ANXA6

ANXA6 is a Ca2+-responsive membrane- and lipid-associated scaffold protein that integrates growth-factor signaling, autophagy, and membrane organization across diverse cell types (PMID:33135350, PMID:23360953). Its best-characterized signaling output is suppression of the EGFR axis: ANXA6 promotes formation of an EGFR-PKCα complex that lowers EGFR and ERK1/2 phosphorylation, a function potentiated by SUMO1 conjugation at lysine K299, with the SUMO-deficient K299R mutant losing this activity and conferring gefitinib resistance (PMID:37528485). The same EGFR-PKCα-restraining activity is engaged downstream of the transcription factor PRRX1 to enhance cisplatin sensitivity in bladder cancer (PMID:39528080). ANXA6 also drives autophagy by inhibiting PI3K/AKT/mTOR (and ERK) signaling and by enabling ATG9A-vesicle trafficking from recycling endosomes to autophagosomes via RAB GTPases and F-actin (PMID:32373608, PMID:33135350), with TRPV2 acting downstream of ANXA6-induced autophagy (PMID:37138336). Consistent with Ca2+-dependent lipid binding, ANXA6 translocates into cholesterol- and sphingomyelin-rich microdomains as intracellular Ca2+ rises (PMID:23360953), and supports SNAP23-dependent membrane translocation that facilitates secretion of extracellular vesicles and pro-inflammatory cytokines. Beyond these roles, ANXA6 acts as a host restriction factor limiting influenza A virus replication (PMID:34673207), suppresses cGAS-STING signaling by promoting K63-linked ubiquitination of cGAS (PMID:41219880), and is required in liver for insulin-modulated suppression of hepatic gluconeogenesis and for alanine-dependent gluconeogenesis (PMID:30110341, PMID:40802799).

1. 2013 Medium

   Established the biophysical basis for ANXA6 membrane targeting by showing that Ca2+ drives its translocation into cholesterol/sphingomyelin-enriched microdomains.

   Evidence DRM fractionation in Niemann-Pick type C cells plus Langmuir monolayer reconstitution with Ca2+ titration

   PMID:23360953

   Open questions at the time

   • Does not identify the protein partners ANXA6 recruits to these microdomains
   • Functional consequence for cholesterol handling in vivo not resolved
2. 2018 Medium

   Connected ANXA6 to systemic metabolism by showing knockout livers fail to suppress gluconeogenesis upon insulin, placing ANXA6 in the hepatic insulin response.

   Evidence AnxA6-KO mice with OGTT/ITT and phospho-Akt/S6 blotting, plus glucose-production assays in depleted hepatocytes

   PMID:30110341

   Open questions at the time

   • Molecular target through which ANXA6 modulates Akt/S6K not defined
   • Direct binding partners in hepatocytes not identified
3. 2020 Medium

   Defined ANXA6 as a positive regulator of autophagy operating both by inhibiting PI3K/AKT/mTOR and by physically enabling ATG9A vesicle delivery to autophagosomes.

   Evidence siRNA knockdown with re-expression rescue, pharmacological PI3K inhibition, and confocal imaging of ATG9A trafficking

   PMID:32373608 PMID:33135350

   Open questions at the time

   • Whether ANXA6 binds ATG9A directly or acts through RAB/F-actin scaffolds is unresolved
   • How the mTOR-inhibitory and trafficking functions are coordinated is unclear
4. 2020 Medium

   Identified ANXA6 as a host target of the EHEC effector EspF, linking it to tight-junction integrity via MLCK/PKCα signaling.

   Evidence FRET and Co-IP with domain mapping, plus tight-junction protein immunofluorescence

   PMID:33425920

   Open questions at the time

   • Does not establish ANXA6's endogenous role at tight junctions absent infection
   • Direct enzymatic consequence of EspF binding to ANXA6 unknown
5. 2021 Medium

   Showed ANXA6 functions as a host restriction factor against influenza A virus.

