CALCIUM-DEPENDENT REGULATION OF CYCLIC-GMP PHOSPHODIESTERASE BY A PROTEIN FROM FROG RETINAL RODS
CALCIUM-DEPENDENT REGULATION OF CYCLIC-GMP PHOSPHODIESTERASE BY A PROTEIN FROM FROG RETINAL RODS
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DOI：
10.1038/349420a0
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发表时间：
1991-01-31
期刊：
影响因子：
64.8
通讯作者：
MURAKAMI, M
中科院分区：
文献类型：
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作者：
KAWAMURA, S;MURAKAMI, M
在脊椎动物的光感受器中，光降低环状GMP浓度并关闭cGMP激活的通道以诱导超极化反应1。由于Ca~(2+)可以渗透到通道内，Na~+-Ca~(2+)交换器不断地释放Ca~(2+)，通道的关闭导致杆间Ca~(2+)浓度降低2-4。这被认为是鸟苷环化酶5-9激活所产生的光适应机制之一。钙离子对cGMP磷酸二酯酶(PDE)的影响已有报道10-15，但其生理意义尚不清楚。我们已经灌流了由内向外准备的蛙杆外段(I/O ROS(Ref.16)，最初称为截断ROS(参考文献17))，发现生理范围内的Ca~(2+)对PDE的光激活有调节作用。因此，Ca~(2+)对PDE的调节必须参与杆状植物的光适应。这种作用是由一种新发现的蛋白质介导的，该蛋白质在高钙浓度下与盘膜结合，延长PDE的激活时间。
IN vertebrate photoreceptors, light reduces cyclic GMP concentration and closes cGMP-activated channels to induce a hyperpolarizing response 1. As Ca2+ can permeate the channels and the Na+ - CA2+ exchanger continuously extrudes Ca2+, closure of the channel results in a reduction of the inter-rod Ca2+ concentration 2-4. This is believed to be one of the mechanisms of light adaptation produced by activation of guanylate cyclase 5-9. Effects of Ca2+ on the cGMP phosphodiesterase (PDE) have been reported 10-15, but their physiological significance has remained unclear. We have perfused the inside-out preparation of a frog rod outer segment (I/O ROS (ref. 16), originally termed truncated ROS (ref. 17)), and find that Ca2+ in a physiological range regulates the light-activation of PDE. Therefore, PDE regulation by Ca2+ must be involved in light-adaptation in rods. The effect is mediated by a newly found protein which binds to disk membranes at high Ca2+ concentrations and prolongs PDE activation.