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Protein kinase-dependent phosphorylation and cannabinoid receptor modulation of potassium A current (I A) in cultured rat hippocampal neurons

Protein kinase-dependent phosphorylation and cannabinoid receptor modulation of potassium A... The potent cannabinoid receptor agonist WIN 55,212-2 produces positive shifts in steady-state inactivation of the potassium A current (I A) in rat hippocampal neurons via an adenosine 3',5'-cyclic monophosphate (cAMP)-, protein kinase A (PKA)-dependent process. This effect is probably mediated by phosphorylation or dephosphorylation of the I A channel protein. The role of protein phosphorylation in this cascade was tested by testing cannabinoid actions in cultured hippocampal neurons (pyramidal cells) that were exposed also to either the catalytic subunit of PKA (PKAc), a PKA-specific phosphorylation inhibitor (IP-20, Walsh peptide), or a potent protein phosphatase inhibitor (okadaic acid). Cannabinoids such as WIN 55,212-2 produce a positive (rightwards) shift in the steady-state inactivation of I A, thus providing increased current at a given membrane voltage. Cells dialyzed with PKAc showed a negative shift in I A inactivation, opposite to that produced by cannabinoids, and similar to that produced by increased levels of cAMP. In addition, PKAc completely blocked the positive shift produced by WIN 55,212-2. In contrast, dialysis of cells with IP-20 produced a positive shift in steady state inactivation of I A, similar to that produced by WIN, but the effects were not additive with cannabinoid receptor activation. The phosphatase inhibitor, okadaic acid produced a small negative shift in I A steady-state inactivation when administered alone, and blocked the positive shift produced by WIN 55,212-2. Okadaic acid also enhanced the negative shift in I A inactivation when co-administered with forskolin. The effects of okadaic acid and WIN 55,212-2 were not additive, suggesting a common pathway. These results demonstrate that I A is altered by direct manipulations of the phosphorylation status of the channel protein, and that cannabinoid effects on I A are probably mediated by dephosphorylation of the I A channel. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Pflügers Archiv European Journal of Physiologyl of Physiology Springer Journals

Protein kinase-dependent phosphorylation and cannabinoid receptor modulation of potassium A current (I A) in cultured rat hippocampal neurons

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Publisher
Springer Journals
Copyright
Copyright © 2000 by Springer-Verlag
Subject
Biomedicine; Human Physiology; Molecular Medicine; Neurosciences; Cell Biology; Receptors
ISSN
0031-6768
eISSN
1432-2013
DOI
10.1007/s004249900231
Publisher site
See Article on Publisher Site

Abstract

The potent cannabinoid receptor agonist WIN 55,212-2 produces positive shifts in steady-state inactivation of the potassium A current (I A) in rat hippocampal neurons via an adenosine 3',5'-cyclic monophosphate (cAMP)-, protein kinase A (PKA)-dependent process. This effect is probably mediated by phosphorylation or dephosphorylation of the I A channel protein. The role of protein phosphorylation in this cascade was tested by testing cannabinoid actions in cultured hippocampal neurons (pyramidal cells) that were exposed also to either the catalytic subunit of PKA (PKAc), a PKA-specific phosphorylation inhibitor (IP-20, Walsh peptide), or a potent protein phosphatase inhibitor (okadaic acid). Cannabinoids such as WIN 55,212-2 produce a positive (rightwards) shift in the steady-state inactivation of I A, thus providing increased current at a given membrane voltage. Cells dialyzed with PKAc showed a negative shift in I A inactivation, opposite to that produced by cannabinoids, and similar to that produced by increased levels of cAMP. In addition, PKAc completely blocked the positive shift produced by WIN 55,212-2. In contrast, dialysis of cells with IP-20 produced a positive shift in steady state inactivation of I A, similar to that produced by WIN, but the effects were not additive with cannabinoid receptor activation. The phosphatase inhibitor, okadaic acid produced a small negative shift in I A steady-state inactivation when administered alone, and blocked the positive shift produced by WIN 55,212-2. Okadaic acid also enhanced the negative shift in I A inactivation when co-administered with forskolin. The effects of okadaic acid and WIN 55,212-2 were not additive, suggesting a common pathway. These results demonstrate that I A is altered by direct manipulations of the phosphorylation status of the channel protein, and that cannabinoid effects on I A are probably mediated by dephosphorylation of the I A channel.

Journal

Pflügers Archiv European Journal of Physiologyl of PhysiologySpringer Journals

Published: Mar 20, 2000

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