GIMAP6

GIMAP6 is a T-cell-enriched nucleotide-binding protein that links the autophagy machinery to lymphocyte survival and immune homeostasis (PMID:28381553, PMID:35551368). It binds the Atg8-family protein GABARAPL2 in the cytosol through its extreme C-terminus, and upon starvation relocates to GABARAPL2/MAP1LC3B-marked autophagosomes where it is itself degraded (PMID:24204963). As part of a cytosolic complex with GABARAPL2 and GIMAP7, GIMAP6 regulates GTPase activity and is required for normal autophagic flux: its loss in CD4+ T cells produces accumulation of lipidated LC3-II, phosphorylated SQSTM1 and TBK1, and increased autophagosome numbers (PMID:29718959, PMID:35551368). Purified GIMAP6 has intrinsic ATPase and GTPase activity, but this hydrolytic activity is dispensable for its anti-apoptotic role (PMID:28381553). GIMAP6 acts as an anti-apoptotic factor in T cells and primary human lymphocytes, supporting NF-κB p65 activation, and is required for peripheral T-cell maintenance (PMID:28381553, PMID:29718959, PMID:33328581). Beyond immune-cell survival, GIMAP6 deficiency disrupts redox balance and polyunsaturated fatty acid lipid metabolism, impairs IFN-γ-inducible antibacterial immunity, and causes vascular and renal pathology in mice (PMID:35551368). Homozygous loss-of-function GIMAP6 variants in humans abolish the protein and cause accelerated lymphocyte apoptosis, defining a human immunodeficiency syndrome (PMID:35551368, PMID:33328581).

1. 2013 High

   Established the first molecular partner of GIMAP6 by showing it engages the autophagy machinery, framing the protein as autophagy-linked rather than free-standing.

   Evidence Biotin tag-affinity purification, cross-linking, deletion mapping, and starvation-induced co-localization in Jurkat T cells

   PMID:24204963

   Open questions at the time

   • Functional consequence of the GABARAPL2 interaction for autophagy was not resolved (over-expression did not alter flux)
   • C-terminal binding determinant defined but structural basis unknown
2. 2017 High

   Defined GIMAP6 as an enzymatically active NTPase yet showed hydrolysis is uncoupled from its cellular role, identifying its anti-apoptotic function as the key activity.

   Evidence In vitro ATPase/GTPase assays on recombinant protein plus hydrolysis-deficient rescue in Huh-7 cells; siRNA and over-expression apoptosis assays across cell types

   PMID:28381553

   Open questions at the time

   • The biochemical role of nucleotide binding/hydrolysis remains undefined
   • Mechanistic link between GIMAP6 and NF-κB p65 phosphorylation is correlative
3. 2018 High

   Moved GIMAP6 from cell-line correlation to an in vivo requirement, demonstrating it sustains the peripheral T-cell pool and normal autophagic flux.

   Evidence Conditional and inducible Cre knockout mice with flow cytometry, autophagy marker western blots, and electron microscopy

   PMID:29718959

   Open questions at the time

   • Whether disrupted autophagy directly causes the T-cell loss versus parallel effects was not separated
   • Mechanism connecting GIMAP6 loss to elevated TBK1/SQSTM1 phosphorylation unclear
4. 2020 Medium

   Provided human genetic validation that GIMAP6 prevents lymphocyte apoptosis in primary cells, extending the anti-apoptotic role to patients.

   Evidence Whole-exome sequencing, protein western blot, and apoptosis assays on patient-derived lymphocytes

   PMID:33328581

   Open questions at the time

   • Small cohort/case-level evidence
   • Did not define the molecular pathway downstream of GIMAP6 loss in patient cells
5. 2022 High

   Integrated the GABARAPL2-GIMAP7-GIMAP6 complex with broad physiological consequences, linking GIMAP6 to GTPase regulation, redox and PUFA-lipid metabolism, antibacterial immunity, and tissue protection.

   Evidence Complex IP and GTPase assays, patient-derived cells, and Gimap6-/- mice with lipidomics, redox assays, infection, and histopathology

   PMID:35551368

   Open questions at the time

   • How GIMAP6 regulates GTPase activity within the complex mechanistically is not detailed
   • Causal chain from autophagy defect to lipid/redox dysregulation and to glomerulosclerosis not fully dissected
6. 2026 Medium

   Expanded the protective role of GIMAP6 to cardiovascular disease, showing its loss drives inflammatory vasculopathy and atherosclerosis independent of hyperlipidemia.

   Evidence Gimap6-/- mouse histopathology and cardiac function plus human rare-variant association (preprint)

   PMID:41743988

   Open questions at the time

   • Preprint, not yet peer-reviewed
   • Cell-type and molecular mechanism driving the vasculopathy not established
   • Relationship to the autophagy/lipid functions of GIMAP6 unclear

• The unifying biochemical mechanism by which GIMAP6's nucleotide binding and GABARAPL2/GIMAP7 complex membership convert into autophagy control, apoptosis resistance, and lipid/redox homeostasis remains undefined.
• No structure of GIMAP6 or its complex
• GTPase regulatory partner/effector within the complex unidentified
• Direct substrate or effector mediating anti-apoptotic activity unknown