co-IP, mass spectrometry identification, blue native-PAGE, mutagenesis validation, replicated across multiple subsequent studies","pmids":["12202038"],"is_preprint":false},{"year":2002,"finding":"INSIG-2, a second ER protein with 59% sequence identity to INSIG-1, binds SCAP in a sterol-regulated fashion and blocks SCAP/SREBP export from the ER to the Golgi, thereby preventing proteolytic SREBP processing. Unlike INSIG-1, INSIG-2 expression does not require nuclear SREBPs.","method":"Coimmunoprecipitation, sterol-regulated binding assays, SREBP processing assays","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal co-IP, functional SREBP processing assays, replicated in subsequent work","pmids":["12242332"],"is_preprint":false},{"year":2002,"finding":"Cholesterol addition to ER membranes in vitro causes a conformational change in SCAP detectable by trypsin cleavage site unmasking. Two sterol-resistant mutants, SCAP(Y298C) and SCAP(D443N), are refractory to this cholesterol-induced conformational change in vitro.","method":"In vitro trypsin cleavage/protease protection assay on ER membranes, mutant SCAP analysis","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution with ER membranes, mutagenesis validation, mechanistically foundational finding replicated in subsequent studies","pmids":["12191470"],"is_preprint":false},{"year":1999,"finding":"Sterols regulate cycling of SCAP between the ER and Golgi: in sterol-depleted cells, N-linked carbohydrates of SCAP are modified by Golgi enzymes (becoming endoglycosidase H-resistant), and SCAP returns to the ER; in sterol-overloaded cells, SCAP fails to leave the ER and Golgi modifications do not occur.","method":"Glycosidase treatment, glycosidase inhibitors, glycosylation-defective mutant cell lines, density gradient fractionation, brefeldin A treatment","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal biochemical methods, functionally linked to SREBP processing, replicated","pmids":["10500160"],"is_preprint":false},{"year":2002,"finding":"Sterols block incorporation of SCAP into COPII-coated vesicles by blocking Sar1-dependent binding of COPII proteins (Sec23/24) to SCAP. SCAP-containing vesicles formed in vitro also contain VSVG (a COPII marker), and sterols selectively block SCAP but not VSVG incorporation.","method":"Immunoisolation of vesicles formed in vitro, reconstitution with recombinant yeast COPII proteins, pulldown assays","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — in vitro vesicle reconstitution, selective inhibition controls, replicated in multiple follow-up studies","pmids":["12193656"],"is_preprint":false},{"year":2004,"finding":"Cholesterol directly binds with high affinity and specificity to the purified 767 amino acid octahelical membrane region of SCAP. The membrane domain of SCAP forms a tetramer, and cholesterol binding is inhibited by cationic amphiphiles. Cholesterol acts through direct receptor-ligand interaction rather than by changing membrane physical properties.","method":"Recombinant SCAP purification in detergent, direct cholesterol binding assay, analytical ultracentrifugation (tetramer determination)","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct in vitro binding with purified recombinant protein, multiple orthogonal methods, landmark mechanistic study","pmids":["15260976"],"is_preprint":false},{"year":2004,"finding":"Cholesterol and 25-hydroxycholesterol (25-HC) inhibit SCAP/SREBP transport by two distinct mechanisms: cholesterol directly binds SCAP (demonstrated by photoactivated cholesterol cross-linking to SCAP membrane domain) and induces a conformational change causing SCAP to bind Insigs; 25-HC does not cross-link to SCAP and does not produce a detectable SCAP conformational change, suggesting it acts indirectly through a separate sensor.","method":"Methyl-β-cyclodextrin cholesterol delivery, trypsin conformational assay, photoactivated cholesterol cross-linking, coimmunoprecipitation with Insigs","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — direct photoaffinity cross-linking, conformational assay, Insig binding assay; multiple orthogonal methods in single study","pmids":["15452130"],"is_preprint":false},{"year":2005,"finding":"Insig proteins are required for sterol-mediated inhibition of Sec23/24 binding to SCAP in vitro. The hexapeptide sequence MELADL in a cytoplasmic loop of SCAP is required for Sec23/24 binding and acts as a sterol-regulated ER sorting signal.","method":"Protein pulldown assays with microsomal membranes, Insig-1 dependency experiments, MELADL mutagenesis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — in vitro reconstitution with microsomal membranes, mutagenesis of sorting signal, Insig requirement demonstrated","pmids":["15899885"],"is_preprint":false},{"year":2007,"finding":"Sterols block COPII binding to the MELADL sorting signal in SCAP by two mechanisms: cholesterol binds directly to SCAP causing a conformational change near MELADL, and oxysterols bind to Insig (not SCAP directly), also producing a conformational change near MELADL. Both conformational changes abrogate COPII binding but not anti-MELADL antibody binding. The distance of MELADL from the ER membrane is implicated as crucial for COPII binding.","method":"Anti-MELADL blocking of COPII binding in vitro, microinjection of Fab anti-MELADL into cells, cysteine labeling conformational assay, mutagenesis","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — in vitro reconstitution, intracellular microinjection, cysteine-labeling conformational assay, mutagenesis; multiple orthogonal approaches","pmids":["17428919"],"is_preprint":false},{"year":1998,"finding":"Point mutations Y298C and D443N within the putative sterol-sensing domain of SCAP render it resistant to sterol-mediated inhibition. In sterol-resistant mutant cells, N-linked carbohydrates of SCAP remain in the endoglycosidase H-resistant (Golgi-processed) form even in the presence of 25-hydroxycholesterol, confirming that these residues are required for sterol-regulated ER retention.","method":"Isolation of CHO mutant cells, endoglycosidase H sensitivity assay, SREBP processing assay","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic loss-of-function (point mutation), biochemical glycosylation assay, functionally linked to SREBP processing; replicated in multiple subsequent studies","pmids":["9789003"],"is_preprint":false},{"year":2002,"finding":"Three independent point mutations in the sterol-sensing domain of SCAP (Y298C, D443N, L315F) each prevent sterol-induced binding of SCAP to Insig-1 and Insig-2, abolishing feedback regulation of SREBP processing. Sterols also fail to inhibit SCAP(L315F)/SREBP packaging into COPII vesicles in vitro.","method":"CHO mutant cell isolation, co-immunoprecipitation with Insigs, in vitro vesicle budding assay","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — three independent mutations all show same phenotype, co-IP with Insigs, in vitro vesicle assay","pmids":["12482938"],"is_preprint":false},{"year":2003,"finding":"Insig proteins lower the concentration of cholesterol required to produce the conformational change in SCAP in vitro. Cationic amphiphiles (chlorpromazine, trifluoperazine, imipramine) also induce this conformational change and are enhanced by Insig proteins, suggesting SCAP monitors the composition of the cytoplasmic leaflet of the ER membrane.","method":"In vitro trypsin cleavage conformational assay with Insig co-expression, cationic amphiphile treatment","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with ER membranes, pharmacological mimicry, single lab with multiple orthogonal approaches","pmids":["12963821"],"is_preprint":false},{"year":2000,"finding":"Overexpression of the membrane domain of SCAP (TM1-6, containing the sterol-sensing domain) prevents sterol-mediated ER retention of SCAP/SREBP, consistent with competition for a putative ER retention protein. The Y298C mutation in TM1-6 abolishes this dominant-negative effect.","method":"Transfection of truncated SCAP(TM1-6), SREBP processing assay, Y298C point mutation abolishing competition","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Moderate — functional transfection competition assay, mutagenesis control, mechanistically predictive of Insig discovery","pmids":["10896675"],"is_preprint":false},{"year":2011,"finding":"Luminal Loop 1 of Scap (245 aa projecting into the ER lumen) is the cholesterol-binding site: recombinant Loop 1 binds sterols with specificity identical to the full membrane domain. Mutation Y234A in Loop 1 locks Loop 6 in the cholesterol-bound conformation even in sterol-depleted cells, preventing SREBP processing.","method":"Recombinant Loop 1 cholesterol binding assay, Y234A point mutation, SREBP processing assay in transfected cells","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — direct binding with recombinant protein, in-cell functional validation by mutagenesis, mechanistic link to COPII binding established","pmids":["21454655"],"is_preprint":false},{"year":2005,"finding":"Conserved Asp-428 in the sixth transmembrane helix of SCAP is essential for SCAP dissociation from Insigs. SCAP(D428A) mutant remains in the Insig-binding conformation even in sterol-depleted cells, failing to transport SREBPs to the Golgi.","method":"Transfection of D428A point mutant, co-immunoprecipitation with Insigs, SREBP transport assay","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Moderate — mutagenesis with co-IP and functional transport assay, single lab, multiple orthogonal methods","pmids":["15728349"],"is_preprint":false},{"year":2013,"finding":"Luminal Loop 7 of Scap must interact with Loop 1 to maintain Loop 6 in a COPII-binding permissive conformation. Point mutation Y640S in Loop 7 prevents Loop 1–Loop 7 interaction (co-immunoprecipitation of separately expressed N- and C-terminal Scap fragments) and locks Loop 6 in the COPII-excluding conformation even without cholesterol.","method":"Y640S point mutation, trypsin cleavage conformational assay, co-immunoprecipitation of Scap N- and C-terminal fragments","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Moderate — mutagenesis, conformational assay, co-IP; multiple orthogonal methods linking Loop 1–Loop 7 interaction to COPII binding","pmids":["23564452"],"is_preprint":false},{"year":2003,"finding":"Reconstitution in Drosophila cells shows that mammalian SCAP and Insig-1 or Insig-2 are the minimal requirements for sterol-regulated ER-to-Golgi transport of SREBP-2. Without mammalian SCAP, mammalian SREBP-2 is not transported to the Golgi in insect cells. Sterols block transport only when mammalian Insig is co-expressed.","method":"Heterologous reconstitution in Drosophila cells, co-expression of mammalian SCAP and Insig","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — reconstitution in heterologous system defining minimal components, systematic co-expression dissection","pmids":["12842885"],"is_preprint":false},{"year":2001,"finding":"SCAP is required in vivo for hepatic lipid synthesis: conditional SCAP deficiency in mouse liver reduces basal cholesterol and fatty acid synthesis by 80% (due to decreases in biosynthetic enzyme mRNAs) and abolishes normal adaptive increases in response to cholesterol deprivation and insulin elevation.","method":"Conditional hepatic Scap knockout via inducible Cre recombinase in mice, mRNA quantification, lipid synthesis measurement","journal":"Genes & development","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean in vivo conditional KO with multiple phenotypic readouts, foundational in vivo mechanistic study","pmids":["11358865"],"is_preprint":false},{"year":2021,"finding":"Cryo-EM structure of human Scap bound to Insig-2 in the presence of 25-hydroxycholesterol (25HC) reveals that a 25HC molecule is sandwiched between S4–S6 segments of Scap and TM3–4 of Insig-2 in the luminal leaflet of