期刊
JOURNAL OF NEUROSCIENCE
卷 39, 期 2, 页码 212-223出版社
SOC NEUROSCIENCE
DOI: 10.1523/JNEUROSCI.1980-18.2018
关键词
bleaching adaptation; G-protein-coupled receptor; GCAP; opsin; rhodopsin; thermal activation
资金
- National Institutes of Health [EY026675, EY019312, EY009339, EY025214, EY02687]
- Research to Prevent Blindness
- NATIONAL EYE INSTITUTE [R01EY009339, P30EY002687] Funding Source: NIH RePORTER
Bleaching adaptation in rod photoreceptors is mediated by apo-opsin, which activates phototransduction with effective activity 10(5) - to 10(6) -fold lower than that of photoactivated rhodopsin (meta II). However, the mechanism that produces such low opsin activity is unknown. To address this question, we sought to record single opsin responses in mouse rods. We used mutant mice lacking efficient calcium feedback to boosts rod responses and generated a small fraction of opsin by photobleaching similar to 1% of rhodopsin. The bleach produced a dramatic increase in the frequency of discrete photoresponse-like events. This activity persisted for hours, was quenched by 11-cis-retinal, and was blocked by uncoupling opsin from phototransduction, all indicating opsin as its source. Opsin-driven discrete activity was also observed in rods containing non-activatable rhodopsin, ruling out transactivation of rhodopsin by opsin. We conclude that bleaching adaptation is mediated by opsin that exists in equilibrium between a predominant inactive and a rare meta II-like state.
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