{"gene":"FIS1","run_date":"2026-06-09T23:54:43","timeline":{"discoveries":[{"year":2003,"finding":"NMR solution structure of human Fis1 revealed a TPR-like helix bundle composed of six alpha-helices forming a slightly twisted slab; the structure suggests Fis1 acts as a molecular adaptor on the mitochondrial outer membrane, with a concave hydrophobic surface predicted to mediate protein-protein interactions, and a C-terminal transmembrane segment for membrane anchoring.","method":"NMR spectroscopy","journal":"Journal of molecular biology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — de novo NMR structure determination, single lab but rigorous structural method with functional inference","pmids":["14623186"],"is_preprint":false},{"year":2004,"finding":"Human Fis1 inserts into the mitochondrial outer membrane via a C-terminal transmembrane domain; this transmembrane domain together with a short basic segment is essential for mitochondrial targeting. Overexpression causes mitochondrial fragmentation suppressible by dominant-negative Drp1(K38A), and RNAi knockdown causes elongation of mitochondrial tubules, establishing hFis1 as a regulator of mitochondrial fission acting upstream of or in concert with Drp1.","method":"Deletion mutagenesis, dominant-negative Drp1 rescue, RNAi knockdown with fluorescence microscopy","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (mutagenesis, dominant-negative rescue, RNAi), replicated in subsequent studies","pmids":["14996942"],"is_preprint":false},{"year":2004,"finding":"Down-regulation of hFis1 by shRNA inhibits apoptosis more potently than down-regulation of Drp1, and at a distinct stage. Cells depleted of Opa1 die spontaneously by a process requiring hFis1 expression, indicating Fis1 has a pro-apoptotic function that Opa1 normally counteracts.","method":"shRNA knockdown, apoptosis assays (flow cytometry, cell death quantification)","journal":"Molecular biology of the cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean shRNA loss-of-function with defined apoptotic phenotype, single lab, two conditions tested","pmids":["15356267"],"is_preprint":false},{"year":2005,"finding":"Human Fis1 localizes to peroxisomes in addition to mitochondria; the transmembrane domain and short C-terminal tail are necessary and sufficient for targeting to both organelles, whereas the N-terminal region is required for organelle fission. Fis1 overexpression promotes peroxisome division and siRNA silencing causes peroxisome tubulation, establishing a role for Fis1 in peroxisomal fission.","method":"Differential tagging, deletion mutagenesis, siRNA, fluorescence microscopy","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal approaches (mutagenesis, siRNA, live imaging), independently replicated in later studies","pmids":["16107562"],"is_preprint":false},{"year":2005,"finding":"Analysis of rat Fis1 by BN-PAGE revealed it forms an ~200 kDa complex at the outer mitochondrial membrane. Domain analysis showed the N-terminal and C-terminal segments are both essential for oligomeric rFis1 interaction, and the middle TPR-like domains regulate proper oligomer assembly; disruption of oligomeric assembly abolishes mitochondrial division-stimulating activity.","method":"Blue-native PAGE, deletion mutagenesis, RNAi, fluorescence microscopy","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — BN-PAGE plus mutagenesis in single lab, two complementary methods","pmids":["15979461"],"is_preprint":false},{"year":2005,"finding":"NMR structure of yeast Fis1 revealed that, unlike the flexible unstructured N-terminus of human Fis1, the longer N-terminus of yeast Fis1 is fixed to the concave face of the TPR domain in an intramolecular fashion. This N-terminal segment is required for Mdv1 recruitment to mitochondria and for rescuing mitochondrial fission in fis1Δ yeast, indicating intramolecular autoinhibitory regulation of Fis1 bioactivity.","method":"NMR spectroscopy, yeast complementation assay, fluorescence microscopy","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — NMR structure plus functional rescue assays, single lab but orthogonal structural and cell biological methods","pmids":["15809300"],"is_preprint":false},{"year":2007,"finding":"Crystal structures of yeast Fis1 in complex with adaptor proteins Mdv1 and Caf4 showed these adaptors use two helices to bind both the concave and convex surfaces of the Fis1 TPR domain — a novel binding mode for TPR domains. Genetic and biochemical studies confirmed both interfaces are important for Mdv1/Caf4 binding and for mitochondrial fission in vivo.","method":"X-ray crystallography, biochemical binding assays, yeast genetics","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structures combined with biochemical and genetic validation, multiple orthogonal methods","pmids":["17998537"],"is_preprint":false},{"year":2007,"finding":"Yeast Fis1 directly binds Dnm1 (the Drp1 ortholog) in a manner negatively regulated by the Fis1 N-terminal arm; the concave surface of the Fis1 TPR domain mediates Dnm1 binding; removal of the arm increases Dnm1 binding >100-fold, indicating the arm acts in an autoinhibitory manner to restrict access to the Dnm1-binding site.","method":"In vitro binding assays, mutagenesis, fluorescence microscopy","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstituted direct binding with mutagenesis, single lab with multiple complementary experiments","pmids":["17884824"],"is_preprint":false},{"year":2007,"finding":"Fis1 localizes to peroxisomes as well as mitochondria in mammalian cells (confirmed by subcellular fractionation). Fis1 directly interacts with the peroxisomal membrane protein Pex11pβ (co-IP and binding studies), and ternary complexes of Fis1–Pex11pβ–DLP1 were detected by chemical crosslinking; Fis1 overexpression induces peroxisome proliferation while Fis1 RNAi causes peroxisome tubulation.","method":"Subcellular fractionation, co-immunoprecipitation, chemical crosslinking, RNAi, fluorescence microscopy","journal":"Experimental cell research","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal binding assays, fractionation, RNAi with phenotypic readout, single lab multiple orthogonal methods","pmids":["17408615"],"is_preprint":false},{"year":2008,"finding":"In yeast, deletion of FIS1 consistently selects for a secondary mutation in WHI2, which rescues the mitochondrial respiratory defect (petite formation) caused by FIS1 deficiency but causes defective growth control. The long-term survival function of Fis1 in this context appears independent of Dnm1 and Mdv1 but may be mediated through the Caf4 adaptor.","method":"Yeast genetics, tiling arrays, genomic sequencing, growth assays","journal":"Cell death and differentiation","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis with sequencing confirmation, single lab, multiple independently derived knockouts","pmids":["18756280"],"is_preprint":false},{"year":2008,"finding":"High-level Fis1 overexpression triggers autophagy (mitophagy) correlating with mitochondrial dysfunction rather than fragmentation per se, as demonstrated by Fis1 mutants with dissociated effects on organelle shape versus function.","method":"Fis1 overexpression/mutagenesis, autophagosome formation assays, fluorescence microscopy","journal":"Biochimica et biophysica acta","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional mutagenesis dissociating shape from dysfunction, single lab","pmids":["18515060"],"is_preprint":false},{"year":2010,"finding":"Fis1 bridges the mitochondria–ER interface by interacting with the ER protein Bap31, facilitating Bap31 cleavage into pro-apoptotic p20Bap31; the Fis1–Bap31 complex (ARCosome) recruits procaspase-8 via the variant death effector domain (vDED) of Bap31, activating procaspase-8 and releasing ER Ca²⁺ to amplify mitochondrial apoptosis in a feedback loop.","method":"Co-immunoprecipitation, subcellular fractionation, apoptosis assays, Ca²⁺ measurements, domain deletion analysis","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP, domain mapping, functional procaspase-8 activation assay, single lab with multiple orthogonal methods","pmids":["21183955"],"is_preprint":false},{"year":2011,"finding":"AKAP121 inhibits Drp1–Fis1 interaction in a PKA-independent manner; reduced AKAP121 availability (via ubiquitin ligase Siah2) relieves inhibition and increases Drp1–Fis1 interaction, resulting in mitochondrial fission under hypoxia. This defines Siah2 as a key upstream regulator of Fis1/Drp1-mediated fission.","method":"Co-immunoprecipitation, genetic knockout (Siah2−/− mice), cardiac ischemia models, C. elegans lifespan assays","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, in vivo knockout mice, multiple disease models, replicated across cell and animal contexts","pmids":["22099302"],"is_preprint":false},{"year":2011,"finding":"The cytosolic domain of Fis1 alone binds lipid vesicles (enhanced by protonation and anionic phospholipids), undergoes a membrane-induced conformational change burying two tryptophan residues, and promotes reversible lipid vesicle clustering, suggesting Fis1 can directly interact with membranes to facilitate fission.","method":"Fluorescence spectroscopy, circular dichroism, light scattering, electron microscopy","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — in vitro reconstituted assay, single lab, no in-cell validation","pmids":["21738650"],"is_preprint":false},{"year":2011,"finding":"Crystal structure of yeast Fis1 at 1.75 Å resolution confirmed the TPR fold creates a concave surface important for fission that is sterically occluded by the N-terminal arm, providing a structural basis for autoinhibition.","method":"X-ray crystallography","journal":"Acta crystallographica. Section F","confidence":"High","confidence_rationale":"Tier 1 / Moderate — high-resolution crystal structure confirming autoinhibitory mechanism, consistent with prior NMR and functional data","pmids":["22102223"],"is_preprint":false},{"year":2012,"finding":"Fis1 directly and efficiently interacts with the Rab-GAP protein TBC1D15 (but not with Drp1) at mitochondria; bacterially expressed Fis1 and TBC1D15 form a direct stable complex in vitro; TBC1D15 localizes to mitochondria only when co-expressed with Fis1, and TBC1D15 knockdown induces mitochondrial network development similar to Fis1 knockdown, indicating Fis1 recruits TBC1D15 to mitochondria to regulate morphology independently of Drp1.","method":"Co-immunoprecipitation from HeLa extracts, bacterial protein reconstitution, RNAi, fluorescence microscopy","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 1 / Moderate — direct in vitro reconstitution of Fis1–TBC1D15 complex plus Co-IP and RNAi phenotype, single lab with orthogonal methods","pmids":["23077178"],"is_preprint":false},{"year":2012,"finding":"A designed point mutation A72P in Fis1 disrupts dimerization and abolishes fission activity, while two nonfunctional Fis1 variants (L80P or E78D/I85T/Y88H) are unexpectedly dimeric; these data support a model in which Fis1 activity depends on its ability to interconvert between monomer and dimer species.","method":"Analytical ultracentrifugation, mutagenesis, yeast fission assays","journal":"Journal of molecular biology","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — designed mutagenesis with biophysical characterization and functional readout, single lab","pmids":["22789569"],"is_preprint":false},{"year":2012,"finding":"DJ-1 promotes proteasomal degradation of Fis1 via the DJ-1/Akt/RNF5 signaling pathway: Akt1 enhances mitochondrial translocation and E3-ligase activity of RNF5, leading to Fis1 ubiquitination and degradation; DJ-1 loss increases Fis1 levels and neuronal vulnerability in an MPTP mouse model.","method":"Western blotting, co-immunoprecipitation, MPTP mouse model, RNF5 E3 ligase activity assay","journal":"The Biochemical journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — identified E3 ligase (RNF5) for Fis1 ubiquitination with in vivo validation, single lab","pmids":["22871147"],"is_preprint":false},{"year":2012,"finding":"miR-484 suppresses translation of Fis1 by binding