Research Projects

G protein-coupled receptors (GPCRs), constitute the largest family of the cell surface receptors with a direct involvement in nearly every aspect of human physiology. Considering their wide-ranging roles across different cellular and physiological processes and accessibility for therapeutic targeting, GPCRs continue to represent the largest family of drug targets. Upon agonist-stimulation, GPCRs couple to, and activate, two distinct signal-transducers namely, the heterotrimeric G-proteins and β-arrestins. Subsequently, activated G-proteins initiate the generation of second messengers via effector molecules leading to downstream signaling while β-arrestins desensitize the G-protein response and also promote receptor endocytosis. The current paradigm of GPCR signaling is conceptualized primarily along this vertical axis involving receptor-transducer-effector cascade although it is conceivable that their activation and signaling may also be allosterically modulated in the membrane through lateral cross-talk with other integral membrane proteins. Our laboratory has recently discovered the interaction of a tetraspanin CD82 with a chemokine receptor, and taking a lead from this discovery, and significant indications of a functional synergy between the tetraspanins and GPCRs, we propose to explore the cross-talk of selected GPCRs with tetraspanins in the current project. Tetraspanins are integral membrane proteins localized primarily in the plasma membrane containing a highly conserved four transmembrane architecture with the N- and C-termini on the intracellular side of the cell. The tetraspanin superfamily consists of thirty-three members in the human genome, and they have a wide-spread role in a range of physiological processes with key contribution in immune response mechanisms. For example, lack of functional tetraspanin CD81 results in profound defects in the development of antibody producing cells leading to severe immunodeficiency with respect to antibody expression. Tetraspanins have also been suggested to facilitate the formation of Tetraspanin-Hub or Tetraspanin-Enriched Microdomains (TEMs) containing multi-protein complexes as hot-spots to regulate localized signaling with possible implications for tumor metastasis and viral infections. Still however, a systematic analysis of their cross-talk with GPCRs and resulting functional outcomes has not been carried out yet. Our preliminary data suggesting the interaction of multiple GPCRs with one of the tetraspanins known as CD82, raises the tantalizing possibility of tetraspanins being a broadly conserved interaction partners and regulatory molecules for GPCRs. In this backdrop, we propose to explore the cross-talk of tetraspanins with GPCRs with an emphasis on allosteric modulation of receptor activation and downstream signaling, and visualizing the molecular details of their interaction at high-resolution in this project.