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

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