Alternative titles; symbols
HGNC Approved Gene Symbol: ARMH3
Cytogenetic location: 10q24.32 Genomic coordinates (GRCh38) : 10:101,845,599-102,056,173 (from NCBI)
ARMH3 is a GBF1 (603698)-binding protein involved in Golgi maintenance and secretion (Chan et al., 2019). ARMH3 interacts with PI4KB (602758), which has implications for viral replication and sphingomyelin (SM) synthesis (McPhail et al., 2020, Mizuike et al., 2023).
Using BLAST searches, Chan et al. (2019) found that C10ORF76 is present in a wide variety of organisms. Analysis of mCherry-tagged C10ORF76 expression in HeLa cells showed that C10ORF76 localized to the Golgi as a peripheral membrane protein that cycled on and off Golgi membranes. Chan et al. (2019) stated that C10ORF76 has a molecular mass of 78.7 kD and contains a DUF1741 domain.
Using fluorescence microscopy, McPhail et al. (2020) showed that GFP-tagged C10ORF76 localized to the Golgi of transfected HEK293 cells.
Gross (2024) mapped the ARMH3 gene to chromosome 10q24.32 based on an alignment of the ARMH3 sequence (GenBank NM_024541) with the genomic sequence (GRCh38).
Using a biotinylation approach, Chan et al. (2019) identified C10ORF76 as a Golgi-localized protein proximal to GBF1 in HeLa cells. Knockdown analysis showed that C10ORF76 was involved in Golgi maintenance and regulation of GBF1 recruitment, as C10ORF76 knockdown resulted in Golgi fragmentation, redistribution of GBF1, and impaired GBF1 recruitment in HeLa cells. Immunoprecipitation analysis revealed that C10ORF76 interacted with GBF1 through its C-terminal region. By binding to GBF1, C10ORF76 rapidly cycled on and off GBF1-positive Golgi structures. Further analysis demonstrated that C10ORF76 was also required for maintaining cellular secretory activity, as C10ORF76 knockdown impaired cellular secretion.
Using pull-down assays, McPhail et al. (2020) showed that C10ORF76 directly interacted with PI4KB. C10ORF76 did not directly bind the PI4KB-binding partners RAB11 (605570) and ACBD3 (606809) alone, but it could form ternary PI4KB-containing complexes with both. Hydrogen-deuterium exchange mass spectrometry (HDX-MS) identified an interface between PI4KB and C10ORF76 mediated by a disorder-to-order transition of a PI4KB N-lobe linker. The PI4KB N-lobe linker contains a consensus PKA motif (RRxS) that corresponds to the conserved Ser496 and was directly phosphorylated by PKA to modulate the affinity of the C10ORF76-PI4KB complex. Analysis with PI4KB and C10ORF76 mutants that disrupted their complex formation but did not alter their catalytic activity or protein folding revealed that PI4KB recruited C10ORF76 to the Golgi and that the C10ORF76-PI4KB interface was required for proper localization of C10ORF76 to the Golgi. Knockout of C10ORF76 in HAP1 cells led to decreased PI4P levels and disruption of GBF1/active ARF1 (103180) localization with minimal effects on Golgi morphology, indicating that C10ORF76 regulated active ARF1 dynamics and maintained Golgi PI4P levels. Furthermore, replication of C10ORF76-dependent enteroviruses required intact C10ORF76-PI4KB interaction, suggesting that functions of C10ORF76 were selectively hijacked by specific viruses.
Fang et al. (2023) identified ARMH3 as a regulator of STING (612374) activation, as deletion of ARMH3 abolished STING activation in HT1080 cells. ARMH3 interacted with the Golgi-localized protein PI4KB and functioned as an adaptor to bridge STING and PI4KB at the Golgi for STING activation. The kinase activity of PI4KB was required for STING activation because PI4KB recruited by ARMH3 synthesized PI4P around STING at the Golgi membrane. PI4P was essential for STING activation, as accumulated cellular PI4P caused CGAS (613973)-independent STING autoactivation, with the participation of PI4P-binding proteins in a lipid environment optimal for STING activation. Analysis of mouse lung fibroblasts with Armh3 deletion and of mice with macrophage-specific deletion of Armh3 indicated that Armh3 was required for the host defense against DNA virus, highlighting the importance of ARMH3 in STING activation and innate immune responses.