the membrane. Unwinding of the middle of the Scap-S4 segment is crucial for 25HC binding and Insig association.","method":"Cryo-electron microscopy of human Scap/Insig-2 complex, resolution 3.7 Å for transmembrane domains","journal":"Science (New York, N.Y.)","confidence":"High","confidence_rationale":"Tier 1 / Strong — cryo-EM structure at 3.7 Å with functionally validated ligand binding site, landmark structural study","pmids":["33446483"],"is_preprint":false},{"year":2021,"finding":"Cryo-EM structures of full-length chicken Scap (wild-type free of Insig, and mutant bound to chicken Insig without cholesterol) reveal that luminal loops L1 and L7 intertwine tightly to form a globular domain (luminal platform) connecting the sterol-sensing domain to the rest of Scap. In the presence of Insig, this platform undergoes a large rotation accompanied by rearrangement of transmembrane helices.","method":"Cryo-EM of full-length chicken Scap in two states; structural comparison of Insig-bound vs. free forms","journal":"Cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — cryo-EM structures of two functional states of full-length Scap, structural basis for conformational change validated","pmids":["34139175"],"is_preprint":false},{"year":2015,"finding":"EGFR signaling, by increasing glucose uptake, promotes N-glycosylation of SCAP, which stabilizes SCAP and reduces its association with Insig-1, allowing SCAP/SREBP movement to the Golgi and proteolytic SREBP-1 activation. Blocking SCAP N-glycosylation inhibits SCAP/SREBP trafficking and ameliorates EGFRvIII-driven glioblastoma xenograft growth.","method":"N-glycosylation site mutagenesis, co-immunoprecipitation (SCAP/Insig-1), Golgi trafficking assay, xenograft tumor studies","journal":"Cancer cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — mutagenesis, co-IP, trafficking assay, and in vivo xenograft validation; multiple orthogonal methods","pmids":["26555173"],"is_preprint":false},{"year":2017,"finding":"25-hydroxyvitamin D (25OHD) inhibits SREBP activation by inducing proteolytic processing and ubiquitin-mediated degradation of SCAP, thereby decreasing SREBP levels. This mechanism is independent of the vitamin D receptor.","method":"Chemical library screen, ubiquitination assay, proteolytic processing assay, SCAP degradation measurement","journal":"Cell chemical biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional SCAP degradation and ubiquitination assays, single lab, vitamin D receptor independence tested","pmids":["28132894"],"is_preprint":false},{"year":2017,"finding":"RNF145, an ER membrane ubiquitin E3 ligase induced by LXR activation, triggers ubiquitination of SCAP on lysine residues within the cytoplasmic loop essential for COPII binding, potentially inhibiting SCAP transport to Golgi and subsequent SREBP-2 processing. RNF145 knockdown or knockout potentiates cholesterol biosynthetic gene expression.","method":"RNF145 overexpression and shRNA knockdown in mouse liver, genetic deletion, ubiquitination assay on SCAP","journal":"eLife","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo KO and overexpression, ubiquitination assay, single lab with multiple approaches","pmids":["29068315"],"is_preprint":false},{"year":2020,"finding":"SCAP interacts with SQSTM1 (p62) via its WD40 domain (SCAP) and the TB domain (SQSTM1), and lycorine promotes SCAP lysosomal degradation via an autophagy-independent SQSTM1-mediated pathway (SMAILD), distinct from sterol-dependent ER retention mechanisms.","method":"Pulldown assay, domain mapping, lysosomal degradation assay, autophagy-independent pathway determination","journal":"Autophagy","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — co-immunoprecipitation domain mapping, degradation assays, autophagy independence demonstrated, single lab","pmids":["32432943"],"is_preprint":false},{"year":2014,"finding":"SCAP Golgi-to-ER recycling requires cleavage of SREBP at site-1. When SREBP cleavage is reduced, SCAP is degraded in lysosomes. SREBP actively prevents premature recycling of the SCAP-SREBP complex until initiation of SREBP cleavage, representing an ancient regulatory mechanism conserved between human cells and yeast.","method":"Inhibition of site-1 protease, lysosomal degradation assays, yeast genetic experiments","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pharmacological and genetic inhibition of S1P cleavage, degradation assays, cross-species conservation","pmids":["24478315"],"is_preprint":false},{"year":2015,"finding":"PAQR3, a Golgi-localized membrane protein, interacts with SCAP and SREBP and tethers them to the Golgi, promoting SCAP/SREBP complex formation and SREBP processing. The interaction between Scap and PAQR3 or Insig-1 is mutually exclusive and regulated by cholesterol level.","method":"Co-immunoprecipitation, PAQR3 knockdown in liver, synthetic peptide disruption of SCAP-PAQR3 interaction","journal":"Nature communications","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — co-IP, in vivo liver knockdown, peptide competition assay; single lab, multiple methods","pmids":["26311497"],"is_preprint":false},{"year":2019,"finding":"Cideb, an ER/lipid droplet-associated protein, selectively promotes loading of SREBP/SCAP into COPII vesicles by interacting with SCAP (interaction enhanced by sterol deprivation) and binding to the guanine nucleotide exchange factor Sec12 to enrich SCAP/SREBP at ER exit sites. Loss of Cideb inhibits SREBP activation.","method":"Co-immunoprecipitation (SCAP-Cideb, Cideb-Sec12), COPII vesicle loading assay, Cideb knockout","journal":"The EMBO journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP of SCAP-Cideb and Cideb-Sec12, sterol-regulated interaction, KO phenotype; single lab","pmids":["30858281"],"is_preprint":false},{"year":2016,"finding":"SCAP translocates from ER via Golgi to perinuclear microsome in a STING-dependent manner upon cytosolic microbial DNA sensing. The N-terminal transmembrane domain of SCAP interacts with STING, and the C-terminal cytosolic (WD40) domain of SCAP binds IRF3, recruiting IRF3 to the STING signalosome. SCAP knockdown mice are more susceptible to HSV-1 infection.","method":"Co-immunoprecipitation (SCAP-STING, SCAP-IRF3), SCAP knockdown (siRNA), HSV-1 infection of knockdown mice, localization by fluorescence microscopy","journal":"PLoS pathogens","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP of SCAP-STING and SCAP-IRF3, in vivo knockdown infection model, domain mapping; single lab","pmids":["26900919"],"is_preprint":false},{"year":2017,"finding":"SCAP binds dengue virus NS2B protein (via its N-terminal transmembrane domain), inhibiting K27-linked polyubiquitination of NS3 and thereby preventing NS2B3 protease complex formation and STING cleavage. Ectopic SCAP impairs DENV infection; SCAP silencing potentiates it.","method":"Co-immunoprecipitation (SCAP-NS2B), ubiquitination assay, SCAP overexpression and knockdown with viral replication readout","journal":"Journal of virology","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — co-IP, ubiquitination assay, gain- and loss-of-function with viral infection readout; single lab","pmids":["28228593"],"is_preprint":false},{"year":2022,"finding":"Ammonia (released from glutamine) promotes SCAP-Insig dissociation and SREBP-1 activation independently of sterols. Ammonia binds to SCAP at a site blocked by 25-hydroxycholesterol. Mutating aspartate D428 to alanine prevents ammonia binding to SCAP and abolishes SREBP-1 activation.","method":"SCAP-Insig co-immunoprecipitation with ammonia treatment, D428A point mutation, ammonia binding assay, tumor xenograft","journal":"Nature metabolism","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP, site-directed mutagenesis, binding competition with 25HC; single lab with multiple approaches","pmids":["35534729"],"is_preprint":false},{"year":2006,"finding":"PI3K/Akt pathway is involved in SCAP/SREBP-2 transport from the ER to the Golgi: PI3K inhibition (LY294002) or dominant-negative Akt expression disrupts SCAP trafficking to the Golgi as shown by fluorescence microscopy, blunting SREBP-2 processing.","method":"PI3K inhibitor (LY294002), dominant-negative Akt expression, immunofluorescence microscopy of SCAP localization","journal":"Molecular biology of the cell","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — pharmacological and genetic inhibition of PI3K/Akt, fluorescence microscopy of SCAP localization, single lab; mechanism not fully resolved","pmids":["16571675"],"is_preprint":false},{"year":2009,"finding":"Insulin promotes SCAP/SREBP-1c transport to the Golgi by selectively reducing Insig-2a protein levels via accelerated mRNA decay (through the 3'-UTR of Insig-2a mRNA), releasing the SCAP/SREBP-1c complex from ER retention. siRNA knockdown of Insig-2a mimics insulin-induced SREBP-1c proteolysis.","method":"Insig-2a mRNA decay assay, siRNA knockdown, exogenous Insig-2a expression, SCAP-COPII association assay in primary hepatocytes","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — siRNA knockdown, rescue experiment, mRNA stability assay, COPII binding assay; single lab","pmids":["19759400"],"is_preprint":false},{"year":2016,"finding":"Complex structure of fission yeast SREBP C-terminus (Sre1-CTD) and SCAP C-terminus (Scp1) shows they form a functional 4:4 oligomer with Sre1-CTD forming a dimer of dimers. Three distinct regions in Sre1-CTD mediate Scp1 binding, Sre1-CTD dimerization, and tetrameric formation; proper oligomeric complex formation is required for Sre1 activation.","method":"Crystal structure of Sre1-CTD at 3.5 Å, cryo-EM of complex at 5.4 Å, in vitro biochemical assembly assays, functional validation in cells","journal":"Cell research","confidence":"High","confidence_rationale":"Tier 1 / Moderate — crystal structure + cryo-EM + biochemical assembly + functional cellular validation; fission yeast ortholog relevant to understanding SCAP WD40-SREBP interaction","pmids":["27811944"],"is_preprint":false},{"year":2017,"finding":"Cholesterol binding to Loop 1 of Scap alters the conformation of the sterol-sensing domain (SSD): in the absence of cholesterol, cytosolic loop 4 is cleaved by trypsin/proteinase K generating a protected fragment; upon cholesterol addition, cleavage of loop 4 is abolished. This conformational change in the SSD is proposed to transmit the cholesterol signal from Loop 1 to Loop 7.","method":"Protease protection assay in sealed membrane vesicles using trypsin or proteinase K, monoclonal antibody detection of protected fragment","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 1–2 / Moderate — in vitro protease protection assay in sealed vesicles, multiple proteases used, single lab","pmids":["28377508"],"is_preprint":false},{"year":2020,"finding":"RNF5, an ER-anchored E3 ubiquitin ligase, mediates Lys-29-linked polyubiquitination of SCAP at K305 in cytosolic loop 2. This ubiquitination enhances interaction between SCAP luminal loop 1 and loop 7, activating SREBP2. K305R SCAP fails to restore the SREBP2 pathway in SCAP-deficient cells.","method":"RNF5 knockdown and overexpression, ubiquitination site mapping (K305), co-immunoprecipitation (loop 1–loop 7 interaction), SREBP2 activation assay","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — specific lysine ubiquitination mapping, co-IP, rescue with K305R mutant; single lab","pmids":["32054686"],"is_preprint":false},{"year":2021,"finding":"ZDHHC3 S-acylates (palmitoylates) SCAP at cysteine C264, which antagonizes HACE1-mediated SCAP ubiquitination and proteasomal degradation. ABHD17A acts as the depalmitoylase. SREBP2 transcriptionally upregulates ZDHHC3, forming a positive feedback loop that sustains SCAP/SREBP2 signaling in HCC.","method":"Palmitoylation assay, ZDHHC3 knockdown/overexpression, co-immunoprecipitation, ubiquitination assay, chromatin immunoprecipitation for SREBP2 at ZDHHC3 promoter","journal":"Cell reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — palmitoylation site mapping, co-IP, ubiquitination assay, ChIP; single lab, multiple methods","pmids":["39522165"],"is_preprint":false},{"year":2021,"finding":"In cholesterol-fed cells, ER-localized SCAP interacts with Sac1 PI4P phosphatase through a VAP-OSBP complex at ER-Golgi membrane contact sites (MCSs), facilitating PI4P turnover and CARTS biogenesis. SCAP knockdown inhibits PI4P turnover and CARTS biogenesis; this is reversed by wild-type SCAP or a Golgi-transport-defective mutant but not by cholesterol-sensing-defective mutants.","method":"Co-immunoprecipitation (SCAP-Sac1, VAP-OSBP), SCAP knockdown, rescue with WT and mutant SCAP, CARTS biogenesis assay","journal":"The Journal of cell biology","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — co-IP, knockdown + rescue with domain-discriminating mutants, functional CARTS biogenesis assay; single lab","pmids":["33156328"],"is_preprint":false},{"year":2023,"finding":"Scap and SREBP1 form a super-complex with IκBα that associates NF-κB near the ER. Upon LPS stimulation, Scap transports this complex to the Golgi where SREBP1 is cleaved by S1P/S2P, liberating IκBα for IKK-mediated phosphorylation and NF-κB activation. Loss of Scap diminishes LPS-induced NF-κB activation.","method":"Co-immunoprecipitation (Scap-SREBP1-IκBα), Scap knockout, S1P/S2P inhibition, NF-κB activation assays, Golgi localization by imaging","journal":"Cell reports","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — co-IP of three-protein complex, loss-of-function, pharmacological inhibition; single lab","pmids":["37267109"],"is_preprint":false},{"year":2021,"finding":"Chromatin remodeling protein BRG1 binds the SCAP promoter in complex with Sp1 to activate SCAP transcription in hepatocytes. BRG1 deficiency reduces SCAP expression and SREBP processing; forced exogenous SCAP expression partially rescues SREBP target gene expression in BRG1-null hepatocytes.","method":"ChIP (BRG1 at SCAP promoter), BRG1 knockdown/KO, exogenous SCAP rescue experiment, SREBP processing assay","journal":"Frontiers in cell and developmental biology","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — ChIP at SCAP promoter, genetic KO with rescue, single lab","pmids":["33718362"],"is_preprint":false},{"year":2022,"finding":"Macrophage SCAP specifically recruits STING and TBK1 onto the Golgi apparatus to activate NF-κB, promoting inflammatory factor release. Macrophage-specific SCAP knockout attenuates STING-NF-κB pathway activation and reduces metaflammation.","method":"Macrophage-specific SCAP knockout mice, co-immunoprecipitation (SCAP-STING-TBK1), NF-κB activation assay, Golgi localization imaging","journal":"Cellular and molecular gastroenterology and hepatology","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — macrophage-specific KO, co-IP of SCAP-STING-TBK1 complex at Golgi, single lab","pmids":["35367665"],"is_preprint":false},{"year":2024,"finding":"STAT3 directly binds the promoter of the SCAP gene to activate its transcription across multiple cancer cell types, and simultaneously activates SREBF1 transcription, cooperatively enhancing fatty acid synthesis.","method":"ChIP (STAT3 at SCAP promoter), STAT3 pharmacological inhibition, SCAP/SREBP-1 expression assays in cancer cells and clinical samples","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — ChIP at SCAP promoter, pharmacological inhibition, clinical correlation; single lab","pmids":["38718868"],"is_preprint":false},{"year":1998,"finding":"Transgenic mice expressing sterol-resistant SCAP(D443N) in liver show increased nuclear SREBP-1 and -2, elevated lipogenic gene mRNAs, and fatty livers. These livers show blunted feedback suppression of SREBP processing in response to high dietary cholesterol, confirming SCAP's sterol-sensing role in vivo.","method":"Transgenic mouse model with liver-specific SCAP(D443N), dietary cholesterol challenge, nuclear SREBP quantification, lipid analysis","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo transgenic model with dominant gain-of-function mutation, dietary challenge, multiple molecular and metabolic readouts","pmids":["9854040"],"is_preprint":false},{"year":2012,"finding":"Scap is required for hepatic steatosis in insulin-resistant ob/ob mice and high-fat diet mice: deletion of Scap in liver abolishes fatty liver despite persistent obesity, hyperinsulinemia, and hyperglycemia. siRNA silencing of Scap in sucrose-fed hamster livers prevents sucrose-induced hypertriglyceridemia by reducing all three nuclear SREBPs.","method":"Conditional hepatic Scap knockout in ob/ob mice, siRNA silencing in hamsters, lipid synthesis measurement, SREBP nuclear levels","journal":"Cell metabolism","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean conditional KO + siRNA in two distinct animal models, multiple metabolic readouts","pmids":["22326225"],"is_preprint":false},{"year":2016,"finding":"Fatostatin directly binds SCAP and blocks its ER-to-Golgi transport independently of Insig proteins. However, fatostatin also inhibits cell growth via SCAP-independent mechanisms and delays ER-to-Golgi transport of VSVG protein, indicating general ER-to-Golgi transport inhibition beyond SCAP.","method":"VSVG trafficking assay, SCAP-null cell growth assay, fatostatin direct binding to SCAP, ER exit assay","journal":"Journal of lipid research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct binding demonstrated, SCAP-null cell experiments, VSVG trafficking control; single lab","pmids":["27324795"],"is_preprint":false},{"year":2021,"finding":"Combined cryo-EM and AI-facilitated structural prediction reveals that luminal loop 1 and a co-folded segment in loop 7 of Scap resemble the luminal/extracellular domain in NPC1 and related proteins. An additional luminal interface between Scap and Insig-2 is observed. SCAP(D428A) shows identical conformation with wild-type when complexed with Insig-2, suggesting constitutive suppression may involve a later trafficking step.","method":"Cryo-EM of human Scap/Insig-2 complex in digitonin, AI structural prediction, comparative structural analysis","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 1 / Moderate — cryo-EM structural study with functional mutant comparison; single study but structural tier","pmids":["34192549"],"is_preprint":false},{"year":2022,"finding":"Tim-4 disturbs the Insig1-SCAP interaction and promotes SCAP-SREBP2 complex translocation to the Golgi, upregulating cholesterol biosynthesis in macrophages and limiting type I IFN responses.","method":"Co-immunoprecipitation (Insig1-SCAP with/without Tim-4), Tim-4 deficiency, SREBP2 activation assay, IFN signaling measurement","journal":"Cell reports","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — co-IP showing disrupted Insig1-SCAP interaction by Tim-4, loss-of-function, single lab","pmids":["36450259"],"is_preprint":false}],"current_model":"SCAP is an octahelical ER membrane protein that functions as a sterol sensor and escort protein: in sterol-depleted cells, its luminal Loop 1 (cholesterol-binding site) interacts with Loop 7 to maintain cytosolic Loop 6 in a conformation that recruits COPII proteins at the MELADL sorting signal, enabling SCAP to transport SREBP transcription factors from ER to Golgi for proteolytic activation of lipid synthesis genes; when ER cholesterol exceeds a threshold, cholesterol binds Loop 1, conformationally rearranges the sterol-sensing domain and Loop 6, and induces SCAP binding to ER-resident INSIG-1/2 retention proteins, blocking COPII recruitment and halting SCAP/SREBP export; additional regulatory inputs include N-glycosylation (stabilizing SCAP and promoting trafficking), ubiquitination by RNF145 (inhibitory) and RNF5 (activatory), S-acylation by ZDHHC3 (protective from degradation), SQSTM1-mediated lysosomal degradation, ammonia-driven SCAP-Insig dissociation, and roles beyond lipid metabolism including recruitment of IRF3 to the STING signalosome and coordination of NF-κB activation at the Golgi."},"narrative":{"mechanistic_narrative":"SCAP is an octahelical ER membrane protein that serves as the cell's principal cholesterol sensor and the escort that controls activation of the SREBP family of lipogenic transcription factors [PMID:15260976, PMID:11358865]. In sterol-depleted cells SCAP packages SREBP into COPII-coated vesicles via the MELADL sorting signal in a cytosolic loop, driving ER-to-Golgi transport where SREBPs are proteolytically processed to their active nuclear forms [PMID:12193656, PMID:15899885]. Cholesterol binds directly and specifically to SCAP's membrane domain, with the 245-residue luminal Loop 1 constituting the cholesterol-binding site, and binding is transmitted through an intertwined Loop 1–Loop 7 luminal platform and the sterol-sensing domain to reposition cytosolic Loop 6, abrogating COPII recruitment [PMID:15260976, PMID:21454655, PMID:23564452, PMID:34139175]. Sterol loading triggers SCAP binding to the ER-resident retention proteins INSIG-1 and INSIG-2, which captures the complex in the ER; oxysterols such as 25-hydroxycholesterol instead bind at the SCAP–INSIG interface, as resolved by cryo-EM of the SCAP/INSIG-2 complex [PMID:12202038, PMID:12242332, PMID:15452130, PMID:33446483]. Point mutations in the sterol-sensing domain (Y298C, D443N, L315F) lock SCAP in a sterol-resistant, constitutively exporting state, and a transgenic SCAP(D443N) liver produces unrestrained lipogenesis and fatty liver, establishing SCAP as the in vivo rate-limiting sensor for hepatic cholesterol and fatty-acid synthesis [PMID:9789003, PMID:12482938, PMID:9854040, PMID:11358865]. SCAP activity is further tuned by post-translational and trafficking inputs—N-glycosylation downstream of growth-factor/glucose signaling stabilizes SCAP and reduces INSIG association, and ubiquitination, S-acylation, and accessory factors modulate its stability and export [PMID:26555173, PMID:29068315, PMID:32054686, PMID:39522165, PMID:30858281]. Beyond lipid metabolism, SCAP scaffolds innate-immune signaling, recruiting IRF3 to the STING signalosome through its cytosolic WD40 domain and coordinating STING/TBK1-driven NF-κB activation at the Golgi [PMID:26900919, PMID:35367665].","teleology":[{"year":1998,"claim":"Established that specific residues in SCAP constitute a functional sterol sensor, by showing point mutations that uncouple SREBP processing from sterol levels.","evidence":"CHO sterol-resistant mutant cells (Y298C, D443N) with endoglycosidase H sensitivity and SREBP processing assays","pmids":["9789003"],"confidence":"High","gaps":["Did not identify the retention factor that wild-type SCAP engages","Mechanism of cholesterol detection not defined"]},{"year":1998,"claim":"Demonstrated in vivo that the SCAP sterol sensor governs whole-organism lipogenesis, by expressing a sterol-resistant mutant in liver.","evidence":"Transgenic mice with liver-specific SCAP(D443N), dietary cholesterol challenge, nuclear SREBP and lipid analysis","pmids":["9854040"],"confidence":"High","gaps":["Did not resolve the molecular retention mechanism","Loss-of-function in vivo not yet tested"]},{"year":1999,"claim":"Showed that sterol regulation operates at the level of SCAP trafficking between ER and Golgi, defining the transport step as the regulated event.","evidence":"Glycosidase sensitivity, glycosylation-defective mutants, density fractionation, brefeldin A in cells","pmids":["10500160"],"confidence":"High","gaps":["Retention protein not identified","Vesicle machinery for export not defined"]},{"year":2001,"claim":"Established SCAP as physiologically required for hepatic lipid synthesis using conditional loss-of-function.","evidence":"Inducible Cre-mediated hepatic Scap knockout in mice with mRNA and lipid synthesis readouts","pmids":["11358865"],"confidence":"High","gaps":["Did not address SCAP roles outside liver","Molecular sensing mechanism