Protein kinase C and protein kinase L in Caenorhabditis elegans

Abstract

Protein kinase C (PKC) is a family of Ser/Thr protein kinases involved in the regulation of many fundamental processes including secretion, growth, differentiation and carcinogenesis. This thesis characterizes a PKC isoform (PKC1) and a novel protein kinase (PKL) in the nematode C. elegans.;A PKC-specific oligonucleotide was used to isolate cDNAs encoding PKC1. The derived amino acid sequence of the PKC1 cDNA is related to that of the PKC{dollar}\epsilon{dollar} isoform of mammals. Alternative promoters and 5{dollar}\sp\prime{dollar} trans/cis splicing provide a novel mechanism for generating two isoforms of PKC1. PKC1 transcripts are either trans-spliced with the classical spliced leader 1 sequence (PKC1B) or cis-spliced at the same acceptor site with a 173 nt 5{dollar}\sp\prime{dollar} extension (PKC1A). The PKC1B promoter is contained in 3 kb of genomic DNA that is adjacent to its trans-splice acceptor site. This DNA sequence serves as part of an intron when the PKC1A promoter is utilized. PKC1A mRNA is produced in a process that involves the utilization of a distal promoter and the incorporation of two additional exons into the mRNA. PKC1A mRNA encodes a predicted kinase of 763 amino acids that contains the entire sequence of PKC1B as well as an N terminal extension of 56 residues. The extension contains a preponderance of basic amino acids.;The levels of transcripts arising from the distal (1A) and proximal (1B) promoters for the PKC1 gene are differentially regulated during C. elegans development. The ratio of 1B mRNA: 1A mRNA varies from 40:1 to unity as the nematodes progress from early larval stages to mature adults. PKC1 protein and PKC1B mRNA are abundant at the earliest larval stage (L1), but their relative concentrations decrease sharply and coordinately in late larvae (L2-L4). In contrast, embryos, which are enriched in PKC1B mRNA, contain little PKC1 protein. Thus, PKC1B expression is negatively regulated at a translational or post-translational level during early development.;Individual cell nuclei engaged in transcription of the PKC1B gene were identified in situ in transgenic C. elegans that carry the lacZ reporter gene under the regulation of the PKC1B promoter. Histochemical staining for {dollar}\beta{dollar}-galactosidase revealed high-level PKC1B promoter activity exclusively in sensory neurons and related interneurons. A high-resolution analysis of the cellular and intracellular distribution of the PKC1 polypeptide was achieved with affinity-purified anti-PKC1 IgGs and confocal immunofluorescence microscopy. PKC1 is evident only in the processes (axons and dendrites) and perinuclear regions of {dollar}\sim{dollar}75 neurons ({dollar}\sim{dollar}8% of total C. elegans cells) that constitute the sensory and integrative circuitry of the nematode.;During the course of cloning PKC cDNAs a novel protein kinase was discovered. The novel protein kinase, PKL, is encoded by two mRNAs of 5.2 and 5.0 kb, that are generated from a single gene by alternative splicing of 3{dollar}\sp\prime{dollar} terminal exons. (Abstract shortened by UMI.).