RESEARCH SUMMARY

Diacylglycerol (DAG) is a lipid with unique functions as a basic membrane component, as a lipid metabolism intermediate, and as a signalling molecule. In eukaryotes, a host of proteins have evolved the ability to bind to DAG and are thus modulated by this lipid, creating additional levels of control to meet the complex needs of multicellular organisms. DAG-regulated proteins participate in neuronal and vascular patterning, as well as synapse transmission and glucose transport, and are critical for a correct immune response. Altered DAG functions are linked to transplant rejection, inflammation, diabetes, allergy and autoimmune disease. Sustained DAG generation, on the other hand, is associated with malignant transformation.

The complexity of DAG-regulated processes emphasises the need for studies to evaluate the potential therapeutic control of DAG generation and clearance.

Our group studies the contribution of DAG-regulated mechanisms to T cell activation and oncogenic transformation, so that steps of these processes can be manipulated for possible therapeutic benefit. Our goal is to demonstrate that modification of DAG metabolism is a novel, understudied strategy in the management of a more effective immune response and/or treatment of cancer. We analyse the mechanisms by which DAG binds and regulates C1 domain-containing proteins.

In addition to the well-characterised PKC family, vertebrates express six additional families of DAG-regulated proteins: chimaerins, DGK (beta and gamma), PKD, Munc13, RasGRP and MRCK. The specific expression in T cells of C1-containing GEFS and GAPS for small GTPases of the Ras and Rho family has uncovered new, strategic DAG functions in the regulation of Ras and Rac. We examine the spatial generation of DAG using fluorescent DAG sensors. Studies from our laboratory have also provided new insight into the mechanisms that govern DAG-mediated regulation of RasGRP1 and α2 chimaerin during T cell activation.

Another important area is the study of diacylglycerol kinases (DGK), which transform DAG into phosphatidic acid, and represent important modulators of DAG-dependent functions. We use biochemical and genetic approaches to better understand how antigen-mediated stimulation determines membrane localization/activation of DGKα and ζ, their site of activation, and the nature of the interacting partners.

We also explore the role of these isoforms in the maintenance of the transformed state through regulation of the PI3K/MTOR pathway. We expect that our findings will help assess the therapeutic potential of the DGK enzyme family as tools for better, more effective management of the immune response and treatment of cancer.