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Nature. 1991 Jan 31;349(6308):420-3.

Calcium-dependent regulation of cyclic GMP phosphodiesterase by a protein from frog retinal rods.

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1
Department of Physiology, Keio University School of Medicine, Tokyo, Japan.

Abstract

In vertebrate photoreceptors, light reduces cyclic GMP concentration and closes cGMP-activated channels to induce a hyperpolarizing response. 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. This is believed to be one of the mechanisms of light-adaptation produced by activation of guanylate cyclase. Effects of Ca2+ on the cGMP phosphodiesterase (PDE) have been reported, but their physiological significance has remained unclear. We have perfused the inside-out preparation of a frog rod outer segment (I/O ROS, originally termed truncated ROS, 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.

PMID:
1846944
DOI:
10.1038/349420a0
[Indexed for MEDLINE]
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