by Emily Mason
Night blindness has been linked to mutations in the G-protein coupled receptor (GPCR) rhodopsin, which, when activated by light, undergoes a conformational change and triggers a cascade of events essential for sight.
Typically, the cascade is turned off by two other proteins, the kinase GRK1 and arrestin-1. Rhodopsin is then regenerated by 11-cis-retinal, which returns it to its original conformation, so that the cycle can begin again.
By studying how rhodopsin mutations alter GRK1 and arrestin-1 interactions, researchers hope to gain insight into disease mechanisms and potential therapeutic targets.
In the November issue of Cellular Signalling, Vsevolod Gurevich, Ph.D., professor of Pharmacology, and colleagues reported a surprising finding: during typical signaling arrestin-1 remains bound until rhodopsin is regenerated, thus preventing background signaling unrelated to light detection.
They also examined two rhodopsin mutations known to cause night blindness in humans. One of them, G90D, released arrestin-1 prematurely, while the other mutation, T941, bound arrestin-1 normally, suggesting that there is more than one mechanism behind night blindness.
This work was supported by National Institutes of Health grants EY011500, GM077561, GM081756, HL086865, HL071818, MH089378 and GM033775, the American Heart Association, and the Swiss National Science Foundation.
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