to the amino acid coding sequence of Fis1 mRNA, inhibiting Fis1-mediated mitochondrial fission and apoptosis; Foxo3a transactivates miR-484 expression, establishing a Foxo3a–miR-484–Fis1 axis regulating mitochondrial fission.","method":"Luciferase reporter assay, miRNA overexpression/knockout mice, Western blot, apoptosis assays","journal":"Nature communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reporter assay confirming direct miR-484 binding to FIS1 coding sequence, in vivo transgenic/knockout validation, single lab","pmids":["22510686"],"is_preprint":false},{"year":2013,"finding":"Both Fis1 and Mff independently contribute to mitochondrial fission and are important for the number and size of Drp1 puncta on mitochondria; either MiD49 or MiD51 can mediate Drp1 recruitment and fission in the absence of both Fis1 and Mff, demonstrating that multiple independent receptors recruit Drp1.","method":"Fis1-null, Mff-null, and Fis1/Mff double-null cell lines, immunofluorescence, Drp1 localization analysis","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic null cells with multiple controls, replicated findings across receptor combinations","pmids":["23283981"],"is_preprint":false},{"year":2013,"finding":"During the fission cycle, Drp1 first binds Mff, then enters a complex including Fis1 and ER proteins at the ER–mitochondrial interface; Fis1 mutations do not affect fission per se but disrupt downstream degradation events when mitochondrial toxins are used, leading to accumulation of large LC3 aggregates, indicating Fis1 acts after Mff to couple stress-induced fission with downstream mitophagy/degradation.","method":"Co-immunoprecipitation, Fis1 point mutations, mitochondrial toxin treatment, LC3 aggregation assays, ER-mitochondria interface imaging","journal":"Molecular biology of the cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP and mutagenesis identifying sequential complex assembly, single lab","pmids":["24196833"],"is_preprint":false},{"year":2013,"finding":"hFis1 depletion causes a severe cell cycle progression defect through G2/M phase (~3-fold reduction in mitotic index); reintroduction of hFis1 restores the cell cycle; G2/M regulators including cyclin B1, Cdk1, Plk1, Aurora kinase A, and Mad2 are suppressed in hFis1-knockdown cells; Plk1 or FoxM1 expression (but not cyclin B1/Cdk1 complex reconstitution) restores mitotic entry, placing hFis1 upstream of Plk1/FoxM1 in G2/M regulation.","method":"shRNA knockdown, flow cytometry, Western blotting, rescue overexpression experiments","journal":"Cellular and molecular life sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — shRNA loss-of-function with epistasis rescue experiments, single lab","pmids":["23907611"],"is_preprint":false},{"year":2016,"finding":"Deep mutational scanning of the Fis1p tail anchor in yeast showed: (1) the positively charged patch at the C-terminus is required for both membrane insertion and organelle specificity; (2) positively charged residues are more acceptable within the membrane-associated domain than negatively charged residues, providing in vivo evidence for lysine/arginine 'snorkeling'; (3) TA length changes of ±3 amino acids do not inhibit mitochondrial targeting.","method":"Next-generation sequencing-based deep mutational scanning, Gal4 reporter assay, fluorescence microscopy of individual mutants","journal":"Genetics","confidence":"High","confidence_rationale":"Tier 1 / Moderate — genome-scale mutagenesis with sequencing plus individual mutant validation, rigorous method","pmids":["28007883"],"is_preprint":false},{"year":2016,"finding":"Fis1 E78A mutation weakens interaction with Mdv1 (identified by NMR-guided pKa analysis), alters mitochondrial morphology, abolishes fission in growth assays, and causes uniform Dnm1 coating of mitochondria rather than puncta formation at low expression, supporting a post-recruitment role for Fis1 in organizing Dnm1 puncta.","method":"NMR pKa measurements, mutagenesis, yeast fission growth assay, fluorescence microscopy","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — NMR-guided mutagenesis with functional validation, single lab","pmids":["27496949"],"is_preprint":false},{"year":2018,"finding":"AMPK is intrinsically activated in AML leukemia stem cells and is upstream of FIS1; FIS1 mediates mitophagy activity essential for LSC self-renewal; FIS1 depletion attenuates mitophagy, inactivates GSK3, induces myeloid differentiation, cell cycle arrest, and loss of LSC self-renewal potential, establishing an AMPK→FIS1→mitophagy axis in LSC maintenance.","method":"shRNA knockdown, AMPK inhibition, mitophagy assays, colony-forming/self-renewal assays, xenograft models","journal":"Cell stem cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss-of-function with multiple cellular phenotypes and epistasis testing, single lab","pmids":["29910151"],"is_preprint":false},{"year":2019,"finding":"Fis1 depletion from the outer mitochondrial membrane causes aberrant STX17 (Syntaxin 17) accumulation on mitochondria; STX17–Fis1 interaction (identified by proteomics) controls dynamic shuttling of STX17 between ER and mitochondria; Fis1 loss exposes the STX17 N-terminus, promotes STX17 self-oligomerization, triggering PINK1/Parkin-independent mitophagy via ATG14 recruitment and Rab7-dependent lysosome fusion.","method":"Super-resolution microscopy (SR-SIM), proteomics, Co-IP, STX17 oligomerization assays, mitophagy flux assays, Rab7 interaction experiments","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — proteomics-identified interaction confirmed by Co-IP, super-resolution imaging, mechanistic dissection of STX17 oligomerization, multiple orthogonal methods","pmids":["31053718"],"is_preprint":false},{"year":2021,"finding":"Met receptor tyrosine kinase directly phosphorylates Fis1 at Tyr38 (Fis1 pY38); Fis1 pY38 promotes mitochondrial fission by recruiting Drp1 to mitochondria; fragmented mitochondria fuel actin remodeling and lamellipodia/invadopodia formation to facilitate HCC cell metastasis in vitro and in vivo.","method":"Structured illumination microscopy, live-cell imaging, in vitro kinase assay, phospho-specific antibody, Drp1 recruitment assays, invasion/migration assays, xenograft models","journal":"Signal transduction and targeted therapy","confidence":"High","confidence_rationale":"Tier 1 / Moderate — direct in vitro phosphorylation assay identifying Met as kinase writing Fis1 pY38, plus in vivo functional validation, multiple methods","pmids":["34848680"],"is_preprint":false},{"year":2022,"finding":"DNA-PKcs translocates to the cytoplasm during AKI, directly interacts with Fis1, and phosphorylates Fis1 at Thr34 (TQ motif); Fis1 pThr34 increases affinity of Fis1 for Drp1, inducing mitochondrial fragmentation and tubular cell death; knock-in T34A mice are protected from AKI and show reduced mitochondrial fragmentation.","method":"Co-immunoprecipitation, in vitro kinase assay, phospho-specific detection, T34A knockin mice, kidney function assays, electron microscopy","journal":"Science signaling","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct kinase assay identifying DNA-PKcs as writer of Fis1 pThr34, knockin mouse genetic validation, multiple orthogonal methods","pmids":["35290083"],"is_preprint":false},{"year":2022,"finding":"Fis1 is SUMOylated at K149, an amino acid residue critical for its mitochondrial localization; SENP3 (stabilized by CHIP downregulation upon DFP treatment) deSUMOylates Fis1, enhancing Fis1 mitochondrial localization; SENP3 depletion abolishes DFP-induced mitophagy; a K149R mutation (preventing SUMOylation) enhances mitochondrial Fis1 localization and restores DFP-induced mitophagy in SENP3-depleted cells.","method":"SUMOylation assays, site-directed mutagenesis (K149R), SENP3 depletion, mitophagy flux assays, fractionation","journal":"EMBO reports","confidence":"High","confidence_rationale":"Tier 2 / Strong — identified SUMO site, writer/eraser (SENP3), functional consequence on localization and mitophagy, rescue by non-SUMOylatable mutant, multiple orthogonal methods","pmids":["34994490"],"is_preprint":false},{"year":2022,"finding":"NMR and X-ray structural studies showed the human Fis1 arm can adopt an intramolecular conformation akin to yeast Fis1; removal of the Fis1 arm reduces Drp1 recruitment and mitochondrial fission in cells similar to yeast; TBC1D15 expression partially rescues arm-less Fis1 function, reminiscent of Mdv1 in yeast, supporting conserved arm-dependent regulation across eukaryotes.","method":"Molecular dynamics simulations, NMR, intrinsic tryptophan fluorescence, cellular DRP1 recruitment assays, TBC1D15 rescue experiments","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — NMR plus computational MD plus cellular functional assays, single lab, orthogonal methods","pmids":["36272645"],"is_preprint":false},{"year":2023,"finding":"Human Fis1 directly binds human Drp1 (KD = 12–68 μM) as measured by NMR, differential scanning fluorimetry, and microscale thermophoresis; similar to yeast, interaction is governed by the Fis1 N-terminal arm and a conserved surface; alanine scanning of the arm identified loss-of-function (N6A → elongated mitochondria) and gain-of-function (E7A → fragmented mitochondria) alleles; Y76A substitution also caused fragmented mitochondria, supporting intramolecular arm–surface interactions regulating Drp1-mediated fission.","method":"NMR, differential scanning fluorimetry, microscale thermophoresis, alanine scanning mutagenesis, mitochondrial morphology assays in human cells","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct in vitro binding quantified by three biophysical methods, mutagenesis with gain- and loss-of-function alleles, cellular validation","pmids":["37866629"],"is_preprint":false},{"year":2023,"finding":"A switch I-adjacent groove (SWAG) on Drp1 is the binding site for the Fis1-derived peptide inhibitor P110; small molecules binding SWAG (e.g., SC9) mimic P110's benefit by selectively inhibiting pathological Drp1–Fis1-mediated fission without blocking physiological Drp1–Mff-mediated fission in cells and in a mouse endotoxemia model.","method":"Peptide mapping, structural modeling, small molecule screening, cellular Drp1–Fis1 interaction assays, mouse endotoxemia model","journal":"Nature communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — SWAG site mapped with P110, pharmacological validation in cells and in vivo, single lab","pmids":["37468472"],"is_preprint":false},{"year":2023,"finding":"Crystal structure of human Fis1 bound to the C-terminal Bap31_vDED region showed that the Bap31 vDED region engages the convex surface of Fis1's TPR domain; one Fis1 conformation features the N-terminal arm (suggestive of autoinhibition); this provides structural basis for Fis1–Bap31 interaction at ER–mitochondria contact sites.","method":"X-ray crystallography (co-crystal structure), structural analysis","journal":"Communications biology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — co-crystal structure defining the Fis1–Bap31 interaction interface at atomic resolution, single study","pmids":["40770055"],"is_preprint":false},{"year":2023,"finding":"A conserved three-residue SKY insert (S45, K46, Y47) in FIS1's first TPR repeat is required for TBC1D15 and DRP1 recruitment to mitochondria; deletion of the SKY insert elongates mitochondrial networks with reduced mitochondrial DRP1 despite enriched DRP1 co-immunoprecipitates; the SKY insert mediates intramolecular interactions with the regulatory Fis1 arm to govern FIS1 activity.","method":"Site-directed mutagenesis/deletion, co-immunoprecipitation, fluorescence microscopy, YFP-TBC1D15 recruitment assays","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mutagenesis with Co-IP and cellular phenotypes, single lab","pmids":["37777154"],"is_preprint":false},{"year":2023,"finding":"SENP1 translocates to endothelial mitochondria under short-term hypoxia and deSUMOylates FIS1; deSUMOylated FIS1 assembles with MFN2 and VDAC1, enhancing MFN2 oligomerization and membrane tethering activity, thereby maintaining mitochondrial integrity and