ABCF3

ABCF3 is a cytoplasmic ABC ATPase of the ABCF subfamily that lacks transmembrane domains and functions at the interface of innate immunity and translational regulation (PMID:11435397). Purified ABCF3 exhibits lipid-stimulated ATPase activity with asymmetric contributions from its two nucleotide-binding domains—NBD1 mediates basal catalysis while NBD2 mediates lysophospholipid-stimulated hydrolysis—and the ABCF3–OAS1B complex localizes to the endoplasmic reticulum membrane, where ABCF3 knockdown specifically increases West Nile virus replication in OAS1B-expressing cells (PMID:31413116, PMID:22623793). ABCF3 binds 2′-5′-oligoadenylate innate immune second messengers produced by OAS enzymes, linking it to the OAS signaling axis (PMID:37676257). The C. elegans ortholog ABCF-3 physically interacts with GCN-1 to promote eIF2α phosphorylation and apoptosis through a pathway distinct from CED-9/BCL-2 signaling, a function conserved with the S. cerevisiae homolog (PMID:25101958).

1. 1996 Medium

   Identification of ABCF3 as a novel ABC superfamily gene and its chromosomal mapping established it as a distinct locus warranting functional characterization.

   Evidence EST database searching and PCR-based mapping on somatic cell and radiation hybrid panels

   PMID:8894702

   Open questions at the time

   • No expression data or functional characterization at this stage
   • Subfamily placement not yet determined
2. 2001 Medium

   Phylogenetic classification of ABCF3 into the transmembrane-domain-lacking ABCF subfamily predicted it acts as a soluble ATPase rather than a transporter, redirecting functional hypotheses away from membrane transport.

   Evidence Phylogenetic analysis of all human ABC nucleotide-binding domain sequences

   PMID:11435397

   Open questions at the time

   • Computational prediction only; no biochemical confirmation of ATPase activity or subcellular localization
3. 2012 High

   Discovery that ABCF3 physically interacts with the flavivirus-resistance protein OAS1B and that ABCF3 knockdown specifically increases West Nile virus replication in OAS1B-expressing cells established a direct role in innate antiviral defense.

   Evidence Yeast two-hybrid, reciprocal co-immunoprecipitation of in vitro-translated and full-length mammalian proteins, RNAi knockdown with viral replication assay

   PMID:22623793

   Open questions at the time

   • Enzymatic mechanism of ABCF3 contribution to OAS1B pathway unknown
   • Whether ABCF3 antiviral function extends beyond flaviviruses untested
4. 2014 High

   The C. elegans ortholog ABCF-3 was shown to interact with GCN-1 and regulate eIF2α phosphorylation to promote apoptosis independently of canonical BCL-2 signaling, revealing an evolutionarily conserved link between ABCF-3 and translational control of cell death.

   Evidence Genetic epistasis, in vivo co-immunoprecipitation, eIF2α phosphorylation assay, cross-species complementation with S. cerevisiae homologs, RNAi

   PMID:25101958

   Open questions at the time

   • Whether mammalian ABCF3 similarly regulates eIF2α phosphorylation not tested
   • Mechanism by which ABCF-3/GCN-1 complex promotes eIF2α kinase activity unresolved
   • Structural basis of ABCF-3–GCN-1 interaction unknown
5. 2019 High

   Biochemical reconstitution demonstrated that ABCF3 is a lipid-stimulated ATPase with functionally asymmetric NBDs, and that it co-localizes with OAS1B at ER membranes and modulates OAS1B protein levels, providing the first mechanistic basis for the ABCF3–OAS1B functional interaction.

   Evidence In vitro ATPase assay with purified protein, Walker motif mutagenesis, fluorescent ATP analog binding, bacterial co-expression growth assay, confocal microscopy

   PMID:31413116

   Open questions at the time

   • Physiological lipid ligand in vivo not identified
   • No structural model of the ABCF3–OAS1B complex
   • How lipid stimulation of ATPase activity connects to antiviral function remains unclear
6. 2023 Medium

   Identification of ABCF3 as a 2′-5′-oligoadenylate-binding protein linked it to the canonical OAS second messenger system, though a direct functional consequence of this binding for ABCF3 could not be demonstrated.

   Evidence Mass spectrometry-based affinity pulldown from human, mouse, and Drosophila lysates; Walker motif mutagenesis (validated for ABCF1)

   PMID:37676257

   Open questions at the time

   • Functional consequence of 2′-5′-OA binding by ABCF3 not established
   • Walker motif requirements validated for ABCF1 but not directly for ABCF3 in this study
   • Whether 2′-5′-OA modulates ABCF3 ATPase activity untested

• It remains unknown whether mammalian ABCF3 regulates eIF2α phosphorylation as its C. elegans ortholog does, how its lipid-stimulated ATPase activity connects mechanistically to antiviral function, and what the structural basis of the ABCF3–OAS1B complex is.
• No mammalian in vivo evidence for eIF2α regulation by ABCF3
• No structural model of ABCF3 or ABCF3–OAS1B complex
• Physiological lipid ligand and its regulation in innate immunity unknown