Three heterotrimeric laminins produced by human keratinocytes

Laminins are a family of glycoproteins composed of alpha, beta and gamma ch ains. Five alpha (alpha 1-alpha 5), three beta (beta 1-beta 3) and two gamm a (gamma 1 and gamma 2) chains have been cloned from human and their replac eable assembly into heterotrimers produces the variety of laminins. Reverse transcription-polymerase chain reaction of mRNAs showed that human keratin ocytes express the alpha 3, alpha 5, beta 1, beta 3, gamma 1 and gamma 2 ge nes at high level among the ten cloned laminin chains. Western blot and imm unoprecipitation of the cell lysate with antiserum directed against mouse l aminin-1 (alpha 1 beta 1 gamma 1) detected two trimers with the composition of alpha x beta 1 gamma 1 (probably laminin-10 with the composition of alp ha 5 beta 1 gamma 1 and alpha y beta 1 gamma 1. Meanwhile, antiserum direct ed against a synthetic peptide of human alpha 3 detected only alpha 3 beta 3 gamma 2 trimer (laminin-5). We thus show that keratinocytes produce three heterotrimeric laminins. We could not detect the assembly of alpha 3 with beta 1 and gamma 1 chains to form alpha 3 beta 1 gamma 1 (laminin-6) in ker atinocytes.