The molecular mechanism whereby protein kinase C (PKC) molecules transduce signals into the cell nucleus is unknown. In this study, we provide evidence that Dictyostelium discoideum contains PKCδ-like protein that is localized in the nucleus. The Dictyostelium PKCδ-like protein has an apparent molecular mass of 76 kDa. This protein is already highly expressed in vegetative Dictyostelium cells. The expression level remained constant up to 12 h of development, and sharply decreased after 16 h. The PKCδ-like protein is phosphorylated in vivo in response to cAMP and phorbol ester stimulation. Immunofluorescent studies, as well as subcellular fractionation experiments, have indicated that Dictyostelium PKCδ-like protein is permanently located in the nucleus. Our results may indicate that PKCδ-like protein in Dictyostelium functions as a link between cAMP and the tumor-promoting phorbol esters, and events that take place in the nucleus.
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Acknowledgment This study was supported by grants from the US-Israel Binational Science Foundation and Israel Cancer Association.
- Protein kinase C-delta