Research

A major goal of my laboratory is to understand the molecular basis of T cell receptor (TCR) induced ion flux and the consequent regulation of T cell signaling, energetics, differentiation and effector functions. Calcium ions are important signaling intermediates and calcium release activated channels (CRACs) constitute one of the major routes of calcium entry in T lymphocytes. Using a highly interdisciplinary approach, our early work identified the two central components of the CRAC channel complex, the pore forming subunit, CRACM/ Orai and alpha- soluble N-ethylmaleimide sensitive factor (NSF) attachment protein (alpha-SNAP), a closely associated protein that is required for the optimum functionality and selectivity of CRACM/ Orai channels.

Point mutations in CRAC channel components have been associated with a wide range of human diseases, spanning a variety of tissues. We have recently shown that mutations resulting in the loss of Orai function versus Orai selectivity stimulate distinct downstream signaling cascades, resulting in divergent defects in CD4 T cell differentiation and function. These and further studies in this direction would help in providing the much-needed mechanistic insights into the diverse immunological phenotypes currently associated with CRAC channel mutations in human patients.

Recently, we have found that store-depletion induces the assembly of Orai1 dimers into multimeric channels, on-site. We further showed that the assembly of fully functional and calcium-selective Orai channels is alpha-SNAP dependent. Based on these findings, we are currently testing the hypothesis that signaling induced assembly of ion channel pore subunits could be more wide-spread. We are further testing the hypothesis that additional members of the SNARE family proteins are involved in CRAC channel assembly and function. Indeed, specific SNAREs have been previously found to directly associate with several different ion channels. Yet the molecular basis of these associations and their relevance in ion channel physiology remains unestablished. One of the long-term goals of my laboratory is to determine whether TCR signaling induces dynamic assembly and activation of CRAC channel pore subunits. A related aim is to test whether TCR induced ion-flux is tunable depending on the strength and type of upstream signals.

In summary, we are interested in systematically characterizing the role of specific SNARE family proteins in the regulation of T cell ion flux, differentiation and function using a highly interdisciplinary, bottom-up approach. The central theme, therefore, is to decipher the fundamental rules that govern antigen receptor induced signaling in T lymphocytes with the ultimate goal of benefiting human patients with immunodeficiency, autoimmunity and cancer.