Is there a relationship between phosphatidylinositol trisphosphate and F-actin polymerization in human neutrophils?
Stimulation of human neutrophils with the chemoattractant N-formyl peptide caused rapid polymerization of F-actin as detected by right angle light scatter and 7-nitrobenz-2-oxa-1,3-diazol (NBD)-phallacidin staining of F-actin. After labeling neutrophils with 32P, exposure to N-formyl peptide induced a fast decrease of phosphatidylinositol 4-bisphosphate (PIP)2, a slow increase of phosphatidic acid, and a rapid rise of phosphatidylinositol 4-trisphosphate (PIP3). Formation of PIP3 as well as actin polymerization was near maximal at 10 s after stimulation. Half-maximal response and PIP3 formation at early time points resulted from stimulation of neutrophils with 0.01 nM N-formyl peptide or occupation of about 200 receptors. Sustained elevation of PIP3, prolonged right angle light scatter response, and F-actin formation required higher concentrations of N-formyl peptide, occupation of thousands of receptors, and high binding rates. When ligand binding was interrupted with an antagonist, F-actin rapidly depolymerized, transient light scatter response recovered immediately, and elevated [32P]PIP3 levels decayed toward initial values. However, recovery of [32P]PIP2 was not influenced by the antagonist. Based on the parallel time courses and dose response of [32P] PIP3, the right angle light scatter response, and F-actin polymerization, PIP3 is more likely than PIP2 to be involved in modulation of actin polymerization and depolymerization in vivo.
Eberle
M
M
Cancer Center, University of New Mexico School of Medicine, Albuquerque 87131.
Traynor-Kaplan
A E
AE
Sklar
L A
LA
Norgauer
J
J
D000199:Actins / Q000097:blood*; D006801:Humans; D007700:Kinetics; D008027:Light; D046911:Macromolecular Substances; D009504:Neutrophils / Q000378:metabolism*; D010710:Phosphates / Q000097:blood; D010743:Phospholipids / Q000097:blood; D012542:Scattering, Radiation
D000199:Actins; D046911:Macromolecular Substances; D010710:Phosphates; D010743:Phospholipids