Showing papers by "Michael D. Pierschbacher published in 1986"

Platelet membrane glycoprotein IIb/IIIa: member of a family of Arg-Gly-Asp--specific adhesion receptors

Abstract: Adhesive interactions of the platelet surface with plasma proteins such as fibrinogen and fibronectin play an important role in thrombosis and hemostasis. The binding of both of these proteins to platelets is inhibited by synthetic peptides containing the sequence Arg-Gly-Asp, which corresponds to the cell adhesion site in fibronectin and is also present in the alpha chain of fibrinogen. An affinity matrix made of an insolubilized heptapeptide containing the Arg-Gly-Asp sequence selectively binds the platelet membrane glycoprotein IIb/IIIa from detergent extracts of platelets. When incorporated into liposome membranes, the isolated protein confers to the liposomes the ability to bind to surfaces coated with fibrinogen, fibronectin, and vitronectin but not to surfaces coated with thrombospondin or albumin. This platelet receptor is related to the previously identified fibronectin and vitronectin receptors in that it recognizes an Arg-Gly-Asp sequence but differs from the other receptors in its wider specificity toward various adhesive proteins. These results establish the existence of a family of adhesion receptors that recognize the sequence Arg-Gly-Asp.

cDNA and amino acid sequences of the cell adhesion protein receptor recognizing vitronectin reveal a transmembrane domain and homologies with other adhesion protein receptors

Abstract: Cells adhere to vitronectin substrates through a cell surface receptor that recognizes an Arg-Gly-Asp sequence in vitronectin. The receptor is a glycoprotein composed of a 150-kDa alpha and a 115-kDa beta subunit. The alpha subunit consists of two disulfide-bonded chains of 125 kDa and 25 kDa. cDNA clones were isolated for the alpha subunit of the vitronectin receptor from a phage lambda gt11 expression library made with RNA from a human fibroblast cell line, IMR-90. The identity of the clones that had been selected from the library based on immunological criteria was verified by comparison of DNA and protein sequences. NH2-terminal sequences were obtained for each of the alpha-subunit chains. The sequence of the 25-kDa chain of the alpha subunit was found in a cDNA clone, and the amino acid sequence deduced from the cDNA establishes the complete amino acid sequence of the 25-kDa chain. This chain contains a membrane-spanning domain as well as a putative intracytoplasmic region that is 32 amino acids long and consists mostly of polar amino acids. Comparison of the cDNA and protein sequences shows that the 25-kDa chain is generated by proteolytic cleavage of an alpha-subunit precursor, the partial sequence of which is contained in the cDNA clones. These clones contain 1910 base pairs of open reading frame and a 3' untranslated sequence. RNA blot hybridization detected one transcript of about 7 kilobases in RNA from fibroblastic and epithelial cells. Together, the cDNA clones cover 4442 bases of this RNA. The alpha-subunit sequence showed strong homology with the sequence of the alpha subunit of fibronectin receptor. Moreover, the NH2-terminal protein sequence of the 125-kDa chain was homologous with the NH2-terminal sequences of two other cell surface proteins, lymphocyte function-associated antigen 1 (LFA-1) and macrophage antigen 1 (Mac-1), which have been implicated as receptors for adhesion proteins of leukocytes. These results establish several of the structural features in the vitronectin receptor and suggest the existence of a superfamily of receptors for cell adhesion proteins.

T-lymphocyte differentiation and the extracellular matrix: identification of a thymocyte subset that attaches specifically to fibronectin.

Abstract: A population of murine thymocytes adheres specifically to fibronectin but not to vitronectin, laminin, or collagen type I. The interaction of these thymocytes with fibronectin could be inhibited by the synthetic peptide Gly-Arg-Gly-Asp-Ser-Pro, which comprises the previously identified cell-attachment determinant of the molecule, suggesting that the cell attachment site on fibronectin is recognized by these cells. A similar peptide, in which the aspartate residue had been replaced with glutamate, had no effect on this adhesion. The fibronectin-adherent thymocytes were found to be cortisone-sensitive; to bind peanut agglutinin; to have a Thy-1.2+, Ia- surface phenotype; and to express H-2 antigen only weakly on their surface. In addition, approximately 80% of the fibronectin-adherent cells expressed L3T4 and 80% expressed Ly-1 on their surface, whereas greater than 95% were positive for Ly-2. The data suggest that these cells, which constitute 10% of all thymic lymphocytes, are cortical thymocytes. We propose that their adhesion to fibronectin may be important for their differentiation. The binding to fibronectin provides a means to selectively isolate these cells for study.