Journal of Biological Chemistry vol:280 issue:44 pages:36873-36882
For several integrins, the existence of multiple conformational states has been studied intensively. For the integrin alpha 2 beta 1, 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 alpha 2 beta 1 because it only binds to the activated state of alpha 2 beta 1 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 alpha 2 beta 1 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 alpha 2 beta 1 are dependent on the cell type where alpha 2 beta 1 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 alpha 2 beta 1-expressing Chinese hamster ovary cells. Finally, we revealed a functional relevance for these different conformational states because the conformation of alpha 2 beta 1, induced after outside manipulation, resulted in significantly more cell spreading on coated collagen compared with nonactivated or inside-out stimulated cells.
Subfaculteit Wetenschappen Campus Kortrijk. Interdisciplinair Research centrum Campus Kortrijk (IRC) Faculteit Geneeskunde. Subfaculteit Geneeskunde Campus Kortrijk. Histologie Campus Kortrijk.