Fundus albipunctatus disease-associated RDH5/L310delinsEV mutation undertakes AMFR-mediated polyubiquitination and degradation in proteasome

Abstract

Genetic mutations in retinol dehydrogenase 5 (RDH5) are associated with the inherited autosomal recessive retinal degeneration diseases, especially fundus albipunctatus (FA). Most of RDH5 mutants exhibit downregulation of RDH5 protein expression. However, the regulatory mechanism remains unclear. Here, we studied the metabolism of RDH5/L310delinsEV mutation, an indel mutation closely associated with the inherited FA disease. The half-life of RDH5/L310delinsEV was much less than RDH5/WT. Unlike RDH5/WT, which normally underwent degradation in autophagy-lysosomes, the RDH5/L310delinsEV reduced its location to the endoplasmic reticulum and was easy to be polyubiquitinated and degraded in the ubiquitin-proteasome pathway. Both RDH5/WT and RDH5/L310delinsEV interacted with autocrine motility factor receptor (AMFR), which is an E3 ligase on the endoplasmic reticulum. Overexpression of or knockdown of AMFR by siRNA increased or reduced the degradation of RDH5/L310delinsEV. The lysine 179 and lysine 263 of RDH5/L310delinsEV protein were polyubiquitination sites by AMFR. Mutation of K179R and K263R in RDH5/L310delinsEV protein reduced AMFR-mediated polyubiquitination and degradation. Taken together, these results highlight that RDH5/L310delinsEV mutant in RDH5 causes a rapid degradation in the ubiquitin-proteasome pathway. The fast degradation of RDH5/L310delinsEV may be associated with the FA development.