STRUCTURE AND EXPRESSION OF THE CAENORHABDITIS-ELEGANS PROTEIN-KINASEC2 GENE - ORIGINS AND REGULATED EXPRESSION OF A FAMILY OF CA2-ACTIVATED PROTEIN-KINASE-C ISOFORMS()

The molecular and cellular basis for concerted Ca2+/lipid signaling in Caenorhabditis elegans was investigated, A unique gene (pkc-2) and co gnate cDNAs that encode six Ca2+/diacylglycerol-stimulated PKC2 isoenz ymes were characterized, PKC2 polypeptides (680-717 amino acid residue s) share identical catalytic, Ca2+-binding, diacylglycerol-activation and pseudosubstrate domains, However, sequences of the N- and C-termin al regions of the kinases diverge, PKC2 diversity is partly due to dif ferential activation of transcription by distinct promoters, Each prom oter precedes an adjacent exon that encodes 5'-untranslated RNA, an in itiator AUG codon and a unique open reading frame. PKC2 mRNAs also inc orporate one of two 3'-terminal exons via alternative splicing. Cells that are capable of receiving and propagating signals carried by Ca2+/ diacylglycerol were identified by assessing activities of pkc-2 gene p romoters in transgenic C. elegans and visualizing the distribution of PKC2 polypeptides via immunofluorescence. Highly-selective expression of certain PKC2 isoforms was observed in distinct subsets of neurons, intestinal and muscle cells, A low level of PKC2 isoforms is observed in embryos, When L1 larvae hatch and interact with the external enviro nment PKC2 content increases 10-fold. Although 77- and 78-kDa PKC2 iso forms are evident throughout post-embryonic development, an 81-kDa iso form appears to be adapted for function in L1 and L2 larvae.