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Robert Duvoisin"Unraveling the sign-inverting synapse between photoreceptors and ON bipolar cells: the mGluR6 signaling pathway."

Abstract :

In the retina, visual information is segregated into pathways that respond to either increases or decreases in light intensity.
Photoreceptors respond to light by hyperpolarizing and reducing the rate of release of the neurotransmitter, glutamate. Two types of postsynaptic cells, the ON- and OFF-bipolar cells, respond to synaptic glutamate with opposite polarity, thus establishing the opposing visual pathways that are maintained throughout the rest of the visual system. The light-induced drop in glutamate release causes ON-bipolar cells to depolarize. This unusual sign-inverting synaptic response is mediated by a metabotropic glutamate receptor, mGluR6, which is negatively coupled to the activation of a nonspecific cation channel via the G protein, Go. I will present two aspects of our research on the signaling mechanism of mGluR6. First, we propose that regulator of G protein signaling (RGS) proteins are necessary for a rapid light response. Second, we have identified TRPM1 as a component of the channel mediating the depolarizing response of ON-bipolar cells. 

Selected publications

Jeffrey BG, Morgans CW, Puthussery T, Wensel TG, Brown RL, Duvoisin RM (2010) R9AP Stabilizes RGS11-Gβ5 in ON-Bipolar Cells and Accelerates the Light Response Measured with the Electroretinogram. Vis Neurosci Jan 26:1-9. Epub ahead of print.
Zhang J, Jeffrey BG, Morgans CW, Burke NS, Haley T, Duvoisin RM, Brown RL (2010) RGS7 and 11 complexes accelerate the ON-bipolar cell light response. Invest Ophthalmol Vis Sci 51:1121-1129.
Morgans CW, Zhang J, Jeffrey BG, Nelson SM, Burke NS, Duvoisin RM, Brown RL (2009) TRPM1 is required for the depolarizing light response in retinal ON-bipolar cells. Proc Natl Acad Sci USA 106:19174-19178.
Morgans CW, Liu W, Wensel TG, Bearnot B, Perez-Leon JA, Brown RL, Duvoisin RM (2007) Gβ5-RGS complexes co-localize with mGluR6 in retinal ON-bipolar cells. Eur J Neurosci 26:2899-2905.

Christophe Mulle