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KMID : 0613820030130060903
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Journal of Life Science
2003 Volume.13 No. 6 p.903 ~ p.910
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Effects of Protein Kinase G on Phospholipase D Activity of Human Neutrophils
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Park Ji-Yeon
Lee Min-Jung
Jang Min-Jung
Lee Sung-Young
Bae Yoe-Sik
Kwak Jong-Young
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Abstract
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Phospholipase D (PLD) plays an important role as a signaling molecule in the activation of neutrophils. In this study, effect of nitric oxide (NO) and cGMP on the activation of PLD in human neutrophils was investigated. Sodium nitroprusside (SNP), an agent to produce NO spontaneously in cells, alone increased PLD activity and the maximal activation was obtained with 0.5 mM SNP. Dibutyryl-cAMP, an agent to increase an intracellular cAMP concentration inhibited formyl-Met-Leu-Phe (fMLP)-stimulated PLD activity but 8-bromo-cGMP (300μM), an agent to increase an intracellular cGMP concentration did not affect basal and fMLP-stimulated PLD activity. NO-induced activation of PLD was not blocked by KT 5823, an inhibitor of cGMP-dependent protein kinase (PKG), suggesting that NO-induced PLD activation is not mediated by cGMP. NO also stimulated p38 mitogen activated protein kinase (MAPK) in human neutrophils, indicated by increased phosphorylation of p38 MAPK in Western blotting. NO-induced phosphorylation of p38 MAPK was not inhibited by KT 5823 or n-butanol. RhoA, an regulatory factor of PLD activation was translocated from cytosolic fraction to plasma membranes by fMLP or phorbol ester, and fMLP-stimulated but not phorbol ester-stimulated translocation of RhoA was inhibited by cGMP. These results suggest that NO stimulates PLD activity through other unidentified factor(s) than cGMP even though cGMP inhibits the activation of RhoA.
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KEYWORD
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Neutrophils, phospholipase D, nitric oxide, cGMP, RhoA, protein kinase G
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