DMXL1

DMXL1 (Rabconnectin-3α) is a large WD-repeat protein that functions as a V-ATPase assembly factor controlling organelle acidification (PMID:10708522, PMID:26442671). It is the central subunit of the heterotrimeric metazoan RAVE complex (mRAVE), associating with WDR7 and the linker subunit ROGDI, which structurally mimics yeast Rav2 binding to Rav1 (PMID:40646309, PMID:40049412). Through an ATP6V1A (subunit A) and subunit D binding interface defined by structural modeling and cross-linking proteomics, DMXL1 (together with DMXL2) engages inactive cytosolic V1 and bridges it to membrane-embedded VO, catalyzing holoenzyme assembly upon dissipation of proton gradients or TRPML1/CASM-dependent lysosomal signaling (PMID:40646309, PMID:40527988). This assembly activity drives lysosomal acidification, autophagic and ATG8/CASM membrane conjugation, and neurotransmitter loading into vesicles (PMID:40646309, PMID:40527988). In vivo, intercalated-cell-specific Dmxl1 deletion raises urine pH and impairs V1–VO co-assembly at the membrane, establishing DMXL1 as required for V-ATPase holoenzyme formation (PMID:38984989), and TPL-2 kinase phosphorylates DMXL1 to promote phagosome acidification and bacterial killing in macrophages (PMID:33881780). DMXL1 is essential for early mouse development, with knockout causing pre-organogenesis embryonic lethality (PMID:41330162). Human cytomegalovirus exploits this axis: its US33A protein recruits the KPC E3 ubiquitin ligase to ubiquitinate and degrade DMXL1, blocking lysosomal acidification and autophagic degradation (PMID:38479395).

1. 2000 Medium

   Established the molecular identity of DMXL1 as a large WD-repeat protein and human homologue of Drosophila DmX, providing the gene structure on which all later functional work was built.

   Evidence cDNA cloning, radiation hybrid mapping, and FISH

   PMID:10708522

   Open questions at the time

   • No functional or biochemical role assigned
   • No interaction partners identified
   • Cellular localization not determined
2. 2015 Medium

   Connected DMXL1 to the V-ATPase by showing physical association and a requirement for vesicle acidification, defining its functional pathway for the first time.

   Evidence MS-based V-ATPase interactome and siRNA knockdown acidification assay in a kidney cell line

   PMID:26442671

   Open questions at the time

   • Did not define which V-ATPase subunits DMXL1 contacts
   • Mechanism of action on V-ATPase not resolved
   • Single cell-line context
3. 2021 High

   Identified a regulatory input on DMXL1, showing that TPL-2 phosphorylation promotes V-ATPase assembly and links DMXL1 to innate-immune bacterial killing.

   Evidence Phagosome proteomics, TPL-2 inhibitor, phosphosite MS, and bacterial killing assays in primary mouse and human macrophages

   PMID:33881780

   Open questions at the time

   • Phosphosite-to-assembly mechanistic link not structurally resolved
   • Other kinases/phosphatases acting on DMXL1 unknown
4. 2024 High

   Provided in vivo proof that DMXL1 is required for V-ATPase holoenzyme assembly in a physiological epithelium, by showing impaired V1–VO co-assembly and acidification on knockout.

   Evidence Intercalated-cell conditional KO mice with urine pH, western blot, fractionation, PLA, and immunofluorescence

   PMID:38984989

   Open questions at the time

   • Molecular interface mediating assembly not yet defined here
   • Tissue-restricted readout
5. 2024 High

   Revealed DMXL1 as a viral target, defining a US33A/KPC ubiquitin-degradation mechanism by which HCMV disables lysosomal acidification and autophagy.

   Evidence HCMV proteomics, deletion mutants, co-IP, lysosome acidification and autophagy assays

   PMID:38479395

   Open questions at the time

   • Ubiquitination site on DMXL1 not mapped
   • Consequences for V-ATPase complex stoichiometry not detailed
6. 2025 High

   Resolved the molecular architecture, defining DMXL1 as the core of the heterotrimeric mRAVE complex with WDR7 and ROGDI and mapping its V1 subunit A/D binding interfaces that catalyze V1–VO supercomplex assembly.

   Evidence Cryo-EM/AlphaFold modeling, cross-linking MS, co-IP, mutagenesis, and acidification/neurotransmitter/ATG8 conjugation assays; ROGDI subunit and TRPML1/CASM-dependent recruitment confirmed across independent studies

   PMID:40049412 PMID:40527988 PMID:40646309

   Open questions at the time

   • Conformational steps of catalyzed assembly not fully visualized
   • Division of labor between DMXL1 and DMXL2 not fully defined
7. 2025 Medium

   Established DMXL1 as an essential mammalian gene, showing knockout causes pre-organogenesis embryonic lethality while patient-orthologous missense alleles were not pathogenic in mice.

   Evidence CRISPR allelic series in mice with embryonic lethality assessment

   PMID:41330162

   Open questions at the time

   • Developmental process requiring DMXL1 not identified
   • Discrepancy with human variant pathogenicity unexplained

• How DMXL1-driven V-ATPase assembly is selectively deployed across tissues, signaling states, and cellular compartments — and the basis of its essential developmental role — remains open.
• Functional distinction between DMXL1 and DMXL2 not resolved
• Developmental substrate of essentiality unknown
• Full catalytic cycle of assembly not structurally defined