ER–mitochondria Ca²⁺ communication; prolonged hypoxia reduces SENP1 availability via miR-138 induction, causing SUMOylated FIS1 accumulation and mitochondrial dysfunction leading to pulmonary hypertension.","method":"Co-immunoprecipitation, MFN2 oligomerization assay, viral-packaged FIS1 mutant knock-in mice, Ca²⁺ communication assays, hypoxia/Sugen rat PH models","journal":"Circulation research","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, MFN2 oligomerization assay, genetic knock-in/knock-out models in multiple animal PH models, multiple orthogonal methods","pmids":["37589160"],"is_preprint":false},{"year":2023,"finding":"Lactylation of Fis1 at lysine 20 (Fis1 K20la), driven by excess lactate produced via SIRT3-mediated PDHA1 hyperacetylation/inactivation, promotes excessive mitochondrial fission leading to ATP depletion, mtROS overproduction, and mitochondrial apoptosis in sepsis-induced AKI; reducing lactate (via DCA or SIRT3 overexpression) decreases Fis1 K20la and alleviates AKI.","method":"Lactylation site identification, PDHA1 acetylation assays, in vitro and in vivo AKI models, mitochondrial morphology assays","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — identified novel PTM site (K20 lactylation) with functional consequence, in vivo validation, single lab","pmids":["37479690"],"is_preprint":false},{"year":2024,"finding":"Under oxidative stress, Fis1 undergoes a conformational change exposing its only cysteine Cys41 (in the α1 helix); exposed Cys41 forms disulfide-bridged Fis1 homodimers that increase Drp1 recruitment to mitochondria and excessive fission; a small molecule SP11 binds specifically to activated (Cys41-exposed) Fis1, blocking homodimerization and preserving mitochondrial integrity; cells lacking Cys41 (C41A) show reduced stress-induced fission.","method":"Structural analysis (activated Fis1–SP11 crystal structure), disulfide crosslinking, C41A knockin cell lines, Drp1 recruitment assays, mitochondrial morphology under oxidative stress","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure of activated Fis1–SP11, genetic knockin cell line validation, small molecule functional probe, multiple orthogonal methods","pmids":["40328741"],"is_preprint":false},{"year":2024,"finding":"FIS1 deSUMOylation by SENP3 interacts with TBC1D17 (a Rab-GAP) in a SUMOylation-dependent manner under hypoxia; hypoxia promotes FIS1 SUMO2/3-ylation, triggering FIS1–TBC1D17 interaction that suppresses hypoxia-induced mitophagy; SENP3-mediated deSUMOylation of FIS1 promotes hypoxia-induced mitophagy and protects against hypoxic cell death.","method":"Co-immunoprecipitation, SUMOylation assays, SENP3 depletion, mitophagy flux assays, glioma patient-derived stem cells","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP identifying FIS1–TBC1D17 interaction, SUMOylation functional assays, single lab","pmids":["39638786"],"is_preprint":false}],"current_model":"FIS1 (human mitochondrial fission protein 1) is a tail-anchored outer mitochondrial membrane protein with a TPR-like cytosolic domain whose N-terminal arm autoinhibits interaction surfaces; it directly binds Drp1 (KD ~12–68 µM) and recruits TBC1D15 to mitochondria to promote fission and mitophagy, forms a bridging complex with ER protein Bap31 at MAMs to activate procaspase-8 and coordinate apoptosis, also localizes to peroxisomes to mediate peroxisomal fission through Pex11pβ interactions, and is regulated by multiple post-translational modifications—including phosphorylation at Tyr38 (by Met), Thr34 (by DNA-PKcs), SUMOylation at K149 (reversed by SENP3/SENP1 to control mitochondrial localization and mitophagy), lactylation at K20 (promoting pathological fission), and oxidative stress-induced Cys41-dependent homodimerization (increasing Drp1 recruitment)—with its activity in pathological fission selectively mediated through a distinct Drp1-binding surface (SWAG groove) separable from physiological Drp1–Mff-mediated fission."},"narrative":{"mechanistic_narrative":"FIS1 is a tail-anchored outer mitochondrial membrane protein that serves as a membrane-bound adaptor coordinating organelle division, mitophagy, and apoptosis [PMID:14623186, PMID:14996942]. Its cytosolic region adopts a TPR-like helical bundle whose concave and convex surfaces mediate protein interactions, while a C-terminal transmembrane segment plus a basic C-terminal patch anchors the protein and confers organelle targeting to both mitochondria and peroxisomes [PMID:14623186, PMID:16107562, PMID:28007883]. FIS1 promotes mitochondrial fission upstream of or in concert with the dynamin-related GTPase Drp1: overexpression fragments mitochondria in a Drp1-dependent manner and depletion elongates the network [PMID:14996942], and FIS1 binds Drp1 directly (KD ~12–68 µM) through a conserved TPR surface gated by an N-terminal arm that interconverts between autoinhibited and active conformations [PMID:17884824, PMID:36272645, PMID:37866629]. This arm-dependent autoinhibition, first defined structurally in yeast Fis1, occludes the Drp1/adaptor-binding surface, and removal of the arm or mutation of arm/SKY-insert residues tunes Drp1 and TBC1D15 recruitment [PMID:15809300, PMID:22102223, PMID:36272645, PMID:37777154]. Beyond Drp1, FIS1 directly recruits the Rab-GAP TBC1D15 to mitochondria to regulate morphology, and FIS1 functions downstream of Mff to couple stress-induced fission to mitophagy and degradation [PMID:23077178, PMID:24196833]. FIS1 independently drives non-canonical, PINK1/Parkin-independent mitophagy by controlling STX17 shuttling between ER and mitochondria [PMID:31053718]. At ER–mitochondria contact sites FIS1 bridges to the ER protein Bap31, forming a procaspase-8-activating complex that amplifies apoptosis, and the Bap31 vDED engages the convex TPR surface [PMID:21183955, PMID:40770055]. FIS1 activity is extensively regulated by post-translational modification: phosphorylation at Tyr38 by Met and at Thr34 by DNA-PKcs each increases Drp1 affinity and pathological fission [PMID:34848680, PMID:35290083]; SUMOylation at K149 controls mitochondrial localization and mitophagy, reversed by SENP3/SENP1 which also redirect FIS1 toward MFN2-dependent tethering [PMID:34994490, PMID:37589160]; and oxidative stress exposes Cys41 to drive disulfide-bridged homodimers that enhance Drp1 recruitment [PMID:40328741]. A distinct Drp1 SWAG groove mediates the pathological FIS1–Drp1 axis separably from physiological Drp1–Mff fission, providing a pharmacological handle [PMID:37468472].","teleology":[{"year":2003,"claim":"Established the fold and adaptor concept of human Fis1 by solving its structure, framing it as a membrane-anchored protein-interaction scaffold rather than an enzyme.","evidence":"NMR solution structure of human Fis1 cytosolic domain","pmids":["14623186"],"confidence":"High","gaps":["No binding partner identified at the structural level","Function of the predicted concave hydrophobic surface untested"]},{"year":2004,"claim":"Defined FIS1 as a functional regulator of mitochondrial fission acting with Drp1, answering whether it controls organelle morphology in cells.","evidence":"Deletion mutagenesis, dominant-negative Drp1(K38A) rescue, and RNAi with microscopy","pmids":["14996942"],"confidence":"High","gaps":["Did not establish whether FIS1 binds Drp1 directly","Stoichiometry and recruitment mechanism unresolved"]},{"year":2004,"claim":"Revealed a pro-apoptotic role for FIS1 distinct from and more potent than Drp1, separating its death function from fission per se.","evidence":"shRNA knockdown with apoptosis assays, including Opa1-depletion epistasis","pmids":["15356267"],"confidence":"Medium","gaps":["Molecular mediators of the apoptotic function not identified","Single lab, limited conditions"]},{"year":2005,"claim":"Showed FIS1 also drives peroxisomal fission and that targeting versus fission functions are separable between its TM tail and N-terminal region.","evidence":"Differential tagging, deletion mutagenesis, siRNA, microscopy in mammalian cells","pmids":["16107562"],"confidence":"High","gaps":["Peroxisomal partner not identified in this study","Whether the same Drp1 machinery operates at peroxisomes untested here"]},{"year":2005,"claim":"Identified intramolecular autoinhibition: the yeast Fis1 N-terminus folds onto the TPR concave face and gates adaptor recruitment, providing a regulatory mechanism for fission activity.","evidence":"NMR structure of yeast Fis1 plus yeast complementation assays","pmids":["15809300"],"confidence":"High","gaps":["Whether the more flexible human Fis1 arm is autoinhibitory left open","Trigger that relieves autoinhibition unknown"]},{"year":2005,"claim":"Linked FIS1 oligomeric assembly to division activity, indicating higher-order organization is required for function.","evidence":"Blue-native PAGE, deletion mutagenesis, RNAi in rat Fis1","pmids":["15979461"],"confidence":"Medium","gaps":["Composition of the ~200 kDa complex not defined","Whether oligomerization is homotypic or includes partners unclear"]},{"year":2007,"claim":"Provided structural and direct-binding proof that the TPR concave surface binds the Drp1 ortholog Dnm1 and that the N-terminal arm autoinhibits this >100-fold, mechanistically uniting structure with fission control.","evidence":"Yeast Fis1–Mdv1/Caf4 co-crystal structures plus in vitro Dnm1 binding and mutagenesis","pmids":["17998537","17884824"],"confidence":"High","gaps":["Direct human Fis1–Drp1 binding not yet quantified","How adaptors and Dnm1 binding are coordinated in time unresolved"]},{"year":2007,"claim":"Identified Pex11pβ as a direct FIS1 partner and detected Fis1–Pex11pβ–DLP1 ternary complexes, defining the peroxisomal fission machinery.","evidence":"Subcellular fractionation, co-IP, chemical crosslinking, RNAi in mammalian cells","pmids":["17408615"],"confidence":"High","gaps":["Binding interface on FIS1 for Pex11pβ not mapped","Regulation of peroxisomal versus mitochondrial partitioning unknown"]},{"year":2008,"claim":"Connected FIS1 to mitophagy/autophagy and long-term cell survival, distinguishing its effects on organelle function from shape.","evidence":"Yeast WHI2 epistasis genetics and Fis1 overexpression autophagy assays","pmids":["18756280","18515060"],"confidence":"Medium","gaps":["Molecular link between Fis1 and the autophagy machinery not defined","Relevance of yeast WHI2 axis to mammals unclear"]},{"year":2011,"claim":"Defined FIS1 as a hub at ER–mitochondria contacts that nucleates a Bap31-containing apoptotic platform, explaining its pro-apoptotic activity mechanistically.","evidence":"Reciprocal co-IP, fractionation, Ca²⁺ measurements, and procaspase-8 activation assays","pmids":["21183955"],"confidence":"High","gaps":["Interaction interface not yet structurally defined","How fission and apoptosis platforms are switched not resolved"]},{"year":2011,"claim":"Placed FIS1 within signaling control of fission by identifying AKAP121/Siah2 as upstream regulators of the Drp1–Fis1 interaction under hypoxia.","evidence":"Co-IP, Siah2−/− mice, cardiac ischemia and C. elegans models","pmids":["22099302"],"confidence":"High","gaps":["Mechanism by which AKAP121 occludes Drp1–Fis1 not defined","Direct versus indirect AKAP121 action unresolved"]},{"year":2011,"claim":"Showed the FIS1 cytosolic domain can directly engage and cluster membranes, suggesting an intrinsic membrane-remodeling capacity.","evidence":"Fluorescence spectroscopy, CD, light scattering, EM with lipid vesicles in vitro","pmids":["21738650"],"confidence":"Medium","gaps":["No in-cell validation of membrane clustering","Physiological relevance to fission untested"]},{"year":2012,"claim":"Identified TBC1D15 as a direct, Drp1-independent FIS1 effector recruited to mitochondria, broadening FIS1's role beyond Drp1-mediated fission.","evidence":"Co-IP, bacterial protein reconstitution, RNAi, microscopy","pmids":["23077178"],"confidence":"High","gaps":["How TBC1D15 recruitment alters morphology mechanistically unclear","Relationship to the Drp1 pathway not fully resolved"]},{"year":2012,"claim":"Established multilayered control of FIS1 abundance through proteasomal