| Abstract No.: | A-B1028 |
| Country: | Canada |
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| Title: | THE ROLE OF ATYPICAL PROTEIN KINASE C (PKC) ZETA IN SYNAPTIC PLASTICITY IN APLYSIA. |
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| Authors/Affiliations: | 1 Joanna Bougie*; 1 Travis Lim; 1 Varsha Manjunath; 1 Ikue Nagakura; 1 Wayne S. Sossin;
1 McGill University, Montreal, QC, Canada
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| Content: | In Aplysia californica, protein kinase Cs (PKCs) are important regulators of synaptic plasticity and learning and memory. A nervous system isoform of atypical PKC zeta in Aplysia, PKC Apl III, has been cloned and characterized. Previous studies indicate that experience induced release of serotonin (5-HT) causes an increase in synaptic strength, known as facilitation. We have found that phosphorylation of Apl III is increased by 5-HT through a PI3K dependent pathway. In vertebrates, a nervous-system specific PKM form of PKC zeta, formed from an alternative start codon, plays an important role in synaptic plasticity; however we find no evidence for a PKM form of Apl III formed by an alternative start site. PKC Apl III appears to be regulated in two ways in Aplysia neurons. We found that PKC Apl III can be cleaved intracellularly to form a PKM. There is a nervous-specific alternatively spliced form of PKC Apl III that provides a calpain cleavage site for putative formation of a PKM from preteolysis. Confocal imaging of over-expressed Apl III tagged at the N-terminus with mRFP revealed a large proportion of mRFP in the nucleus of Aplysia sensory or motor neurons; nuclear mRFP was not seen with mRFP tagged PKC Apl II or when the same tagged mRFP Apl III is expressed in heterologous cells, suggesting specific recruitment of PKC Apl III to the nucleus in neurons. Immunostaining with a carboxy-terminal antibody to PKC Apl III revealed staining mainly in the cytoplasm, consistent with cleavage of PKC Apl III to a PKM form followed by the loss of the PKM form from the nucleus. Consistent with this model, an antibody to the N-terminus of PKC Apl III still showed enriched in the nucleus. Thus, cleavage of PKC Apl III can be detected by an increase in the proportion of carboxy-terminal antibody staining in the cytoplasm. This is greatly increased by over-expression of the construct, but decreased by applications of inhibitors of the protease calpain. We are further determining whether cleavage can be induced by 5-HT in motor neurons or activity coupled with 5-HT in sensory neurons. |
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