Photopigment quenching is Ca2+ dependent and controls response duration in salamander L-cone photoreceptors.
Photopigment quenching is Ca2+ dependent and controls response duration in salamander L-cone photoreceptors.
复制标题
感光色素猝灭是 Ca2+ 依赖性的，并控制蝾螈 L 锥光感受器的响应持续时间。
DOI：
10.1085/jgp.200910394
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发表时间：
2010
期刊：
影响因子：
--
通讯作者：
Sampath,AlapakkamP
中科院分区：
文献类型：
--
作者：
Matthews,HughR;Sampath,AlapakkamP
A major focus of phototransduction research over the past decade has been to understand the mechanisms governing the recovery of the light response, as these influence the visual system’s ability to respond to repeated or prolonged stimulation (for review see Burns and Baylor, 2001; Fain et al., 2001; Lamb and Pugh, 2006). Sensory transduction in rods and cones is initiated by the light activation of a G protein–coupled receptor, which, along with a covalently bound 11-cis retinal chromophore, forms the photopigment. Light-activated photopigment (R*) activates a heterotrimeric G protein (transducin), which disinhibits an effector enzyme, cyclic guanosine monophosphate (cGMP) phosphodiesterase (PDE). The increase in PDE activity hydrolyzes cGMP and allows CNG channels to close, hyperpolarizing the photoreceptor and reducing synaptic glutamate release. The ensuing reduction in Ca2+ influx through the CNG channels is accompanied by continuing Ca2+ efflux via Na-Ca, K exchange, leading to a decline in outer segment [Ca2+] during the light response (Yau and Nakatani, 1985), which acts to accelerate cGMP synthesis by guanylyl cyclase (Koch and Stryer, 1988), to speed R* quenching by phosphorylation (Kawamura, 1993) and increase the cGMP affinity of the CNG channel (Hsu and Molday, 1993).