not addressed"]},{"year":2002,"claim":"Identified INSIG-1 and INSIG-2 as the sterol-regulated ER retention proteins that bind SCAP's sterol-sensing domain, resolving how sterols halt SREBP export.","evidence":"Reciprocal co-IP, mass spectrometry, blue native-PAGE, SREBP processing assays, mutant SCAP(Y298C)","pmids":["12202038","12242332"],"confidence":"High","gaps":["Whether cholesterol acts directly on SCAP or via membrane not resolved","Structural basis of binding unknown"]},{"year":2002,"claim":"Connected the molecular events by showing sterols induce a SCAP conformational change and block COPII (Sec23/24) incorporation, with sterol-resistant mutants refractory.","evidence":"In vitro trypsin conformational assay on ER membranes, in vitro vesicle reconstitution with recombinant COPII, mutant analysis","pmids":["12191470","12193656","12482938"],"confidence":"High","gaps":["Direct ligand binding not yet demonstrated","Sorting signal recognized by COPII not mapped"]},{"year":2003,"claim":"Defined the minimal sterol-regulated transport module and showed INSIG sensitizes the SCAP conformational switch, refining how the sensor reads membrane composition.","evidence":"Heterologous reconstitution in Drosophila cells; in vitro conformational assay with INSIG co-expression and cationic amphiphiles","pmids":["12842885","12963821"],"confidence":"High","gaps":["Direct cholesterol receptor activity not yet proven","25-HC mechanism distinct from cholesterol unresolved"]},{"year":2004,"claim":"Proved SCAP is a direct cholesterol receptor and distinguished cholesterol (direct binding) from 25-HC (indirect) as separate regulatory inputs.","evidence":"Purified recombinant SCAP membrane domain direct binding, photoaffinity cross-linking, analytical ultracentrifugation, INSIG co-IP","pmids":["15260976","15452130"],"confidence":"High","gaps":["Precise cholesterol-binding subdomain not localized","How conformational change reaches the sorting signal unknown"]},{"year":2005,"claim":"Mapped the MELADL hexapeptide as the COPII sorting signal and defined Asp-428 as essential for sterol-dependent INSIG dissociation.","evidence":"In vitro microsomal pulldowns with INSIG dependency, MELADL mutagenesis, D428A co-IP and transport assay","pmids":["15899885","15728349"],"confidence":"High","gaps":["Spatial relationship of MELADL to membrane not resolved","Path of signal from sensor to MELADL undefined"]},{"year":2007,"claim":"Resolved that cholesterol (on SCAP) and oxysterols (on INSIG) converge on a conformational change near MELADL that excludes COPII.","evidence":"Anti-MELADL blocking in vitro, intracellular Fab microinjection, cysteine-labeling conformational assay","pmids":["17428919"],"confidence":"High","gaps":["Luminal determinants of cholesterol binding not yet localized","Structural model absent"]},{"year":2013,"claim":"Localized the cholesterol-binding site to luminal Loop 1 and showed Loop 1–Loop 7 interaction maintains the COPII-permissive Loop 6 conformation, building the intramolecular signal-relay model.","evidence":"Recombinant Loop 1 binding, Y234A and Y640S mutations, conformational assays, co-IP of N- and C-terminal fragments","pmids":["21454655","23564452","28377508"],"confidence":"High","gaps":["Atomic structure of luminal domain still lacking","Quantitative coupling between loops not defined"]},{"year":2021,"claim":"Provided the structural basis of sterol sensing with cryo-EM of SCAP free, SCAP/INSIG, and the 25HC-bound complex, defining the luminal platform and ligand pocket.","evidence":"Cryo-EM of human SCAP/INSIG-2 with 25HC, full-length chicken SCAP in two states, AI-assisted comparative analysis","pmids":["33446483","34139175","34192549"],"confidence":"High","gaps":["Dynamics of the conformational transition not captured","Structure of the SREBP-bound exporting state unresolved"]},{"year":2016,"claim":"Defined the structural basis of the SCAP C-terminus–SREBP interaction via the ortholog complex, explaining how SCAP engages its cargo.","evidence":"Crystal and cryo-EM structures of fission yeast Sre1-CTD/Scp1 4:4 oligomer with biochemical and cellular validation","pmids":["27811944"],"confidence":"High","gaps":["Mammalian SCAP WD40–SREBP complex structure not solved","Relationship of oligomer to vesicle loading unclear"]},{"year":2009,"claim":"Showed hormonal/signaling inputs override sterol control: insulin and PI3K/Akt promote SCAP/SREBP export, broadening regulation beyond sterols.","evidence":"Insig-2a mRNA decay and siRNA in hepatocytes; PI3K inhibitor and dominant-negative Akt with SCAP localization imaging","pmids":["19759400","16571675"],"confidence":"Medium","gaps":["Direct kinase target on SCAP not defined","PI3K/Akt mechanism on trafficking not fully resolved"]},{"year":2017,"claim":"Established post-translational control of SCAP stability and trafficking via glycosylation and ubiquitination, linking growth-factor signaling and LXR to lipogenesis.","evidence":"N-glycosylation mutagenesis with xenografts; RNF145 KO/overexpression with ubiquitination assays; 25OHD-induced degradation; RNF5 K305 mapping","pmids":["26555173","29068315","28132894","32054686"],"confidence":"Medium","gaps":["Interplay among competing E3 ligases unresolved","Quantitative contribution of each modification in vivo unknown"]},{"year":2020,"claim":"Identified additional stability and trafficking modulators of SCAP, including SQSTM1-mediated lysosomal degradation, S-acylation, and accessory tethering/loading factors.","evidence":"SQSTM1 domain-mapped pulldown and degradation; ZDHHC3 palmitoylation at C264; PAQR3 Golgi tethering; Cideb-Sec12 COPII loading; SREBP-cleavage-dependent recycling","pmids":["32432943","39522165","26311497","30858281","24478315"],"confidence":"Medium","gaps":["Hierarchy among these modulators undefined","Most validated in single labs without reciprocal confirmation"]},{"year":2012,"claim":"Established SCAP as required for diet- and insulin-resistance-driven hepatic steatosis, defining it as a therapeutic node in metabolic disease.","evidence":"Conditional hepatic Scap KO in ob/ob and high-fat-diet mice; siRNA in hamster; fatostatin direct binding and transport block","pmids":["22326225","27324795"],"confidence":"High","gaps":["Fatostatin shows SCAP-independent effects, limiting selectivity","On-target small-molecule pharmacology incomplete"]},{"year":2016,"claim":"Revealed SCAP functions beyond lipid metabolism by scaffolding innate-immune signaling and coordinating NF-κB activation.","evidence":"Co-IP of SCAP-STING and SCAP-IRF3 with domain mapping and HSV-1 infection; SCAP-NS2B binding; macrophage-specific KO with STING/TBK1 co-IP; Scap-SREBP1-IκBα super-complex; Tim-4 disruption of Insig1-SCAP","pmids":["26900919","28228593","35367665","37267109","36450259"],"confidence":"Medium","gaps":["Whether immune scaffolding requires sterol-sensing activity unclear","Most findings from single labs without independent replication"]},{"year":2024,"claim":"Identified transcriptional control of the SCAP gene itself by BRG1/Sp1 and STAT3, linking chromatin and oncogenic signaling to SCAP abundance.","evidence":"ChIP of BRG1 and STAT3 at the SCAP promoter, knockdown/KO with rescue, pharmacological inhibition in cancer cells","pmids":["33718362","38718868"],"confidence":"Medium","gaps":["Integration of transcriptional and post-translational control not modeled","In vivo relevance of these transcriptional inputs incompletely tested"]},{"year":null,"claim":"How the multiple competing regulatory layers—sterol sensing, ammonia and hormonal inputs, ubiquitination/acylation, and immune scaffolding—are integrated on a single SCAP molecule, and the structure of the active SREBP-bound exporting complex, remain unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structure of SCAP–SREBP–COPII exporting complex","Quantitative crosstalk among regulatory modifications undefined","In vivo significance of non-lipid SCAP functions incompletely established"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140299","term_label":"molecular sensor activity","supporting_discovery_ids":[5,6,13,11]},{"term_id":"GO:0008289","term_label":"lipid binding","supporting_discovery_ids":[5,13,18]},{"term_id":"GO:0038024","term_label":"cargo receptor activity","supporting_discovery_ids":[4,7]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[27,37]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,1]}],"localization":[{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[0,3,5]},{"term_id":"GO:0005794","term_label":"Golgi apparatus","supporting_discovery_ids":[3,4,39]},{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[5]}],"pathway":[{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[17,41,42]},{"term_id":"R-HSA-5653656","term_label":"Vesicle-mediated transport","supporting_discovery_ids":[3,4,7]},{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[17,41]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[27,39,37]},{"term_id":"R-HSA-9609507","term_label":"Protein localization","supporting_discovery_ids":[3,4]}],"complexes":["SCAP/SREBP complex","SCAP/INSIG complex","STING signalosome","Scap-SREBP1-IκBα super-complex"],"partners":["INSIG1","INSIG2","SREBF2","STING1","IRF3","RNF145","RNF5","PAQR3"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9NP31","full_name":"SH2 domain-containing protein 2A","aliases":["SH2 domain-containing adapter protein","T cell-specific adapter protein","TSAd","VEGF receptor-associated protein"],"length_aa":389,"mass_kda":42.9,"function":"Could be a T-cell-specific adapter protein involved in the control of T-cell activation. May play a role in the CD4-p56-LCK-dependent signal transduction pathway. Could also play an important role in normal and pathological angiogenesis. Could be an adapter protein that facilitates and regulates interaction of KDR with effector proteins important to endothelial cell survival and proliferation","subcellular_location":"Cytoplasm","url":"https://www.uniprot.org/uniprotkb/Q9NP31/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/SCAP","classification":"Not Classified","n_dependent_lines":853,"n_total_lines":1208,"dependency_fraction":0.7061258278145696},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/SCAP","total_profiled":1310},"omim":[{"mim_id":"620640","title":"RING FINGER PROTEIN 145; RNF145","url":"https://www.omim.org/entry/620640"},{"mim_id":"617968","title":"WD REPEAT-CONTAINING PROTEIN 63; WDR63","url":"https://www.omim.org/entry/617968"},{"mim_id":"614168","title":"PHOSPHOENOLPYRUVATE CARBOXYKINASE 1, SOLUBLE; PCK1","url":"https://www.omim.org/entry/614168"},{"mim_id":"608660","title":"INSULIN-INDUCED GENE 2; INSIG2","url":"https://www.omim.org/entry/608660"},{"mim_id":"605537","title":"ACTIVATING TRANSCRIPTION FACTOR 6; ATF6","url":"https://www.omim.org/entry/605537"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/SCAP"},"hgnc":{"alias_symbol":["KIAA0199"],"prev_symbol":[]},"alphafold":{"accession":"Q9NP31","domains":[{"cath_id":"3.30.505.10","chopping":"67-186","consensus_level":"high","plddt":93.9623,"start":67,"end":186}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NP31","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NP31-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NP31-F1-predicted_aligned_error_v6.png","plddt_mean":61.16},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=SCAP","jax_strain_url":"https://www.jax.org/strain/search?query=SCAP"},"sequence":{"accession":"Q9NP31","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9NP31.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9NP31/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NP31"}},"corpus_meta":[{"pmid":"12202038","id":"PMC_12202038","title":"Crucial step in cholesterol 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Mutant SCAP(Y298C) fails to bind INSIG-1 and is resistant to sterol-mediated ER retention.