title: Mutation of the cytoplasmic domain of the integrin beta 3 subunit. Differential effects on cell spreading, recruitment to adhesion plaques, endocytosis, and phagocytosis.
abstract: The cytoplasmic domain of the beta subunit of the alpha IIb beta 3 integrin is required for cell spreading on fibrinogen. Here we report that deletion of six amino acids from the COOH terminus of the beta 3 (I757TYRGT) totally abolished cell spreading and formation of adhesion plaques, whereas retaining Ile757 partially preserved these functions. We further found that substitution of Tyr747 with Ala also abolished alpha IIb beta a-mediated cell spreading. The effects of these and other mutations on additional functions of alpha IIb beta 3 were also studied. Progressive truncations of beta 3, in which stop codons were inserted at amino acid positions 759-756, caused partial defects in the recruitment of alpha IIb beta 3 to preestablished adhesion plaques and a gradual decrease in the ability of alpha IIb beta 3 to mediate internalization of fibrinogen-coated particles. The Tyr747-->Ala substitution mutant was almost totally inactive in both of these assays. Point mutations at Tyr759, and at a conserved area close to the transmembrane domain of beta 3, decreased integrin recruitment to preestablished adhesion plaques but allowed alpha IIb beta 3-mediated formation of these structures and partial cell spreading. Deletion of the cytoplasmic domain of beta 3 did not affect the constitutive endocytosis of alpha IIb beta 3.
authors.affiliation: Department of Biochemistry, University of Helsinki, Finland.
authors.forename: J
authors.initials: J
authors.lastname: Ylänne
authors.forename: J
authors.initials: J
authors.lastname: Huuskonen
authors.forename: T E
authors.initials: TE
authors.lastname: O'Toole
authors.forename: M H
authors.initials: MH
authors.lastname: Ginsberg
authors.forename: I
authors.initials: I
authors.lastname: Virtanen
authors.forename: C G
authors.initials: CG
authors.lastname: Gahmberg
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D016466:CHO Cells; D002448:Cell Adhesion; D006224:Cricetinae; D003593:Cytoplasm; D004705:Endocytosis; D039661:Integrin beta3; D016023:Integrins / Q000737:chemistry / Q000502:physiology*; D008969:Molecular Sequence Data; D009154:Mutation; D010587:Phagocytosis; D013329:Structure-Activity Relationship
chemical_list: D039661:Integrin beta3; D016023:Integrins