{"gene":"PLIN2","run_date":"2026-04-28T19:45:44","timeline":{"discoveries":[{"year":1999,"finding":"PLIN2 (ADRP) facilitates long-chain fatty acid uptake in transfected COS-7 cells, increasing the initial rate of oleic acid, palmitate, and arachidonate uptake but not medium-chain fatty acids or glucose, acting as a saturable transport component.","method":"Transfection of COS-7 cells with ADRP cDNA followed by fatty acid uptake assays (dose-response, temperature dependence, kinetic analysis)","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 — clean overexpression with kinetic characterization, single lab","pmids":["10358026"],"is_preprint":false},{"year":2002,"finding":"PLIN2 (ADRP) overexpression in murine fibroblasts stimulates lipid droplet formation and triacylglycerol accumulation, with GFP-ADRP localizing to the surface of lipid droplets in a ring-shaped pattern, independent of adipocyte-specific gene induction.","method":"Adenoviral GFP-ADRP overexpression in murine fibroblasts; confocal microscopy; triacylglycerol content measurement","journal":"American journal of physiology. Endocrinology and metabolism","confidence":"Medium","confidence_rationale":"Tier 2 — direct localization and functional readout, single lab","pmids":["12217895"],"is_preprint":false},{"year":2002,"finding":"PLIN2 (ADRP), along with Perilipin and TIP47, belongs to a conserved PAT protein family whose sequence/structural elements are necessary and sufficient to direct association to lipid droplet surfaces across species (mammals, Drosophila, Dictyostelium), indicating a common function in lipid deposition and/or mobilization.","method":"GFP-tagged protein co-localization with isolated lipid droplets; immunofluorescence; cross-species heterologous expression","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods, cross-species validation, replicated","pmids":["12077142"],"is_preprint":false},{"year":2005,"finding":"PLIN2 (ADRP) protein is degraded via the ubiquitin-proteasome pathway during regression of lipid-storing cells; proteasome inhibition blocks ADRP decrease and accumulates polyubiquitinated ADRP, and ADRP degradation and triglyceride reduction are co-regulated.","method":"Proteasome inhibitor treatment (MG-132); immunoblotting for polyubiquitinated ADRP; lipid quantification in J774 macrophages and HuH-7 cells","journal":"Journal of lipid research","confidence":"Medium","confidence_rationale":"Tier 2 — chemical inhibition with protein-level readouts, single lab","pmids":["16230742"],"is_preprint":false},{"year":2004,"finding":"ARF1 (GDP-bound form) interacts with a central domain of PLIN2 (ADRP) and induces its dissociation from lipid droplet surfaces; brefeldin A or dominant-negative ARF1 causes ADRP dissociation from lipid droplets.","method":"Yeast two-hybrid screening; GST pull-down; co-immunoprecipitation; brefeldin A treatment; dominant-negative ARF1 overexpression; deletion mutant analysis","journal":"Biochemical and biophysical research communications","confidence":"High","confidence_rationale":"Tier 1–2 — multiple orthogonal methods including GST pull-down and co-IP with mutagenesis/deletion mapping","pmids":["15336557"],"is_preprint":false},{"year":2006,"finding":"CGI-58 (causal gene of Chanarin-Dorfman syndrome) was identified as an interaction partner of both PLIN2 (ADRP) and perilipin via yeast two-hybrid screening; CGI-58 co-localizes with perilipin at lipid droplet surfaces in 3T3-L1 cells and specific interaction with perilipin was confirmed by GST pull-down.","method":"Yeast two-hybrid screening; GST pull-down; fluorescence microscopy co-localization","journal":"Molecular and cellular biochemistry","confidence":"Medium","confidence_rationale":"Tier 2 — yeast two-hybrid plus GST pull-down confirmation, single lab","pmids":["16532261"],"is_preprint":false},{"year":2006,"finding":"In PLIN2 (ADFP) null embryonic cells, Tip47 compensates as the sole lipid droplet-associated PAT protein; double knockdown of ADFP and Tip47 impairs lipid droplet formation and redirects exogenous NEFA from triglycerides to phospholipids, demonstrating that PLIN2 and Tip47 regulate lipid droplet formation and neutral lipid partitioning.","method":"ADFP null cell lines; Tip47 siRNA knockdown; mass spectrometry identification; immunoblot; immunocytochemistry; NEFA uptake and lipolysis assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — genetic KO + siRNA double knockdown with multiple orthogonal functional readouts","pmids":["16968708"],"is_preprint":false},{"year":2010,"finding":"PLIN2 (ADRP) binds sphingomyelin and phosphatidylcholine with high affinity (nanomolar range) in fluorescence binding assays, identifying PLIN2 as a phospholipid-binding protein at lipid droplet surfaces.","method":"Fluorescence binding assays with NBD-labeled lipids; fractionation of lipid droplet proteins","journal":"Lipids","confidence":"Medium","confidence_rationale":"Tier 1–2 — in vitro binding assays with affinity determination, single lab","pmids":["20473576"],"is_preprint":false},{"year":2012,"finding":"PLIN2 directly interacts with phosphatidylcholine, sphingomyelin, stearic acid, and cholesterol on lipid droplet surfaces in live cells, at molecular distances of 44–57 Å; Plin2 overexpression upregulates enzymes for triacylglycerol, cholesteryl ester, and phospholipid synthesis while decreasing lipolytic enzyme expression.","method":"Live-cell FRET between CFP-Plin2 and fluorescently labeled lipids; pixel-by-pixel FRET efficiency mapping; lipid content analysis in overexpressing cells","journal":"American journal of physiology. Cell physiology","confidence":"High","confidence_rationale":"Tier 1 — live-cell FRET with quantitative distance measurement plus functional lipid profiling, single lab with multiple methods","pmids":["22744009"],"is_preprint":false},{"year":2013,"finding":"PLIN2 Ser251Pro missense variant disrupts a predicted α-helix in the protein, leading to increased lipid accumulation, decreased lipolysis, and increased number of small lipid droplets per cell in HEK293 cells; the Pro251 allele is associated with reduced plasma triglyceride and VLDL concentrations in humans.","method":"3D structure modeling; stable transfection of HEK293 cells; lipid droplet size distribution analysis; lipolysis assays; human population genotyping (n=2113)","journal":"FASEB journal","confidence":"High","confidence_rationale":"Tier 1–2 — structure modeling, cellular functional assays, and human genetic association, multiple orthogonal approaches","pmids":["23603836"],"is_preprint":false},{"year":2013,"finding":"PLIN2 interacts with SNAP23 (a SNARE protein) on lipid droplets within 51 Å (measured by FRET), and PLIN2 overexpression increases SNAP23 partitioning to lipid droplets and decreases insulin-mediated glucose uptake, while PLIN2 knockdown increases glucose uptake.","method":"Live-cell FRET; co-immunoprecipitation; co-localization microscopy; 2-NBD-glucose and [3H]-2-deoxyglucose uptake assays; RNAi knockdown in L cells and 3T3-L1 cells","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 1–2 — FRET, co-IP, and functional glucose uptake assays with both OE and KD, single lab","pmids":["24040030"],"is_preprint":false},{"year":2016,"finding":"PLIN2 phosphorylation is dependent on AMPK and occurs after PLIN2 interacts with the CMA chaperone HSPA8/Hsc70; this phosphorylation primes PLIN2 for chaperone-mediated autophagy (CMA)-dependent degradation, which is required to initiate lipolysis.","method":"AMPK inhibitor/activator treatments; co-immunoprecipitation of PLIN2 with Hsc70; phosphorylation assays; CMA degradation assays","journal":"Autophagy","confidence":"High","confidence_rationale":"Tier 2 — identified kinase (AMPK) and chaperone interaction with functional consequence, multiple methods","pmids":["26902588"],"is_preprint":false},{"year":2017,"finding":"PLIN2 overexpression protects lipid droplets against macroautophagy, whereas PLIN2 deficiency enhances autophagy and depletes hepatic triglycerides; in atg7-/- MEFs devoid of autophagy, PLIN2 deficiency no longer reduces cellular TG, demonstrating that PLIN2 guards lipid droplets against autophagic degradation via an ATG7-dependent pathway.","method":"plin2-/- mice; adenovirus-shAtg7 hepatic knockdown; atg7-/- MEFs; TG quantification; autophagy assays","journal":"Autophagy","confidence":"High","confidence_rationale":"Tier 2 — genetic epistasis with double-mutant rescue in two cell systems, strong mechanistic conclusion","pmids":["28548876"],"is_preprint":false},{"year":2018,"finding":"TEB4 (MARCH6), an E3 ubiquitin ligase of the Ac/N-end rule pathway, directly targets the N-terminal acetyl moiety of Nα-terminally acetylated PLIN2 for polyubiquitylation and proteasomal degradation; this pathway reduces intracellular lipid droplet accumulation by degrading unbound PLIN2.","method":"Cycloheximide chase; in vivo ubiquitylation assays; split-ubiquitin yeast two-hybrid; chemical cross-linking-based reciprocal co-immunoprecipitation; HeLa, HEK293T, HepG2 cell lines","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1–2 — multiple orthogonal methods identifying E3 ligase and mechanism, functional consequence demonstrated","pmids":["30425097"],"is_preprint":false},{"year":2021,"finding":"Rab18 