By genomewide knockout screening, Mizuike et al. (2023) identified C10ORF76, ACBD3, and PI4KB as genes related to resistance to lysenin, a sphingomyelin (SM)-binding cytolysin. The 3 genes were involved in the metabolism of Golgi-embedded phosphatidylinositol 4-monophosphate (PtdIns(4)P) at the membrane contact sites (MCSs) between the ER and the Golgi apparatus. Moreover, all 3 genes were involved in endoplasmic reticulum-to-Golgi trafficking of ceramide by CERT (604677), and ceramide transferred by CERT was converted to sphingomyelin. Knockout of PI4KB, ACBD3, or C10ORF76 conferred lysenin resistance to HeLa cells, with PI4KB knockout alone providing full lysenin-resistance and knockout of either ACBD3 or C10ORF76 providing only partial resistance, suggesting that ACBD3 and C10ORF76 may have essentially distinct but partially redundant roles. Moreover, in cells with PI4KB, ACBD3, or C10ORF76 knockout, the content of SM was decreased, as these genes were required for the CERT-mediated synthesis of SM. However, neither the phosphoregulation nor the protein expression of CERT was compromised by disruption of PI4KB, ACBD3, and C10ORF76. Instead, PI4KB, ACBD3, and recruitment of CERT to the Golgi apparatus caused a reduction in the synthesis of SM in cells with the deletion of those genes. ACBD3, C10ORF76, or both, were required for the Golgi recruitment of PI4KB. However, C10ORF76 was predominantly localized at distal Golgi regions where SM synthesis primarily occurs, whereas the majority of ACBD3 was localized at more proximal Golgi regions, indicating that distinct pools of PtdIns(4)P were generated in different subregions, even within the same organelle, to facilitate interorganelle metabolic channeling for the ceramide-to-SM conversion.
Chan, C. J., Le, R., Burns, K., Ahmed, K., Coyaud, E., Laurent, E. M. N., Raught, B., Melancon, P. BioID performed on Golgi enriched fractions identify C10orf76 as a GBF1 binding protein essential for Golgi maintenance and secretion. Molec. Cell. Proteomics 18: 2285-2297, 2019. [PubMed: 31519766] [Full Text: https://doi.org/10.1074/mcp.RA119.001645]
Fang, R., Jiang, Q., Jia, X., Jiang, Z. ARMH3-mediated recruitment of PI4KB directs Golgi-to-endosome trafficking and activation of the antiviral effector STING. Immunity 56: 500-515, 2023. [PubMed: 36921576] [Full Text: https://doi.org/10.1016/j.immuni.2023.02.004]
Gross, M. B. Personal Communication. Baltimore, Md. 7/2/2024.
McPhail, J. A., Lyoo, H., Pemberton, J. G., Hoffmann, R. M., van Elst, W., Strating, J. R. P. M., Jenkins, M. L., Stariha, J. T. B., Powell, C. J., Boulanger, M. J., Balla, T., van Kuppeveld, F. J. M., Burke, J. E. Characterization of the c10orf76-PI4KB complex and its necessity for Golgi PI4P levels and enterovirus replication. EMBO Rep. 21: e48441, 2020. [PubMed: 31829496] [Full Text: https://doi.org/10.15252/embr.201948441]
Mizuike, A., Sakai, S., Katoh, K., Yamaji, T., Hanada, K. The C10orf76-PI4KB axis orchestrates CERT-mediated ceramide trafficking to the distal Golgi. J. Cell Biol. 222: e202111069, 2023. [PubMed: 37195633] [Full Text: https://doi.org/10.1083/jcb.202111069]