degradation, translational repression, and a monomer–dimer functional switch.","evidence":"DJ-1/Akt/RNF5 degradation in MPTP mice, Foxo3a–miR-484 reporter and transgenic assays, and analytical ultracentrifugation mutants","pmids":["22871147","22510686","22789569"],"confidence":"Medium","gaps":["How dimer state links to Drp1 recruitment not directly shown","Interplay among these regulatory layers untested"]},{"year":2013,"claim":"Showed FIS1 is one of multiple redundant Drp1 receptors and acts after Mff to couple stress-induced fission to downstream mitophagy/degradation.","evidence":"Fis1/Mff single- and double-null cells, co-IP, mitochondrial toxin and LC3 aggregation assays","pmids":["23283981","24196833"],"confidence":"High","gaps":["Quantitative contribution of each receptor in vivo unclear","Molecular step linking FIS1 to degradation not defined"]},{"year":2013,"claim":"Linked FIS1 to cell cycle progression, placing it upstream of Plk1/FoxM1 in G2/M entry.","evidence":"shRNA knockdown, flow cytometry, and rescue overexpression","pmids":["23907611"],"confidence":"Medium","gaps":["Mechanism connecting FIS1 to mitotic regulators unknown","Whether the effect is via fission or independent unresolved"]},{"year":2016,"claim":"Resolved how the FIS1 tail anchor achieves membrane insertion and organelle specificity, and refined the post-recruitment role of FIS1 in organizing Dnm1 puncta.","evidence":"Deep mutational scanning of the tail anchor and NMR-guided E78A mutagenesis with yeast fission assays","pmids":["28007883","27496949"],"confidence":"High","gaps":["Targeting determinants validated chiefly in yeast","How FIS1 organizes puncta versus uniform Dnm1 coating mechanistically unclear"]},{"year":2019,"claim":"Defined a Drp1-independent FIS1 function: controlling STX17 ER–mitochondria shuttling to gate PINK1/Parkin-independent mitophagy.","evidence":"Super-resolution microscopy, proteomics, co-IP, STX17 oligomerization and mitophagy flux assays","pmids":["31053718"],"confidence":"High","gaps":["How FIS1 occludes the STX17 N-terminus structurally unclear","Interplay with canonical PINK1/Parkin mitophagy not defined"]},{"year":2021,"claim":"Identified Tyr38 phosphorylation by Met as an activating modification that promotes Drp1 recruitment and metastasis-supporting fission.","evidence":"In vitro kinase assay, phospho-specific antibody, SIM imaging, invasion and xenograft assays","pmids":["34848680"],"confidence":"High","gaps":["Structural basis of how pY38 enhances Drp1 binding unknown","Whether other RTKs write this site untested"]},{"year":2022,"claim":"Identified Thr34 phosphorylation by cytoplasmic DNA-PKcs as a fission-promoting modification driving tubular cell death in acute kidney injury.","evidence":"Co-IP, in vitro kinase assay, T34A knock-in mice, kidney function and EM","pmids":["35290083"],"confidence":"High","gaps":["How pThr34 increases Drp1 affinity structurally unresolved","Relationship between pThr34 and pTyr38 regulation unknown"]},{"year":2022,"claim":"Established SUMOylation at K149 and its reversal by SENP3 as a switch controlling FIS1 mitochondrial localization and mitophagy.","evidence":"SUMOylation assays, K149R mutant, SENP3 depletion, mitophagy flux and fractionation","pmids":["34994490"],"confidence":"High","gaps":["SUMO ligase writing K149 not identified","How SUMOylation alters membrane localization mechanistically unclear"]},{"year":2022,"claim":"Confirmed that human FIS1 retains arm-dependent autoinhibition conserved from yeast, with arm removal reducing Drp1 recruitment and TBC1D15 partially substituting.","evidence":"MD simulations, NMR, tryptophan fluorescence, cellular Drp1 recruitment and TBC1D15 rescue","pmids":["36272645"],"confidence":"High","gaps":["Physiological trigger that opens the human arm undefined","Quantitative coupling of arm state to fission unresolved"]},{"year":2023,"claim":"Quantified direct human FIS1–Drp1 binding and mapped arm and surface residues as gain- and loss-of-function alleles, cementing the autoinhibitory model in human cells.","evidence":"NMR, DSF, microscale thermophoresis, alanine scanning, morphology assays in human cells","pmids":["37866629"],"confidence":"High","gaps":["Affinity is weak (µM); how it is potentiated in cells unclear","Co-receptor contributions to functional binding not addressed"]},{"year":2023,"claim":"Provided atomic-resolution insight into the FIS1–Bap31 apoptotic interface, showing Bap31 vDED engages the convex TPR surface.","evidence":"Co-crystal structure of human Fis1 with Bap31 vDED","pmids":["40770055"],"confidence":"High","gaps":["How procaspase-8 is positioned by the complex not structurally shown","Regulation switching FIS1 between fission and apoptosis platforms unclear"]},{"year":2023,"claim":"Defined a SWAG groove on Drp1 as the pathological FIS1-binding site, separable from physiological Drp1–Mff fission and druggable for selective inhibition.","evidence":"Peptide mapping of P110, structural modeling, small-molecule (SC9) screening, cell and endotoxemia models","pmids":["37468472"],"confidence":"Medium","gaps":["Direct structure of FIS1 bound at SWAG not resolved","How pathological signals route FIS1 to SWAG unclear"]},{"year":2023,"claim":"Identified the SKY insert in the first TPR repeat as required for TBC1D15 and Drp1 recruitment via intramolecular interaction with the regulatory arm.","evidence":"Site-directed deletion/mutagenesis, co-IP, TBC1D15 recruitment assays, microscopy","pmids":["37777154"],"confidence":"Medium","gaps":["Why SKY-deleted FIS1 still co-IPs DRP1 but fails to recruit it unresolved","Structural detail of the SKY–arm interaction lacking"]},{"year":2023,"claim":"Revealed that SENP1-mediated deSUMOylation can redirect FIS1 from fission toward MFN2/VDAC1-dependent tethering, balancing mitochondrial integrity and ER–mitochondria Ca²⁺ signaling.","evidence":"Co-IP, MFN2 oligomerization assay, FIS1 mutant knock-in mice, hypoxia/Sugen rat PH models","pmids":["37589160"],"confidence":"High","gaps":["How deSUMOylated FIS1 promotes MFN2 oligomerization mechanistically unclear","Reconciliation with K149/SENP3 SUMO control not addressed"]},{"year":2023,"claim":"Identified K20 lactylation, driven by SIRT3/PDHA1-controlled lactate, as a pathological modification promoting excessive fission in sepsis-induced AKI.","evidence":"Lactylation site identification, PDHA1 acetylation assays, in vitro and in vivo AKI models","pmids":["37479690"],"confidence":"Medium","gaps":["Lactyltransferase writing K20 not identified","How K20la alters FIS1 conformation/binding unknown"]},{"year":2024,"claim":"Established an oxidative-stress sensing mechanism: Cys41 exposure drives disulfide-linked FIS1 homodimers that boost Drp1 recruitment and excessive fission, and defined a small-molecule probe of the activated state.","evidence":"Activated Fis1–SP11 crystal structure, disulfide crosslinking, C41A knock-in cells, Drp1 recruitment assays","pmids":["40328741"],"confidence":"High","gaps":["How dimerization geometrically enhances Drp1 recruitment unresolved","Interplay with arm autoinhibition not defined"]},{"year":2024,"claim":"Showed SUMOylation-dependent FIS1–TBC1D17 interaction suppresses hypoxia-induced mitophagy, with SENP3 deSUMOylation relieving the block.","evidence":"Co-IP, SUMOylation assays, SENP3 depletion, mitophagy flux in glioma patient-derived stem cells","pmids":["39638786"],"confidence":"Medium","gaps":["Mechanism by which FIS1–TBC1D17 suppresses mitophagy unclear","Relationship to the FIS1–TBC1D15 axis not resolved"]},{"year":null,"claim":"How the many regulatory inputs (arm autoinhibition, SKY insert, phosphorylation, SUMOylation, lactylation, Cys41 dimerization) are integrated to switch FIS1 between physiological fission, pathological fission, mitophagy, tethering, and apoptosis remains unresolved.","evidence":"","pmids":[],"confidence":"High","gaps":["No unified structural model coupling PTMs to arm conformation and partner choice","Quantitative hierarchy among redundant Drp1 receptors in vivo undefined","Switch determining fission-platform versus Bap31 apoptotic-platform engagement unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[0,15,11,25]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[1,7,30]},{"term_id":"GO:0008289","term_label":"lipid binding","supporting_discovery_ids":[13]}],"localization":[{"term_id":"GO:0005777","term_label":"peroxisome","supporting_discovery_ids":[3,8]},{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[11,20,25]}],"pathway":[{"term_id":"R-HSA-1852241","term_label":"Organelle biogenesis and maintenance","supporting_discovery_ids":[1,3,19]},{"term_id":"R-HSA-9612973","term_label":"Autophagy","supporting_discovery_ids":[24,25,28]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[2,11]},{"term_id":"R-HSA-8953897","term_label":"Cellular responses to stimuli","supporting_discovery_ids":[12,36,34]}],"complexes":["Fis1–Bap31 (ARCosome)","Fis1–Pex11pβ–DLP1 ternary complex","Drp1–Fis1 fission complex"],"partners":["DNM1L/DRP1","TBC1D15","BCAP31/BAP31","PEX11B/PEX11PΒ","STX17","SENP3","MFN2","TBC1D17"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9Y3D6","full_name":"Mitochondrial fission 1 protein","aliases":["FIS1 homolog","hFis1","Tetratricopeptide repeat protein 11","TPR repeat protein 11"],"length_aa":152,"mass_kda":16.9,"function":"Involved in the fragmentation of the mitochondrial network and its perinuclear clustering (PubMed:12783892, PubMed:12861026, PubMed:14996942, PubMed:23283981). Plays a minor role in the recruitment and association of the fission mediator dynamin-related protein 1 (DNM1L) to the mitochondrial surface and mitochondrial fission (PubMed:12861026, PubMed:16118244, PubMed:23283981, PubMed:23530241, PubMed:24196833). May not be essential for the assembly of functional fission complexes and the subsequent membrane scission event (PubMed:23530241, PubMed:24196833). Also mediates peroxisomal fission (PubMed:16107562). May act when the products of fission are directed toward mitochondrial homeostasis, mitophagy, or apoptosis (PubMed:24196833). Can induce cytochrome c release from the mitochondrion to the cytosol, ultimately leading to apoptosis (PubMed:12783892)","subcellular_location":"Mitochondrion outer membrane; Peroxisome membrane","url":"https://www.uniprot.org/uniprotkb/Q9Y3D6/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/FIS1","classification":"Not Classified","n_dependent_lines":316,"n_total_lines":1208,"dependency_fraction":0.26158940397350994},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/FIS1","total_profiled":1310},"omim":[{"mim_id":"615498","title":"MITOCHONDRIAL ELONGATION FACTOR 2; MIEF2","url":"https://www.omim.org/entry/615498"},{"mim_id":"615497","title":"MITOCHONDRIAL ELONGATION FACTOR 1; MIEF1","url":"https://www.omim.org/entry/615497"},{"mim_id":"612662","title":"TBC1 DOMAIN FAMILY, MEMBER 15; TBC1D15","url":"https://www.omim.org/entry/612662"},{"mim_id":"612492","title":"UBIQUITIN-SPECIFIC PROTEASE 30; USP30","url":"https://www.omim.org/entry/612492"},{"mim_id":"609003","title":"FISSION, MITOCHONDRIAL 1; FIS1","url":"https://www.omim.org/entry/609003"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Mitochondria","reliability":"Supported"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/FIS1"},"hgnc":{"alias_symbol":["CGI-135","H_NH0132A01.6"],"prev_symbol":["TTC11"]},"alphafold":{"accession":"Q9Y3D6","domains":[],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9Y3D6","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9Y3D6-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9Y3D6-F1-predicted_aligned_error_v6.png","plddt_mean":77.94},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=FIS1","jax_strain_url":"https://www.jax.org/strain/search?query=FIS1"},"sequence":{"accession":"Q9Y3D6","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9Y3D6.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9Y3D6/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9Y3D6"}},"corpus_meta":[{"pmid":"23283981","id":"PMC_23283981","title":"Fis1, Mff, MiD49, and MiD51 mediate Drp1 recruitment in mitochondrial fission.","date":"2013","source":"Molecular biology 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anchoring.