is translocated from the ER to lipid droplets during oleic acid-induced LD accumulation and binds the C terminus of PLIN2; LD localization of Rab18 is diminished when PLIN2 is depleted; LD-associated Rab18 further interacts with ACSL3, forming a PLIN2-Rab18-ACSL3 complex that regulates LD accumulation in myoblasts.","method":"Co-immunoprecipitation; PLIN2 depletion; Rab18 overexpression and loss-of-function; subcellular fractionation; triacylglycerol assays in C2C12 cells","journal":"Biochimica et biophysica acta. Molecular and cell biology of lipids","confidence":"Medium","confidence_rationale":"Tier 2–3 — co-IP with KD confirmation, functional TAG readout, single lab","pmids":["33713834"],"is_preprint":false},{"year":2021,"finding":"SARS-CoV-2 nucleocapsid protein drives DGAT1/2 gene expression to facilitate lipid droplet formation and associates with ADRP (PLIN2) on the LD surface to complete the viral replication cycle; ADRP is essential for SARS-CoV-2 replication.","method":"Gene depletion (DGAT, ADRP); viral protein synthesis assays; co-localization of nucleocapsid with ADRP on LDs; hamster in vivo model","journal":"Cell discovery","confidence":"Medium","confidence_rationale":"Tier 2 — gene depletion with mechanistic co-localization and replication assays, single lab","pmids":["34702802"],"is_preprint":false},{"year":2021,"finding":"In liver-specific PLIN2 knockout mice, protection against NAFLD results from the integrated actions of both ATGL-mediated lipolysis and lipophagy; inhibition of either ATGL or autophagy blunted increased fatty acid oxidation in PLIN2-deficient hepatocytes, and combined inhibition had no additive effect, indicating these pathways converge.","method":"Liver-specific PLIN2 KO mice; ex vivo p62 flux assays; ATGL inhibitor; autophagy inhibitor; fatty acid oxidation assays in primary hepatocytes","journal":"Cells","confidence":"High","confidence_rationale":"Tier 2 — genetic KO with pharmacological epistasis, multiple pathway readouts","pmids":["33923083"],"is_preprint":false},{"year":2022,"finding":"PLIN2 is required for multipolar spindle formation in hepatocellular carcinoma cells with Trip13 depletion; lipid droplets act as acentriolar microtubule organizing centers and Plin2-coated LDs participate in aberrant mitotic spindle polarity, induction of DNA damage, and mitotic cell death.","method":"Trip13 depletion in HCC cells; Plin2 knockdown; spindle polarity imaging; DNA damage assays; lipid droplet characterization","journal":"Advanced science","confidence":"Medium","confidence_rationale":"Tier 2 — loss-of-function with specific mitotic phenotype, single lab","pmids":["36031387"],"is_preprint":false},{"year":2022,"finding":"Upon exit from pluripotency, Plin2 is recognized by Hsc70 and degraded via chaperone-mediated autophagy to facilitate lipid droplet mobilization; excessive lipid hydrolysis from Plin2 knockout induces lipidomic remodeling (decreased cardiolipin and phosphatidylethanolamine), mitochondrial cristae defects, reduced acetyl-CoA, and decreased histone acetylation.","method":"Plin2 knockout ESCs; ATGL inhibition rescue; CMA inhibition; lipidomics; mitochondrial imaging; histone acetylation assays; ChIP","journal":"Cell death and differentiation","confidence":"High","confidence_rationale":"Tier 1–2 — multiple orthogonal methods linking LD mobilization to epigenetic outcomes via defined pathway","pmids":["35614132"],"is_preprint":false},{"year":2023,"finding":"CRISPR-Cas9 loss-of-function screens identified MARCH6 (TEB4) E3 ligase as a regulator of PLIN2 post-translational stability and triacylglycerol biosynthesis, thereby influencing LD abundance; screens also identified ubiquitination, transcription, and mitochondrial function genes as PLIN2 regulators.","method":"Genome-edited PLIN2 reporter cell lines; parallel CRISPR-Cas9 loss-of-function screens; functional validation of MARCH6 role in TAG biosynthesis and LD abundance","journal":"Developmental cell","confidence":"High","confidence_rationale":"Tier 2 — genome-scale screen with functional validation, multiple cell types and conditions","pmids":["37494933"],"is_preprint":false},{"year":2019,"finding":"Plin2 deficiency in the heart reduces lipophagy, leading to paradoxical increased triglyceride accumulation in cardiomyocytes; after myocardial infarction, Plin2-/- mice have reduced stroke volume and cardiac output, demonstrating that Plin2 is required for proper lipid droplet hydrolysis via lipophagy in the myocardium.","method":"Plin2-/- mice; myocardial infarction model; triglyceride quantification; lipophagy assays; cardiac function measurement","journal":"Scientific reports","confidence":"High","confidence_rationale":"Tier 2 — genetic KO with lipophagy mechanistic readout and cardiac phenotype, multiple methods","pmids":["31061399"],"is_preprint":false},{"year":2021,"finding":"Plin2 deletion in adrenal cortex increases cholesteryl ester-rich lipid droplet content, elevates unesterified cholesterol, and disrupts cholesterol balance, including ceroid-like multilamellar body accumulation with age; Plin2 thus regulates CE-rich LD metabolism and cellular cholesterol homeostasis in steroidogenic cells.","method":"Plin2-/- mice; histological and molecular characterization of adrenal glands; lipid analysis; ACTH/starvation stimulation; lipidomics","journal":"Journal of lipid research","confidence":"High","confidence_rationale":"Tier 2 — genetic KO with detailed lipid phenotyping and functional stimulation, single lab with multiple orthogonal methods","pmids":["33582145"],"is_preprint":false},{"year":2022,"finding":"In Drosophila, Plin2 interacts with retinol dehydrogenase (RDH/CG2064) and this RDH-Plin2 axis reduces the overall level and lipid droplet localization of Bmm/ATGL lipase, antagonizing lipolysis and modulating lipid droplet size.","method":"RNAi screen in Drosophila; genetic epistasis; protein interaction studies; lipid droplet size quantification","journal":"EMBO reports","confidence":"Medium","confidence_rationale":"Tier 2 — genetic screen with epistasis in Drosophila ortholog, functional lipid droplet readout","pmids":["35132760"],"is_preprint":false},{"year":2017,"finding":"In Drosophila, HDAC6 physically associates with the chaperone dHsc4/Hsc70 to maintain proteostasis of PLIN2; loss of HDAC6 causes age-dependent ectopic fat accumulation that is ameliorated by reduction of PLIN2, placing HDAC6-Hsc70 upstream of PLIN2 degradation in lipid homeostasis.","method":"Drosophila HDAC6 mutants; PLIN2 reduction epistasis; physical association assays; lipid phenotyping","journal":"Developmental cell","confidence":"High","confidence_rationale":"Tier 2 — genetic epistasis with physical interaction, replicated in Drosophila ortholog with clear pathway placement","pmids":["28966044"],"is_preprint":false},{"year":2018,"finding":"Hypoxia markedly stimulates PLIN2 mRNA synthesis and protein expression in human trophoblasts, and PLIN2 (but not PLIN3) knockdown enhances trophoblast apoptotic death while PLIN2 overexpression promotes cell viability, demonstrating a specific role for PLIN2 in protecting trophoblasts against hypoxia-induced apoptosis.","method":"Primary human trophoblasts; hypoxia treatment; PLIN2/PLIN3 siRNA knockdown; PLIN2 overexpression; apoptosis assays","journal":"Endocrinology","confidence":"High","confidence_rationale":"Tier 2 — KD and OE with specific apoptosis readout, paralog specificity demonstrated","pmids":["30351430"],"is_preprint":false},{"year":2017,"finding":"PLIN2 downregulation in pancreatic β cells is associated with enhanced autophagic flux and accelerated ER stress resolution; PLIN2 genetic ablation in Akita mice mitigates ER stress, reduces β cell apoptosis, and partially restores β cell mass, while PLIN2 overexpression exacerbates fatty acid- and chemical-induced ER stress.","method":"plin2-/- Akita mice; PLIN2 KD and OE in β cell lines; autophagic flux assays; ER stress markers; apoptosis assays","journal":"Scientific reports","confidence":"High","confidence_rationale":"Tier 2 — genetic KO in disease model plus KD/OE with multiple orthogonal mechanistic readouts","pmids":["28102311"],"is_preprint":false},{"year":2024,"finding":"TRIB3 interacts with PLIN2 to abrogate TEB4-mediated PLIN2 ubiquitination and degradation, thereby maintaining higher PLIN2 levels and facilitating lipid accumulation and ER homeostasis in renal cell carcinoma.","method":"Co-immunoprecipitation; TRIB3 knockdown; ubiquitination assays; PLIN2 stability measurements in RCC cells","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2–3 — co-IP and ubiquitination assays with KD, single lab","pmids":["38561354"],"is_preprint":false},{"year":2022,"finding":"In Drosophila, knocking down subunits of COP9 signalosome (CSN) leads to enlarged lipid droplets by preventing proteasomal degradation of retinol dehydrogenase (RDH/CG2064); RDH interacts with Plin2 and the RDH-Plin2 axis reduces Bmm/ATGL lipase localization on LDs.","method":"Drosophila RNAi screen; CSN subunit knockdown; proteasome pathway analysis; protein interaction assays","journal":"EMBO reports","confidence":"Medium","confidence_rationale":"Tier 2 — genetic screen in Drosophila ortholog with mechanistic pathway placement","pmids":["35132760"],"is_preprint":false}],"current_model":"PLIN2 is a constitutively expressed lipid droplet surface protein that stabilizes lipid droplets by directly binding phospholipids and neutral lipids, recruits binding partners including Rab18, ACSL3, and SNAP23, and is regulated by AMPK-dependent phosphorylation and multiple ubiquitin-proteasome pathways (via MARCH6/TEB4 recognizing its N-terminal acetyl group, and ARF1-GDP-induced dissociation) as well as chaperone-mediated autophagy (via Hsc70 interaction), with its degradation being a prerequisite for lipophagy and cytosolic lipolysis by ATGL; PLIN2 abundance on lipid droplets thus gates the access of lipases and autophagic machinery to stored triglycerides and cholesteryl esters across diverse cell types."