WDSUB1

WDSUB1 is a U-box domain-containing E3 ubiquitin ligase that functions within the ankle-link complex (ALC) of inner-ear hair cells to regulate the stability of USH2A (PMID:37066759). WDSUB1 binds phosphorylated WHRN and ubiquitinates USH2A, promoting its degradation; this interaction is controlled upstream by ADGRV1, which suppresses WHRN phosphorylation through regional cAMP-PKA signaling, and a deafness-associated ADGRV1 frameshift mutation abolishes this regulation (PMID:37066759). In intestinal epithelial contexts, WDSUB1 positively regulates NF-κB-mediated inflammatory cytokine expression, as its knockdown in a mouse colitis model reduces IL-6, COX-2, and TNF-α levels and alters IκBα protein abundance (PMID:36073209).

1. 2010 Low

   Computational identification of WDSUB1 as a U-box E3 ubiquitin ligase established its predicted enzymatic class, but left its substrates and biological roles unknown.

   Evidence Phylogenetic and structural domain analysis across metazoan genomes

   PMID:20979629

   Open questions at the time

   • No direct enzymatic assay confirming E3 ubiquitin ligase activity
   • No substrates or biological processes identified
   • Computational inference only, awaits biochemical reconstitution
2. 2022 Medium

   In vivo knockdown in a colitis model showed that WDSUB1 promotes NF-κB-dependent inflammatory signaling in intestinal epithelium, revealing a biological function but not a direct E3 substrate.

   Evidence siRNA knockdown in DSS-induced colitis in C57BL/6 mice with Western blot and RT-PCR readouts

   PMID:36073209

   Open questions at the time

   • No direct biochemical link between WDSUB1 E3 activity and IκBα or other NF-κB pathway substrates
   • siRNA specificity not independently validated by rescue or genetic knockout
   • Mechanism by which WDSUB1 regulates NF-κB signaling (direct ubiquitination target) remains unidentified
3. 2023 High

   Identification of WHRN as a direct binding partner and USH2A as a ubiquitination target established the first complete substrate-pathway assignment for WDSUB1 within the hair-cell ankle-link complex, placing it downstream of ADGRV1-cAMP-PKA signaling.

   Evidence Yeast two-hybrid, NMR spectrometry, FlAsH-BRET, mutagenesis, and Adgrv1 mutant mouse model

   PMID:37066759

   Open questions at the time

   • In vitro reconstitution of WDSUB1-catalyzed USH2A ubiquitination with purified components has not been reported
   • Structural basis for WDSUB1 U-box domain engagement with E2 enzymes is unknown
   • Whether WDSUB1 ubiquitinates additional substrates beyond USH2A in hair cells or other tissues is unresolved

• It remains unknown whether WDSUB1's E3 ligase activity directly ubiquitinates NF-κB pathway components, whether USH2A is the sole physiological substrate in hair cells, and what structural features govern WDSUB1 substrate selectivity.
• No structural model of WDSUB1 U-box or WD-repeat domains exists
• The relationship between the hair-cell and inflammatory signaling functions is unexplored
• No in vivo hair-cell phenotype from WDSUB1 loss-of-function has been reported