α-Arylidene diacylglycerol-lactones (DAG-Lactones) as selective ras guanine-releasing protein 3 (RasGRP3) ligands

Abstract

Diacylglycerol-lactones have proven to be a powerful template for the design of potent ligands targeting CI domains, the recognition motif for the cellular second messenger diacylglycerol. A major objective has been to better understand the structure activity relations distinguishing the seven families of signaling proteins that contain such domains, of which the protein kinase C (PKC) and RasGRP families are of particular interest. Here, we synthesize a series of aryl- and alkyl-substituted diacylglycerol-lactones and probe their relative selectivities for RasGRP3 versus PKC. Compound 96 showed 73-fold selectivity relative to PKC alpha 45 and 45-fold selectivity relative to PKC epsilon for in vitro binding activity. Likewise, in intact cells, compound 96 induced Ras activation, a downstream response to RasGRP stimulation, with 8-29 fold selectivity relative to PKC delta S299 phosphorylation, a measure of PKC delta stimulation.