Lab Research Focus
HIV-1 replication is strongly dependent on the cellular machinery to produce progeny virus. The discovery of cellular factors that participate in HIV replication pathways has provided new insights into the molecular basis of virus–host cell interactions. Elucidation of the molecular interactions between the host cell and HIV are important for understanding the virus replication and the subsequent cytopathogenesis in the infected cell, which will aid in the development of more efficient antiviral drugs. We are interested in the underlying structural basis by which HIV proteins interact with cellular constituents during the virus replication cycle. A major component of our research program is directed towards understanding key protein-protein and protein-membrane interactions that are critical for HIV replication. Another aspect of our research is to identify small molecule inhibitors that are able to block virus-host protein-protein complexes and ultimately serve as potential anti HIV drugs. The results generated from this research will provide new insights into these mechanisms and identify new attractive targets that will ultimately aid in rational drug design.
Apoptosis is a strictly regulated process by which abnormal cells are removed from the body without altering the immune system or generating an inflammatory response. Inappropriate apoptosis (enhanced or diminished) is linked to many human diseases including neurodegenerative and autoimmune disorders, AIDS, and many types of cancers. The apoptotic pathway is normally initiated by cell surface death receptors such as Fas. These receptors undergo a conformational change in response to their cognate ligands (FasL), allowing them to interact with adaptor proteins such as Fas-associated death domain (FADD). Fas-FasL interaction leads to activation of caspase 8 (by FADD) and formation of death-inducing signaling complex (DISC). DISC formation and subsequent protein recruitment is a critical initial step in regulating Fas-mediated apoptosis. There is compelling evidence that Fas interacts with various molecules, suggesting that Fas signaling is complex and regulated by multiple proteins. Among these is calmodulin (CaM), which is recruited into DISC in cholangiocarcinoma cells. It has been hypothesized that Fas-CaM interaction may affect Fas-FADD interaction and thus regulates DISC assembly and inhibits apoptosis in cholangiocarcinoma and other cancer cells. Thus, Fas-CaM interaction appears to be an inhibitory component of DISC and may play a vital role in obstruction of caspases activation. Our lab is interested in understanding the structural determinants of Fas-CaM interaction, which will be critical to understanding the precise molecular mechanism of Fas-mediated apoptosis and mechanism of inhibition. These studies will likely lead to new strategies to develop inhibitors of these interactions and thus to cancer treatment.
Structural Biology and Biophysics:
We employ a set of structural biology, biophysical and biochemical tools to understand how HIV proteins interact with cellular proteins and membranes during the virus replication cycle. These methods allow us to identify key protein-protein and protein-lipid interactions. Among the diverse techniques we utilize are: Nuclear magnetic resonance (NMR), X-ray crystallography, isothermal titration calirometry (ITC), surface plasmon resonance (SPR), analytical ultracentrifugation (AUC), florescence, mass spectrometry (MS), and computational biology. State-of-the-art high-resolution NMR instruments (850, 700, 600 and 500 MHz NMR) equipped with cryogenic probes are utilized. My lab has developed new NMR strategies to study protein-protein and protein-lipid interactions. Additionally, we developed a rapid NMR-based assay that, in a single experiment (20 minutes), enables us to: (i) detect direct binding, (ii) determine binding affinity, (iii) identify the binding site on the protein, (iv) determine the stoichiometry of binding, and (v) assess whether small molecules block interactions.