The receptor for the basement membrane glycoprotein entactin is the integrin α3/β1

Entactin is a glycoprotein found in basement membranes in complex with laminin, and purified entactin can promote the attachment and spreading of cells. We report here the isolation and identification of the plasma membrane receptor for entactin from PC-3 human prostate carcinoma cells which attach and spread on entactin. The receptor was isolated by affinity chromatography on mouse recombinant entactin-Sepharose of ¹²⁵I surface-labeled octyl glucoside cell extracts. The receptor, which consisted of two polypeptides of relative molecular masses of 150 and 116 kDa, bound to the entactin-Sepharose matrix in the presence of CaCl₂, MgCl₂, and MnCl₂, and was eluted with EDTA, but not with Arg-Gly-Asp-containing peptides. Utilizing anti-integrin antibodies, the heterodimeric receptor was identified as the integrin α3β1. Purified α3β1 bound to entactin Sepharose in a divalent cation-dependent manner and liposomes prepared with fractions eluted from the entactin-Sepharose matrix, as well as purified α3/β1 also bound to entactin. Liposomes prepared with other integrins such as α2β1 did not bind to entactin. Antibody inhibition assays demonstrated that an anti-α3 antibody (P1B5) inhibited the attachment of PC-3 cells to entactin whereas this antibody did not inhibit the attachment of these cells to laminin. Attachment to laminin was, however, blocked by anti-α6 antibody (GOH3). These data demonstrate that the cell surface receptor for entactin on these prostate carcinoma cells is the integrin α3β1 and that these cells utilize α6β1 as the receptor for laminin.