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J. Biol. Chem., Vol. 265, Issue 4, 1866-1873, Feb, 1990
MC Pike, ME Bruck, C Arndt and CS Lee
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.
Chemoattractants stimulate phosphatidylinositol-4-phosphate kinase in human polymorphonuclear leukocytes
Arthritis Unit, Massachusetts General Hospital, Harvard Medical School, Boston 02114.
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