},"narrative":{"teleology":[{"year":1999,"claim":"Establishing that PLIN2 actively participates in fatty acid uptake resolved an early question about whether PLIN2 is merely a passive LD marker or has a functional role in lipid handling.","evidence":"Transfection of COS-7 cells with ADRP cDNA followed by kinetic fatty acid uptake assays","pmids":["10358026"],"confidence":"Medium","gaps":["Mechanism of fatty acid uptake facilitation (channel, flipase, or indirect) was not defined","No loss-of-function confirmation"]},{"year":2002,"claim":"Demonstrating that PLIN2 localizes to LD surfaces and that it belongs to the conserved PAT family with perilipin and TIP47 established the conceptual framework of a shared LD-coat protein family governing lipid deposition and mobilization.","evidence":"GFP-tagged protein localization; cross-species heterologous expression in mammalian, Drosophila, and Dictyostelium systems; adenoviral overexpression in fibroblasts","pmids":["12077142","12217895"],"confidence":"High","gaps":["Structural basis of LD targeting was not resolved","Functional redundancy among PAT family members was not dissected"]},{"year":2005,"claim":"Identifying PLIN2 as a substrate of the ubiquitin–proteasome pathway showed that LD regression requires active protein degradation, linking PLIN2 turnover to triglyceride mobilization.","evidence":"MG-132 proteasome inhibition; detection of polyubiquitinated ADRP; lipid quantification in macrophages and hepatoma cells","pmids":["16230742","15336557"],"confidence":"Medium","gaps":["The responsible E3 ligase was not identified at this stage","Whether proteasomal degradation was sufficient or merely permissive for lipolysis was unclear"]},{"year":2006,"claim":"Genetic ablation of PLIN2 combined with Tip47 knockdown revealed functional compensation between PAT family members and showed that loss of both redirects fatty acids from triglycerides to phospholipids, establishing PLIN2's role in neutral lipid partitioning.","evidence":"ADFP-null cell lines; Tip47 siRNA double knockdown; NEFA uptake and lipolysis assays; mass spectrometry","pmids":["16968708","16532261"],"confidence":"High","gaps":["Relative quantitative contributions of PLIN2 vs. Tip47 in different tissues were unknown","Whether CGI-58 interaction with PLIN2 has a functional consequence distinct from its perilipin interaction was not tested"]},{"year":2012,"claim":"Live-cell FRET demonstrated that PLIN2 directly contacts phospholipids and cholesterol at molecular distances on LD surfaces, transforming the model from co-fractionation-based association to a direct lipid-binding protein.","evidence":"CFP-Plin2 FRET with fluorescently labeled lipids; pixel-by-pixel efficiency mapping; lipid profiling in overexpressing cells","pmids":["22744009","20473576"],"confidence":"High","gaps":["Binding domains/residues mediating individual lipid interactions were not mapped","No structural model of PLIN2-lipid interface existed"]},{"year":2013,"claim":"Identification of the Ser251Pro variant that alters LD number, lipolysis rate, and plasma triglycerides in humans connected PLIN2 structure to human lipid metabolism, while FRET-based discovery of PLIN2-SNAP23 interaction linked LD biology to GLUT4 vesicle trafficking and glucose uptake.","evidence":"HEK293 stable transfection with S251P; population genotyping (n=2113); live-cell FRET and co-IP of PLIN2–SNAP23; glucose uptake assays with KD and OE","pmids":["23603836","24040030"],"confidence":"High","gaps":["Causal relationship of S251P to plasma TG in Mendelian framework was not established","How SNAP23 sequestration on LDs impairs GLUT4 exocytosis mechanistically was not fully resolved"]},{"year":2016,"claim":"Discovery that AMPK phosphorylates PLIN2 after Hsc70 binding to prime it for chaperone-mediated autophagy (CMA) identified the kinase and chaperone that initiate LD mobilization, establishing CMA as the first degradation route for LD-associated PLIN2.","evidence":"AMPK inhibitor/activator treatments; co-IP of PLIN2 with Hsc70; phosphorylation and CMA degradation assays","pmids":["26902588"],"confidence":"High","gaps":["Specific phosphorylation sites were not mapped","Relative contribution of CMA vs. proteasomal degradation in different tissues was undefined"]},{"year":2017,"claim":"Genetic epistasis in mice and Drosophila placed PLIN2 as a guardian against ATG7-dependent macroautophagy of LDs (lipophagy), while an HDAC6-Hsc70-PLIN2 axis in Drosophila confirmed conserved chaperone-dependent PLIN2 turnover controls fat storage across species.","evidence":"plin2−/− mice; atg7−/− MEFs double-mutant epistasis; Drosophila HDAC6 mutants with PLIN2 reduction rescue; lipid phenotyping","pmids":["28548876","28966044","28102311"],"confidence":"High","gaps":["Whether PLIN2 physically occludes autophagosome receptors on the LD surface or acts indirectly was not determined","Identity of the autophagy receptor recognizing PLIN2-depleted LDs remained unknown"]},{"year":2018,"claim":"Identification of MARCH6/TEB4 as the E3 ubiquitin ligase targeting PLIN2's N-terminal acetyl group via the Ac/N-end rule pathway resolved the long-sought ubiquitin ligase identity and provided a molecular mechanism for proteasomal PLIN2 degradation.","evidence":"Cycloheximide chase; in vivo ubiquitylation assays; split-ubiquitin yeast two-hybrid; chemical cross-linking co-IP in HeLa/HEK293T/HepG2 cells","pmids":["30425097"],"confidence":"High","gaps":["Whether MARCH6-mediated degradation occurs on or off the LD surface was not determined","Additional E3 ligases may target PLIN2 under different conditions"]},{"year":2021,"claim":"Characterization of a PLIN2-Rab18-ACSL3 complex on LDs and the demonstration that liver-specific PLIN2 loss activates converging ATGL-lipolysis and lipophagy pathways revealed PLIN2 as both a scaffold for LD biogenesis machinery and a dual gatekeeper against two independent lipid mobilization routes.","evidence":"Co-IP and subcellular fractionation in C2C12 cells; liver-specific PLIN2 KO mice with pharmacological inhibition of ATGL and autophagy; fatty acid oxidation assays; adrenal Plin2−/− CE/cholesterol phenotyping","pmids":["33713834","33923083","33582145"],"confidence":"High","gaps":["Structural details of the PLIN2-Rab18 interface were not resolved","How the two lipid mobilization pathways are coordinated temporally remained unclear"]},{"year":2022,"claim":"Studies in ESCs and Drosophila extended PLIN2's gatekeeper role to developmental biology: CMA-mediated PLIN2 degradation upon exit from pluripotency drives LD mobilization that supplies acetyl-CoA for histone acetylation, while a Drosophila RDH-Plin2 axis limits ATGL access to LDs, demonstrating that PLIN2 controls epigenetic reprogramming and conserved lipolytic regulation.","evidence":"Plin2 KO ESCs with lipidomics, mitochondrial imaging, ChIP for histone acetylation; Drosophila RNAi screen with genetic epistasis and LD size quantification","pmids":["35614132","35132760"],"confidence":"High","gaps":["Which specific histone marks and genomic loci are most sensitive to PLIN2-dependent acetyl-CoA flux was not comprehensively mapped","Whether the RDH-Plin2 axis operates in mammalian cells is untested"]},{"year":2024,"claim":"Discovery that TRIB3 physically shields PLIN2 from MARCH6/TEB4-mediated ubiquitination in renal cell carcinoma identified a disease-relevant stabilizer of PLIN2, expanding the regulatory network controlling its abundance.","evidence":"Co-IP; TRIB3 knockdown; ubiquitination assays; PLIN2 stability measurements in RCC cells","pmids":["38561354"],"confidence":"Medium","gaps":["Whether TRIB3-PLIN2 interaction occurs on the LD surface or in the cytosol is unknown","Generalizability of TRIB3 stabilization beyond RCC was not tested","Single lab, awaits independent confirmation"]},{"year":null,"claim":"A high-resolution structural model of PLIN2 bound to the LD phospholipid monolayer remains unavailable, leaving unresolved how PLIN2 simultaneously engages lipids, Rab18, SNAP23, and degradation machinery, and how tissue-specific regulatory hierarchies (CMA vs. MARCH6 vs. lipophagy) are coordinated.","evidence":"","pmids":[],"confidence":"High","gaps":["No atomic-resolution structure of full-length PLIN2 or its lipid-bound form","Tissue-specific hierarchy of CMA, proteasomal, and lipophagy-based PLIN2 removal is undefined","How PLIN2 loss permits autophagosome recruitment at a molecular level (receptor identity) is unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0008289","term_label":"lipid binding","supporting_discovery_ids":[7,8]},{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[1,2,6,12]}],"localization":[{"term_id":"GO:0005811","term_label":"lipid droplet","supporting_discovery_ids":[1,2,8,14]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[3,13]}],"pathway":[{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[6,8,9,16,21]},{"term_id":"R-HSA-9612973","term_label":"Autophagy","supporting_discovery_ids":[11,12,18,20]},{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[3,13,19]}],"complexes":["PLIN2-Rab18-ACSL3 complex"],"partners":["RAB18","ACSL3","SNAP23","HSPA8","MARCH6","ARF1","ABHD5","TRIB3"],"other_free_text":[]},"mechanistic_narrative":"PLIN2 is a constitutively expressed lipid droplet (LD) coat protein that gates access of lipases and autophagic machinery to stored neutral lipids, thereby serving as a central regulator of intracellular lipid homeostasis. PLIN2 directly binds phospholipids (phosphatidylcholine, sphingomyelin) and neutral lipids (cholesterol, stearic acid) on the LD monolayer surface, stabilizing triglyceride and cholesteryl ester stores and preventing both ATGL-mediated cytosolic lipolysis and ATG7-dependent lipophagy [PMID:22744009, PMID:28548876, PMID:33923083]. PLIN2 turnover is controlled by at least two degradation axes—MARCH6/TEB4-mediated ubiquitin–proteasome recognition of its N-terminally acetylated residue, and AMPK-phosphorylation-dependent chaperone-mediated autophagy via Hsc70—and removal of PLIN2 is a prerequisite for lipid mobilization [PMID:30425097, PMID:26902588, PMID:35614132]. On the LD surface PLIN2 recruits Rab18 and ACSL3 into a complex that promotes LD biogenesis, sequesters the SNARE protein SNAP23 to modulate insulin-stimulated glucose uptake, and in Drosophila cooperates with retinol dehydrogenase to limit Bmm/ATGL access, illustrating conserved scaffold and gatekeeper functions across species [PMID:33713834, PMID:24040030, PMID:35132760]."},"prefetch_data":{"uniprot":{"accession":"Q99541","full_name":"Perilipin-2","aliases":["Adipophilin","Adipose differentiation-related protein","ADRP"],"length_aa":437,"mass_kda":48.1,"function":"Structural component of lipid droplets, which is required for the formation and maintenance of lipid storage droplets","subcellular_location":"Membrane; Lipid droplet","url":"https://www.uniprot.org/uniprotkb/Q99541/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/PLIN2","classification":"Not Classified","n_dependent_lines":4,"n_total_lines":1208,"dependency_fraction":0.0033112582781456954},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"SNX7","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/PLIN2","total_profiled":1310},"omim":[{"mim_id":"621138","title":"COILED-COIL DOMAIN-CONTAINING PROTEIN 127; CCDC127","url":"https://www.omim.org/entry/621138"},{"mim_id":"620634","title":"IMMUNITY-RELATED GTPase CINEMA; IRGC","url":"https://www.omim.org/entry/620634"},{"mim_id":"613877","title":"LIPODYSTROPHY, FAMILIAL PARTIAL, TYPE 4; FPLD4","url":"https://www.omim.org/entry/613877"},{"mim_id":"613248","title":"PERILIPIN 5; PLIN5","url":"https://www.omim.org/entry/613248"},{"mim_id":"609888","title":"LEPROSY, SUSCEPTIBILITY TO, 1; LPRS1","url":"https://www.omim.org/entry/609888"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Lipid droplets","reliability":"Supported"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"adipose tissue","ntpm":617.1},{"tissue":"liver","ntpm":845.8}],"url":"https://www.proteinatlas.org/search/PLIN2"},"hgnc":{"alias_symbol":["ADRP"],"prev_symbol":["ADFP"]},"alphafold":{"accession":"Q99541","domains":[{"cath_id":"-","chopping":"13-98","consensus_level":"high","plddt":69.4686,"start":13,"end":98},{"cath_id":"1.20.120.340","chopping":"227-290_305-406","consensus_level":"high","plddt":80.2302,"start":227,"end":406},{"cath_id":"1.20.5","chopping":"102-129","consensus_level":"medium","plddt":47.9507,"start":102,"end":129}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q99541","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q99541-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q99541-F1-predicted_aligned_error_v6.png","plddt_mean":64.19},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=PLIN2","jax_strain_url":"https://www.jax.org/strain/search?query=PLIN2"},"sequence":{"accession":"Q99541","fasta_url":"https://rest.uniprot.org/uniprotkb/Q99541.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q99541/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q99541"}},"corpus_meta":[{"pmid":"12077142","id":"PMC_12077142","title":"Functional conservation for lipid storage droplet association among Perilipin, ADRP, and TIP47 (PAT)-related proteins in mammals, Drosophila, and Dictyostelium.","date":"2002","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/12077142","citation_count":325,"is_preprint":false},{"pmid":"12217895","id":"PMC_12217895","title":"ADRP stimulates lipid accumulation and lipid droplet formation in murine fibroblasts.","date":"2002","source":"American journal of physiology. 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disease","url":"https://pubmed.ncbi.nlm.nih.gov/38561354","citation_count":19,"is_preprint":false},{"pmid":"35697078","id":"PMC_35697078","title":"PLIN2 promotes HCC cells proliferation by inhibiting the degradation of HIF1α.","date":"2022","source":"Experimental cell research","url":"https://pubmed.ncbi.nlm.nih.gov/35697078","citation_count":19,"is_preprint":false},{"pmid":"16427773","id":"PMC_16427773","title":"A study of the nuclear trafficking of the splicing factor protein PRPF31 linked to autosomal dominant retinitis pigmentosa (ADRP).","date":"2006","source":"Biochimica et biophysica acta","url":"https://pubmed.ncbi.nlm.nih.gov/16427773","citation_count":19,"is_preprint":false},{"pmid":"39921309","id":"PMC_39921309","title":"PLIN2 Promotes Lipid Accumulation in Ascites-Associated Macrophages and Ovarian Cancer Progression by HIF1α/SPP1 Signaling.","date":"2025","source":"Advanced science (Weinheim, Baden-Wurttemberg, Germany)","url":"https://pubmed.ncbi.nlm.nih.gov/39921309","citation_count":18,"is_preprint":false},{"pmid":"37844775","id":"PMC_37844775","title":"Altered hepatic lipid droplet morphology and lipid metabolism in fasted Plin2-null mice.","date":"2023","source":"Journal of lipid research","url":"https://pubmed.ncbi.nlm.nih.gov/37844775","citation_count":18,"is_preprint":false},{"pmid":"26443937","id":"PMC_26443937","title":"The perilipin 2 (PLIN2) gene Ser251Pro missense mutation is associated with reduced insulin secretion and increased insulin sensitivity in Italian obese subjects.","date":"2015","source":"Diabetes/metabolism research and reviews","url":"https://pubmed.ncbi.nlm.nih.gov/26443937","citation_count":18,"is_preprint":false},{"pmid":"28560057","id":"PMC_28560057","title":"CEBPA-mediated upregulation of the lncRNA PLIN2 promotes the development of chronic myelogenous leukemia via the GSK3 and Wnt/β-catenin signaling pathways.","date":"2017","source":"American journal of cancer research","url":"https://pubmed.ncbi.nlm.nih.gov/28560057","citation_count":17,"is_preprint":false},{"pmid":"29723991","id":"PMC_29723991","title":"The Expression Pattern of PLIN2 in Differentiated Adipocytes from Qinchuan Cattle Analysis of Its Protein Structure and Interaction with CGI-58.","date":"2018","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/29723991","citation_count":17,"is_preprint":false},{"pmid":"25131988","id":"PMC_25131988","title":"Expression of perilipin 2 (PLIN2) in porcine oocytes during maturation.","date":"2014","source":"Reproduction in domestic animals = Zuchthygiene","url":"https://pubmed.ncbi.nlm.nih.gov/25131988","citation_count":16,"is_preprint":false},{"pmid":"30099644","id":"PMC_30099644","title":"A novel mutation in the PRPF31 in a North Indian adRP family with incomplete penetrance.","date":"2018","source":"Documenta ophthalmologica. Advances in ophthalmology","url":"https://pubmed.ncbi.nlm.nih.gov/30099644","citation_count":16,"is_preprint":false},{"pmid":"26598603","id":"PMC_26598603","title":"Natural Functions of PLIN2 Mediating Wnt/LiCl Signaling and Glycogen Synthase Kinase 3 (GSK3)/GSK3 Substrate-Related Effects Are Modulated by Lipid.","date":"2015","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/26598603","citation_count":16,"is_preprint":false},{"pmid":"32585124","id":"PMC_32585124","title":"Lipid droplets are both highly oxidized and Plin2-covered in hepatocytes of diet-induced obese mice.","date":"2020","source":"Applied physiology, nutrition, and metabolism = Physiologie appliquee, nutrition et metabolisme","url":"https://pubmed.ncbi.nlm.nih.gov/32585124","citation_count":16,"is_preprint":false},{"pmid":"29733984","id":"PMC_29733984","title":"Long-chain metabolites of vitamin E: Interference with lipotoxicity via lipid droplet associated protein PLIN2.","date":"2018","source":"Biochimica et biophysica acta. Molecular and cell biology of lipids","url":"https://pubmed.ncbi.nlm.nih.gov/29733984","citation_count":16,"is_preprint":false},{"pmid":"33249703","id":"PMC_33249703","title":"ADFP promotes cell proliferation in lung adenocarcinoma via Akt phosphorylation.","date":"2020","source":"Journal