Regulation of phosphatidic acid phosphohydrolase activity during stimulation of human polymorphonuclear leukocytes.
Phosphatidic acid phosphohydrolase (PPH) activity was determined in human polymorphonuclear leukocytes (PMNs) by measuring the hydrolysis of [32P]phosphatidic acid (PA) added to cell sonicates. Enzyme activity was localized primarily to a soluble fraction. Soluble and particulate activities required magnesium and were inhibited by calcium, N-ethylmaleimide, sphingosine, and propranolol. The activity in unstimulated PMNs was 0.64 +/- 0.11 nmol of PA hydrolyzed.mg protein-1.min-1 in particulate and 4.20 +/- 0.42 in soluble fractions. Stimulation of PMNs with 1 microM f-Met-Leu-Phe (FMLP) for 10 min caused a slight decrease in soluble activity and a small increase in the activity of particulate fractions. Preincubation with 10 microM cytochalasin B for 5 min before FMLP stimulation markedly enhanced both of these changes. The effect of FMLP plus cytochalasin B was rapid (less than 10 s), whereas the calcium ionophore A23187 (1 microM) and phorbol myristate acetate (100 ng/ml) caused slower and smaller changes in enzyme activity. These results indicate that after chemoattractant stimulation; PPH activity decreases in the soluble fraction and increases in the particulate fraction suggesting that PPH may participate in signal transduction in the PMN.
Truett
A P
AP
Department of Medicine, Vanderbilt University, Medical Center, Nashville, Tennessee 37232-0111.
Bocckino
S B
SB
Murray
J J
JJ
D000001:Calcimycin / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D009504:Neutrophils / Q000187:drug effects / Q000201:enzymology*; D010711:Phosphatidate Phosphatase / Q000378:metabolism*; D015398:Signal Transduction; D013347:Subcellular Fractions / Q000201:enzymology; D013379:Substrate Specificity; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013997:Time Factors
D000001:Calcimycin; D009240:N-Formylmethionine Leucyl-Phenylalanine; D010711:Phosphatidate Phosphatase; D013755:Tetradecanoylphorbol Acetate