Three heterotrimeric laminins produced by human keratinocytes.

Laminins are a family of glycoproteins composed of alpha,beta and gamma chains. Five alpha(alpha1-alpha5), three beta (beta1-beta3) and twogamma (gamma1 and gamma2) chains have been cloned fromhuman and their replaceable assembly into heterotrimers producesthe variety of laminins. Reverse transcription-polymerase chainreaction of mRNAs showed that human keratinocytes express thealpha3, alpha5, beta1, beta3, gamma1 andgamma2 genes at high level among the ten cloned lamininchains. Western blot and immunoprecipitation of the cell lysatewith antiserum directed against mouse laminin-1(alpha1beta1gamma1) detected two trimers with thecomposition of alphaxbeta1gamma1 (probablylaminin-10 with the composition of alpha5beta1gamma1and alphaybeta1gamma1. Meanwhile, antiserum directedagainst a synthetic peptide of human alpha3 detected onlyalpha3beta3gamma2 trimer (laminin-5). We thus show thatkeratinocytes produce three heterotrimeric laminins. We couldnot detect the assembly of alpha3 with beta1 and gamma1chains to form alpha3beta1gamma1 (laminin-6) in keratinocytes.