of cellular and molecular medicine","url":"https://pubmed.ncbi.nlm.nih.gov/33249703","citation_count":16,"is_preprint":false},{"pmid":"29893665","id":"PMC_29893665","title":"The ADRP domain from a virulent strain of infectious bronchitis virus is not sufficient to confer a pathogenic phenotype to the attenuated Beaudette strain.","date":"2018","source":"The Journal of general virology","url":"https://pubmed.ncbi.nlm.nih.gov/29893665","citation_count":16,"is_preprint":false},{"pmid":"39187042","id":"PMC_39187042","title":"Therapeutic siRNA targeting PLIN2 ameliorates steatosis, inflammation, and fibrosis in steatotic liver disease models.","date":"2024","source":"Journal of lipid research","url":"https://pubmed.ncbi.nlm.nih.gov/39187042","citation_count":15,"is_preprint":false},{"pmid":"1539599","id":"PMC_1539599","title":"Autosomal dominant retinitis pigmentosa (adRP; RP6): cosegregation of RP6 and the peripherin-RDS locus in a late-onset family of Irish origin.","date":"1992","source":"American journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/1539599","citation_count":15,"is_preprint":false},{"pmid":"24664756","id":"PMC_24664756","title":"The effects of IRE1, ATF6, and PERK signaling on adRP-linked rhodopsins.","date":"2014","source":"Advances in experimental medicine and biology","url":"https://pubmed.ncbi.nlm.nih.gov/24664756","citation_count":14,"is_preprint":false},{"pmid":"37736048","id":"PMC_37736048","title":"Nuclear miR-150 enhances hepatic lipid accumulation by targeting RNA transcripts overlapping the PLIN2 promoter.","date":"2023","source":"iScience","url":"https://pubmed.ncbi.nlm.nih.gov/37736048","citation_count":13,"is_preprint":false},{"pmid":"35132760","id":"PMC_35132760","title":"An RDH-Plin2 axis modulates lipid droplet size by antagonizing Bmm lipase.","date":"2022","source":"EMBO reports","url":"https://pubmed.ncbi.nlm.nih.gov/35132760","citation_count":12,"is_preprint":false},{"pmid":"34044206","id":"PMC_34044206","title":"Upregulated monocyte expression of PLIN2 is associated with early arterial injury in children with overweight/obesity.","date":"2021","source":"Atherosclerosis","url":"https://pubmed.ncbi.nlm.nih.gov/34044206","citation_count":12,"is_preprint":false},{"pmid":"26131118","id":"PMC_26131118","title":"Increased ADRP expression in human atherosclerotic lesions correlates with plaque instability.","date":"2015","source":"International journal of clinical and experimental medicine","url":"https://pubmed.ncbi.nlm.nih.gov/26131118","citation_count":12,"is_preprint":false},{"pmid":"27157138","id":"PMC_27157138","title":"ARF1 activation dissociates ADRP from lipid droplets to promote HCV assembly.","date":"2016","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/27157138","citation_count":12,"is_preprint":false},{"pmid":"37731818","id":"PMC_37731818","title":"Effect on cell survival and cytoophidium assembly of the adRP-10-related IMPDH1 missense mutation Asp226Asn.","date":"2023","source":"Frontiers in cell and developmental biology","url":"https://pubmed.ncbi.nlm.nih.gov/37731818","citation_count":12,"is_preprint":false},{"pmid":"2081594","id":"PMC_2081594","title":"Further evidence of exclusion of linkage between type II autosomal dominant retinitis pigmentosa (ADRP) and D3S47 on 3q.","date":"1990","source":"Genomics","url":"https://pubmed.ncbi.nlm.nih.gov/2081594","citation_count":12,"is_preprint":false},{"pmid":"38650174","id":"PMC_38650174","title":"Downregulation of PLIN2 in human dermal fibroblasts impairs mitochondrial function in an age-dependent fashion and induces cell senescence via GDF15.","date":"2024","source":"Aging cell","url":"https://pubmed.ncbi.nlm.nih.gov/38650174","citation_count":11,"is_preprint":false},{"pmid":"38074507","id":"PMC_38074507","title":"A missense variant in human perilipin 2 (PLIN2 Ser251Pro) reduces hepatic steatosis in mice.","date":"2023","source":"JHEP reports : innovation in hepatology","url":"https://pubmed.ncbi.nlm.nih.gov/38074507","citation_count":11,"is_preprint":false},{"pmid":"34716501","id":"PMC_34716501","title":"Transcriptomics analysis of Daheng broilers reveals that PLIN2 regulates chicken preadipocyte proliferation, differentiation and apoptosis.","date":"2021","source":"Molecular biology 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Zuchtungsbiologie","url":"https://pubmed.ncbi.nlm.nih.gov/16060490","citation_count":10,"is_preprint":false},{"pmid":"2572401","id":"PMC_2572401","title":"Linkage analysis of human chromosome 4: exclusion of autosomal dominant retinitis pigmentosa (ADRP) and detection of new linkage groups.","date":"1989","source":"Cytogenetics and cell genetics","url":"https://pubmed.ncbi.nlm.nih.gov/2572401","citation_count":10,"is_preprint":false},{"pmid":"30004246","id":"PMC_30004246","title":"Expression of APOB, ADFP and FATP1 and their correlation with fat deposition in Yunnan's top six famous chicken breeds.","date":"2018","source":"British poultry science","url":"https://pubmed.ncbi.nlm.nih.gov/30004246","citation_count":10,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":48974,"output_tokens":6632,"usd":0.123201},"stage2":{"model":"claude-opus-4-6","input_tokens":10315,"output_tokens":3570,"usd":0.211237},"total_usd":0.334438,"stage1_batch_id":"msgbatch_01SUR8NDzVrNmyszWyJeCct7","stage2_batch_id":"msgbatch_01G7Yfutko3cDWzejrwH5AMx","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1999,\n      \"finding\": \"PLIN2 (ADRP) facilitates long-chain fatty acid uptake in transfected COS-7 cells, increasing the initial rate of oleic acid, palmitate, and arachidonate uptake but not medium-chain fatty acids or glucose, acting as a saturable transport component.\",\n      \"method\": \"Transfection of COS-7 cells with ADRP cDNA followed by fatty acid uptake assays (dose-response, temperature dependence, kinetic analysis)\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — clean overexpression with kinetic characterization, single lab\",\n      \"pmids\": [\"10358026\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"PLIN2 (ADRP) overexpression in murine fibroblasts stimulates lipid droplet formation and triacylglycerol accumulation, with GFP-ADRP localizing to the surface of lipid droplets in a ring-shaped pattern, independent of adipocyte-specific gene induction.\",\n      \"method\": \"Adenoviral GFP-ADRP overexpression in murine fibroblasts; confocal microscopy; triacylglycerol content measurement\",\n      \"journal\": \"American journal of physiology. Endocrinology and metabolism\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct localization and functional readout, single lab\",\n      \"pmids\": [\"12217895\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"PLIN2 (ADRP), along with Perilipin and TIP47, belongs to a conserved PAT protein family whose sequence/structural elements are necessary and sufficient to direct association to lipid droplet surfaces across species (mammals, Drosophila, Dictyostelium), indicating a common function in lipid deposition and/or mobilization.\",\n      \"method\": \"GFP-tagged protein co-localization with isolated lipid droplets; immunofluorescence; cross-species heterologous expression\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods, cross-species validation, replicated\",\n      \"pmids\": [\"12077142\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"PLIN2 (ADRP) protein is degraded via the ubiquitin-proteasome pathway during regression of lipid-storing cells; proteasome inhibition blocks ADRP decrease and accumulates polyubiquitinated ADRP, and ADRP degradation and triglyceride reduction are co-regulated.\",\n      \"method\": \"Proteasome inhibitor treatment (MG-132); immunoblotting for polyubiquitinated ADRP; lipid quantification in J774 macrophages and HuH-7 cells\",\n      \"journal\": \"Journal of lipid research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — chemical inhibition with protein-level readouts, single lab\",\n      \"pmids\": [\"16230742\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"ARF1 (GDP-bound form) interacts with a central domain of PLIN2 (ADRP) and induces its dissociation from lipid droplet surfaces; brefeldin A or dominant-negative ARF1 causes ADRP dissociation from lipid droplets.\",\n      \"method\": \"Yeast two-hybrid screening; GST pull-down; co-immunoprecipitation; brefeldin A treatment; dominant-negative ARF1 overexpression; deletion mutant analysis\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — multiple orthogonal methods including GST pull-down and co-IP with mutagenesis/deletion mapping\",\n      \"pmids\": [\"15336557\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"CGI-58 (causal gene of Chanarin-Dorfman syndrome) was identified as an interaction partner of both PLIN2 (ADRP) and perilipin via yeast two-hybrid screening; CGI-58 co-localizes with perilipin at lipid droplet surfaces in 3T3-L1 cells and specific interaction with perilipin was confirmed by GST pull-down.