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Possible Involvement of Mitogen‐Activated Protein Kinase in Phospholipase D Activation Induced by H 2 O 2 , but Not by Carbachol, in Rat Pheochromocytoma PC12 Cells
Author(s) -
Ito Yuzuru,
Nakashima Shigeru,
Nozawa Yoshinori
Publication year - 1998
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.1998.71062278.x
Subject(s) - carbachol , protein kinase a , mitogen activated protein kinase , chemistry , microbiology and biotechnology , protein kinase c , pheochromocytoma , phospholipase c , kinase , endocrinology , biochemistry , biology , signal transduction , receptor
Abstract: We have previously reported that hydrogen peroxide (H 2 O 2 ) induced a considerable increase of phospholipase D (PLD) activity and phosphorylation of mitogen‐activated protein (MAP) kinase in PC12 cells. H 2 O 2 ‐induced PLD activation and MAP kinase phosphorylation were dose‐dependently inhibited by a specific MAP kinase kinase inhibitor, PD 098059. In contrast, carbachol‐mediated PLD activation was not inhibited by the PD 098059 pretreatment whereas MAP kinase phosphorylation was prevented. These findings indicated that MAP kinase is implicated in the PLD activation induced by H 2 O 2 , but not by carbachol. In the present study, H 2 O 2 also caused a marked release of oleic acid (OA) from membrane phospholipids in PC12 cells. As we have previously shown that OA stimulates PLD activity in PC12 cells, the mechanism of H 2 O 2 ‐induced fatty acid liberation and its relation to PLD activation were investigated. Pretreatment of the cells with methylarachidonyl fluorophosphonate (MAFP), a phospholipase A 2 (PLA 2 ) inhibitor, almost completely prevented the release of [ 3 H]OA by H 2 O 2 treatment. From the preferential release of OA and sensitivity to other PLA 2 inhibitors, the involvement of a Ca 2+ ‐independent cytosolic PLA 2 ‐type enzyme was suggested. In contrast, to OA release, MAFP did not inhibit PLD activation by H 2 O 2 . The inhibitory profile of the OA release by PD 098059 did not show any correlation with that of MAP kinase. These results lead us to suggest that H 2 O 2 ‐induced PLD activation may be mediated by MAP kinase and also that H 2 O 2 ‐mediated OA release, which would be catalyzed by a Ca 2+ ‐independent cytosolic PLA 2 ‐like enzyme, is not linked to the PLD activation in PC12 cells.