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Characterization of protein phosphatases type 1 and type 2A in Limulus nervous tissue: Their light regulation in the lateral eye and evidence of involvement in the photoresponse

Published online by Cambridge University Press:  02 June 2009

Samuel C. Edwards ,
Peter M. O'Day  and
Desiree C. Herrera
Samuel C. Edwards
Affiliation:
Departments of Biology and Pharmacology and Therapeutics and the Institute for Biomolecular Sciences, University of South Florida, Tampa
Peter M. O'Day
Affiliation:
Institute of Neuroscience and Department of Biology, University of Oregon, Eugene
Desiree C. Herrera
Affiliation:
Departments of Biology and Pharmacology and Therapeutics and the Institute for Biomolecular Sciences, University of South Florida, Tampa
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Abstract

The activities of both protein phosphatases and protein kinases are responsible for the transient changes in the levels of phosphorylation and probably the functions of protein intermediates involved in the biochemical and physiological mechanisms underlying the photoresponse in photoreceptor cells from both vertebrate and invertebrate organisms. Of the known protein serine/threonine phosphatases, various forms of type I (PP 1) and type 2A (PP 2A) protein phosphatases are responsible for dephosphorylating many of the known phosphoproteins including those involved in photoreceptor cell function. In this report, we provide biochemical evidence for both PP 1– and PP 2A-like activities in the visual and nonvisual tissue of the horseshoe crab, Limulus polyphemus, that membrane and soluble forms of both enzymes are present, and that the activities of both enzymes are greater in light- than in dark-adapted lateral eyes. These activities were characterized using glycogen phosphorylase a, a substrate for both PP 1 and PP 2A, and various protein phosphatase inhibitors, including okadaic acid. We also report that okadaic acid, at concentrations required to inhibit PP 1, inhibited physiological functions of photoreceptor cells from the ventral eye, causing a delayed reduction of the resting membrane, and slowing and reducing light responses.

Keywords

Limulus polyphemusPhotoreceptorLight regulationProtein phosphataseOkadaic acid
Type
Research Articles
Information
Visual Neuroscience , Volume 13 , Issue 1 , January 1996 , pp. 73 - 85
Copyright
Copyright © Cambridge University Press 1996

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