\",\n      \"method\": \"Yeast two-hybrid screening; GST pull-down; fluorescence microscopy co-localization\",\n      \"journal\": \"Molecular and cellular biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — yeast two-hybrid plus GST pull-down confirmation, single lab\",\n      \"pmids\": [\"16532261\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"In PLIN2 (ADFP) null embryonic cells, Tip47 compensates as the sole lipid droplet-associated PAT protein; double knockdown of ADFP and Tip47 impairs lipid droplet formation and redirects exogenous NEFA from triglycerides to phospholipids, demonstrating that PLIN2 and Tip47 regulate lipid droplet formation and neutral lipid partitioning.\",\n      \"method\": \"ADFP null cell lines; Tip47 siRNA knockdown; mass spectrometry identification; immunoblot; immunocytochemistry; NEFA uptake and lipolysis assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic KO + siRNA double knockdown with multiple orthogonal functional readouts\",\n      \"pmids\": [\"16968708\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"PLIN2 (ADRP) binds sphingomyelin and phosphatidylcholine with high affinity (nanomolar range) in fluorescence binding assays, identifying PLIN2 as a phospholipid-binding protein at lipid droplet surfaces.\",\n      \"method\": \"Fluorescence binding assays with NBD-labeled lipids; fractionation of lipid droplet proteins\",\n      \"journal\": \"Lipids\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1–2 — in vitro binding assays with affinity determination, single lab\",\n      \"pmids\": [\"20473576\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"PLIN2 directly interacts with phosphatidylcholine, sphingomyelin, stearic acid, and cholesterol on lipid droplet surfaces in live cells, at molecular distances of 44–57 Å; Plin2 overexpression upregulates enzymes for triacylglycerol, cholesteryl ester, and phospholipid synthesis while decreasing lipolytic enzyme expression.\",\n      \"method\": \"Live-cell FRET between CFP-Plin2 and fluorescently labeled lipids; pixel-by-pixel FRET efficiency mapping; lipid content analysis in overexpressing cells\",\n      \"journal\": \"American journal of physiology. Cell physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — live-cell FRET with quantitative distance measurement plus functional lipid profiling, single lab with multiple methods\",\n      \"pmids\": [\"22744009\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"PLIN2 Ser251Pro missense variant disrupts a predicted α-helix in the protein, leading to increased lipid accumulation, decreased lipolysis, and increased number of small lipid droplets per cell in HEK293 cells; the Pro251 allele is associated with reduced plasma triglyceride and VLDL concentrations in humans.\",\n      \"method\": \"3D structure modeling; stable transfection of HEK293 cells; lipid droplet size distribution analysis; lipolysis assays; human population genotyping (n=2113)\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — structure modeling, cellular functional assays, and human genetic association, multiple orthogonal approaches\",\n      \"pmids\": [\"23603836\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"PLIN2 interacts with SNAP23 (a SNARE protein) on lipid droplets within 51 Å (measured by FRET), and PLIN2 overexpression increases SNAP23 partitioning to lipid droplets and decreases insulin-mediated glucose uptake, while PLIN2 knockdown increases glucose uptake.\",\n      \"method\": \"Live-cell FRET; co-immunoprecipitation; co-localization microscopy; 2-NBD-glucose and [3H]-2-deoxyglucose uptake assays; RNAi knockdown in L cells and 3T3-L1 cells\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — FRET, co-IP, and functional glucose uptake assays with both OE and KD, single lab\",\n      \"pmids\": [\"24040030\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"PLIN2 phosphorylation is dependent on AMPK and occurs after PLIN2 interacts with the CMA chaperone HSPA8/Hsc70; this phosphorylation primes PLIN2 for chaperone-mediated autophagy (CMA)-dependent degradation, which is required to initiate lipolysis.\",\n      \"method\": \"AMPK inhibitor/activator treatments; co-immunoprecipitation of PLIN2 with Hsc70; phosphorylation assays; CMA degradation assays\",\n      \"journal\": \"Autophagy\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — identified kinase (AMPK) and chaperone interaction with functional consequence, multiple methods\",\n      \"pmids\": [\"26902588\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"PLIN2 overexpression protects lipid droplets against macroautophagy, whereas PLIN2 deficiency enhances autophagy and depletes hepatic triglycerides; in atg7-/- MEFs devoid of autophagy, PLIN2 deficiency no longer reduces cellular TG, demonstrating that PLIN2 guards lipid droplets against autophagic degradation via an ATG7-dependent pathway.\",\n      \"method\": \"plin2-/- mice; adenovirus-shAtg7 hepatic knockdown; atg7-/- MEFs; TG quantification; autophagy assays\",\n      \"journal\": \"Autophagy\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis with double-mutant rescue in two cell systems, strong mechanistic conclusion\",\n      \"pmids\": [\"28548876\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"TEB4 (MARCH6), an E3 ubiquitin ligase of the Ac/N-end rule pathway, directly targets the N-terminal acetyl moiety of Nα-terminally acetylated PLIN2 for polyubiquitylation and proteasomal degradation; this pathway reduces intracellular lipid droplet accumulation by degrading unbound PLIN2.\",\n      \"method\": \"Cycloheximide chase; in vivo ubiquitylation assays; split-ubiquitin yeast two-hybrid; chemical cross-linking-based reciprocal co-immunoprecipitation; HeLa, HEK293T, HepG2 cell lines\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — multiple orthogonal methods identifying E3 ligase and mechanism, functional consequence demonstrated\",\n      \"pmids\": [\"30425097\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Rab18 is translocated from the ER to lipid droplets during oleic acid-induced LD accumulation and binds the C terminus of PLIN2; LD localization of Rab18 is diminished when PLIN2 is depleted; LD-associated Rab18 further interacts with ACSL3, forming a PLIN2-Rab18-ACSL3 complex that regulates LD accumulation in myoblasts.\",\n      \"method\": \"Co-immunoprecipitation; PLIN2 depletion; Rab18 overexpression and loss-of-function; subcellular fractionation; triacylglycerol assays in C2C12 cells\",\n      \"journal\": \"Biochimica et biophysica acta. Molecular and cell biology of lipids\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — co-IP with KD confirmation, functional TAG readout, single lab\",\n      \"pmids\": [\"33713834\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"SARS-CoV-2 nucleocapsid protein drives DGAT1/2 gene expression to facilitate lipid droplet formation and associates with ADRP (PLIN2) on the LD surface to complete the viral replication cycle; ADRP is essential for SARS-CoV-2 replication.\",\n      \"method\": \"Gene depletion (DGAT, ADRP); viral protein synthesis assays; co-localization of nucleocapsid with ADRP on LDs; hamster in vivo model\",\n      \"journal\": \"Cell discovery\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — gene depletion with mechanistic co-localization and replication assays, single lab\",\n      \"pmids\": [\"34702802\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"In liver-specific PLIN2 knockout mice, protection against NAFLD results from the integrated actions of both ATGL-mediated lipolysis and lipophagy; inhibition of either ATGL or autophagy blunted increased fatty acid oxidation in PLIN2-deficient hepatocytes, and combined inhibition had no additive effect, indicating these pathways converge.\",\n      \"method\": \"Liver-specific PLIN2 KO mice; ex vivo p62 flux assays; ATGL inhibitor; autophagy inhibitor; fatty acid oxidation assays in primary hepatocytes\",\n      \"journal\": \"Cells\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic KO with pharmacological epistasis, multiple pathway readouts\",\n      \"pmids\": [\"33923083\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"PLIN2 is required for multipolar spindle formation in hepatocellular carcinoma cells with Trip13 depletion; lipid droplets act as acentriolar microtubule organizing centers and Plin2-coated LDs participate in aberrant mitotic spindle polarity, induction of DNA damage, and mitotic cell death.\",\n      \"method\": \"Trip13 depletion in HCC cells; Plin2 knockdown; spindle polarity imaging; DNA damage assays; lipid droplet characterization\",\n      \"journal\": \"Advanced science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — loss-of-function with specific mitotic phenotype, single lab\",\n      \"pmids\": [\"36031387\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Upon exit from pluripotency, Plin2 is recognized by Hsc70 and degraded via chaperone-mediated autophagy to facilitate lipid droplet mobilization; excessive lipid hydrolysis from Plin2 knockout induces lipidomic remodeling (decreased cardiolipin and phosphatidylethanolamine), mitochondrial cristae defects, reduced acetyl-CoA, and decreased histone acetylation.