Molecular cloning of the rat integrin alpha 1-subunit: a receptor for laminin and collagen.

Abstract

Abstract. Integrin heterodimers mediate a variety of adhesive interactions, including neuronal attachment to and process outgrowth on laminin. We report here the cloning and primary sequence of an Mr-200 kD integrin oL subunit that associates with the integrin ~, subunit to form a receptor for both laminin and collagen. Similarities in ligand-binding specificity, relative molecular mass and NH2-terminal sequence make this a strong candidate for the rat homologue of the ot subunit of the human integrin VLA-1. The full-length rat oL1 cDNAs encode a protein containing a putative signal sequence and a mature polypeptide of 1,152 amino acids, with extracellular, transmembrane and cytoplasmic domains. Several structural features are conserved with other integrin o~ chains, including (a) a sequence motif repeated seven times in the NH2-terminal half; (b) potential Ca2+/Mg 2+ binding sites in repeats 5, 6, and 7, and (c) alignment of at least 14 of 23 cysteine residues. This rat ¢x~ sequence also contains a 206-amino acid I domain, inserted between repeats 2 and 3, that is homologous to I domains found in the same position in the alpha subunits of several integrins (VLA-2, Mac-l, LFA-1, p150). The rat o~t and human VLA-2 ¢x subunits share >50% sequence identity in the seven repeats and I domain, suggesting that these sequence identities may underlie some of their similar ligand-binding specificities. However, the rat integrin ¢x~ subunit has several unique features, including a 38-residue insert between two Ca2+/Mg 2+ binding domains, and a divergent 15-residue cytoplasmic sequence, that may potentially account for unique functions of this integrin.

Interaction of type IV collagen with the isolated integrins α1β1 and α2β1

“…Similar inhibitory or regulatory effects of Ca2+ were observed for the adhesion of platelets to collagen and the binding of a2p1 to collagen ligands (Santoro, 1986;Grzesiak et al, 1992). alp1 and a2pl are described as typical collagen and laminin receptors (Tomaselli et al, 1988;Kramer and Marks, 1989;Clyman et al, 1990;Staats et al, 1989;Ignatius et al, 1990;Hynes, 1987;Hall et al, 1990;Languino et al, 1989). To test our system, we compared the binding of the two integrins to several extracellular constituents.…”

“…Data represent means of triplicates, deviation below 10%. Marks, 1989;Clyman et al, 1990;Staatz et al, 1989;Ignatius et al, 1990), e.g. the fiber forming collagens I and I11 ( Fig.…”

Laminin-binding integrin alpha 7 beta 1: functional characterization and expression in normal and malignant melanocytes.

“…Rat monoclonal antia6 (GoH3) and rabbit anti-a6 was a gift from Dr. Arnoud Sonnenberg, Netherlands Cancer Institute (Sonnenberg et al, 1988). Rabbit antiserum to C-terminal peptide of al and a2 was provided by Dr. Louis Reichardt, University of California, San Francisco (Ignatius et al, 1990), whereas rabbit antibodies to the C-terminus of a3 and a5 were a gift from Dr. Richard Hynes, MIT, Cambridge, MA. Goat anti-mouse IgG-Sepharose and goat anti-rat IgG-Sepharose were from Sigma Chemical Co. (St. Louis, MO).…”

A synthetic peptide derived from the carboxy terminus of the laminin A chain represents a binding site for the alpha 3 beta 1 integrin

“…Interactions of cells with laminin have been shown to be mediated by both integrin-type cell surface receptors (Hemler et al, 1987;Gehlsen et al, 1989;Sonnenberg et al, 1988;Ignatius et al, 1990) and by other nonintegrin molecules including a 67-kD protein (Malinoff and Wicha, 1983;Wewer et al ., 1987) and 01,4 galactosyltransferase (Begovac et al ., 1991) .…”