.alpha.1.beta.1 Integrin heterodimer functions as a dual laminin/collagen receptor in neural cells

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Abstract
A monoclonal antibody (3A3) raised against a rat neural cell line (PC12) was shown previously to bind to the surfaces of these cells, inhibiting substratum adhesion. Immunochemical and other data indicated that the heterodimer recognized by 3A3 was a member of the integrin family of adhesive receptors and had a .beta.1 subunit. The relationship of the .alpha. subunit to other integrins was unknown. Here we show that 3A3 recognizes in rat tissues a heterodimer (.apprx. 185 kDa, .apprx. 110 kDa; unreduced) that is electrophorectically and immunochemically indistinguishable from the antigen in PC12 cells. Immunoaffinity purification of the heterodimer from neonatal rats and protein microsequencing indicate that the .alpha. subunit is identical at 11 or 13 N-terminal residues with VLA-1, an integrin on human hematopoietic cells. Monoclonal antibody 3A3 inhibits the attachment of rat astrocytes to laminin or collagen but not to fibronectin or polylysine. These data suggest strongly that the integrin recognized by 3A3 is the rat homologue of VLA-1, i.e., .alpha.1.beta.1, and that .alpha.1.beta.1 is a dual laminin/collagen receptor.

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