FAM177A1

FAM177A1 is a Golgi-localized protein that functions at the intersection of Golgi membrane dynamics, inflammatory signaling, and mitochondrial redox homeostasis. It physically interacts with the bulk lipid transfer protein VPS13B at the Golgi complex, and its loss delays Golgi membrane reformation after Brefeldin A-induced disruption, phenocopying VPS13B deficiency; genetic interaction between fam177a1 and vps13b is confirmed in zebrafish (PMID:39331042). FAM177A1 negatively regulates IL-1β/NF-κB signaling by competitively binding the E3 ubiquitin ligase TRAF6 and blocking its interaction with the E2-conjugating enzyme Ubc13, thereby inhibiting TRAF6-mediated polyubiquitination (PMID:34799425). In vascular smooth muscle cells, FAM177A1 disrupts the SIRT3–SOD2 deacetylation axis, elevating SOD2 K68 acetylation and mitochondrial ROS to drive phenotypic switching, and its deficiency suppresses neointimal hyperplasia and atherosclerosis in rodent models (PMID:41943851).

1. 2009 Medium

   Before any functional role was known, the expression pattern and regulation of FAM177A1 (then c14orf24) were established: it is a cytoplasmic protein highly expressed in proliferating cells whose levels decline during neurogenesis via miR-124a-mediated translational repression, framing it as a differentiation-responsive gene.

   Evidence qRT-PCR, 3′-UTR luciferase reporter assays with miR-124a, subcellular fractionation/imaging in P19 mouse embryonic carcinoma cells

   PMID:19663910

   Open questions at the time

   • No molecular function or pathway assignment was made
   • miR-124a regulation demonstrated only in one cell line with a single reporter system
   • Endogenous protein–protein interactions unknown
2. 2021 Medium

   The first molecular function was identified: FAM177A1 negatively regulates NF-κB signaling by competitively binding TRAF6 and disrupting the TRAF6–Ubc13 E2–E3 interaction, establishing it as an anti-inflammatory modulator.

   Evidence Overexpression/knockdown in human cells; co-immunoprecipitation of FAM177A1–TRAF6 and impaired TRAF6–Ubc13 association; NF-κB luciferase reporter and inflammatory gene transcription assays

   PMID:34799425

   Open questions at the time

   • Binding interface between FAM177A1 and TRAF6 not mapped; competitive mechanism inferred from Co-IP without structural data
   • In vivo relevance of the anti-inflammatory function not tested
   • Relationship between Golgi localization and TRAF6 binding unexplored
3. 2024 High

   FAM177A1 was localized to the Golgi complex and shown to be a functional partner of the lipid transfer protein VPS13B: loss of FAM177A1 delays Golgi reformation after Brefeldin A treatment, phenocopying VPS13B loss, and the two genes genetically interact in zebrafish, establishing FAM177A1 as a Golgi membrane dynamics factor.

   Evidence Super-resolution imaging for Golgi localization; BFA washout assay in FAM177A1 KO and VPS13B KO human cells; zebrafish double-mutant/knockdown epistasis; protein–protein interaction with VPS13B

   PMID:38767059 PMID:39331042

   Open questions at the time

   • Mechanism by which FAM177A1 supports VPS13B-mediated lipid transfer is unknown
   • No structural basis for the FAM177A1–VPS13B interaction
   • Whether Golgi dysfunction accounts for the inflammatory and metabolic transcriptomic changes seen in FAM177A1-deficient cells is unclear
4. 2026 High

   A distinct mitochondrial-metabolic mechanism was uncovered: FAM177A1 disrupts SIRT3–SOD2 binding, increasing SOD2 K68 acetylation and mitochondrial ROS while shifting metabolism from oxidative phosphorylation to glycolysis, thereby driving vascular smooth muscle cell phenotypic switching and neointimal hyperplasia in vivo.

   Evidence Global Fam177a1 KO rats (carotid balloon injury), VSMC-specific AAV knockdown in mice (carotid ligation), ApoE−/− mice on high-fat diet; Co-IP for SIRT3–SOD2; SOD2 K68 acetylation by mass spectrometry/immunoblot; mitochondrial functional assays

   PMID:41943851

   Open questions at the time

   • Direct physical interaction between FAM177A1 and SIRT3 or SOD2 not demonstrated—disruption of the SIRT3–SOD2 axis could be indirect
   • How a Golgi-localized protein influences a mitochondrial deacetylation axis is mechanistically unexplained
   • Relevance of the SIRT3–SOD2 mechanism to non-vascular cell types is untested

• It remains unknown how FAM177A1's Golgi-localized function with VPS13B, its cytoplasmic anti-inflammatory role via TRAF6, and its effect on the mitochondrial SIRT3–SOD2 axis are mechanistically integrated—whether these reflect independent activities, context-dependent pools of the protein, or a unified membrane-trafficking mechanism.
• No structural or domain-level information to explain multifunctionality
• No disease-causing mutations in humans have been mechanistically characterized
• Tissue-specific and cell-type-specific functions are poorly resolved