Integrins α1β1 and α2β1: The Generalist Collagen Receptors

Four members of the large integrin family have the capability to directly recognize specific collagenous motifs in proteins. These integrins can be found in all vertebrates, but not in other animals. Thus, direct cell adhesion to collagens has evolved concomitantly with, e.g., the development of musculoskeletal system, closed blood circulatory system, and acquired immunity. Two integrin-type collagen receptors α1β1 and α2β1 are abundantly expressed in vertebrates and a growing pile of evidence indicates their involvement in numerous physiological functions. At the same time, the corresponding knockout mouse models show no obvious developmental defects. Thus, α1β1 and α2β1 are not critical for organogenesis, but they can be considered as generalist integrins that have evolved to support and intensify processes driven by other receptors and proteins.