α- β- or γ-chain -specific RNA interference of laminin assembly in Drosophila Kc167 cells

Drosophila laminin alpha beta gamma trimer assembly in Kc167 cells was perturbed by chain-specific RNA interference (RNAi). The intracellular pool of alpha and gamma chains remained unchanged under beta -chain RNAi by lipofection of double-stranded RNA encoding a beta -chain partial sequence. This was also the case for the intracellular pool of alpha and beta chains under gamma -chain-specific RNAi. Nonetheless, the intracellular pool of beta and gamma chains increased markedly under alpha -chain-speciflic RNAi. Non-reducing SDS/PAGE revealed that some of the increased beta and gamma chains migrated as disulphide-linked beta gamma dimers but that the rest migrated as monomers. Since the monomeric beta and gamma bands detected under alpha -chain RNAi were denser than the beta band under gamma -chain RNAi and the gamma band under beta -chain RNAi, respectively, beta and gamma also appeared to accumulate by forming beta gamma dimers without the disulphide linkage. We suggest that interconversion of these beta gamma dimers is crucial for the replaceable and selective assembly of the alpha chain for alpha beta gamma trimer formation.