We studied the degranulation reaction of electropermeabilized human neutrophils induced by 1,2-didecanoyl-3-sn-phosphatidic acid (PA10). PA10 dose-dependently induced the release of β-glucuronidase, an enzyme of azurophil granules, but did not induce the release of lactoferrin, a protein of specific granules. The enzyme release by PA10 absolutely required Ca2+, ATP, and Mg2+ and the concentrations for the half-maximal response were 2.5 μM, 60 μM, and 0.25 mM, respectively. Although Ca2+ alone at concentrations higher than 10 μM induced the release of both β-glucuronidase and lactoferrin, the extents of the release were far less than that of the β-glucuronidase release by PA10. Phorbol myristate acetate (PMA) and 1-oleoyl-2-acetyl-sn-glycerol induced the release of lactoferrin alone at concentrations of Ca2+ below 0.5 μM while they induced the release of both β-glucuronidase and lactoferrin at higher Ca2+ concentrations, indicating that the degranulation induced by PA10 is not mediated by diacylglycerol which might be formed from PA. The degranulation reactions induced by PA10 and PMA were dose-dependently inhibited by staurosporine and calphostin C, protein kinase C inhibitors, although no direct activation of protein kinase C by PA10 was observed. The extent of the β-glucuronidase release by PA10 was not enhanced by the addition of PMA. Propranolol, which inhibits protein kinase C as well as phosphatidic acid phosphohydrolase, strongly inhibited the degranulation reactions induced by PA10 and PMA. Ethanol, a metabolic modulator of phospholipase D, and cyclic AMP did not affect the degranulation reactions by PMA and PA10. These observations suggest that selective enzyme release from azurophil granules of the permeabilized neutrophils might be induced through the activation of protein kinase C or some other protein kinase sensitive to the protein kinase C inhibitors and that phospholipase D may not be involved in the PMA-induced release.
|Number of pages||7|
|Journal||Journal of biochemistry|
|Publication status||Published - Feb 1994|
All Science Journal Classification (ASJC) codes
- Molecular Biology