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Calcium rather than protein kinase C is the major factor to activate phospholipase D in FMLP-stimulated rabbit peritoneal neutrophils. Possible involvement of calmodulin/myosin L chain kinase pathway.
- Source :
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Journal of immunology (Baltimore, Md. : 1950) [J Immunol] 1992 Jul 15; Vol. 149 (2), pp. 622-8. - Publication Year :
- 1992
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Abstract
- In the present study, we first investigated which of the factors, protein kinase C (PKC) or Ca2+, plays an important role in activation of phospholipase D (PLD) of rabbit peritoneal neutrophils stimulated by the chemoattractant FMLP. PLD activity was assessed by measuring [3H]phosphatidylethanol ([3H]PEt), the unambiguous marker of PLD, generated by [3H]lyso platelet-activating factor-prelabeled neutrophils in the presence of ethanol. PKC inhibitors, staurosporine and 1-(5-isoquinolinesulfonyl-2-methylpiperazine dihydrochloride, augmented the plateau level of [3H]PEt produced in FMLP-stimulated cells, although they had no effect on the initial rate of the formation. Furthermore, it was found that the FMLP-stimulated [3H]PEt formation was inhibited by pretreatment of cells with PMA, a PKC activator, and exposure of cells to staurosporine before PMA pretreatment moderately blocked the PMA inhibition. Ca2+ ionophore ionomycin, as well as FMLP, stimulated [3H]PEt formation, accompanied by a decrease in [3H]phosphatidylcholine, in a time- and concentration-dependent manner. Both FMLP and ionomycin absolutely required extracellular Ca2+ to increase [3H]PEt formation. These results imply that elevated intercellular Ca2+ by FMLP stimulation is the major factor for PLD activation and that PKC rather negatively regulates the enzyme activity. Interestingly, a calmodulin inhibitor, N-(6-aminohexyl)-5-chloro-1- naphthalenesulfonamide, and a myosin L chain kinase inhibitor, 1-(5-iodonaphthalene-1-sulfonyl)-1H-h exahydro-1,4-diazepine hydrochloride, both inhibited the ionomycin- and FMLP-stimulated [3H]PEt formation in a concentration-dependent manner. Results obtained in this study suggest that, in FMLP-stimulated rabbit peritoneal neutrophils, increased intracellular Ca2+ activates PLD through calmodulin/myosin L chain kinase pathway and, thereafter, the enzyme activation is turned off by simultaneously activated PKC.
- Subjects :
- Animals
Arachidonic Acid pharmacology
Enzyme Activation
In Vitro Techniques
Peritoneal Cavity cytology
Phosphatidylethanolamines metabolism
Rabbits
Sulfonamides pharmacology
Tetradecanoylphorbol Acetate pharmacology
Calcium physiology
Calmodulin physiology
Myosin-Light-Chain Kinase physiology
N-Formylmethionine Leucyl-Phenylalanine pharmacology
Neutrophils enzymology
Phospholipase D analysis
Protein Kinase C physiology
Subjects
Details
- Language :
- English
- ISSN :
- 0022-1767
- Volume :
- 149
- Issue :
- 2
- Database :
- MEDLINE
- Journal :
- Journal of immunology (Baltimore, Md. : 1950)
- Publication Type :
- Academic Journal
- Accession number :
- 1624805