Biosynthesis and enzymology of the Caenorhabditis elegans cuticle: identification and characterization of a novel serine protease inhibitor.

The nematode Caenorhabditis elegans represents an excellent model in which to examine nematode gene expression and function. A completed genome, straightforward transgenesis, available mutants and practical genome-wide RNAi approaches provide an invaluable toolkit in the characterization of nematode genes. We have performed a targeted RNAi screen in an attempt to identify components of the cuticle collagen biosynthetic pathway. Collagen biosynthesis and cuticle assembly are multi-step processes that involve numerous key enzymes involved in post-translational modification, trimer folding, procollagen processing and subsequent cross-linking stages. Many of these steps, the modifications and the enzymes are unique to nematodes and may represent attractive targets for the control of parasitic nematodes. A novel serine protease inhibitor was uncovered during our targeted screen, which is involved in collagen maturation, proper cuticle assembly and the moulting process. We have confirmed a link between this inhibitor and the previously uncharacterized bli-5 locus in C. elegans. The mutant phenotype, spatial expression pattern and the over-expression phenotype of the BLI-5 protease inhibitor and their relevance to collagen biosynthesis are discussed