B-50/GAP-43 binds to actin filaments without affecting actin polymerization and filament organization.
To investigate a possible function of the nervous tissue-specific protein kinase C substrate B-50/GAP-43 in regulation of the dynamics of the submembranous cytoskeleton, we studied the interaction between purified B-50 and actin. Both the phosphorylated and dephosphorylated forms of B-50 cosedimented with filamentous actin (F-actin) in a Ca(2+)-independent manner. Neither B-50 nor phospho-B-50 had any effect on the kinetics of actin polymerization and on the critical concentration at steady state, as measured using pyrenylated actin. Light scattering of F-actin samples was not increased in the presence of B-50, suggesting that B-50 does not bundle actin filaments. The number of actin filaments, determined by [3H]cytochalasin B binding, was not affected by either phospho- or dephospho-B-50, indicating that B-50 has neither a severing nor a capping effect. These observations were confirmed by electron microscopic evaluation of negatively stained F-actin samples, which did not reveal any structural changes in the actin meshwork on addition of B-50. We conclude that B-50 is an actin-binding protein that does not directly affect actin dynamics.
Department of Medical Pharmacology, Rudolf Magnus Institute, University of Utrecht, The Netherlands.
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Hens
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Benfenati
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Nielander
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Valtorta
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Gispen
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De Graan
D000199:Actins / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D003571:Cytochalasin B / Q000378:metabolism; D019922:GAP-43 Protein; D007382:Intermediate Filaments / Q000648:ultrastructure*; D008562:Membrane Glycoproteins / Q000378:metabolism*; D008854:Microscopy, Electron; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D016900:Neurofilament Proteins / Q000378:metabolism*; D011108:Polymers / Q000378:metabolism*; D011493:Protein Kinase C / Q000494:pharmacology; D011817:Rabbits
D000199:Actins; D019922:GAP-43 Protein; D008562:Membrane Glycoproteins; D009419:Nerve Tissue Proteins; D016900:Neurofilament Proteins; D011108:Polymers; D003571:Cytochalasin B; D011493:Protein Kinase C; D002118:Calcium