title: Actin polymerization localizes to the activated epidermal growth factor receptor in the plasma membrane, independent of the cytosolic free calcium transient.
abstract: Epidermal growth factor (EGF) induces rapid actin filament assembly in the membrane skeleton of A431 cells, leading to a approximately 30% rise in cellular filamentous actin levels. EGF-induced actin polymerization depends upon EGF receptor (EGFR) tyrosine kinase activity, since the selective tyrosine kinase inhibitor AG213 abolishes EGF-induced actin polymerization. In accordance, confocal laser scanning microscopy shows that newly assembled actin filaments localize selectively to the tyrosine-phosphorylated EGFR in the plasma membrane, since actin polymerization is not observed at the internalized tyrosine-phosphorylated EGFR. Actin binding proteins (ABP's) are generally believed to regulate actin filament assembly. Ca2+ is known as one of the important regulatory factors for the activity of ABP's in vitro [15]. Therefore, we investigated the importance of the EGF-induced transient rise in [Ca2+]i for the regulation of actin polymerization in vivo. Continuous high [Ca2+]i in the millimolar range induces a prominent rise in cellular filamentous actin levels to approximately 50% over control cells. However, actin polymerization is unimpaired under conditions which effectively block the EGF-induced [Ca2+]i transient. These data demonstrate that EGF-induced actin polymerization localizes to the activated EGFR in the membrane skeleton, independent of the cytosolic free calcium transient.
authors.affiliation: Department of Molecular Cell Biology, University of Utrecht, The Netherlands.
authors.forename: P J
authors.initials: PJ
authors.lastname: Rijken
authors.forename: S M
authors.initials: SM
authors.lastname: Post
authors.forename: W J
authors.initials: WJ
authors.lastname: Hage
authors.forename: P M
authors.initials: PM
authors.lastname: van Bergen en Henegouwen
authors.forename: A J
authors.initials: AJ
authors.lastname: Verkleij
authors.forename: J
authors.initials: J
authors.lastname: Boonstra
mesh_terms: D000199:Actins / Q000032:analysis / Q000187:drug effects / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002294:Carcinoma, Squamous Cell; D002396:Catechols / Q000494:pharmacology; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D004533:Egtazic Acid / Q000494:pharmacology; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D066246:ErbB Receptors / Q000032:analysis / Q000037:antagonists & inhibitors / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D006801:Humans; D007700:Kinetics; D046911:Macromolecular Substances; D018613:Microscopy, Confocal; D009570:Nitriles / Q000494:pharmacology; D010766:Phosphorylation; D012878:Skin Neoplasms; D013997:Time Factors; D014407:Tumor Cells, Cultured; D020032:Tyrphostins
chemical_list: D000199:Actins; D002396:Catechols; D046911:Macromolecular Substances; D009570:Nitriles; D020032:Tyrphostins; C060152:tyrphostin 47; D000001:Calcimycin; D004533:Egtazic Acid; D004815:Epidermal Growth Factor; D000255:Adenosine Triphosphate; D066246:ErbB Receptors; D002118:Calcium