The co-chaperone and reductase ERdj5 facilitates rod opsin biogenesis and quality control

Abstract

Mutations in rhodopsin, the light-sensitive protein of rod cells, are the most common cause of autosomal dominant retinitis pigmentosa (ADRP). Many rod opsin mutations, such as P23H, lead to misfolding of rod opsin with detrimental effects on photoreceptor function and viability. Misfolded P23H rod opsin and other mutations in the intradiscal domain are characterized by the formation of an incorrect disulphide bond between C185 and C187, as opposed to the correct and highly conserved C110–C187 disulphide bond. Therefore, we tested the hypothesis that incorrect disulphide bond formation might be a factor that affects the biogenesis of rod opsin by studying wild-type (WT) or P23H rod opsin in combination with amino acid substitutions that prevent the formation of incorrect disulphide bonds involving C185. These mutants had altered traffic dynamics, suggesting a requirement for regulation of disulphide bond formation/reduction during rod opsin biogenesis. Here, we show that the BiP co-chaperone and reductase protein ERdj5 (DNAJC10) regulates this process. ERdj5 overexpression promoted the degradation, improved the endoplasmic reticulum mobility and prevented the aggregation of P23H rod opsin. ERdj5 reduction by shRNA delayed rod opsin degradation and promoted aggregation. The reductase and co-chaperone activity of ERdj5 were both required for these effects on P23H rod opsin. Furthermore, mutations in these functional domains acted as dominant negatives that affected WT rod opsin biogenesis. Collectively, these data identify ERdj5 as a member of the proteostasis network that regulates rod opsin biogenesis and supports a role for disulphide bond formation/reduction in rod opsin biogenesis and disease.

RETRACTED ARTICLE: Role of oxidative stress in Retinitis pigmentosa: new involved pathways by an RNA-Seq analysis

“…The downexpression of HSPA1A could be explained considering the reduction of the synthesis of proteins substrate of Hsp70. [48,[150][151][152][153][154][155][156][157][158][159][160][161][162][163] SMALL GTPASE SUPERFAMILY ALTERED SIGNALLING Under stress conditions KRAS (already known to be involved in Noonan syndrome) upregulation could determine an uncontrolled RPE cell proliferation or functional alterations.…”

The role of the ER stress-response protein PERK in rhodopsin retinitis pigmentosa

“…SK-N-SH human neuroblastoma cells were maintained and transfected essentially as previously described ( 41 ). Three hours after transfection and 2 h after recovery in serum, cells were either left untreated or treated with 100 nM to up to 1 μΜ GSK2606414A for 18 h. Immunofluorescence was performed as previously described ( 44 ).…”

Mechanisms of Photoreceptor Death in Retinitis Pigmentosa

“…The chaperone network involving ER degradation-enhancing α-mannisidose-like protein 1 (EDEM1), ER-resident protein containing DNA-J 5 (ERdj5) and binding immunoglobulin protein (BiP) mediates ER quality control and has been shown to interact with mutant rhodopsin [ 189 ]. Over-expression of these chaperones in vitro reduces P23H Rho aggregation and promotes the degradation of mutant protein [ 189 , 190 , 191 ]. Over-expression of BiP was also found to reduce CHOP expression and photoreceptor death in Rho P23H rats; this was proposed to be due to suppression of ER stress-induced apoptosis rather than improved protein folding [ 192 ].…”