期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2020
卷号：117
期号：37
页码：23033-23043
DOI：10.1073/pnas.2010417117
出版社：The National Academy of Sciences of the United States of America
摘要：Numerous rhodopsin mutations have been implicated in night blindness and retinal degeneration, often with unclear etiology. D190N-rhodopsin (D190N-Rho) is a well-known inherited human mutation causing retinitis pigmentosa. Both higher-than-normal spontaneous-isomerization activity and misfolding/mistargeting of the mutant protein have been proposed as causes of the disease, but neither explanation has been thoroughly examined. We replaced wild-type rhodopsin (WT-Rho) in Rho D190N/WT mouse rods with a largely “functionally silenced” rhodopsin mutant to isolate electrical responses triggered by D190N-Rho activity, and found that D190N-Rho at the single-molecule level indeed isomerizes more frequently than WT-Rho by over an order of magnitude. Importantly, however, this higher molecular dark activity does not translate into an overall higher cellular dark noise, owing to diminished D190N-Rho content in the rod outer segment. Separately, we found that much of the degeneration and shortened outer-segment length of Rho D190N/WT mouse rods was not averted by ablating rod transducin in phototransduction—also consistent with D190N-Rho’s higher isomerization activity not being the primary cause of disease. Instead, the low pigment content, shortened outer-segment length, and a moderate unfolded protein response implicate protein misfolding as the major pathogenic problem. Finally, D190N-Rho also provided some insight into the mechanism of spontaneous pigment excitation.
关键词：D190N-rhodopsin ; spontaneous isomerization ; protein misfolding ; night blindness ; retinitis pigmentosa