\",\n      \"method\": \"NMR spectroscopy\",\n      \"journal\": \"Journal of molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — de novo NMR structure determination, single lab but rigorous structural method with functional inference\",\n      \"pmids\": [\"14623186\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Human Fis1 inserts into the mitochondrial outer membrane via a C-terminal transmembrane domain; this transmembrane domain together with a short basic segment is essential for mitochondrial targeting. Overexpression causes mitochondrial fragmentation suppressible by dominant-negative Drp1(K38A), and RNAi knockdown causes elongation of mitochondrial tubules, establishing hFis1 as a regulator of mitochondrial fission acting upstream of or in concert with Drp1.\",\n      \"method\": \"Deletion mutagenesis, dominant-negative Drp1 rescue, RNAi knockdown with fluorescence microscopy\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (mutagenesis, dominant-negative rescue, RNAi), replicated in subsequent studies\",\n      \"pmids\": [\"14996942\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Down-regulation of hFis1 by shRNA inhibits apoptosis more potently than down-regulation of Drp1, and at a distinct stage. Cells depleted of Opa1 die spontaneously by a process requiring hFis1 expression, indicating Fis1 has a pro-apoptotic function that Opa1 normally counteracts.\",\n      \"method\": \"shRNA knockdown, apoptosis assays (flow cytometry, cell death quantification)\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean shRNA loss-of-function with defined apoptotic phenotype, single lab, two conditions tested\",\n      \"pmids\": [\"15356267\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Human Fis1 localizes to peroxisomes in addition to mitochondria; the transmembrane domain and short C-terminal tail are necessary and sufficient for targeting to both organelles, whereas the N-terminal region is required for organelle fission. Fis1 overexpression promotes peroxisome division and siRNA silencing causes peroxisome tubulation, establishing a role for Fis1 in peroxisomal fission.\",\n      \"method\": \"Differential tagging, deletion mutagenesis, siRNA, fluorescence microscopy\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal approaches (mutagenesis, siRNA, live imaging), independently replicated in later studies\",\n      \"pmids\": [\"16107562\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Analysis of rat Fis1 by BN-PAGE revealed it forms an ~200 kDa complex at the outer mitochondrial membrane. Domain analysis showed the N-terminal and C-terminal segments are both essential for oligomeric rFis1 interaction, and the middle TPR-like domains regulate proper oligomer assembly; disruption of oligomeric assembly abolishes mitochondrial division-stimulating activity.\",\n      \"method\": \"Blue-native PAGE, deletion mutagenesis, RNAi, fluorescence microscopy\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — BN-PAGE plus mutagenesis in single lab, two complementary methods\",\n      \"pmids\": [\"15979461\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"NMR structure of yeast Fis1 revealed that, unlike the flexible unstructured N-terminus of human Fis1, the longer N-terminus of yeast Fis1 is fixed to the concave face of the TPR domain in an intramolecular fashion. This N-terminal segment is required for Mdv1 recruitment to mitochondria and for rescuing mitochondrial fission in fis1Δ yeast, indicating intramolecular autoinhibitory regulation of Fis1 bioactivity.\",\n      \"method\": \"NMR spectroscopy, yeast complementation assay, fluorescence microscopy\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — NMR structure plus functional rescue assays, single lab but orthogonal structural and cell biological methods\",\n      \"pmids\": [\"15809300\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Crystal structures of yeast Fis1 in complex with adaptor proteins Mdv1 and Caf4 showed these adaptors use two helices to bind both the concave and convex surfaces of the Fis1 TPR domain — a novel binding mode for TPR domains. Genetic and biochemical studies confirmed both interfaces are important for Mdv1/Caf4 binding and for mitochondrial fission in vivo.\",\n      \"method\": \"X-ray crystallography, biochemical binding assays, yeast genetics\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structures combined with biochemical and genetic validation, multiple orthogonal methods\",\n      \"pmids\": [\"17998537\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Yeast Fis1 directly binds Dnm1 (the Drp1 ortholog) in a manner negatively regulated by the Fis1 N-terminal arm; the concave surface of the Fis1 TPR domain mediates Dnm1 binding; removal of the arm increases Dnm1 binding >100-fold, indicating the arm acts in an autoinhibitory manner to restrict access to the Dnm1-binding site.\",\n      \"method\": \"In vitro binding assays, mutagenesis, fluorescence microscopy\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstituted direct binding with mutagenesis, single lab with multiple complementary experiments\",\n      \"pmids\": [\"17884824\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Fis1 localizes to peroxisomes as well as mitochondria in mammalian cells (confirmed by subcellular fractionation). Fis1 directly interacts with the peroxisomal membrane protein Pex11pβ (co-IP and binding studies), and ternary complexes of Fis1–Pex11pβ–DLP1 were detected by chemical crosslinking; Fis1 overexpression induces peroxisome proliferation while Fis1 RNAi causes peroxisome tubulation.\",\n      \"method\": \"Subcellular fractionation, co-immunoprecipitation, chemical crosslinking, RNAi, fluorescence microscopy\",\n      \"journal\": \"Experimental cell research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal binding assays, fractionation, RNAi with phenotypic readout, single lab multiple orthogonal methods\",\n      \"pmids\": [\"17408615\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"In yeast, deletion of FIS1 consistently selects for a secondary mutation in WHI2, which rescues the mitochondrial respiratory defect (petite formation) caused by FIS1 deficiency but causes defective growth control. The long-term survival function of Fis1 in this context appears independent of Dnm1 and Mdv1 but may be mediated through the Caf4 adaptor.\",\n      \"method\": \"Yeast genetics, tiling arrays, genomic sequencing, growth assays\",\n      \"journal\": \"Cell death and differentiation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis with sequencing confirmation, single lab, multiple independently derived knockouts\",\n      \"pmids\": [\"18756280\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"High-level Fis1 overexpression triggers autophagy (mitophagy) correlating with mitochondrial dysfunction rather than fragmentation per se, as demonstrated by Fis1 mutants with dissociated effects on organelle shape versus function.\",\n      \"method\": \"Fis1 overexpression/mutagenesis, autophagosome formation assays, fluorescence microscopy\",\n      \"journal\": \"Biochimica et biophysica acta\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional mutagenesis dissociating shape from dysfunction, single lab\",\n      \"pmids\": [\"18515060\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Fis1 bridges the mitochondria–ER interface by interacting with the ER protein Bap31, facilitating Bap31 cleavage into pro-apoptotic p20Bap31; the Fis1–Bap31 complex (ARCosome) recruits procaspase-8 via the variant death effector domain (vDED) of Bap31, activating procaspase-8 and releasing ER Ca²⁺ to amplify mitochondrial apoptosis in a feedback loop.\",\n      \"method\": \"Co-immunoprecipitation, subcellular fractionation, apoptosis assays, Ca²⁺ measurements, domain deletion analysis\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP, domain mapping, functional procaspase-8 activation assay, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"21183955\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"AKAP121 inhibits Drp1–Fis1 interaction in a PKA-independent manner; reduced AKAP121 availability (via ubiquitin ligase Siah2) relieves inhibition and increases Drp1–Fis1 interaction, resulting in mitochondrial fission under hypoxia. This defines Siah2 as a key upstream regulator of Fis1/Drp1-mediated fission.\",\n      \"method\": \"Co-immunoprecipitation, genetic knockout (Siah2−/− mice), cardiac ischemia models, C. elegans lifespan assays\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, in vivo knockout mice, multiple disease models, replicated across cell and animal contexts\",\n      \"pmids\": [\"22099302\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"The cytosolic domain of Fis1 alone binds lipid vesicles (enhanced by protonation and anionic phospholipids), undergoes a membrane-induced conformational change burying two tryptophan residues, and promotes reversible lipid vesicle clustering, suggesting Fis1 can directly interact with membranes to facilitate fission.\",\n      \"method\": \"Fluorescence spectroscopy, circular dichroism, light scattering, electron microscopy\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — in vitro reconstituted assay, single lab, no in-cell validation\",\n      \"pmids\": [\"21738650\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Crystal structure of yeast Fis1 at 1.75 Å resolution confirmed the TPR fold creates a concave surface important for fission that is sterically occluded by the N-terminal arm, providing a structural basis for autoinhibition.\",\n      \"method\": \"X-ray crystallography\",\n      \"journal\": \"Acta crystallographica. Section F\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — high-resolution crystal structure confirming autoinhibitory mechanism, consistent with prior NMR and functional data\",\n      \"pmids\": [\"22102223\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Fis1 directly and efficiently interacts with the Rab-GAP protein TBC1D15 (but not with Drp1) at mitochondria; bacterially expressed Fis1 and TBC1D15 form a direct stable complex in vitro; TBC1D15 localizes to mitochondria only when co-expressed with Fis1, and TBC1D15 knockdown induces mitochondrial network development similar to Fis1 knockdown, indicating Fis1 recruits TBC1D15 to mitochondria to regulate morphology independently of Drp1.\",\n      \"method\": \"Co-immunoprecipitation from HeLa extracts, bacterial protein reconstitution, RNAi, fluorescence microscopy\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — direct in vitro reconstitution of Fis1–TBC1D15 complex plus Co-IP and RNAi phenotype, single lab with orthogonal methods\",\n      \"pmids\": [\"23077178\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"A designed point mutation A72P in Fis1 disrupts dimerization and abolishes fission activity, while two nonfunctional Fis1 variants (L80P or E78D/I85T/Y88H) are unexpectedly dimeric; these data support a model in which Fis1 activity depends on its ability to interconvert between monomer and dimer species.\",\n      \"method\": \"Analytical ultracentrifugation, mutagenesis, yeast fission assays\",\n      \"journal\": \"Journal of molecular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — designed mutagenesis with biophysical characterization and functional readout, single lab\",\n      \"pmids\": [\"22789569\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"DJ-1 promotes proteasomal degradation of Fis1 via the DJ-1/Akt/RNF5 signaling pathway: Akt1 enhances mitochondrial translocation and E3-ligase activity of RNF5, leading to Fis1 ubiquitination and degradation; DJ-1 loss increases Fis1 levels and neuronal vulnerability in an MPTP mouse model.