title: The human integrin alpha 8 beta 1 functions as a receptor for tenascin, fibronectin, and vitronectin.
abstract: The integrin family of adhesion receptors consists of at least 21 heterodimeric transmembrane proteins that differ in their tissue distribution and ligand specificity. The recently identified alpha 8 integrin subunit associates with beta 1 and is predominantly expressed in smooth muscle and other contractile cells in adult tissues, and in mesenchymal and neural cells during development. We now show that alpha 8 beta 1 specifically localizes to focal contacts in cells plated on the extracellular matrix proteins fibronectin or vitronectin. In addition we show that human embryonic kidney cells (293), transfected with alpha 8 cDNA, express alpha 8 beta 1 on their surface and use this receptor for adhesion to fibronectin and vitronectin. Furthermore, alpha 8 beta 1 binds to both fibronectin- and vitronectin-Sepharose and can be specifically eluted from either matrix protein by the arginine-glycine-aspartic acid (RGD)-containing peptide, GRGDSP. Because fibronectin and vitronectin adhesion appeared to be mediated by RGD, we examined additional RGD-containing proteins, including tenascin, fibrinogen, thrombospondin, osteopontin, and denatured collagen type I. We found that only tenascin was able to mediate adhesion of alpha 8-transfected 293 cells. By using recombinant fragments of tenascin in adhesion assays, we were able to localize the alpha 8 beta 1 binding domain of tenascin to the RGD-containing third fibronectin type III repeat. These data strongly suggest that tenascin, fibronectin, and vitronectin are ligands for alpha 8 beta 1 and that this integrin binds to the RGD site in each of these ligands through mechanisms that are distinct and separate from alpha 5- and alpha v-containing integrins.
authors.affiliation: Department of Medicine, University of California, San Francisco 94143, USA.
authors.forename: L M
authors.initials: LM
authors.lastname: Schnapp
authors.forename: N
authors.initials: N
authors.lastname: Hatch
authors.forename: D M
authors.initials: DM
authors.lastname: Ramos
authors.forename: I V
authors.initials: IV
authors.lastname: Klimanskaya
authors.forename: D
authors.initials: D
authors.lastname: Sheppard
authors.forename: R
authors.initials: R
authors.lastname: Pytela
mesh_terms: D000328:Adult; D000375:Aging; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D002846:Chromatography, Affinity; D017931:DNA Primers; D004622:Embryo, Mammalian; D005353:Fibronectins / Q000378:metabolism*; D006801:Humans; D016023:Integrins / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism*; D007668:Kidney; D008969:Molecular Sequence Data; D009130:Muscle, Smooth / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism*; D009842:Oligopeptides / Q000494:pharmacology; D016133:Polymerase Chain Reaction; D051381:Rats; D011946:Receptors, Antigen / Q000378:metabolism; D017469:Receptors, Fibronectin / Q000378:metabolism; D019030:Receptors, Vitronectin / Q000378:metabolism; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism; D019063:Tenascin / Q000378:metabolism*; D014162:Transfection; D014407:Tumor Cells, Cultured; D019096:Vitronectin / Q000378:metabolism*
chemical_list: D017931:DNA Primers; D005353:Fibronectins; D016023:Integrins; D009842:Oligopeptides; D011946:Receptors, Antigen; D017469:Receptors, Fibronectin; D019030:Receptors, Vitronectin; D011994:Recombinant Proteins; D019063:Tenascin; C028641:Tn receptor; D019096:Vitronectin; C094866:integrin alpha8beta1