Actin Polymerization Induced by GTPS in Permeabilized Neutrophils Is Induced and Maintained by Free Barbed Ends

To address the mechanisms through which agonists stimulate actin polymerization, we examined the roles of monomer sequestering proteins and free barbed ends on actin polymerization induced by guanosine 5′-3- O -(thio)triphosphate (GTP S) in neutrophils permeabilized with streptolysin O. Addition o...

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Bibliographic Details
Published in:The Journal of biological chemistry Vol. 270; no. 47; p. 28075
Main Authors: Marianne Tardif, Sherry Huang, Tim Redmond, Daniel Safer, Martin Pring, Sally H. Zigmond
Format: Journal Article
Language:English
Published: American Society for Biochemistry and Molecular Biology 24-11-1995
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Summary:To address the mechanisms through which agonists stimulate actin polymerization, we examined the roles of monomer sequestering proteins and free barbed ends on actin polymerization induced by guanosine 5′-3- O -(thio)triphosphate (GTP S) in neutrophils permeabilized with streptolysin O. Addition of profilin (without GTP S) caused a net decrease in F-actin. Thus, merely making profilin available in the cell was not sufficient to induce actin polymerization. On the other hand, addition of profilin hardly affected the polymerization induced by GTP S, while thymosin β or DNase I decreased this polymerization. These data suggested that GTP S induced polymerization by increasing the availability of barbed ends. In the presence of cytochalasin B, profilin did inhibit polymerization induced by GTP S, demonstrating that GTP S did not inhibit profilin's monomer sequestering ability. The F-actin induced by GTP S was not limited by a time-dependent loss of G-actin or G-proteins from permeabilized cells since, following stimulation with suboptimal concentrations of GTP S, addition of more GTP S induced further polymerization. Barbed ends remained free after F-actin reached plateau since ( a ) cytochalasin B caused depolymerization of induced F-actin and ( b ) profilin did not depolymerize induced F-actin unless the cells were first treated with cytochalasin to cap barbed ends. The data indicate that GTP S maintains an increased level of F-actin by keeping at least a few barbed ends available for polymerization.
ISSN:0021-9258
1083-351X
DOI:10.1074/jbc.270.47.28075