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.
Cancer Center, University of New Mexico School of Medicine, Albuquerque 87131.
M
M
Eberle
A E
AE
Traynor-Kaplan
L A
LA
Sklar
J
J
Norgauer
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