\",\n      \"method\": \"Coimmunoprecipitation, tandem mass spectrometry, blue native-PAGE, mutant SCAP analysis\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — reciprocal co-IP, mass spectrometry identification, blue native-PAGE, mutagenesis validation, replicated across multiple subsequent studies\",\n      \"pmids\": [\"12202038\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"INSIG-2, a second ER protein with 59% sequence identity to INSIG-1, binds SCAP in a sterol-regulated fashion and blocks SCAP/SREBP export from the ER to the Golgi, thereby preventing proteolytic SREBP processing. Unlike INSIG-1, INSIG-2 expression does not require nuclear SREBPs.\",\n      \"method\": \"Coimmunoprecipitation, sterol-regulated binding assays, SREBP processing assays\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal co-IP, functional SREBP processing assays, replicated in subsequent work\",\n      \"pmids\": [\"12242332\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Cholesterol addition to ER membranes in vitro causes a conformational change in SCAP detectable by trypsin cleavage site unmasking. Two sterol-resistant mutants, SCAP(Y298C) and SCAP(D443N), are refractory to this cholesterol-induced conformational change in vitro.\",\n      \"method\": \"In vitro trypsin cleavage/protease protection assay on ER membranes, mutant SCAP analysis\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution with ER membranes, mutagenesis validation, mechanistically foundational finding replicated in subsequent studies\",\n      \"pmids\": [\"12191470\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Sterols regulate cycling of SCAP between the ER and Golgi: in sterol-depleted cells, N-linked carbohydrates of SCAP are modified by Golgi enzymes (becoming endoglycosidase H-resistant), and SCAP returns to the ER; in sterol-overloaded cells, SCAP fails to leave the ER and Golgi modifications do not occur.\",\n      \"method\": \"Glycosidase treatment, glycosidase inhibitors, glycosylation-defective mutant cell lines, density gradient fractionation, brefeldin A treatment\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal biochemical methods, functionally linked to SREBP processing, replicated\",\n      \"pmids\": [\"10500160\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Sterols block incorporation of SCAP into COPII-coated vesicles by blocking Sar1-dependent binding of COPII proteins (Sec23/24) to SCAP. SCAP-containing vesicles formed in vitro also contain VSVG (a COPII marker), and sterols selectively block SCAP but not VSVG incorporation.\",\n      \"method\": \"Immunoisolation of vesicles formed in vitro, reconstitution with recombinant yeast COPII proteins, pulldown assays\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — in vitro vesicle reconstitution, selective inhibition controls, replicated in multiple follow-up studies\",\n      \"pmids\": [\"12193656\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Cholesterol directly binds with high affinity and specificity to the purified 767 amino acid octahelical membrane region of SCAP. The membrane domain of SCAP forms a tetramer, and cholesterol binding is inhibited by cationic amphiphiles. Cholesterol acts through direct receptor-ligand interaction rather than by changing membrane physical properties.\",\n      \"method\": \"Recombinant SCAP purification in detergent, direct cholesterol binding assay, analytical ultracentrifugation (tetramer determination)\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct in vitro binding with purified recombinant protein, multiple orthogonal methods, landmark mechanistic study\",\n      \"pmids\": [\"15260976\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Cholesterol and 25-hydroxycholesterol (25-HC) inhibit SCAP/SREBP transport by two distinct mechanisms: cholesterol directly binds SCAP (demonstrated by photoactivated cholesterol cross-linking to SCAP membrane domain) and induces a conformational change causing SCAP to bind Insigs; 25-HC does not cross-link to SCAP and does not produce a detectable SCAP conformational change, suggesting it acts indirectly through a separate sensor.\",\n      \"method\": \"Methyl-β-cyclodextrin cholesterol delivery, trypsin conformational assay, photoactivated cholesterol cross-linking, coimmunoprecipitation with Insigs\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — direct photoaffinity cross-linking, conformational assay, Insig binding assay; multiple orthogonal methods in single study\",\n      \"pmids\": [\"15452130\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Insig proteins are required for sterol-mediated inhibition of Sec23/24 binding to SCAP in vitro. The hexapeptide sequence MELADL in a cytoplasmic loop of SCAP is required for Sec23/24 binding and acts as a sterol-regulated ER sorting signal.\",\n      \"method\": \"Protein pulldown assays with microsomal membranes, Insig-1 dependency experiments, MELADL mutagenesis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — in vitro reconstitution with microsomal membranes, mutagenesis of sorting signal, Insig requirement demonstrated\",\n      \"pmids\": [\"15899885\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Sterols block COPII binding to the MELADL sorting signal in SCAP by two mechanisms: cholesterol binds directly to SCAP causing a conformational change near MELADL, and oxysterols bind to Insig (not SCAP directly), also producing a conformational change near MELADL. Both conformational changes abrogate COPII binding but not anti-MELADL antibody binding. The distance of MELADL from the ER membrane is implicated as crucial for COPII binding.\",\n      \"method\": \"Anti-MELADL blocking of COPII binding in vitro, microinjection of Fab anti-MELADL into cells, cysteine labeling conformational assay, mutagenesis\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — in vitro reconstitution, intracellular microinjection, cysteine-labeling conformational assay, mutagenesis; multiple orthogonal approaches\",\n      \"pmids\": [\"17428919\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Point mutations Y298C and D443N within the putative sterol-sensing domain of SCAP render it resistant to sterol-mediated inhibition. In sterol-resistant mutant cells, N-linked carbohydrates of SCAP remain in the endoglycosidase H-resistant (Golgi-processed) form even in the presence of 25-hydroxycholesterol, confirming that these residues are required for sterol-regulated ER retention.\",\n      \"method\": \"Isolation of CHO mutant cells, endoglycosidase H sensitivity assay, SREBP processing assay\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic loss-of-function (point mutation), biochemical glycosylation assay, functionally linked to SREBP processing; replicated in multiple subsequent studies\",\n      \"pmids\": [\"9789003\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Three independent point mutations in the sterol-sensing domain of SCAP (Y298C, D443N, L315F) each prevent sterol-induced binding of SCAP to Insig-1 and Insig-2, abolishing feedback regulation of SREBP processing. Sterols also fail to inhibit SCAP(L315F)/SREBP packaging into COPII vesicles in vitro.\",\n      \"method\": \"CHO mutant cell isolation, co-immunoprecipitation with Insigs, in vitro vesicle budding assay\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — three independent mutations all show same phenotype, co-IP with Insigs, in vitro vesicle assay\",\n      \"pmids\": [\"12482938\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Insig proteins lower the concentration of cholesterol required to produce the conformational change in SCAP in vitro. Cationic amphiphiles (chlorpromazine, trifluoperazine, imipramine) also induce this conformational change and are enhanced by Insig proteins, suggesting SCAP monitors the composition of the cytoplasmic leaflet of the ER membrane.\",\n      \"method\": \"In vitro trypsin cleavage conformational assay with Insig co-expression, cationic amphiphile treatment\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with ER membranes, pharmacological mimicry, single lab with multiple orthogonal approaches\",\n      \"pmids\": [\"12963821\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Overexpression of the membrane domain of SCAP (TM1-6, containing the sterol-sensing domain) prevents sterol-mediated ER retention of SCAP/SREBP, consistent with competition for a putative ER retention protein. The Y298C mutation in TM1-6 abolishes this dominant-negative effect.\",\n      \"method\": \"Transfection of truncated SCAP(TM1-6), SREBP processing assay, Y298C point mutation abolishing competition\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional transfection competition assay, mutagenesis control, mechanistically predictive of Insig discovery\",\n      \"pmids\": [\"10896675\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Luminal Loop 1 of Scap (245 aa projecting into the ER lumen) is the cholesterol-binding site: recombinant Loop 1 binds sterols with specificity identical to the full membrane domain. Mutation Y234A in Loop 1 locks Loop 6 in the cholesterol-bound conformation even in sterol-depleted cells, preventing SREBP processing.\",\n      \"method\": \"Recombinant Loop 1 cholesterol binding assay, Y234A point mutation, SREBP processing assay in transfected cells\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — direct binding with recombinant protein, in-cell functional validation by mutagenesis, mechanistic link to COPII binding established\",\n      \"pmids\": [\"21454655\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Conserved Asp-428 in the sixth transmembrane helix of SCAP is essential for SCAP dissociation from Insigs. SCAP(D428A) mutant remains in the Insig-binding conformation even in sterol-depleted cells, failing to transport SREBPs to the Golgi.\",\n      \"method\": \"Transfection of D428A point mutant, co-immunoprecipitation with Insigs, SREBP transport assay\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mutagenesis with co-IP and functional transport assay, single lab, multiple orthogonal methods\",\n      \"pmids\": [\"15728349\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Luminal Loop 7 of Scap must interact with Loop 1 to maintain Loop 6 in a COPII-binding permissive conformation. Point mutation Y640S in Loop 7 prevents Loop 1–Loop 7 interaction (co-immunoprecipitation of separately expressed N- and C-terminal Scap fragments) and locks Loop 6 in the COPII-excluding conformation even without cholesterol.\",\n      \"method\": \"Y640S point mutation, trypsin cleavage conformational assay, co-immunoprecipitation of Scap N- and C-terminal fragments\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mutagenesis, conformational assay, co-IP; multiple orthogonal methods linking Loop 1–Loop 7 interaction to COPII binding\",\n      \"pmids\": [\"23564452\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Reconstitution in Drosophila cells shows that mammalian SCAP and Insig-1 or Insig-2 are the minimal requirements for sterol-regulated ER-to-Golgi transport of SREBP-2. Without mammalian SCAP, mammalian SREBP-2 is not transported to the Golgi in insect cells. Sterols block transport only when mammalian Insig is co-expressed.\",\n      \"method\": \"Heterologous reconstitution in Drosophila cells, co-expression of mammalian SCAP and Insig\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — reconstitution in heterologous system defining minimal components, systematic co-expression dissection\",\n      \"pmids\": [\"12842885\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"SCAP is required in vivo for hepatic lipid synthesis: conditional SCAP deficiency in mouse liver reduces basal cholesterol and fatty acid synthesis by 80% (due to decreases in biosynthetic enzyme mRNAs) and abolishes normal adaptive increases in response to cholesterol deprivation and insulin elevation.