STRUCTURE, EXPRESSION, AND PROPERTIES OF AN ATYPICAL PROTEIN-KINASE-C(PKC3) FROM CAENORHABDITIS-ELEGANS - PKC3 IS REQUIRED FOR THE NORMAL PROGRESSION OF EMBRYOGENESIS AND VIABILITY OF THE ORGANISM

Little is known about differential expression, functions, regulation, and targeting of ''atypical'' protein kinase C (aPKC) isoenzymes in vi vo, We have cloned and characterized a novel cDNA that encodes a Caeno rhabditis elegans aPKC (PKC3) composed of 597 amino acids, In post-emb ryonic animals, a 647 base pair segment of promoter/enhancer DNA direc ts transcription of the 3.6-kilobase pair pkc-3 gene and coordinates a ccumulation of PKC3 protein in similar to 85 muscle, epithelial, and h ypodermal cells, These cells are incorporated into tissues involved in feeding, digestion, excretion, and reproduction, Mammalian aPKCs prom ote mitogenesis and survival of cultured cells, In contrast, C. elegan s PKC3 accumulates in non-dividing, terminally differentiated cells th at will not undergo apoptosis. Thus, aPKCs may control cell functions that are independent of cell cycle progression and programmed cell dea th. PKC3 is also expressed during embryogenesis, Ablation of PKC3 func tion by microinjection of antisense RNA into oocytes yields disorganiz ed, developmentally arrested embryos. Thus, PKC3 is essential for viab ility, PKC3 is enriched in particulate fractions of disrupted embryos and larvae, Immunofluorescence microscopy revealed that PKC3 accumulat es near cortical actin cytoskeleton/plasma membrane at the apical surf ace of intestinal cells and in embryonic cells, A candidate anchoring/ targeting protein, which binds PKC3 in vitro, has been identified.