The protein kinase C (PKC) family, consisting of multiple isotypes, plays a major role in cellular signaling. In the nematode Caenorhabditis elegans, four pkc genes,
tpa-1,
pkc-1,
pkc-2 and
pkc-3, have been identified and investigated. Molecular analysis of
tpa-1,
pkc-1, and
pkc-2 has shown that each gene encodes multiple PKC isoforms with different expression patterns. One of the
tpa-1 isoforms, which is expressed in vulval cells, is found to play a role in nicotine-induced adaptation. The expression of
pkc-1 seems to be specific to neurons, while that of
pkc-2 is detected in several types of cells including neurons and muscle cells. An aPKC member encoded by
pkc-3 has been shown to play an essential role in establishing the polarity of the zygote. Recent studies have revealed that the mechanism of polarity establishment mediated by aPKC is evolutionarily conserved in diverse organisms from nematodes to mammals. C. elegans provides an excellent model system for molecular dissection of the cellular