\",\n      \"method\": \"Western blotting, co-immunoprecipitation, MPTP mouse model, RNF5 E3 ligase activity assay\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — identified E3 ligase (RNF5) for Fis1 ubiquitination with in vivo validation, single lab\",\n      \"pmids\": [\"22871147\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"miR-484 suppresses translation of Fis1 by binding to the amino acid coding sequence of Fis1 mRNA, inhibiting Fis1-mediated mitochondrial fission and apoptosis; Foxo3a transactivates miR-484 expression, establishing a Foxo3a–miR-484–Fis1 axis regulating mitochondrial fission.\",\n      \"method\": \"Luciferase reporter assay, miRNA overexpression/knockout mice, Western blot, apoptosis assays\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reporter assay confirming direct miR-484 binding to FIS1 coding sequence, in vivo transgenic/knockout validation, single lab\",\n      \"pmids\": [\"22510686\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Both Fis1 and Mff independently contribute to mitochondrial fission and are important for the number and size of Drp1 puncta on mitochondria; either MiD49 or MiD51 can mediate Drp1 recruitment and fission in the absence of both Fis1 and Mff, demonstrating that multiple independent receptors recruit Drp1.\",\n      \"method\": \"Fis1-null, Mff-null, and Fis1/Mff double-null cell lines, immunofluorescence, Drp1 localization analysis\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic null cells with multiple controls, replicated findings across receptor combinations\",\n      \"pmids\": [\"23283981\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"During the fission cycle, Drp1 first binds Mff, then enters a complex including Fis1 and ER proteins at the ER–mitochondrial interface; Fis1 mutations do not affect fission per se but disrupt downstream degradation events when mitochondrial toxins are used, leading to accumulation of large LC3 aggregates, indicating Fis1 acts after Mff to couple stress-induced fission with downstream mitophagy/degradation.\",\n      \"method\": \"Co-immunoprecipitation, Fis1 point mutations, mitochondrial toxin treatment, LC3 aggregation assays, ER-mitochondria interface imaging\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP and mutagenesis identifying sequential complex assembly, single lab\",\n      \"pmids\": [\"24196833\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"hFis1 depletion causes a severe cell cycle progression defect through G2/M phase (~3-fold reduction in mitotic index); reintroduction of hFis1 restores the cell cycle; G2/M regulators including cyclin B1, Cdk1, Plk1, Aurora kinase A, and Mad2 are suppressed in hFis1-knockdown cells; Plk1 or FoxM1 expression (but not cyclin B1/Cdk1 complex reconstitution) restores mitotic entry, placing hFis1 upstream of Plk1/FoxM1 in G2/M regulation.\",\n      \"method\": \"shRNA knockdown, flow cytometry, Western blotting, rescue overexpression experiments\",\n      \"journal\": \"Cellular and molecular life sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — shRNA loss-of-function with epistasis rescue experiments, single lab\",\n      \"pmids\": [\"23907611\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Deep mutational scanning of the Fis1p tail anchor in yeast showed: (1) the positively charged patch at the C-terminus is required for both membrane insertion and organelle specificity; (2) positively charged residues are more acceptable within the membrane-associated domain than negatively charged residues, providing in vivo evidence for lysine/arginine 'snorkeling'; (3) TA length changes of ±3 amino acids do not inhibit mitochondrial targeting.\",\n      \"method\": \"Next-generation sequencing-based deep mutational scanning, Gal4 reporter assay, fluorescence microscopy of individual mutants\",\n      \"journal\": \"Genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — genome-scale mutagenesis with sequencing plus individual mutant validation, rigorous method\",\n      \"pmids\": [\"28007883\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Fis1 E78A mutation weakens interaction with Mdv1 (identified by NMR-guided pKa analysis), alters mitochondrial morphology, abolishes fission in growth assays, and causes uniform Dnm1 coating of mitochondria rather than puncta formation at low expression, supporting a post-recruitment role for Fis1 in organizing Dnm1 puncta.\",\n      \"method\": \"NMR pKa measurements, mutagenesis, yeast fission growth assay, fluorescence microscopy\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — NMR-guided mutagenesis with functional validation, single lab\",\n      \"pmids\": [\"27496949\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"AMPK is intrinsically activated in AML leukemia stem cells and is upstream of FIS1; FIS1 mediates mitophagy activity essential for LSC self-renewal; FIS1 depletion attenuates mitophagy, inactivates GSK3, induces myeloid differentiation, cell cycle arrest, and loss of LSC self-renewal potential, establishing an AMPK→FIS1→mitophagy axis in LSC maintenance.\",\n      \"method\": \"shRNA knockdown, AMPK inhibition, mitophagy assays, colony-forming/self-renewal assays, xenograft models\",\n      \"journal\": \"Cell stem cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function with multiple cellular phenotypes and epistasis testing, single lab\",\n      \"pmids\": [\"29910151\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Fis1 depletion from the outer mitochondrial membrane causes aberrant STX17 (Syntaxin 17) accumulation on mitochondria; STX17–Fis1 interaction (identified by proteomics) controls dynamic shuttling of STX17 between ER and mitochondria; Fis1 loss exposes the STX17 N-terminus, promotes STX17 self-oligomerization, triggering PINK1/Parkin-independent mitophagy via ATG14 recruitment and Rab7-dependent lysosome fusion.\",\n      \"method\": \"Super-resolution microscopy (SR-SIM), proteomics, Co-IP, STX17 oligomerization assays, mitophagy flux assays, Rab7 interaction experiments\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — proteomics-identified interaction confirmed by Co-IP, super-resolution imaging, mechanistic dissection of STX17 oligomerization, multiple orthogonal methods\",\n      \"pmids\": [\"31053718\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Met receptor tyrosine kinase directly phosphorylates Fis1 at Tyr38 (Fis1 pY38); Fis1 pY38 promotes mitochondrial fission by recruiting Drp1 to mitochondria; fragmented mitochondria fuel actin remodeling and lamellipodia/invadopodia formation to facilitate HCC cell metastasis in vitro and in vivo.\",\n      \"method\": \"Structured illumination microscopy, live-cell imaging, in vitro kinase assay, phospho-specific antibody, Drp1 recruitment assays, invasion/migration assays, xenograft models\",\n      \"journal\": \"Signal transduction and targeted therapy\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — direct in vitro phosphorylation assay identifying Met as kinase writing Fis1 pY38, plus in vivo functional validation, multiple methods\",\n      \"pmids\": [\"34848680\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"DNA-PKcs translocates to the cytoplasm during AKI, directly interacts with Fis1, and phosphorylates Fis1 at Thr34 (TQ motif); Fis1 pThr34 increases affinity of Fis1 for Drp1, inducing mitochondrial fragmentation and tubular cell death; knock-in T34A mice are protected from AKI and show reduced mitochondrial fragmentation.\",\n      \"method\": \"Co-immunoprecipitation, in vitro kinase assay, phospho-specific detection, T34A knockin mice, kidney function assays, electron microscopy\",\n      \"journal\": \"Science signaling\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct kinase assay identifying DNA-PKcs as writer of Fis1 pThr34, knockin mouse genetic validation, multiple orthogonal methods\",\n      \"pmids\": [\"35290083\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Fis1 is SUMOylated at K149, an amino acid residue critical for its mitochondrial localization; SENP3 (stabilized by CHIP downregulation upon DFP treatment) deSUMOylates Fis1, enhancing Fis1 mitochondrial localization; SENP3 depletion abolishes DFP-induced mitophagy; a K149R mutation (preventing SUMOylation) enhances mitochondrial Fis1 localization and restores DFP-induced mitophagy in SENP3-depleted cells.\",\n      \"method\": \"SUMOylation assays, site-directed mutagenesis (K149R), SENP3 depletion, mitophagy flux assays, fractionation\",\n      \"journal\": \"EMBO reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — identified SUMO site, writer/eraser (SENP3), functional consequence on localization and mitophagy, rescue by non-SUMOylatable mutant, multiple orthogonal methods\",\n      \"pmids\": [\"34994490\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"NMR and X-ray structural studies showed the human Fis1 arm can adopt an intramolecular conformation akin to yeast Fis1; removal of the Fis1 arm reduces Drp1 recruitment and mitochondrial fission in cells similar to yeast; TBC1D15 expression partially rescues arm-less Fis1 function, reminiscent of Mdv1 in yeast, supporting conserved arm-dependent regulation across eukaryotes.\",\n      \"method\": \"Molecular dynamics simulations, NMR, intrinsic tryptophan fluorescence, cellular DRP1 recruitment assays, TBC1D15 rescue experiments\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — NMR plus computational MD plus cellular functional assays, single lab, orthogonal methods\",\n      \"pmids\": [\"36272645\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Human Fis1 directly binds human Drp1 (KD = 12–68 μM) as measured by NMR, differential scanning fluorimetry, and microscale thermophoresis; similar to yeast, interaction is governed by the Fis1 N-terminal arm and a conserved surface; alanine scanning of the arm identified loss-of-function (N6A → elongated mitochondria) and gain-of-function (E7A → fragmented mitochondria) alleles; Y76A substitution also caused fragmented mitochondria, supporting intramolecular arm–surface interactions regulating Drp1-mediated fission.\",\n      \"method\": \"NMR, differential scanning fluorimetry, microscale thermophoresis, alanine scanning mutagenesis, mitochondrial morphology assays in human cells\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct in vitro binding quantified by three biophysical methods, mutagenesis with gain- and loss-of-function alleles, cellular validation\",\n      \"pmids\": [\"37866629\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"A switch I-adjacent groove (SWAG) on Drp1 is the binding site for the Fis1-derived peptide inhibitor P110; small molecules binding SWAG (e.g., SC9) mimic P110's benefit by selectively inhibiting pathological Drp1–Fis1-mediated fission without blocking physiological Drp1–Mff-mediated fission in cells and in a mouse endotoxemia model.\",\n      \"method\": \"Peptide mapping, structural modeling, small molecule screening, cellular Drp1–Fis1 interaction assays, mouse endotoxemia model\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — SWAG site mapped with P110, pharmacological validation in cells and in vivo, single lab\",\n      \"pmids\": [\"37468472\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Crystal structure of human Fis1 bound to the C-terminal Bap31_vDED region showed that the Bap31 vDED region engages the convex surface of Fis1's TPR domain; one Fis1 conformation features the N-terminal arm (suggestive of autoinhibition); this provides structural basis for Fis1–Bap31 interaction at ER–mitochondria contact sites.\",\n      \"method\": \"X-ray crystallography (co-crystal structure), structural analysis\",\n      \"journal\": \"Communications biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — co-crystal structure defining the Fis1–Bap31 interaction interface at atomic resolution, single study\",\n      \"pmids\": [\"40770055\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"A conserved three-residue SKY insert (S45, K46, Y47) in FIS1's first TPR repeat is required for TBC1D15 and DRP1 recruitment to mitochondria; deletion of the SKY insert elongates mitochondrial networks with reduced mitochondrial DRP1 despite enriched DRP1 co-immunoprecipitates; the SKY insert mediates intramolecular interactions with the regulatory Fis1 arm to govern FIS1 activity.