   Evidence CRISPR-Cas9 knockout in HEK293FT with TCID50 and viral growth-curve readouts

   PMID:34673207

   Open questions at the time

   • Step of the viral life cycle ANXA6 acts on is not mechanistically pinned
   • No viral or host binding partner identified
6. 2023 High

   Revealed that SUMO1 modification at K299 is required for ANXA6 to suppress EGFR-ERK signaling, mechanistically tying a post-translational modification to drug response.

   Evidence MS-mapped SUMOylation site validated by K299R mutagenesis, Co-IP of EGFR-PKCα complex, and xenograft model

   PMID:37528485

   Open questions at the time

   • The SUMO E3 ligase and conditions controlling K299 modification are not defined
   • Structural basis of SUMO-dependent EGFR binding unknown
7. 2023 Medium

   Extended the autophagy axis by identifying TRPV2 as a downstream effector of ANXA6-induced, AKT/mTOR-dependent autophagy in head and neck cancer metastasis.

   Evidence Gain/loss-of-function in vitro and in a lymphatic metastasis model, Co-IP, and TRPV2 pharmacological rescue

   PMID:37138336

   Open questions at the time

   • Whether ANXA6-TRPV2 binding is direct and Ca2+-dependent is unresolved
   • Reciprocal validation of the interaction is limited
8. 2024 Medium

   Placed the EGFR-suppressive ANXA6 function within a transcriptional circuit, showing PRRX1 directly drives ANXA6 expression to enhance chemosensitivity.

   Evidence ChIP-PCR and dual-luciferase for PRRX1 binding, MS and Co-IP for EGFR-PKCα complex, and xenograft model

   PMID:39528080

   Open questions at the time

   • Generality of PRRX1 control of ANXA6 beyond bladder cancer untested
   • Does not address how SUMOylation and PRRX1 regulation interrelate
9. 2025 Medium

   Resolved the metabolic phenotype to a specific defect, showing ANXA6 is required for alanine-dependent hepatic gluconeogenesis and fasting glucose maintenance.

   Evidence Anxa6-/- mice with calorimetry, tolerance tests, and expression profiling of Gpt2/Ldha2/SNAT4

   PMID:40802799

   Open questions at the time

   • Mechanism linking ANXA6 to alanine-handling gene expression not defined
   • Whether the effect is cell-autonomous in hepatocytes vs systemic is unclear
10. 2025 Medium

    Connected ANXA6 to innate-immune and ferroptosis control by showing it promotes K63-linked ubiquitination of cGAS to restrain cGAS-STING signaling.

    Evidence Co-localization, ubiquitination assays, cGAS-STING pathway blotting, and ROS/lipid-peroxide measurements after ANXA6 knockdown in cervical cancer cells

    PMID:41219880

    Open questions at the time

    • The E3 ligase ANXA6 recruits to cGAS is not identified
    • Whether ANXA6 binds cGAS directly is not established
11. 2025 Medium

    Implicated ANXA6 in macrophage inflammatory programming at the maternal-fetal interface via NF-κB/NLRP3-driven pyroptosis.

    Evidence ANXA6 overexpression in primary decidual macrophages with ROS/membrane-potential assays, NLRP3-inhibitor rescue, and trophoblast co-culture

    PMID:40959268

    Open questions at the time

    • Direct molecular trigger upstream of NF-κB activation by ANXA6 unknown
    • Endogenous relevance versus overexpression artifact not separated

• How ANXA6's Ca2+-dependent membrane binding mechanistically unifies its disparate roles in EGFR scaffolding, autophagic trafficking, ubiquitin-mediated immune control, and hepatic metabolism remains unresolved.
• No structural model linking lipid binding to partner recruitment
• Direct enzymatic or adaptor activity not biochemically reconstituted
• Whether SUMOylation gates membrane translocation across contexts is untested