title: Phospholipid-sensitive Ca2+-dependent protein kinase and its substrates in human neutrophils.
abstract: Phospholipid-sensitive Ca2+-dependent protein kinase (PL-Ca-PK) was found to be present at a high level in human neutrophils, with its activity localized in the particulate fraction. In contrast, cyclic AMP-dependent protein kinase (A-PK) and cyclic GMP-dependent protein kinase (G-PK), present at lower levels compared to PL-Ca-PK, were localized in the cytosolic fraction. Phosphorylation of several endogenous proteins (mol. wts. 89,000, 38,000, 34,000, 17,000 and 15,000), also localized in the particulate fraction, was stimulated specifically by a combination of phosphatidylserine and Ca2+, whereas no substrate proteins were observed for the calmodulin-sensitive Ca2+-dependent protein kinase system under the same incubation conditions. Although no substrate proteins for G-PK were detected, one substrate (mol. wt. 19,000) for A-PK was observed. Phosphorylation of substrates for PL-Ca-PK, but not that for A-PK and for enzymes independent of Ca2+ or cyclic AMP, was inhibited by a variety of agents, including trifluoperazine, W-7 [N-(6-aminohexyl)-5-chloro-1-naphthalene-sulfonamide], adriamycin, palmitoylcarnitine, and melittin. The present findings suggest that the phospholipid/Ca2+-stimulated protein phosphorylation system may be important in the membrane associated functions of human neutrophils.
mesh_terms: D000328:Adult; D002118:Calcium / Q000494:pharmacology*; D002462:Cell Membrane / Q000201:enzymology; D000242:Cyclic AMP / Q000494:pharmacology; D006152:Cyclic GMP / Q000494:pharmacology; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D009504:Neutrophils / Q000201:enzymology*; D010743:Phospholipids / Q000494:pharmacology*; D010766:Phosphorylation; D011494:Protein Kinases / Q000097:blood*; D012995:Solubility; D013379:Substrate Specificity
chemical_list: D010743:Phospholipids; D000242:Cyclic AMP; D011494:Protein Kinases; D006152:Cyclic GMP; D002118:Calcium