\",\n      \"method\": \"Site-directed mutagenesis/deletion, co-immunoprecipitation, fluorescence microscopy, YFP-TBC1D15 recruitment assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mutagenesis with Co-IP and cellular phenotypes, single lab\",\n      \"pmids\": [\"37777154\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"SENP1 translocates to endothelial mitochondria under short-term hypoxia and deSUMOylates FIS1; deSUMOylated FIS1 assembles with MFN2 and VDAC1, enhancing MFN2 oligomerization and membrane tethering activity, thereby maintaining mitochondrial integrity and ER–mitochondria Ca²⁺ communication; prolonged hypoxia reduces SENP1 availability via miR-138 induction, causing SUMOylated FIS1 accumulation and mitochondrial dysfunction leading to pulmonary hypertension.\",\n      \"method\": \"Co-immunoprecipitation, MFN2 oligomerization assay, viral-packaged FIS1 mutant knock-in mice, Ca²⁺ communication assays, hypoxia/Sugen rat PH models\",\n      \"journal\": \"Circulation research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, MFN2 oligomerization assay, genetic knock-in/knock-out models in multiple animal PH models, multiple orthogonal methods\",\n      \"pmids\": [\"37589160\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Lactylation of Fis1 at lysine 20 (Fis1 K20la), driven by excess lactate produced via SIRT3-mediated PDHA1 hyperacetylation/inactivation, promotes excessive mitochondrial fission leading to ATP depletion, mtROS overproduction, and mitochondrial apoptosis in sepsis-induced AKI; reducing lactate (via DCA or SIRT3 overexpression) decreases Fis1 K20la and alleviates AKI.\",\n      \"method\": \"Lactylation site identification, PDHA1 acetylation assays, in vitro and in vivo AKI models, mitochondrial morphology assays\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — identified novel PTM site (K20 lactylation) with functional consequence, in vivo validation, single lab\",\n      \"pmids\": [\"37479690\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Under oxidative stress, Fis1 undergoes a conformational change exposing its only cysteine Cys41 (in the α1 helix); exposed Cys41 forms disulfide-bridged Fis1 homodimers that increase Drp1 recruitment to mitochondria and excessive fission; a small molecule SP11 binds specifically to activated (Cys41-exposed) Fis1, blocking homodimerization and preserving mitochondrial integrity; cells lacking Cys41 (C41A) show reduced stress-induced fission.\",\n      \"method\": \"Structural analysis (activated Fis1–SP11 crystal structure), disulfide crosslinking, C41A knockin cell lines, Drp1 recruitment assays, mitochondrial morphology under oxidative stress\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure of activated Fis1–SP11, genetic knockin cell line validation, small molecule functional probe, multiple orthogonal methods\",\n      \"pmids\": [\"40328741\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"FIS1 deSUMOylation by SENP3 interacts with TBC1D17 (a Rab-GAP) in a SUMOylation-dependent manner under hypoxia; hypoxia promotes FIS1 SUMO2/3-ylation, triggering FIS1–TBC1D17 interaction that suppresses hypoxia-induced mitophagy; SENP3-mediated deSUMOylation of FIS1 promotes hypoxia-induced mitophagy and protects against hypoxic cell death.\",\n      \"method\": \"Co-immunoprecipitation, SUMOylation assays, SENP3 depletion, mitophagy flux assays, glioma patient-derived stem cells\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP identifying FIS1–TBC1D17 interaction, SUMOylation functional assays, single lab\",\n      \"pmids\": [\"39638786\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"FIS1 (human mitochondrial fission protein 1) is a tail-anchored outer mitochondrial membrane protein with a TPR-like cytosolic domain whose N-terminal arm autoinhibits interaction surfaces; it directly binds Drp1 (KD ~12–68 µM) and recruits TBC1D15 to mitochondria to promote fission and mitophagy, forms a bridging complex with ER protein Bap31 at MAMs to activate procaspase-8 and coordinate apoptosis, also localizes to peroxisomes to mediate peroxisomal fission through Pex11pβ interactions, and is regulated by multiple post-translational modifications—including phosphorylation at Tyr38 (by Met), Thr34 (by DNA-PKcs), SUMOylation at K149 (reversed by SENP3/SENP1 to control mitochondrial localization and mitophagy), lactylation at K20 (promoting pathological fission), and oxidative stress-induced Cys41-dependent homodimerization (increasing Drp1 recruitment)—with its activity in pathological fission selectively mediated through a distinct Drp1-binding surface (SWAG groove) separable from physiological Drp1–Mff-mediated fission.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"FIS1 is a tail-anchored outer mitochondrial membrane protein that serves as a membrane-bound adaptor coordinating organelle division, mitophagy, and apoptosis [#0, #1]. Its cytosolic region adopts a TPR-like helical bundle whose concave and convex surfaces mediate protein interactions, while a C-terminal transmembrane segment plus a basic C-terminal patch anchors the protein and confers organelle targeting to both mitochondria and peroxisomes [#0, #3, #22]. FIS1 promotes mitochondrial fission upstream of or in concert with the dynamin-related GTPase Drp1: overexpression fragments mitochondria in a Drp1-dependent manner and depletion elongates the network [#1], and FIS1 binds Drp1 directly (KD ~12–68 µM) through a conserved TPR surface gated by an N-terminal arm that interconverts between autoinhibited and active conformations [#7, #29, #30]. This arm-dependent autoinhibition, first defined structurally in yeast Fis1, occludes the Drp1/adaptor-binding surface, and removal of the arm or mutation of arm/SKY-insert residues tunes Drp1 and TBC1D15 recruitment [#5, #14, #29, #33]. Beyond Drp1, FIS1 directly recruits the Rab-GAP TBC1D15 to mitochondria to regulate morphology, and FIS1 functions downstream of Mff to couple stress-induced fission to mitophagy and degradation [#15, #20]. FIS1 independently drives non-canonical, PINK1/Parkin-independent mitophagy by controlling STX17 shuttling between ER and mitochondria [#25]. At ER–mitochondria contact sites FIS1 bridges to the ER protein Bap31, forming a procaspase-8-activating complex that amplifies apoptosis, and the Bap31 vDED engages the convex TPR surface [#11, #32]. FIS1 activity is extensively regulated by post-translational modification: phosphorylation at Tyr38 by Met and at Thr34 by DNA-PKcs each increases Drp1 affinity and pathological fission [#26, #27]; SUMOylation at K149 controls mitochondrial localization and mitophagy, reversed by SENP3/SENP1 which also redirect FIS1 toward MFN2-dependent tethering [#28, #34]; and oxidative stress exposes Cys41 to drive disulfide-bridged homodimers that enhance Drp1 recruitment [#36]. A distinct Drp1 SWAG groove mediates the pathological FIS1–Drp1 axis separably from physiological Drp1–Mff fission, providing a pharmacological handle [#31].\",\n  \"teleology\": [\n    {\n      \"year\": 2003,\n      \"claim\": \"Established the fold and adaptor concept of human Fis1 by solving its structure, framing it as a membrane-anchored protein-interaction scaffold rather than an enzyme.\",\n      \"evidence\": \"NMR solution structure of human Fis1 cytosolic domain\",\n      \"pmids\": [\"14623186\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No binding partner identified at the structural level\", \"Function of the predicted concave hydrophobic surface untested\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Defined FIS1 as a functional regulator of mitochondrial fission acting with Drp1, answering whether it controls organelle morphology in cells.\",\n      \"evidence\": \"Deletion mutagenesis, dominant-negative Drp1(K38A) rescue, and RNAi with microscopy\",\n      \"pmids\": [\"14996942\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not establish whether FIS1 binds Drp1 directly\", \"Stoichiometry and recruitment mechanism unresolved\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Revealed a pro-apoptotic role for FIS1 distinct from and more potent than Drp1, separating its death function from fission per se.\",\n      \"evidence\": \"shRNA knockdown with apoptosis assays, including Opa1-depletion epistasis\",\n      \"pmids\": [\"15356267\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular mediators of the apoptotic function not identified\", \"Single lab, limited conditions\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Showed FIS1 also drives peroxisomal fission and that targeting versus fission functions are separable between its TM tail and N-terminal region.\",\n      \"evidence\": \"Differential tagging, deletion mutagenesis, siRNA, microscopy in mammalian cells\",\n      \"pmids\": [\"16107562\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Peroxisomal partner not identified in this study\", \"Whether the same Drp1 machinery operates at peroxisomes untested here\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Identified intramolecular autoinhibition: the yeast Fis1 N-terminus folds onto the TPR concave face and gates adaptor recruitment, providing a regulatory mechanism for fission activity.\",\n      \"evidence\": \"NMR structure of yeast Fis1 plus yeast complementation assays\",\n      \"pmids\": [\"15809300\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether the more flexible human Fis1 arm is autoinhibitory left open\", \"Trigger that relieves autoinhibition unknown\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Linked FIS1 oligomeric assembly to division activity, indicating higher-order organization is required for function.\",\n      \"evidence\": \"Blue-native PAGE, deletion mutagenesis, RNAi in rat Fis1\",\n      \"pmids\": [\"15979461\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Composition of the ~200 kDa complex not defined\", \"Whether oligomerization is homotypic or includes partners unclear\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Provided structural and direct-binding proof that the TPR concave surface binds the Drp1 ortholog Dnm1 and that the N-terminal arm autoinhibits this >100-fold, mechanistically uniting structure with fission control.\",\n      \"evidence\": \"Yeast Fis1–Mdv1/Caf4 co-crystal structures plus in vitro Dnm1 binding and mutagenesis\",\n      \"pmids\": [\"17998537\", \"17884824\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct human Fis1–Drp1 binding not yet quantified\", \"How adaptors and Dnm1 binding are coordinated in time unresolved\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Identified Pex11pβ as a direct FIS1 partner and detected Fis1–Pex11pβ–DLP1 ternary complexes, defining the peroxisomal fission machinery.\",\n      \"evidence\": \"Subcellular fractionation, co-IP, chemical crosslinking, RNAi in mammalian cells\",\n      \"pmids\": [\"17408615\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Binding interface on FIS1 for Pex11pβ not mapped\", \"Regulation of peroxisomal versus mitochondrial partitioning unknown\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Connected FIS1 to mitophagy/autophagy and long-term cell survival, distinguishing its effects on organelle function from shape.\",\n      \"evidence\": \"Yeast WHI2 epistasis genetics and Fis1 overexpression autophagy assays\",\n      \"pmids\": [\"18756280\", \"18515060\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular link between Fis1 and the autophagy machinery not defined\", \"Relevance of yeast WHI2 axis to mammals unclear\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Defined FIS1 as a hub at ER–mitochondria contacts that nucleates a Bap31-containing apoptotic platform, explaining its pro-apoptotic activity mechanistically.\",\n      \"evidence\": \"Reciprocal co-IP, fractionation, Ca²⁺ measurements, and procaspase-8 activation assays\",\n      \"pmids\": [\"21183955\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Interaction interface not yet structurally defined\", \"How fission and apoptosis platforms are switched not resolved\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Placed FIS1 within signaling control of fission by identifying AKAP121/Siah2 as upstream regulators of the Drp1–Fis1 interaction under hypoxia.