Signal transduction via G protein-coupled receptors (GPCRs) plays a central role in a variety of physiological processes including vision. Phototransduction has served as a prototype for GPCR-mediated signaling systems. Despite the importance of these signaling cascades, an accurate mechanistic description of these systems is unavailable. Data are still largely interpreted within the framework of classical schemes. These types of schemes have served an important role in earlier studies that led to the initial characterization of GPCR-mediated systems, but are in need of an update. The advancement in our molecular understanding of these systems will require a combination of innovative biophysical, biochemical, and genetic approaches that provide structural, spatial, and temporal information, which will define the limits from which signal transduction can occur. This framework will pinpoint areas in classical schemes that require modifications and will provide insights that will provide a more realistic view of GPCR-mediated signaling.
Rhodopsin, the light receptor in the visual system, is one of the main GPCRs that we study in the laboratory. The light receptor is found in the rod outer segments of the retina and initiates phototransdution, a set of biochemical events that occurs in the initial stages of vision. Mutations in rhodopsin are directly associated with vision-related disorders such as retinitis pigmentosa and congenital night blindness. Rhodopsin is a prototypical GPCR and offers several advantages over other systems, which allows for the application of novel biophysical approaches thereby advancing our current understanding of GPCR-mediated signaling events.
The major goal of our laboratory is to understand the mechanism of signal transmission at the molecular level in phototransduction and other G protein-coupled receptor-mediated signaling systems. The specific aims of our research that will help us achieve our goal include: 1) to test the validity of assumptions in classical schemes of signaling and to explore more recent paradigms of signal transmission, 2) develop and characterize methodologies to detect and monitor molecular interactions formed by receptors, 3) develop and characterize tools that will allow for live cell and/or in vivo monitoring of signaling events, 4) to understand at a molecular level the mechanism by which mutations in rhodopsin lead to vision-related disorders. We use modern biophysical approaches to tackle these issues including atomic force microscopy (AFM), single-molecule force spectroscopy (SMFS), and fluorescence-based methods.