title: Direct binding of F actin to the cytoplasmic domain of the alpha 2 integrin chain in vitro.
abstract: The transmembrane integrins have been shown to interact with the cytoskeleton via noncovalent binding between cytoplasmic domains (CDs) of integrin beta chains and various actin binding proteins within the focal adhesion complex. Direct or indirect integrin alpha chain CD binding to the actin cytoskeleton has not been reported. We show here that actin, as an abundant constituent of focal adhesion complex proteins isolated from fibroblasts, binds strongly and specifically to alpha 2 CD, but not to alpha 1 CD peptide. Similar specific binding to alpha 2 CD peptide was seen for highly purified F actin, free of putative actin-binding proteins. The bound complex of actin and peptide was visualized directly by coprecipitation, and actin binding was abrogated by removal of a five amino acid sequence from the alpha 2 CD peptide. Our findings may explain the earlier observation that, while integrins alpha 2 beta 1 and alpha 1 beta 1 both bind to collagen, only alpha 2 beta 1 can mediate contraction of extracellular collagen matrices.
authors.affiliation: Harvard Skin Disease Research Center, Division of Dermatology, Brigham and Women's Hospital, Boston, MA 02115, USA.
authors.forename: J D
authors.initials: JD
authors.lastname: Kieffer
authors.forename: G
authors.initials: G
authors.lastname: Plopper
authors.forename: D E
authors.initials: DE
authors.lastname: Ingber
authors.forename: J H
authors.initials: JH
authors.lastname: Hartwig
authors.forename: T S
authors.initials: TS
authors.lastname: Kupper
mesh_terms: D000199:Actins / Q000378:metabolism*; D000595:Amino Acid Sequence; D015703:Antigens, CD / Q000378:metabolism*; D002448:Cell Adhesion; D002478:Cells, Cultured; D003593:Cytoplasm / Q000378:metabolism; D018260:Gelsolin / Q000378:metabolism; D006801:Humans; D039421:Integrin alpha2; D046911:Macromolecular Substances; D008297:Male; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism; D010456:Peptides, Cyclic / Q000378:metabolism; D011485:Protein Binding
chemical_list: D000199:Actins; D015703:Antigens, CD; D018260:Gelsolin; D039421:Integrin alpha2; D046911:Macromolecular Substances; D010446:Peptide Fragments; D010456:Peptides, Cyclic; C017613:phallacidin