\",\n      \"method\": \"Conditional hepatic Scap knockout via inducible Cre recombinase in mice, mRNA quantification, lipid synthesis measurement\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean in vivo conditional KO with multiple phenotypic readouts, foundational in vivo mechanistic study\",\n      \"pmids\": [\"11358865\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Cryo-EM structure of human Scap bound to Insig-2 in the presence of 25-hydroxycholesterol (25HC) reveals that a 25HC molecule is sandwiched between S4–S6 segments of Scap and TM3–4 of Insig-2 in the luminal leaflet of the membrane. Unwinding of the middle of the Scap-S4 segment is crucial for 25HC binding and Insig association.\",\n      \"method\": \"Cryo-electron microscopy of human Scap/Insig-2 complex, resolution 3.7 Å for transmembrane domains\",\n      \"journal\": \"Science (New York, N.Y.)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — cryo-EM structure at 3.7 Å with functionally validated ligand binding site, landmark structural study\",\n      \"pmids\": [\"33446483\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Cryo-EM structures of full-length chicken Scap (wild-type free of Insig, and mutant bound to chicken Insig without cholesterol) reveal that luminal loops L1 and L7 intertwine tightly to form a globular domain (luminal platform) connecting the sterol-sensing domain to the rest of Scap. In the presence of Insig, this platform undergoes a large rotation accompanied by rearrangement of transmembrane helices.\",\n      \"method\": \"Cryo-EM of full-length chicken Scap in two states; structural comparison of Insig-bound vs. free forms\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — cryo-EM structures of two functional states of full-length Scap, structural basis for conformational change validated\",\n      \"pmids\": [\"34139175\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"EGFR signaling, by increasing glucose uptake, promotes N-glycosylation of SCAP, which stabilizes SCAP and reduces its association with Insig-1, allowing SCAP/SREBP movement to the Golgi and proteolytic SREBP-1 activation. Blocking SCAP N-glycosylation inhibits SCAP/SREBP trafficking and ameliorates EGFRvIII-driven glioblastoma xenograft growth.\",\n      \"method\": \"N-glycosylation site mutagenesis, co-immunoprecipitation (SCAP/Insig-1), Golgi trafficking assay, xenograft tumor studies\",\n      \"journal\": \"Cancer cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — mutagenesis, co-IP, trafficking assay, and in vivo xenograft validation; multiple orthogonal methods\",\n      \"pmids\": [\"26555173\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"25-hydroxyvitamin D (25OHD) inhibits SREBP activation by inducing proteolytic processing and ubiquitin-mediated degradation of SCAP, thereby decreasing SREBP levels. This mechanism is independent of the vitamin D receptor.\",\n      \"method\": \"Chemical library screen, ubiquitination assay, proteolytic processing assay, SCAP degradation measurement\",\n      \"journal\": \"Cell chemical biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional SCAP degradation and ubiquitination assays, single lab, vitamin D receptor independence tested\",\n      \"pmids\": [\"28132894\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"RNF145, an ER membrane ubiquitin E3 ligase induced by LXR activation, triggers ubiquitination of SCAP on lysine residues within the cytoplasmic loop essential for COPII binding, potentially inhibiting SCAP transport to Golgi and subsequent SREBP-2 processing. RNF145 knockdown or knockout potentiates cholesterol biosynthetic gene expression.\",\n      \"method\": \"RNF145 overexpression and shRNA knockdown in mouse liver, genetic deletion, ubiquitination assay on SCAP\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo KO and overexpression, ubiquitination assay, single lab with multiple approaches\",\n      \"pmids\": [\"29068315\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"SCAP interacts with SQSTM1 (p62) via its WD40 domain (SCAP) and the TB domain (SQSTM1), and lycorine promotes SCAP lysosomal degradation via an autophagy-independent SQSTM1-mediated pathway (SMAILD), distinct from sterol-dependent ER retention mechanisms.\",\n      \"method\": \"Pulldown assay, domain mapping, lysosomal degradation assay, autophagy-independent pathway determination\",\n      \"journal\": \"Autophagy\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — co-immunoprecipitation domain mapping, degradation assays, autophagy independence demonstrated, single lab\",\n      \"pmids\": [\"32432943\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"SCAP Golgi-to-ER recycling requires cleavage of SREBP at site-1. When SREBP cleavage is reduced, SCAP is degraded in lysosomes. SREBP actively prevents premature recycling of the SCAP-SREBP complex until initiation of SREBP cleavage, representing an ancient regulatory mechanism conserved between human cells and yeast.\",\n      \"method\": \"Inhibition of site-1 protease, lysosomal degradation assays, yeast genetic experiments\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pharmacological and genetic inhibition of S1P cleavage, degradation assays, cross-species conservation\",\n      \"pmids\": [\"24478315\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"PAQR3, a Golgi-localized membrane protein, interacts with SCAP and SREBP and tethers them to the Golgi, promoting SCAP/SREBP complex formation and SREBP processing. The interaction between Scap and PAQR3 or Insig-1 is mutually exclusive and regulated by cholesterol level.\",\n      \"method\": \"Co-immunoprecipitation, PAQR3 knockdown in liver, synthetic peptide disruption of SCAP-PAQR3 interaction\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — co-IP, in vivo liver knockdown, peptide competition assay; single lab, multiple methods\",\n      \"pmids\": [\"26311497\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Cideb, an ER/lipid droplet-associated protein, selectively promotes loading of SREBP/SCAP into COPII vesicles by interacting with SCAP (interaction enhanced by sterol deprivation) and binding to the guanine nucleotide exchange factor Sec12 to enrich SCAP/SREBP at ER exit sites. Loss of Cideb inhibits SREBP activation.\",\n      \"method\": \"Co-immunoprecipitation (SCAP-Cideb, Cideb-Sec12), COPII vesicle loading assay, Cideb knockout\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP of SCAP-Cideb and Cideb-Sec12, sterol-regulated interaction, KO phenotype; single lab\",\n      \"pmids\": [\"30858281\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"SCAP translocates from ER via Golgi to perinuclear microsome in a STING-dependent manner upon cytosolic microbial DNA sensing. The N-terminal transmembrane domain of SCAP interacts with STING, and the C-terminal cytosolic (WD40) domain of SCAP binds IRF3, recruiting IRF3 to the STING signalosome. SCAP knockdown mice are more susceptible to HSV-1 infection.\",\n      \"method\": \"Co-immunoprecipitation (SCAP-STING, SCAP-IRF3), SCAP knockdown (siRNA), HSV-1 infection of knockdown mice, localization by fluorescence microscopy\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP of SCAP-STING and SCAP-IRF3, in vivo knockdown infection model, domain mapping; single lab\",\n      \"pmids\": [\"26900919\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"SCAP binds dengue virus NS2B protein (via its N-terminal transmembrane domain), inhibiting K27-linked polyubiquitination of NS3 and thereby preventing NS2B3 protease complex formation and STING cleavage. Ectopic SCAP impairs DENV infection; SCAP silencing potentiates it.\",\n      \"method\": \"Co-immunoprecipitation (SCAP-NS2B), ubiquitination assay, SCAP overexpression and knockdown with viral replication readout\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — co-IP, ubiquitination assay, gain- and loss-of-function with viral infection readout; single lab\",\n      \"pmids\": [\"28228593\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Ammonia (released from glutamine) promotes SCAP-Insig dissociation and SREBP-1 activation independently of sterols. Ammonia binds to SCAP at a site blocked by 25-hydroxycholesterol. Mutating aspartate D428 to alanine prevents ammonia binding to SCAP and abolishes SREBP-1 activation.\",\n      \"method\": \"SCAP-Insig co-immunoprecipitation with ammonia treatment, D428A point mutation, ammonia binding assay, tumor xenograft\",\n      \"journal\": \"Nature metabolism\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP, site-directed mutagenesis, binding competition with 25HC; single lab with multiple approaches\",\n      \"pmids\": [\"35534729\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"PI3K/Akt pathway is involved in SCAP/SREBP-2 transport from the ER to the Golgi: PI3K inhibition (LY294002) or dominant-negative Akt expression disrupts SCAP trafficking to the Golgi as shown by fluorescence microscopy, blunting SREBP-2 processing.\",\n      \"method\": \"PI3K inhibitor (LY294002), dominant-negative Akt expression, immunofluorescence microscopy of SCAP localization\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — pharmacological and genetic inhibition of PI3K/Akt, fluorescence microscopy of SCAP localization, single lab; mechanism not fully resolved\",\n      \"pmids\": [\"16571675\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Insulin promotes SCAP/SREBP-1c transport to the Golgi by selectively reducing Insig-2a protein levels via accelerated mRNA decay (through the 3'-UTR of Insig-2a mRNA), releasing the SCAP/SREBP-1c complex from ER retention. siRNA knockdown of Insig-2a mimics insulin-induced SREBP-1c proteolysis.\",\n      \"method\": \"Insig-2a mRNA decay assay, siRNA knockdown, exogenous Insig-2a expression, SCAP-COPII association assay in primary hepatocytes\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — siRNA knockdown, rescue experiment, mRNA stability assay, COPII binding assay; single lab\",\n      \"pmids\": [\"19759400\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Complex structure of fission yeast SREBP C-terminus (Sre1-CTD) and SCAP C-terminus (Scp1) shows they form a functional 4:4 oligomer with Sre1-CTD forming a dimer of dimers. Three distinct regions in Sre1-CTD mediate Scp1 binding, Sre1-CTD dimerization, and tetrameric formation; proper oligomeric complex formation is required for Sre1 activation.\",\n      \"method\": \"Crystal structure of Sre1-CTD at 3.5 Å, cryo-EM of complex at 5.4 Å, in vitro biochemical assembly assays, functional validation in cells\",\n      \"journal\": \"Cell research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — crystal structure + cryo-EM + biochemical assembly + functional cellular validation; fission yeast ortholog relevant to understanding SCAP WD40-SREBP interaction\",\n      \"pmids\": [\"27811944\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Cholesterol binding to Loop 1 of Scap alters the conformation of the sterol-sensing domain (SSD): in the absence of cholesterol, cytosolic loop 4 is cleaved by trypsin/proteinase K generating a protected fragment; upon cholesterol addition, cleavage of loop 4 is abolished. This conformational change in the SSD is proposed to transmit the cholesterol signal from Loop 1 to Loop 7.\",\n      \"method\": \"Protease protection assay in sealed membrane vesicles using trypsin or proteinase K, monoclonal antibody detection of protected fragment\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — in vitro protease protection assay in sealed vesicles, multiple proteases used, single lab\",\n      \"pmids\": [\"28377508\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"RNF5, an ER-anchored E3 ubiquitin ligase, mediates Lys-29-linked polyubiquitination of SCAP at K305 in cytosolic loop 2. This ubiquitination enhances interaction between SCAP luminal loop 1 and loop 7, activating SREBP2. K305R SCAP fails to restore the SREBP2 pathway in SCAP-deficient cells.