ATYPICAL PROTEIN-KINASE-C COOPERATES WITH PAR-3 TO ESTABLISH EMBRYONIC POLARITY IN CAENORHABDITIS-ELEGANS

Asymmetric cell divisions, critically important to specify cell types in the development of multicellular organisms, require polarized distr ibution of cytoplasmic components and the proper alignment of the mito tic apparatus. In Caenorhabditis elegans, the maternally expressed pro tein, PAR-3, is localized to one pole of asymmetrically dividing blast omeres and is required for these asymmetric divisions. In this paper, we report that an atypical protein kinase C (PKC-3) is essential for p roper asymmetric cell divisions and co-localizes with PAR-3. Embryos d epleted of PKC-3 by RNA interference die showing Par-like phenotypes i ncluding defects in early asymmetric divisions and mislocalized germli ne-specific granules (P granules). The defective phenotypes of PKC-3-d epleted embryos are similar to those exhibited by mutants for par-3 an d another par gene, par-6. Direct interaction of PKC-3 with PAR-3 is s hown by in vitro binding analysis. This result is reinforced by the ob servation that PKC-3 and PAR-3 co-localize in vivo. Furthermore, PKC-3 and PAR-3 show mutual dependence on each other and on three of the ot her par genes for their localization. We conclude that PKC-3 plays an indispensable role in establishing embryonic polarity through interact ion with PAR-3.