Demonstration of inositol phosphate 5-phosphomonoesterase activity in rabbit neutrophils: absence of a role for protein kinase C.
Rabbit peritoneal neutrophils, permeabilized with Triton X-100, contain inositol phosphate 5-phosphomonoesterase activity capable of converting [3H]inositol 1,4,5-trisphosphate (Ins-1,4,5-P3) to [3H]inositol 1,4-bisphosphate. This activity is found predominantly associated with the soluble component of fractionated neutrophils. It is comprised of specific and nonspecific activities toward Ins-1,4,5-P3 which can be separated by cation exchange chromatography. Treatment of neutrophils with phorbol 12-myristate 13-acetate (PMA) prior to permeabilization does not affect the rate of Ins-1,4,5-P3 breakdown by these cells. In addition, activation of endogenous protein kinase C in a soluble fraction prepared from neutrophils does not affect the specific inositol phosphate 5-phosphomonoesterase activity of this fraction. Taken together, these results provide evidence that activation of protein kinase C in the neutrophil does not affect its 5-phosphomonoesterase activity. Unlike platelets, the phosphorylation of a 5-phosphomonoesterase, if it occurs, may not play a role in the inhibitory effects of PMA on neutrophil responsiveness.
Kennedy
S P
SP
Department of Pathology, University of Connecticut Health Center, Farmington 06032.
Sha'afi
R I
RI
Becker
E L
EL
D000818:Animals; D003600:Cytosol / Q000201:enzymology; D006868:Hydrolysis; D009504:Neutrophils / Q000201:enzymology* / Q000378:metabolism; D010086:Oxidative Phosphorylation Coupling Factors / Q000378:metabolism; D010529:Peritoneal Cavity / Q000166:cytology; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism*; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism / Q000502:physiology*; D011817:Rabbits; D013755:Tetradecanoylphorbol Acetate; D013997:Time Factors
D010086:Oxidative Phosphorylation Coupling Factors; D011493:Protein Kinase C; D010744:Phosphoric Monoester Hydrolases; C021822:myo-inositol-1 (or 4)-monophosphatase; D013755:Tetradecanoylphorbol Acetate