\",\n      \"method\": \"RNF5 knockdown and overexpression, ubiquitination site mapping (K305), co-immunoprecipitation (loop 1–loop 7 interaction), SREBP2 activation assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — specific lysine ubiquitination mapping, co-IP, rescue with K305R mutant; single lab\",\n      \"pmids\": [\"32054686\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"ZDHHC3 S-acylates (palmitoylates) SCAP at cysteine C264, which antagonizes HACE1-mediated SCAP ubiquitination and proteasomal degradation. ABHD17A acts as the depalmitoylase. SREBP2 transcriptionally upregulates ZDHHC3, forming a positive feedback loop that sustains SCAP/SREBP2 signaling in HCC.\",\n      \"method\": \"Palmitoylation assay, ZDHHC3 knockdown/overexpression, co-immunoprecipitation, ubiquitination assay, chromatin immunoprecipitation for SREBP2 at ZDHHC3 promoter\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — palmitoylation site mapping, co-IP, ubiquitination assay, ChIP; single lab, multiple methods\",\n      \"pmids\": [\"39522165\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"In cholesterol-fed cells, ER-localized SCAP interacts with Sac1 PI4P phosphatase through a VAP-OSBP complex at ER-Golgi membrane contact sites (MCSs), facilitating PI4P turnover and CARTS biogenesis. SCAP knockdown inhibits PI4P turnover and CARTS biogenesis; this is reversed by wild-type SCAP or a Golgi-transport-defective mutant but not by cholesterol-sensing-defective mutants.\",\n      \"method\": \"Co-immunoprecipitation (SCAP-Sac1, VAP-OSBP), SCAP knockdown, rescue with WT and mutant SCAP, CARTS biogenesis assay\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — co-IP, knockdown + rescue with domain-discriminating mutants, functional CARTS biogenesis assay; single lab\",\n      \"pmids\": [\"33156328\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Scap and SREBP1 form a super-complex with IκBα that associates NF-κB near the ER. Upon LPS stimulation, Scap transports this complex to the Golgi where SREBP1 is cleaved by S1P/S2P, liberating IκBα for IKK-mediated phosphorylation and NF-κB activation. Loss of Scap diminishes LPS-induced NF-κB activation.\",\n      \"method\": \"Co-immunoprecipitation (Scap-SREBP1-IκBα), Scap knockout, S1P/S2P inhibition, NF-κB activation assays, Golgi localization by imaging\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — co-IP of three-protein complex, loss-of-function, pharmacological inhibition; single lab\",\n      \"pmids\": [\"37267109\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Chromatin remodeling protein BRG1 binds the SCAP promoter in complex with Sp1 to activate SCAP transcription in hepatocytes. BRG1 deficiency reduces SCAP expression and SREBP processing; forced exogenous SCAP expression partially rescues SREBP target gene expression in BRG1-null hepatocytes.\",\n      \"method\": \"ChIP (BRG1 at SCAP promoter), BRG1 knockdown/KO, exogenous SCAP rescue experiment, SREBP processing assay\",\n      \"journal\": \"Frontiers in cell and developmental biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — ChIP at SCAP promoter, genetic KO with rescue, single lab\",\n      \"pmids\": [\"33718362\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Macrophage SCAP specifically recruits STING and TBK1 onto the Golgi apparatus to activate NF-κB, promoting inflammatory factor release. Macrophage-specific SCAP knockout attenuates STING-NF-κB pathway activation and reduces metaflammation.\",\n      \"method\": \"Macrophage-specific SCAP knockout mice, co-immunoprecipitation (SCAP-STING-TBK1), NF-κB activation assay, Golgi localization imaging\",\n      \"journal\": \"Cellular and molecular gastroenterology and hepatology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — macrophage-specific KO, co-IP of SCAP-STING-TBK1 complex at Golgi, single lab\",\n      \"pmids\": [\"35367665\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"STAT3 directly binds the promoter of the SCAP gene to activate its transcription across multiple cancer cell types, and simultaneously activates SREBF1 transcription, cooperatively enhancing fatty acid synthesis.\",\n      \"method\": \"ChIP (STAT3 at SCAP promoter), STAT3 pharmacological inhibition, SCAP/SREBP-1 expression assays in cancer cells and clinical samples\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — ChIP at SCAP promoter, pharmacological inhibition, clinical correlation; single lab\",\n      \"pmids\": [\"38718868\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Transgenic mice expressing sterol-resistant SCAP(D443N) in liver show increased nuclear SREBP-1 and -2, elevated lipogenic gene mRNAs, and fatty livers. These livers show blunted feedback suppression of SREBP processing in response to high dietary cholesterol, confirming SCAP's sterol-sensing role in vivo.\",\n      \"method\": \"Transgenic mouse model with liver-specific SCAP(D443N), dietary cholesterol challenge, nuclear SREBP quantification, lipid analysis\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo transgenic model with dominant gain-of-function mutation, dietary challenge, multiple molecular and metabolic readouts\",\n      \"pmids\": [\"9854040\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Scap is required for hepatic steatosis in insulin-resistant ob/ob mice and high-fat diet mice: deletion of Scap in liver abolishes fatty liver despite persistent obesity, hyperinsulinemia, and hyperglycemia. siRNA silencing of Scap in sucrose-fed hamster livers prevents sucrose-induced hypertriglyceridemia by reducing all three nuclear SREBPs.\",\n      \"method\": \"Conditional hepatic Scap knockout in ob/ob mice, siRNA silencing in hamsters, lipid synthesis measurement, SREBP nuclear levels\",\n      \"journal\": \"Cell metabolism\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean conditional KO + siRNA in two distinct animal models, multiple metabolic readouts\",\n      \"pmids\": [\"22326225\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Fatostatin directly binds SCAP and blocks its ER-to-Golgi transport independently of Insig proteins. However, fatostatin also inhibits cell growth via SCAP-independent mechanisms and delays ER-to-Golgi transport of VSVG protein, indicating general ER-to-Golgi transport inhibition beyond SCAP.\",\n      \"method\": \"VSVG trafficking assay, SCAP-null cell growth assay, fatostatin direct binding to SCAP, ER exit assay\",\n      \"journal\": \"Journal of lipid research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct binding demonstrated, SCAP-null cell experiments, VSVG trafficking control; single lab\",\n      \"pmids\": [\"27324795\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Combined cryo-EM and AI-facilitated structural prediction reveals that luminal loop 1 and a co-folded segment in loop 7 of Scap resemble the luminal/extracellular domain in NPC1 and related proteins. An additional luminal interface between Scap and Insig-2 is observed. SCAP(D428A) shows identical conformation with wild-type when complexed with Insig-2, suggesting constitutive suppression may involve a later trafficking step.\",\n      \"method\": \"Cryo-EM of human Scap/Insig-2 complex in digitonin, AI structural prediction, comparative structural analysis\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — cryo-EM structural study with functional mutant comparison; single study but structural tier\",\n      \"pmids\": [\"34192549\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Tim-4 disturbs the Insig1-SCAP interaction and promotes SCAP-SREBP2 complex translocation to the Golgi, upregulating cholesterol biosynthesis in macrophages and limiting type I IFN responses.\",\n      \"method\": \"Co-immunoprecipitation (Insig1-SCAP with/without Tim-4), Tim-4 deficiency, SREBP2 activation assay, IFN signaling measurement\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — co-IP showing disrupted Insig1-SCAP interaction by Tim-4, loss-of-function, single lab\",\n      \"pmids\": [\"36450259\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"SCAP is an octahelical ER membrane protein that functions as a sterol sensor and escort protein: in sterol-depleted cells, its luminal Loop 1 (cholesterol-binding site) interacts with Loop 7 to maintain cytosolic Loop 6 in a conformation that recruits COPII proteins at the MELADL sorting signal, enabling SCAP to transport SREBP transcription factors from ER to Golgi for proteolytic activation of lipid synthesis genes; when ER cholesterol exceeds a threshold, cholesterol binds Loop 1, conformationally rearranges the sterol-sensing domain and Loop 6, and induces SCAP binding to ER-resident INSIG-1/2 retention proteins, blocking COPII recruitment and halting SCAP/SREBP export; additional regulatory inputs include N-glycosylation (stabilizing SCAP and promoting trafficking), ubiquitination by RNF145 (inhibitory) and RNF5 (activatory), S-acylation by ZDHHC3 (protective from degradation), SQSTM1-mediated lysosomal degradation, ammonia-driven SCAP-Insig dissociation, and roles beyond lipid metabolism including recruitment of IRF3 to the STING signalosome and coordination of NF-κB activation at the Golgi.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"SCAP is an octahelical ER membrane protein that serves as the cell's principal cholesterol sensor and the escort that controls activation of the SREBP family of lipogenic transcription factors [#5, #17]. In sterol-depleted cells SCAP packages SREBP into COPII-coated vesicles via the MELADL sorting signal in a cytosolic loop, driving ER-to-Golgi transport where SREBPs are proteolytically processed to their active nuclear forms [#4, #7]. Cholesterol binds directly and specifically to SCAP's membrane domain, with the 245-residue luminal Loop 1 constituting the cholesterol-binding site, and binding is transmitted through an intertwined Loop 1\\u2013Loop 7 luminal platform and the sterol-sensing domain to reposition cytosolic Loop 6, abrogating COPII recruitment [#5, #13, #15, #19]. Sterol loading triggers SCAP binding to the ER-resident retention proteins INSIG-1 and INSIG-2, which captures the complex in the ER; oxysterols such as 25-hydroxycholesterol instead bind at the SCAP\\u2013INSIG interface, as resolved by cryo-EM of the SCAP/INSIG-2 complex [#0, #1, #6, #18]. Point mutations in the sterol-sensing domain (Y298C, D443N, L315F) lock SCAP in a sterol-resistant, constitutively exporting state, and a transgenic SCAP(D443N) liver produces unrestrained lipogenesis and fatty liver, establishing SCAP as the in vivo rate-limiting sensor for hepatic cholesterol and fatty-acid synthesis [#9, #10, #41, #17]. SCAP activity is further tuned by post-translational and trafficking inputs\\u2014N-glycosylation downstream of growth-factor/glucose signaling stabilizes SCAP and reduces INSIG association, and ubiquitination, S-acylation, and accessory factors modulate its stability and export [#20, #22, #34, #35, #26]. Beyond lipid metabolism, SCAP scaffolds innate-immune signaling, recruiting IRF3 to the STING signalosome through its cytosolic WD40 domain and coordinating STING/TBK1-driven NF-\\u03baB activation at the Golgi [#27, #39].\",\n  \"teleology\": [\n    {\n      \"year\": 1998,\n      \"claim\": \"Established that specific residues in SCAP constitute a functional sterol sensor, by showing point mutations that uncouple SREBP processing from sterol levels.\",\n      \"evidence\": \"CHO sterol-resistant mutant cells (Y298C, D443N) with endoglycosidase H sensitivity and SREBP processing assays\",\n      \"pmids\": [\"9789003\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not identify the retention factor that wild-type SCAP engages\", \"Mechanism of cholesterol detection not defined\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Demonstrated in vivo that the SCAP sterol sensor governs whole-organism lipogenesis, by expressing a sterol-resistant mutant in liver.