GIMAP7

GIMAP7 is a dimerization-activated GTPase of the GIMAP family that regulates autophagy, apoptosis, and cell survival through both intrinsic enzymatic activity and participation in heteromeric signaling complexes. Its GTP hydrolysis is stimulated by homodimerization via a trans-acting catalytic arginine mechanism, and GIMAP7 similarly activates the GTPase activity of GIMAP2 through heterodimerization; it also forms a ternary complex with GIMAP6 and GABARAPL2 to regulate autophagy-related GTPase function (PMID:23454188, PMID:35551368). GIMAP7 localizes to lipid droplets and membranous organelles including the Golgi apparatus, endoplasmic reticulum, and lysosomes, and directly binds LC3B to convert incomplete autophagy to complete autophagy flux, promoting apoptosis during respiratory syncytial virus infection (PMID:23454188, PMID:40728050). In disease-relevant contexts, GIMAP7 inhibits the SHH/Smo signaling axis to promote apoptosis and oxidative stress in ovarian granulosa cells and to suppress epithelial–mesenchymal transition and glycolysis in lung adenocarcinoma (PMID:36581994, PMID:38151913).

1. 2013 High

   Determining how GIMAP family GTPases are activated: crystal structure and mutagenesis revealed that GIMAP7 homodimerization through G domains positions a catalytic arginine in trans to stimulate GTP hydrolysis, and that this same mechanism operates in GIMAP7–GIMAP2 heterodimers on lipid droplets.

   Evidence Crystal structure of GTP-bound GIMAP7 homodimer; in vitro GTPase assays; active-site mutagenesis; subcellular fractionation showing lipid droplet localization

   PMID:23454188

   Open questions at the time

   • Physiological triggers that control dimerization in vivo are unknown
   • Downstream effectors of GIMAP7 GTP hydrolysis have not been identified
   • Whether GIMAP7 GTPase activity is required for its roles in autophagy or apoptosis is untested
2. 2022 Medium

   Extending GIMAP7 from a homodimer/binary heterodimer context to a ternary complex: GIMAP7 was shown to associate with GIMAP6 and GABARAPL2, linking its GTPase regulatory capacity to autophagy and immune cell homeostasis.

   Evidence Co-immunoprecipitation and biochemical complex analysis in the context of a Gimap6-knockout mouse model

   PMID:35551368

   Open questions at the time

   • Stoichiometry and structure of the GIMAP6–GABARAPL2–GIMAP7 complex remain unresolved
   • Whether GIMAP7 activates GIMAP6 GTPase activity through the same trans-arginine mechanism is untested
   • GIMAP7-specific functional consequences within this complex are not separated from GIMAP6 loss
3. 2022 Medium

   Establishing a cell-biological role for GIMAP7 beyond GTPase biochemistry: GIMAP7 promotes oxidative stress and apoptosis in ovarian granulosa cells by suppressing the SHH/SMO/Gli1 signaling pathway, with cyclopamine rescue confirming pathway specificity.

   Evidence siRNA knockdown in KGN granulosa cells; PCOS rat model; oxidative stress assays; pharmacological rescue with SHH inhibitor cyclopamine

   PMID:36581994

   Open questions at the time

   • Mechanism by which GIMAP7 inhibits SHH pathway activation is not defined
   • Whether GTPase activity is required for SHH pathway suppression is unknown
   • Findings from a single lab and cell line
4. 2023 Medium

   Broadening the anti-tumorigenic role of GIMAP7: overexpression suppressed EMT and glycolysis in lung adenocarcinoma through the Smo/AMPK axis, confirmed by agonist rescue experiments and xenograft tumor suppression.

   Evidence Overexpression and siRNA knockdown in lung adenocarcinoma cells; ECAR/OCR metabolic assays; xenograft nude mouse model; rescue with Smo agonist SAG and AMPK agonist GSK621

   PMID:38151913

   Open questions at the time

   • Direct physical interaction between GIMAP7 and Smo or AMPK has not been demonstrated
   • Relationship between GIMAP7 GTPase activity and Smo/AMPK suppression is unexplored
   • Single-lab study without independent replication
5. 2025 Medium

   Revealing a direct role for GIMAP7 in autophagy: GIMAP7 binds LC3B and converts RSV-induced incomplete autophagy to complete autophagic flux, thereby promoting apoptosis and restricting viral replication, while localizing to Golgi, ER, and lysosomes.

   Evidence Co-immunoprecipitation of GIMAP7–LC3B interaction; autophagy flux assays; subcellular localization analysis in overexpression system

   PMID:40728050

   Open questions at the time

   • LC3B-binding interface on GIMAP7 (e.g., LIR motif) has not been mapped
   • Whether GTPase activity or nucleotide state regulates LC3B binding is unknown
   • Reciprocal validation of the GIMAP7–LC3B interaction (e.g., endogenous co-IP or structural data) is lacking

• It remains unknown how GIMAP7 GTPase activity is mechanistically coupled to its downstream functions in autophagy, SHH/Smo pathway suppression, and apoptosis, and whether nucleotide cycling controls its localization or interaction partner selectivity.
• No structural data on GIMAP7 heterodimeric complexes (with GIMAP6 or within the ternary complex)
• The mechanism connecting GTPase activity to SHH/Smo inhibition is entirely undefined
• Whether GIMAP7 functions as a tumor suppressor through a unified or context-dependent mechanism is unresolved