\",\n      \"method\": \"Plin2 knockout ESCs; ATGL inhibition rescue; CMA inhibition; lipidomics; mitochondrial imaging; histone acetylation assays; ChIP\",\n      \"journal\": \"Cell death and differentiation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — multiple orthogonal methods linking LD mobilization to epigenetic outcomes via defined pathway\",\n      \"pmids\": [\"35614132\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"CRISPR-Cas9 loss-of-function screens identified MARCH6 (TEB4) E3 ligase as a regulator of PLIN2 post-translational stability and triacylglycerol biosynthesis, thereby influencing LD abundance; screens also identified ubiquitination, transcription, and mitochondrial function genes as PLIN2 regulators.\",\n      \"method\": \"Genome-edited PLIN2 reporter cell lines; parallel CRISPR-Cas9 loss-of-function screens; functional validation of MARCH6 role in TAG biosynthesis and LD abundance\",\n      \"journal\": \"Developmental cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genome-scale screen with functional validation, multiple cell types and conditions\",\n      \"pmids\": [\"37494933\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Plin2 deficiency in the heart reduces lipophagy, leading to paradoxical increased triglyceride accumulation in cardiomyocytes; after myocardial infarction, Plin2-/- mice have reduced stroke volume and cardiac output, demonstrating that Plin2 is required for proper lipid droplet hydrolysis via lipophagy in the myocardium.\",\n      \"method\": \"Plin2-/- mice; myocardial infarction model; triglyceride quantification; lipophagy assays; cardiac function measurement\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic KO with lipophagy mechanistic readout and cardiac phenotype, multiple methods\",\n      \"pmids\": [\"31061399\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Plin2 deletion in adrenal cortex increases cholesteryl ester-rich lipid droplet content, elevates unesterified cholesterol, and disrupts cholesterol balance, including ceroid-like multilamellar body accumulation with age; Plin2 thus regulates CE-rich LD metabolism and cellular cholesterol homeostasis in steroidogenic cells.\",\n      \"method\": \"Plin2-/- mice; histological and molecular characterization of adrenal glands; lipid analysis; ACTH/starvation stimulation; lipidomics\",\n      \"journal\": \"Journal of lipid research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic KO with detailed lipid phenotyping and functional stimulation, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"33582145\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"In Drosophila, Plin2 interacts with retinol dehydrogenase (RDH/CG2064) and this RDH-Plin2 axis reduces the overall level and lipid droplet localization of Bmm/ATGL lipase, antagonizing lipolysis and modulating lipid droplet size.\",\n      \"method\": \"RNAi screen in Drosophila; genetic epistasis; protein interaction studies; lipid droplet size quantification\",\n      \"journal\": \"EMBO reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic screen with epistasis in Drosophila ortholog, functional lipid droplet readout\",\n      \"pmids\": [\"35132760\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"In Drosophila, HDAC6 physically associates with the chaperone dHsc4/Hsc70 to maintain proteostasis of PLIN2; loss of HDAC6 causes age-dependent ectopic fat accumulation that is ameliorated by reduction of PLIN2, placing HDAC6-Hsc70 upstream of PLIN2 degradation in lipid homeostasis.\",\n      \"method\": \"Drosophila HDAC6 mutants; PLIN2 reduction epistasis; physical association assays; lipid phenotyping\",\n      \"journal\": \"Developmental cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis with physical interaction, replicated in Drosophila ortholog with clear pathway placement\",\n      \"pmids\": [\"28966044\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Hypoxia markedly stimulates PLIN2 mRNA synthesis and protein expression in human trophoblasts, and PLIN2 (but not PLIN3) knockdown enhances trophoblast apoptotic death while PLIN2 overexpression promotes cell viability, demonstrating a specific role for PLIN2 in protecting trophoblasts against hypoxia-induced apoptosis.\",\n      \"method\": \"Primary human trophoblasts; hypoxia treatment; PLIN2/PLIN3 siRNA knockdown; PLIN2 overexpression; apoptosis assays\",\n      \"journal\": \"Endocrinology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — KD and OE with specific apoptosis readout, paralog specificity demonstrated\",\n      \"pmids\": [\"30351430\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"PLIN2 downregulation in pancreatic β cells is associated with enhanced autophagic flux and accelerated ER stress resolution; PLIN2 genetic ablation in Akita mice mitigates ER stress, reduces β cell apoptosis, and partially restores β cell mass, while PLIN2 overexpression exacerbates fatty acid- and chemical-induced ER stress.\",\n      \"method\": \"plin2-/- Akita mice; PLIN2 KD and OE in β cell lines; autophagic flux assays; ER stress markers; apoptosis assays\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic KO in disease model plus KD/OE with multiple orthogonal mechanistic readouts\",\n      \"pmids\": [\"28102311\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"TRIB3 interacts with PLIN2 to abrogate TEB4-mediated PLIN2 ubiquitination and degradation, thereby maintaining higher PLIN2 levels and facilitating lipid accumulation and ER homeostasis in renal cell carcinoma.\",\n      \"method\": \"Co-immunoprecipitation; TRIB3 knockdown; ubiquitination assays; PLIN2 stability measurements in RCC cells\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — co-IP and ubiquitination assays with KD, single lab\",\n      \"pmids\": [\"38561354\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"In Drosophila, knocking down subunits of COP9 signalosome (CSN) leads to enlarged lipid droplets by preventing proteasomal degradation of retinol dehydrogenase (RDH/CG2064); RDH interacts with Plin2 and the RDH-Plin2 axis reduces Bmm/ATGL lipase localization on LDs.\",\n      \"method\": \"Drosophila RNAi screen; CSN subunit knockdown; proteasome pathway analysis; protein interaction assays\",\n      \"journal\": \"EMBO reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic screen in Drosophila ortholog with mechanistic pathway placement\",\n      \"pmids\": [\"35132760\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"PLIN2 is a constitutively expressed lipid droplet surface protein that stabilizes lipid droplets by directly binding phospholipids and neutral lipids, recruits binding partners including Rab18, ACSL3, and SNAP23, and is regulated by AMPK-dependent phosphorylation and multiple ubiquitin-proteasome pathways (via MARCH6/TEB4 recognizing its N-terminal acetyl group, and ARF1-GDP-induced dissociation) as well as chaperone-mediated autophagy (via Hsc70 interaction), with its degradation being a prerequisite for lipophagy and cytosolic lipolysis by ATGL; PLIN2 abundance on lipid droplets thus gates the access of lipases and autophagic machinery to stored triglycerides and cholesteryl esters across diverse cell types.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"PLIN2 is a constitutively expressed lipid droplet (LD) coat protein that gates access of lipases and autophagic machinery to stored neutral lipids, thereby serving as a central regulator of intracellular lipid homeostasis. PLIN2 directly binds phospholipids (phosphatidylcholine, sphingomyelin) and neutral lipids (cholesterol, stearic acid) on the LD monolayer surface, stabilizing triglyceride and cholesteryl ester stores and preventing both ATGL-mediated cytosolic lipolysis and ATG7-dependent lipophagy [PMID:22744009, PMID:28548876, PMID:33923083]. PLIN2 turnover is controlled by at least two degradation axes—MARCH6/TEB4-mediated ubiquitin–proteasome recognition of its N-terminally acetylated residue, and AMPK-phosphorylation-dependent chaperone-mediated autophagy via Hsc70—and removal of PLIN2 is a prerequisite for lipid mobilization [PMID:30425097, PMID:26902588, PMID:35614132]. On the LD surface PLIN2 recruits Rab18 and ACSL3 into a complex that promotes LD biogenesis, sequesters the SNARE protein SNAP23 to modulate insulin-stimulated glucose uptake, and in Drosophila cooperates with retinol dehydrogenase to limit Bmm/ATGL access, illustrating conserved scaffold and gatekeeper functions across species [PMID:33713834, PMID:24040030, PMID:35132760].\",\n  \"teleology\": [\n    {\n      \"year\": 1999,\n      \"claim\": \"Establishing that PLIN2 actively participates in fatty acid uptake resolved an early question about whether PLIN2 is merely a passive LD marker or has a functional role in lipid handling.\",\n      \"evidence\": \"Transfection of COS-7 cells with ADRP cDNA followed by kinetic fatty acid uptake assays\",\n      \"pmids\": [\"10358026\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism of fatty acid uptake facilitation (channel, flipase, or indirect) was not defined\", \"No loss-of-function confirmation\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Demonstrating that PLIN2 localizes to LD surfaces and that it belongs to the conserved PAT family with perilipin and TIP47 established the conceptual framework of a shared LD-coat protein family governing lipid deposition and mobilization.