\",\n      \"evidence\": \"Transgenic mice with liver-specific SCAP(D443N), dietary cholesterol challenge, nuclear SREBP and lipid analysis\",\n      \"pmids\": [\"9854040\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not resolve the molecular retention mechanism\", \"Loss-of-function in vivo not yet tested\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Showed that sterol regulation operates at the level of SCAP trafficking between ER and Golgi, defining the transport step as the regulated event.\",\n      \"evidence\": \"Glycosidase sensitivity, glycosylation-defective mutants, density fractionation, brefeldin A in cells\",\n      \"pmids\": [\"10500160\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Retention protein not identified\", \"Vesicle machinery for export not defined\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Established SCAP as physiologically required for hepatic lipid synthesis using conditional loss-of-function.\",\n      \"evidence\": \"Inducible Cre-mediated hepatic Scap knockout in mice with mRNA and lipid synthesis readouts\",\n      \"pmids\": [\"11358865\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not address SCAP roles outside liver\", \"Molecular sensing mechanism not addressed\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Identified INSIG-1 and INSIG-2 as the sterol-regulated ER retention proteins that bind SCAP's sterol-sensing domain, resolving how sterols halt SREBP export.\",\n      \"evidence\": \"Reciprocal co-IP, mass spectrometry, blue native-PAGE, SREBP processing assays, mutant SCAP(Y298C)\",\n      \"pmids\": [\"12202038\", \"12242332\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether cholesterol acts directly on SCAP or via membrane not resolved\", \"Structural basis of binding unknown\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Connected the molecular events by showing sterols induce a SCAP conformational change and block COPII (Sec23/24) incorporation, with sterol-resistant mutants refractory.\",\n      \"evidence\": \"In vitro trypsin conformational assay on ER membranes, in vitro vesicle reconstitution with recombinant COPII, mutant analysis\",\n      \"pmids\": [\"12191470\", \"12193656\", \"12482938\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct ligand binding not yet demonstrated\", \"Sorting signal recognized by COPII not mapped\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Defined the minimal sterol-regulated transport module and showed INSIG sensitizes the SCAP conformational switch, refining how the sensor reads membrane composition.\",\n      \"evidence\": \"Heterologous reconstitution in Drosophila cells; in vitro conformational assay with INSIG co-expression and cationic amphiphiles\",\n      \"pmids\": [\"12842885\", \"12963821\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct cholesterol receptor activity not yet proven\", \"25-HC mechanism distinct from cholesterol unresolved\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Proved SCAP is a direct cholesterol receptor and distinguished cholesterol (direct binding) from 25-HC (indirect) as separate regulatory inputs.\",\n      \"evidence\": \"Purified recombinant SCAP membrane domain direct binding, photoaffinity cross-linking, analytical ultracentrifugation, INSIG co-IP\",\n      \"pmids\": [\"15260976\", \"15452130\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Precise cholesterol-binding subdomain not localized\", \"How conformational change reaches the sorting signal unknown\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Mapped the MELADL hexapeptide as the COPII sorting signal and defined Asp-428 as essential for sterol-dependent INSIG dissociation.\",\n      \"evidence\": \"In vitro microsomal pulldowns with INSIG dependency, MELADL mutagenesis, D428A co-IP and transport assay\",\n      \"pmids\": [\"15899885\", \"15728349\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Spatial relationship of MELADL to membrane not resolved\", \"Path of signal from sensor to MELADL undefined\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Resolved that cholesterol (on SCAP) and oxysterols (on INSIG) converge on a conformational change near MELADL that excludes COPII.\",\n      \"evidence\": \"Anti-MELADL blocking in vitro, intracellular Fab microinjection, cysteine-labeling conformational assay\",\n      \"pmids\": [\"17428919\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Luminal determinants of cholesterol binding not yet localized\", \"Structural model absent\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Localized the cholesterol-binding site to luminal Loop 1 and showed Loop 1\\u2013Loop 7 interaction maintains the COPII-permissive Loop 6 conformation, building the intramolecular signal-relay model.\",\n      \"evidence\": \"Recombinant Loop 1 binding, Y234A and Y640S mutations, conformational assays, co-IP of N- and C-terminal fragments\",\n      \"pmids\": [\"21454655\", \"23564452\", \"28377508\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Atomic structure of luminal domain still lacking\", \"Quantitative coupling between loops not defined\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Provided the structural basis of sterol sensing with cryo-EM of SCAP free, SCAP/INSIG, and the 25HC-bound complex, defining the luminal platform and ligand pocket.\",\n      \"evidence\": \"Cryo-EM of human SCAP/INSIG-2 with 25HC, full-length chicken SCAP in two states, AI-assisted comparative analysis\",\n      \"pmids\": [\"33446483\", \"34139175\", \"34192549\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Dynamics of the conformational transition not captured\", \"Structure of the SREBP-bound exporting state unresolved\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Defined the structural basis of the SCAP C-terminus\\u2013SREBP interaction via the ortholog complex, explaining how SCAP engages its cargo.\",\n      \"evidence\": \"Crystal and cryo-EM structures of fission yeast Sre1-CTD/Scp1 4:4 oligomer with biochemical and cellular validation\",\n      \"pmids\": [\"27811944\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mammalian SCAP WD40\\u2013SREBP complex structure not solved\", \"Relationship of oligomer to vesicle loading unclear\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Showed hormonal/signaling inputs override sterol control: insulin and PI3K/Akt promote SCAP/SREBP export, broadening regulation beyond sterols.\",\n      \"evidence\": \"Insig-2a mRNA decay and siRNA in hepatocytes; PI3K inhibitor and dominant-negative Akt with SCAP localization imaging\",\n      \"pmids\": [\"19759400\", \"16571675\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct kinase target on SCAP not defined\", \"PI3K/Akt mechanism on trafficking not fully resolved\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Established post-translational control of SCAP stability and trafficking via glycosylation and ubiquitination, linking growth-factor signaling and LXR to lipogenesis.\",\n      \"evidence\": \"N-glycosylation mutagenesis with xenografts; RNF145 KO/overexpression with ubiquitination assays; 25OHD-induced degradation; RNF5 K305 mapping\",\n      \"pmids\": [\"26555173\", \"29068315\", \"28132894\", \"32054686\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Interplay among competing E3 ligases unresolved\", \"Quantitative contribution of each modification in vivo unknown\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Identified additional stability and trafficking modulators of SCAP, including SQSTM1-mediated lysosomal degradation, S-acylation, and accessory tethering/loading factors.\",\n      \"evidence\": \"SQSTM1 domain-mapped pulldown and degradation; ZDHHC3 palmitoylation at C264; PAQR3 Golgi tethering; Cideb-Sec12 COPII loading; SREBP-cleavage-dependent recycling\",\n      \"pmids\": [\"32432943\", \"39522165\", \"26311497\", \"30858281\", \"24478315\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Hierarchy among these modulators undefined\", \"Most validated in single labs without reciprocal confirmation\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Established SCAP as required for diet- and insulin-resistance-driven hepatic steatosis, defining it as a therapeutic node in metabolic disease.\",\n      \"evidence\": \"Conditional hepatic Scap KO in ob/ob and high-fat-diet mice; siRNA in hamster; fatostatin direct binding and transport block\",\n      \"pmids\": [\"22326225\", \"27324795\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Fatostatin shows SCAP-independent effects, limiting selectivity\", \"On-target small-molecule pharmacology incomplete\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Revealed SCAP functions beyond lipid metabolism by scaffolding innate-immune signaling and coordinating NF-\\u03baB activation.\",\n      \"evidence\": \"Co-IP of SCAP-STING and SCAP-IRF3 with domain mapping and HSV-1 infection; SCAP-NS2B binding; macrophage-specific KO with STING/TBK1 co-IP; Scap-SREBP1-I\\u03baB\\u03b1 super-complex; Tim-4 disruption of Insig1-SCAP\",\n      \"pmids\": [\"26900919\", \"28228593\", \"35367665\", \"37267109\", \"36450259\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether immune scaffolding requires sterol-sensing activity unclear\", \"Most findings from single labs without independent replication\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Identified transcriptional control of the SCAP gene itself by BRG1/Sp1 and STAT3, linking chromatin and oncogenic signaling to SCAP abundance.\",\n      \"evidence\": \"ChIP of BRG1 and STAT3 at the SCAP promoter, knockdown/KO with rescue, pharmacological inhibition in cancer cells\",\n      \"pmids\": [\"33718362\", \"38718868\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Integration of transcriptional and post-translational control not modeled\", \"In vivo relevance of these transcriptional inputs incompletely tested\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How the multiple competing regulatory layers\\u2014sterol sensing, ammonia and hormonal inputs, ubiquitination/acylation, and immune scaffolding\\u2014are integrated on a single SCAP molecule, and the structure of the active SREBP-bound exporting complex, remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structure of SCAP\\u2013SREBP\\u2013COPII exporting complex\", \"Quantitative crosstalk among regulatory modifications undefined\", \"In vivo significance of non-lipid SCAP functions incompletely established\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140299\", \"supporting_discovery_ids\": [5, 6, 13, 11]},\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [5, 13, 18]},\n      {\"term_id\": \"GO:0038024\", \"supporting_discovery_ids\": [4, 7]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [27, 37]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 1]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [0, 3, 5]},\n      {\"term_id\": \"GO:0005794\", \"supporting_discovery_ids\": [3, 4, 39]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [5]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [17, 41, 42]},\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [3, 4, 7]},\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [17, 41]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [27, 39, 37]},\n      {\"term_id\": \"R-HSA-9609507\", \"supporting_discovery_ids\": [3, 4]}\n    ],\n    \"complexes\": [\n      \"SCAP/SREBP complex\",\n      \"SCAP/INSIG complex\",\n      \"STING signalosome\",\n      \"Scap-SREBP1-I\\u03baB\\u03b1 super-complex\"\n    ],\n    \"partners\": [\n      \"INSIG1\",\n      \"INSIG2\",\n      \"SREBF2\",\n      \"STING1\",\n      \"IRF3\",\n      \"RNF145\",\n      \"RNF5\",\n      \"PAQR3\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}