Cofilin undergoes rapid dephosphorylation in stimulated neutrophils and translocates to ruffled membranes enriched in products of the NADPH oxidase complex. Evidence for a novel cycle of phosphorylation and dephosphorylation.
Neutrophils contain a 21-kDa phosphoprotein that undergoes rapid dephosphorylation upon stimulation of these cells with the chemoattractant N-fMet-Leu-Phe (fMLP), activators of protein kinase C [e.g., 4 beta-phorbol 12-myristate 13-acetate (PMA)] or the calcium ionophore A23187. This phosphoprotein was identified as the non-muscle form of cofilin by peptide sequencing and immunoblotting with specific antibodies. Evidence is presented that in neutrophils cofilin is regulated by a continual cycle of phosphorylation and dephosphorylation, and that the phosphatase undergoes activation during cell stimulation. Experiments with a wide variety of antagonists further suggested that the protein kinase that participates in these reactions may be a novel enzyme. The kinetics of cofilin dephosphorylation in neutrophils stimulated with fMLP or PMA were very similar to those observed for superoxide (O2-) release. Immunofluorescent studies revealed that cofilin was present throughout the cytosol of resting neutrophils and underwent rapid translocation to the F-actin-rich, ruffled membranes of stimulated cells. Cytochemical analysis further revealed that the ruffled membranes also contained large amounts of hydrogen peroxide (H2O2), a product of the O2-/H2O2-generating activity of stimulated neutrophils (NADPH oxidase). Cofilin is therefore well placed to participate in the continual polymerization and depolymerization of F-actin that is thought to give rise to the oscillatory pattern of H2O2 production observed under certain conditions.
Heyworth
P G
PG
Department of Molecular and Experimental Medicine, Scripps Research Institute, La Jolla, California, USA.
Robinson
J M
JM
Ding
J
J
Ellis
B A
BA
Badwey
J A
JA
D051339:Actin Depolymerizing Factors; D000199:Actins / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D002462:Cell Membrane / Q000378:metabolism; D004075:Diglycerides / Q000494:pharmacology; D004224:Diterpenes; D006168:Guinea Pigs; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism; D015151:Immunoblotting; D008387:Marine Toxins; D008840:Microfilament Proteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D019255:NADPH Oxidases; D018375:Neutrophil Activation; D009504:Neutrophils / Q000187:drug effects / Q000378:metabolism*; D019319:Okadaic Acid / Q000494:pharmacology; D010080:Oxazoles / Q000494:pharmacology; D010087:Oxides / Q000378:metabolism; D010766:Phosphorylation; D019311:Staurosporine / Q000494:pharmacology; D013729:Terpenes / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D051339:Actin Depolymerizing Factors; D000199:Actins; D004075:Diglycerides; D004224:Diterpenes; D008387:Marine Toxins; D008840:Microfilament Proteins; D010080:Oxazoles; D010087:Oxides; D013729:Terpenes; C044295:1,2-dioctanoylglycerol; D019319:Okadaic Acid; C011309:mezerein; D000001:Calcimycin; D009240:N-Formylmethionine Leucyl-Phenylalanine; C059041:calyculin A; D006861:Hydrogen Peroxide; D019255:NADPH Oxidases; D019311:Staurosporine; D013755:Tetradecanoylphorbol Acetate