Regulation of Lipid Signaling by Peripheral Membrane Proteins

The major research theme of my laboratory is focused on understanding the structural basis of signal transduction events that occur at membrane surfaces. These events involve reversible association of peripheral signaling proteins with membranes in response to different stimuli, and we are particularly interested in deciphering how multi-modular protein architectures support these signaling functions. To develop detailed structural pictures of protein-lipid recognition events that underlie numerous signal transduction and membrane trafficking processes, we apply integrative structural biology approaches that include NMR spectroscopy, atomistic molecular dynamics simulations, and X-ray crystallography. I will discuss three aspects of our recent progress in understanding the structural biology of two peripheral protein systems: protein kinase C (PKC), a lipid activated Thr/Ser kinase implicated in the progression of cancer, cardiovascular, and neurodegenerative diseases; and (ii) the yeast Sec14, a founding member of the phosphatidylinositol/phosphatidylcholine exchange proteins (PITP) family, which has emerged as an attractive target for next-generation antifungal drugs. Our work on PKC revealed the mechanism of stereospecific recognition of signaling lipid diacylglycerol, provided high-resolution guides for the design of therapeutic agents, and led to the proposal of a novel mechanism of PKC downregulation. The Sec14 study revealed the structural basis of lipid exchange inhibition by small molecule inhibitors (SMIs) of four distinct chemotypes and generated new insights into the mechanics of the Sec14 phospholipid exchange cycle from the perspective of protein, phospholipid, and SMI dynamics. Our results show that SMIs are powerful tool compounds that will enable us to further probe other aspects of the Sec14 phospholipid exchange cycle such as atomic-level details of the membrane docking step and the role of allostery in Sec14-lipid interactions.