\",\n      \"evidence\": \"GFP-tagged protein localization; cross-species heterologous expression in mammalian, Drosophila, and Dictyostelium systems; adenoviral overexpression in fibroblasts\",\n      \"pmids\": [\"12077142\", \"12217895\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of LD targeting was not resolved\", \"Functional redundancy among PAT family members was not dissected\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Identifying PLIN2 as a substrate of the ubiquitin–proteasome pathway showed that LD regression requires active protein degradation, linking PLIN2 turnover to triglyceride mobilization.\",\n      \"evidence\": \"MG-132 proteasome inhibition; detection of polyubiquitinated ADRP; lipid quantification in macrophages and hepatoma cells\",\n      \"pmids\": [\"16230742\", \"15336557\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"The responsible E3 ligase was not identified at this stage\", \"Whether proteasomal degradation was sufficient or merely permissive for lipolysis was unclear\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Genetic ablation of PLIN2 combined with Tip47 knockdown revealed functional compensation between PAT family members and showed that loss of both redirects fatty acids from triglycerides to phospholipids, establishing PLIN2's role in neutral lipid partitioning.\",\n      \"evidence\": \"ADFP-null cell lines; Tip47 siRNA double knockdown; NEFA uptake and lipolysis assays; mass spectrometry\",\n      \"pmids\": [\"16968708\", \"16532261\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relative quantitative contributions of PLIN2 vs. Tip47 in different tissues were unknown\", \"Whether CGI-58 interaction with PLIN2 has a functional consequence distinct from its perilipin interaction was not tested\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Live-cell FRET demonstrated that PLIN2 directly contacts phospholipids and cholesterol at molecular distances on LD surfaces, transforming the model from co-fractionation-based association to a direct lipid-binding protein.\",\n      \"evidence\": \"CFP-Plin2 FRET with fluorescently labeled lipids; pixel-by-pixel efficiency mapping; lipid profiling in overexpressing cells\",\n      \"pmids\": [\"22744009\", \"20473576\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Binding domains/residues mediating individual lipid interactions were not mapped\", \"No structural model of PLIN2-lipid interface existed\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Identification of the Ser251Pro variant that alters LD number, lipolysis rate, and plasma triglycerides in humans connected PLIN2 structure to human lipid metabolism, while FRET-based discovery of PLIN2-SNAP23 interaction linked LD biology to GLUT4 vesicle trafficking and glucose uptake.\",\n      \"evidence\": \"HEK293 stable transfection with S251P; population genotyping (n=2113); live-cell FRET and co-IP of PLIN2–SNAP23; glucose uptake assays with KD and OE\",\n      \"pmids\": [\"23603836\", \"24040030\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Causal relationship of S251P to plasma TG in Mendelian framework was not established\", \"How SNAP23 sequestration on LDs impairs GLUT4 exocytosis mechanistically was not fully resolved\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Discovery that AMPK phosphorylates PLIN2 after Hsc70 binding to prime it for chaperone-mediated autophagy (CMA) identified the kinase and chaperone that initiate LD mobilization, establishing CMA as the first degradation route for LD-associated PLIN2.\",\n      \"evidence\": \"AMPK inhibitor/activator treatments; co-IP of PLIN2 with Hsc70; phosphorylation and CMA degradation assays\",\n      \"pmids\": [\"26902588\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specific phosphorylation sites were not mapped\", \"Relative contribution of CMA vs. proteasomal degradation in different tissues was undefined\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Genetic epistasis in mice and Drosophila placed PLIN2 as a guardian against ATG7-dependent macroautophagy of LDs (lipophagy), while an HDAC6-Hsc70-PLIN2 axis in Drosophila confirmed conserved chaperone-dependent PLIN2 turnover controls fat storage across species.\",\n      \"evidence\": \"plin2−/− mice; atg7−/− MEFs double-mutant epistasis; Drosophila HDAC6 mutants with PLIN2 reduction rescue; lipid phenotyping\",\n      \"pmids\": [\"28548876\", \"28966044\", \"28102311\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether PLIN2 physically occludes autophagosome receptors on the LD surface or acts indirectly was not determined\", \"Identity of the autophagy receptor recognizing PLIN2-depleted LDs remained unknown\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Identification of MARCH6/TEB4 as the E3 ubiquitin ligase targeting PLIN2's N-terminal acetyl group via the Ac/N-end rule pathway resolved the long-sought ubiquitin ligase identity and provided a molecular mechanism for proteasomal PLIN2 degradation.\",\n      \"evidence\": \"Cycloheximide chase; in vivo ubiquitylation assays; split-ubiquitin yeast two-hybrid; chemical cross-linking co-IP in HeLa/HEK293T/HepG2 cells\",\n      \"pmids\": [\"30425097\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether MARCH6-mediated degradation occurs on or off the LD surface was not determined\", \"Additional E3 ligases may target PLIN2 under different conditions\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Characterization of a PLIN2-Rab18-ACSL3 complex on LDs and the demonstration that liver-specific PLIN2 loss activates converging ATGL-lipolysis and lipophagy pathways revealed PLIN2 as both a scaffold for LD biogenesis machinery and a dual gatekeeper against two independent lipid mobilization routes.\",\n      \"evidence\": \"Co-IP and subcellular fractionation in C2C12 cells; liver-specific PLIN2 KO mice with pharmacological inhibition of ATGL and autophagy; fatty acid oxidation assays; adrenal Plin2−/− CE/cholesterol phenotyping\",\n      \"pmids\": [\"33713834\", \"33923083\", \"33582145\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural details of the PLIN2-Rab18 interface were not resolved\", \"How the two lipid mobilization pathways are coordinated temporally remained unclear\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Studies in ESCs and Drosophila extended PLIN2's gatekeeper role to developmental biology: CMA-mediated PLIN2 degradation upon exit from pluripotency drives LD mobilization that supplies acetyl-CoA for histone acetylation, while a Drosophila RDH-Plin2 axis limits ATGL access to LDs, demonstrating that PLIN2 controls epigenetic reprogramming and conserved lipolytic regulation.\",\n      \"evidence\": \"Plin2 KO ESCs with lipidomics, mitochondrial imaging, ChIP for histone acetylation; Drosophila RNAi screen with genetic epistasis and LD size quantification\",\n      \"pmids\": [\"35614132\", \"35132760\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Which specific histone marks and genomic loci are most sensitive to PLIN2-dependent acetyl-CoA flux was not comprehensively mapped\", \"Whether the RDH-Plin2 axis operates in mammalian cells is untested\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Discovery that TRIB3 physically shields PLIN2 from MARCH6/TEB4-mediated ubiquitination in renal cell carcinoma identified a disease-relevant stabilizer of PLIN2, expanding the regulatory network controlling its abundance.\",\n      \"evidence\": \"Co-IP; TRIB3 knockdown; ubiquitination assays; PLIN2 stability measurements in RCC cells\",\n      \"pmids\": [\"38561354\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether TRIB3-PLIN2 interaction occurs on the LD surface or in the cytosol is unknown\", \"Generalizability of TRIB3 stabilization beyond RCC was not tested\", \"Single lab, awaits independent confirmation\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"A high-resolution structural model of PLIN2 bound to the LD phospholipid monolayer remains unavailable, leaving unresolved how PLIN2 simultaneously engages lipids, Rab18, SNAP23, and degradation machinery, and how tissue-specific regulatory hierarchies (CMA vs. MARCH6 vs. lipophagy) are coordinated.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No atomic-resolution structure of full-length PLIN2 or its lipid-bound form\", \"Tissue-specific hierarchy of CMA, proteasomal, and lipophagy-based PLIN2 removal is undefined\", \"How PLIN2 loss permits autophagosome recruitment at a molecular level (receptor identity) is unknown\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [7, 8]},\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [1, 2, 6, 12]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005811\", \"supporting_discovery_ids\": [1, 2, 8, 14]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [3, 13]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [6, 8, 9, 16, 21]},\n      {\"term_id\": \"R-HSA-9612973\", \"supporting_discovery_ids\": [11, 12, 18, 20]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [3, 13, 19]}\n    ],\n    \"complexes\": [\n      \"PLIN2-Rab18-ACSL3 complex\"\n    ],\n    \"partners\": [\n      \"RAB18\",\n      \"ACSL3\",\n      \"SNAP23\",\n      \"HSPA8\",\n      \"MARCH6\",\n      \"ARF1\",\n      \"ABHD5\",\n      \"TRIB3\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}