\",\n      \"evidence\": \"Co-IP, Siah2−/− mice, cardiac ischemia and C. elegans models\",\n      \"pmids\": [\"22099302\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which AKAP121 occludes Drp1–Fis1 not defined\", \"Direct versus indirect AKAP121 action unresolved\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Showed the FIS1 cytosolic domain can directly engage and cluster membranes, suggesting an intrinsic membrane-remodeling capacity.\",\n      \"evidence\": \"Fluorescence spectroscopy, CD, light scattering, EM with lipid vesicles in vitro\",\n      \"pmids\": [\"21738650\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No in-cell validation of membrane clustering\", \"Physiological relevance to fission untested\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Identified TBC1D15 as a direct, Drp1-independent FIS1 effector recruited to mitochondria, broadening FIS1's role beyond Drp1-mediated fission.\",\n      \"evidence\": \"Co-IP, bacterial protein reconstitution, RNAi, microscopy\",\n      \"pmids\": [\"23077178\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How TBC1D15 recruitment alters morphology mechanistically unclear\", \"Relationship to the Drp1 pathway not fully resolved\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Established multilayered control of FIS1 abundance through proteasomal degradation, translational repression, and a monomer–dimer functional switch.\",\n      \"evidence\": \"DJ-1/Akt/RNF5 degradation in MPTP mice, Foxo3a–miR-484 reporter and transgenic assays, and analytical ultracentrifugation mutants\",\n      \"pmids\": [\"22871147\", \"22510686\", \"22789569\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"How dimer state links to Drp1 recruitment not directly shown\", \"Interplay among these regulatory layers untested\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Showed FIS1 is one of multiple redundant Drp1 receptors and acts after Mff to couple stress-induced fission to downstream mitophagy/degradation.\",\n      \"evidence\": \"Fis1/Mff single- and double-null cells, co-IP, mitochondrial toxin and LC3 aggregation assays\",\n      \"pmids\": [\"23283981\", \"24196833\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Quantitative contribution of each receptor in vivo unclear\", \"Molecular step linking FIS1 to degradation not defined\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Linked FIS1 to cell cycle progression, placing it upstream of Plk1/FoxM1 in G2/M entry.\",\n      \"evidence\": \"shRNA knockdown, flow cytometry, and rescue overexpression\",\n      \"pmids\": [\"23907611\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism connecting FIS1 to mitotic regulators unknown\", \"Whether the effect is via fission or independent unresolved\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Resolved how the FIS1 tail anchor achieves membrane insertion and organelle specificity, and refined the post-recruitment role of FIS1 in organizing Dnm1 puncta.\",\n      \"evidence\": \"Deep mutational scanning of the tail anchor and NMR-guided E78A mutagenesis with yeast fission assays\",\n      \"pmids\": [\"28007883\", \"27496949\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Targeting determinants validated chiefly in yeast\", \"How FIS1 organizes puncta versus uniform Dnm1 coating mechanistically unclear\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Defined a Drp1-independent FIS1 function: controlling STX17 ER–mitochondria shuttling to gate PINK1/Parkin-independent mitophagy.\",\n      \"evidence\": \"Super-resolution microscopy, proteomics, co-IP, STX17 oligomerization and mitophagy flux assays\",\n      \"pmids\": [\"31053718\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How FIS1 occludes the STX17 N-terminus structurally unclear\", \"Interplay with canonical PINK1/Parkin mitophagy not defined\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Identified Tyr38 phosphorylation by Met as an activating modification that promotes Drp1 recruitment and metastasis-supporting fission.\",\n      \"evidence\": \"In vitro kinase assay, phospho-specific antibody, SIM imaging, invasion and xenograft assays\",\n      \"pmids\": [\"34848680\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of how pY38 enhances Drp1 binding unknown\", \"Whether other RTKs write this site untested\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Identified Thr34 phosphorylation by cytoplasmic DNA-PKcs as a fission-promoting modification driving tubular cell death in acute kidney injury.\",\n      \"evidence\": \"Co-IP, in vitro kinase assay, T34A knock-in mice, kidney function and EM\",\n      \"pmids\": [\"35290083\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How pThr34 increases Drp1 affinity structurally unresolved\", \"Relationship between pThr34 and pTyr38 regulation unknown\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Established SUMOylation at K149 and its reversal by SENP3 as a switch controlling FIS1 mitochondrial localization and mitophagy.\",\n      \"evidence\": \"SUMOylation assays, K149R mutant, SENP3 depletion, mitophagy flux and fractionation\",\n      \"pmids\": [\"34994490\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"SUMO ligase writing K149 not identified\", \"How SUMOylation alters membrane localization mechanistically unclear\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Confirmed that human FIS1 retains arm-dependent autoinhibition conserved from yeast, with arm removal reducing Drp1 recruitment and TBC1D15 partially substituting.\",\n      \"evidence\": \"MD simulations, NMR, tryptophan fluorescence, cellular Drp1 recruitment and TBC1D15 rescue\",\n      \"pmids\": [\"36272645\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological trigger that opens the human arm undefined\", \"Quantitative coupling of arm state to fission unresolved\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Quantified direct human FIS1–Drp1 binding and mapped arm and surface residues as gain- and loss-of-function alleles, cementing the autoinhibitory model in human cells.\",\n      \"evidence\": \"NMR, DSF, microscale thermophoresis, alanine scanning, morphology assays in human cells\",\n      \"pmids\": [\"37866629\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Affinity is weak (µM); how it is potentiated in cells unclear\", \"Co-receptor contributions to functional binding not addressed\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Provided atomic-resolution insight into the FIS1–Bap31 apoptotic interface, showing Bap31 vDED engages the convex TPR surface.\",\n      \"evidence\": \"Co-crystal structure of human Fis1 with Bap31 vDED\",\n      \"pmids\": [\"40770055\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How procaspase-8 is positioned by the complex not structurally shown\", \"Regulation switching FIS1 between fission and apoptosis platforms unclear\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Defined a SWAG groove on Drp1 as the pathological FIS1-binding site, separable from physiological Drp1–Mff fission and druggable for selective inhibition.\",\n      \"evidence\": \"Peptide mapping of P110, structural modeling, small-molecule (SC9) screening, cell and endotoxemia models\",\n      \"pmids\": [\"37468472\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct structure of FIS1 bound at SWAG not resolved\", \"How pathological signals route FIS1 to SWAG unclear\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Identified the SKY insert in the first TPR repeat as required for TBC1D15 and Drp1 recruitment via intramolecular interaction with the regulatory arm.\",\n      \"evidence\": \"Site-directed deletion/mutagenesis, co-IP, TBC1D15 recruitment assays, microscopy\",\n      \"pmids\": [\"37777154\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Why SKY-deleted FIS1 still co-IPs DRP1 but fails to recruit it unresolved\", \"Structural detail of the SKY–arm interaction lacking\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Revealed that SENP1-mediated deSUMOylation can redirect FIS1 from fission toward MFN2/VDAC1-dependent tethering, balancing mitochondrial integrity and ER–mitochondria Ca²⁺ signaling.\",\n      \"evidence\": \"Co-IP, MFN2 oligomerization assay, FIS1 mutant knock-in mice, hypoxia/Sugen rat PH models\",\n      \"pmids\": [\"37589160\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How deSUMOylated FIS1 promotes MFN2 oligomerization mechanistically unclear\", \"Reconciliation with K149/SENP3 SUMO control not addressed\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Identified K20 lactylation, driven by SIRT3/PDHA1-controlled lactate, as a pathological modification promoting excessive fission in sepsis-induced AKI.\",\n      \"evidence\": \"Lactylation site identification, PDHA1 acetylation assays, in vitro and in vivo AKI models\",\n      \"pmids\": [\"37479690\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Lactyltransferase writing K20 not identified\", \"How K20la alters FIS1 conformation/binding unknown\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Established an oxidative-stress sensing mechanism: Cys41 exposure drives disulfide-linked FIS1 homodimers that boost Drp1 recruitment and excessive fission, and defined a small-molecule probe of the activated state.\",\n      \"evidence\": \"Activated Fis1–SP11 crystal structure, disulfide crosslinking, C41A knock-in cells, Drp1 recruitment assays\",\n      \"pmids\": [\"40328741\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How dimerization geometrically enhances Drp1 recruitment unresolved\", \"Interplay with arm autoinhibition not defined\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Showed SUMOylation-dependent FIS1–TBC1D17 interaction suppresses hypoxia-induced mitophagy, with SENP3 deSUMOylation relieving the block.\",\n      \"evidence\": \"Co-IP, SUMOylation assays, SENP3 depletion, mitophagy flux in glioma patient-derived stem cells\",\n      \"pmids\": [\"39638786\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism by which FIS1–TBC1D17 suppresses mitophagy unclear\", \"Relationship to the FIS1–TBC1D15 axis not resolved\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How the many regulatory inputs (arm autoinhibition, SKY insert, phosphorylation, SUMOylation, lactylation, Cys41 dimerization) are integrated to switch FIS1 between physiological fission, pathological fission, mitophagy, tethering, and apoptosis remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No unified structural model coupling PTMs to arm conformation and partner choice\", \"Quantitative hierarchy among redundant Drp1 receptors in vivo undefined\", \"Switch determining fission-platform versus Bap31 apoptotic-platform engagement unknown\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [0, 15, 11, 25]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [1, 7, 30]},\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [13]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005741\", \"supporting_discovery_ids\": [1, 22]},\n      {\"term_id\": \"GO:0005777\", \"supporting_discovery_ids\": [3, 8]},\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [11, 20, 25]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1852241\", \"supporting_discovery_ids\": [1, 3, 19]},\n      {\"term_id\": \"R-HSA-9612973\", \"supporting_discovery_ids\": [24, 25, 28]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [2, 11]},\n      {\"term_id\": \"R-HSA-8953897\", \"supporting_discovery_ids\": [12, 36, 34]}\n    ],\n    \"complexes\": [\n      \"Fis1–Bap31 (ARCosome)\",\n      \"Fis1–Pex11pβ–DLP1 ternary complex\",\n      \"Drp1–Fis1 fission complex\"\n    ],\n    \"partners\": [\n      \"DNM1L/Drp1\",\n      \"TBC1D15\",\n      \"BCAP31/Bap31\",\n      \"PEX11B/Pex11pβ\",\n      \"STX17\",\n      \"SENP3\",\n      \"MFN2\",\n      \"TBC1D17\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":9,"faith_total":9,"faith_pct":100.0}}