title: Chemoattractants stimulate phosphatidylinositol-4-phosphate kinase in human polymorphonuclear leukocytes.
abstract: Chemoattractant receptor-mediated hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP2) by phospholipase C is instrumental for leukocyte activation. Previous studies have demonstrated that chemoattractant treatment of intact polymorphonuclear leukocytes (PMN) causes a transient decrease in PIP2 due to phospholipase C activation, followed by an increase in cellular PIP2 levels. The present study determined whether chemoattractants altered the activities of the two enzymes responsible for the synthesis of PIP2, phosphatidylinositol kinase, and phosphatidylinositol-4-phosphate (PIP) kinase. Incubation of intact PMN with the N-formylated peptide chemoattractant formyl-methionyl-leucyl-phenylalanine at 37 degrees C caused a rapid (3 min), 2-fold stimulation of PIP kinase activity isolated from a particulate membrane fraction. The increase in PIP kinase was dose-dependent for a variety of N-formylated chemoattractants as well as leukotriene B4. Lineweaver-Burk analysis showed that the Vmax of PIP kinase was increased 2-fold by formyl-methionyl-leucyl-phenylalanine, without a significant change in the apparent Km of the enzyme for ATP. Phosphatidylinositol kinase was, however, not altered by any chemoattractants tested. Nonchemotactic activators of the oxidative burst in leukocytes such as phorbol myristate acetate and ionophore A23187 did not significantly alter PIP kinase, suggesting a specificity for chemotactic agents. These findings demonstrate direct, chemoattractant-induced stimulation of PMN PIP kinase which may serve to replenish the important phospholipid, PIP2, in the membrane following its hydrolysis by phospholipase C.
authors: Arthritis Unit, Massachusetts General Hospital, Harvard Medical School, Boston 02114.
authors: M C
authors: MC
authors: Pike
authors: M E
authors: ME
authors: Bruck
authors: C
authors: C
authors: Arndt
authors: C S
authors: CS
authors: Lee
mesh_terms: D019870:1-Phosphatidylinositol 4-Kinase; D000255:Adenosine Triphosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002630:Chemotactic Factors / Q000494:pharmacology*; D003571:Cytochalasin B / Q000494:pharmacology; D006801:Humans; D007700:Kinetics; D008969:Molecular Sequence Data; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000031:analogs & derivatives* / Q000494:pharmacology*; D009504:Neutrophils / Q000201:enzymology*; D010770:Phosphotransferases / Q000097:blood*; D017853:Phosphotransferases (Alcohol Group Acceptor); D013329:Structure-Activity Relationship; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D002630:Chemotactic Factors; D003571:Cytochalasin B; D009240:N-Formylmethionine Leucyl-Phenylalanine; D000255:Adenosine Triphosphate; D010770:Phosphotransferases; D017853:Phosphotransferases (Alcohol Group Acceptor); D019870:1-Phosphatidylinositol 4-Kinase; C020077:1-phosphatidylinositol-4-phosphate 5-kinase; D013755:Tetradecanoylphorbol Acetate