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

Abstract

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.

EphA4 Signaling Regulates Phospholipase Cγ1 Activation, Cofilin Membrane Association, and Dendritic Spine Morphology

“…This is in contrast to the transferrin receptor, a nonraft localized receptor associated with the cell membrane, whose membrane association was not altered by U73122 treatment. These results are in accordance with other reports that indicate that a portion of cofilin is associated with the cell periphery (Suzuki et al, 1995;Heyworth et al, 1997). Interestingly, we also found that transfection of EphA4 alone could reduce the levels of cofilin found in the membrane fraction.…”

Vascular Endothelial Growth Factor Causes Translocation of p47 to Membrane Ruffles through WAVE1

“…Oxidant production is also most prominent in actively migrating endothelial cells at the margin of a monolayer wound and, in particular, is concentrated in membrane ruffles of these highly motile cells (10). This localization of oxidant production is comparable to that found in phorbol-ester-stimulated neutrophils whose oxidative burst is concentrated within ruffling membranes (11). Consistent with these observations, we recently found constitutive localization of the NADPH oxidase subunit p47 phox to the cytoskeleton of endothelial cells with translocation of p47-GFP to membrane ruffles (12).…”

Interaction of Cofilin with Triose-phosphate Isomerase Contributes Glycolytic Fuel for Na,K-ATPase via Rho-mediated Signaling Pathway

“…In recent studies, it has been shown that human cofilin forms oligomers, which exhibit actin severing activity, and human cyclase-associated protein-1 is a key factor in the recycling of cofilin and actin (9,10). It has been reported that in some cell types, the dephosphorylation of cofilin occurs in a calcium-dependent or -independent manner and accompanies nuclear uptake (11)(12)(13)(14)(15)(16)(17)(18). On the other hand, dephosphorylation without nuclear uptake occurs in thyroid cells, and nuclear accumulation without dephosphorylation occurs in myotubes (19,20).…”