Structure and expression of a novel, neuronal protein kinase C (PKC1B) from Caenorhabditis elegans: PKC1B is expressed selectively in neurons that receive, transmit, and process environmental signals

The nematode Caenorhabditis elegans provides an advantageous system for investigating the regulation, expression, and functions of protein kinase C (PKC) isoforms. We cloned and characterized cDNAs encoding a novel C. elegans PKC designated PKC1B. The predicted PKC1B polypeptide contains features characteristic of the nPKC subfamily of PKC isoforms. The levels of PKC1B and its cognate mRNA vary over a 7-fold range during C. elegans postembryonic development. PKC1B protein and mRNA are abundant at the earliest larval stage, but their relative concentrations decrease coordinately in late larvae. Embryos, which are enriched in PKC1B mRNA, contain little PKC1B protein. Thus, PKC1B expression is regulated at a translational or post-translational level during early development. Cells engaged in PKC1B gene transcription were identified in transgenic C. elegans that carry the lacZ gene under the regulation of the PKC1B promoter. Staining for β-galactosidase revealed PKC1B promoter activity exclusively in sensory neurons and interneurons. Immunofluorescence microscopy disclosed that the PKC1B polypeptide is located in the processes (axons and dendrites) and perinuclear regions of ∼ 75 neurons that constitute the sensory circuitry of the nematode. The intracellular localization of PKC1B and the enzyme's differential solubility in ionic and nonionic detergents suggest that the kinase is associated with membranes and the cytoskeleton.