Synthesis and Evaluation of Dimeric Derivatives of Diacylglycerol-Lactones as Protein Kinase C Ligands.

Protein kinase C (PKC) mediates a central cellular signal transduction pathway involved in disorders such as cancer and Alzheimer's disease. PKC is regulated by binding of the second messenger sn-1,2-diacylglycerol (DAG) to its tandem C1 domains, designated C1a and C1b, leading both to PKC activation and to its translocation to the plasma membrane and to internal organelles. Depending on the isoform, there may be differences in the ligand selectivity of the C1a and C1b domains, and there is different spacing between the C1 domains of the conventional and novel PKCs. Bivalent ligands have the potential to exploit these differences between isoforms, yielding isoform selectivity. In the present study, we describe the synthesis of a series of dimeric derivatives of conformationally constrained diacylglycerol (DAG) analogs (DAG-lactones). We characterize the derivatives in vitro for their binding affinities, both to a single C1 domain (the C1b domain of PKCδ) as well as to the conventional PKCα isoform and the novel PKCδ isoform, and we measure their abilities to cause translocation of PKCδ and PKCε in intact cells. The dimeric compound with the 10-carbon linker was modestly more effective for the isolated PKCδ C1b domain than was the monomeric compound. For the intact PKCα and PKCδ, the shortest DAG-lactone dimer had similar affinity to the monomer and affinity decreased progressively up to the 16-carbon linker. The dimeric derivatives did not cause the Golgi accumulation of PKCδ. The present results provide important insights into the development of new chemical tools for biological studies on PKC.