Serine endoprotease which cleaves proproteins at paired basic amino acids (Probable). Involved in cuticle biosynthesis probably by cleaving pro-collagen into its mature form. Acts in ASEL sensory neurons to regulate high salt chemotaxis responses probably by cleaving insulin-like protein ins-6 into its mature and active form (PubMed:24013594). Essential for embryonic and larval development (PubMed:7774813, PubMed:10903434, pubmed:19716386). isoform a, isoform e, isoform f, isoform g and isoform h are involved in cuticle biosynthesis but are dispensable for larval development (PubMed:7774813, PubMed:10903434). Binds 3 calcium ions per subunit. In larvae and adults, expressed in all hypodermal cells, vulva and ventral nerve cords. Expression starts at the two-fold embryonic stage throughout adulthood (PubMed:7774813, PubMed:19716386). Expression increases during L2-L3, L3-L4 and L4-adult molting stages (PubMed:19716386). RNAi-mediated knockdown causes an arrest at the L1 developmental stage (PubMed:19716386). RNAi-mediated knockdown in ASEL neuron results in a severe reduction in Ca(2+) signal in ASEL neuron and in chemotaxis in response to high salt concentrations (PubMed:24013594). Belongs to the peptidase S8 family. Furin subfamily.