title: Two functional active conformations of the integrin {alpha}2{beta}1, depending on activation condition and cell type.
abstract: For several integrins, the existence of multiple conformational states has been studied intensively. For the integrin alpha2beta1, a major collagen receptor on platelets and other cell types, however, no such experimental data were available thus far. Recently, our group has developed a monoclonal antibody IAC-1 sensitive to the molecular conformation of alpha2beta1 because it only binds to the activated state of alpha2beta1 on platelets, induced upon inside-out signaling. By investigating IAC-1 binding in combination with collagen binding after inside-out stimulation and outside manipulation, we demonstrated the existence of three different conformations of alpha2beta1 on platelets and Chinese hamster ovary cells as follows: (i) a nonactivated, resting state with no collagen nor IAC-1 binding; (ii) an intermediate state, induced by outside manipulation, with collagen but no IAC-1 binding; and (iii) a fully activated state, induced after inside-out stimulation, with both collagen and IAC-1 binding. Moreover, these different conformational states of alpha2beta1 are dependent on the cell type where alpha2beta1 is expressed, as IAC-1 binding to peripheral blood mononuclear cells and Jurkat cells could also be induced by outside manipulation, in contrast to platelets and alpha2beta1-expressing Chinese hamster ovary cells. Finally, we revealed a functional relevance for these different conformational states because the conformation of alpha2beta1, induced after outside manipulation, resulted in significantly more cell spreading on coated collagen compared with nonactivated or inside-out stimulated cells.
authors.affiliation: Laboratories for Thrombosis Research, Interdisciplinary Research Centre, Katholieke Universiteit Leuven, Campus Kortrijk, 8500 Kortrijk, Belgium.
authors.forename: Gerlinde R
authors.initials: GR
authors.lastname: Van de Walle
authors.forename: Karen
authors.initials: K
authors.lastname: Vanhoorelbeke
authors.forename: Zsuzsa
authors.initials: Z
authors.lastname: Majer
authors.forename: Eszter
authors.initials: E
authors.lastname: Illyés
authors.forename: Johan
authors.initials: J
authors.lastname: Baert
authors.forename: Inge
authors.initials: I
authors.lastname: Pareyn
authors.forename: Hans
authors.initials: H
authors.lastname: Deckmyn
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology*; D001792:Blood Platelets / Q000276:immunology / Q000378:metabolism*; D016466:CHO Cells; D002448:Cell Adhesion; D024042:Collagen Type I / Q000378:metabolism*; D006224:Cricetinae; D006801:Humans; D038982:Integrin alpha2beta1 / Q000737:chemistry* / Q000276:immunology / Q000378:metabolism*; D019169:Jurkat Cells; D007963:Leukocytes, Mononuclear / Q000378:metabolism; D010446:Peptide Fragments / Q000138:chemical synthesis / Q000378:metabolism; D010973:Platelet Adhesiveness / Q000276:immunology; D011487:Protein Conformation
chemical_list: D000199:Actins; D000911:Antibodies, Monoclonal; D024042:Collagen Type I; D038982:Integrin alpha2beta1; D010446:Peptide Fragments