Frontiers in Cellular Neuroscience Cellular Neuroscience

Abstract

In vision and olfaction, two senses involving GPCRs as main detectors, RGS9-1 and RGS2 respectively have been reported to attenuate light or odorant responses (Sinnarajah et al., 2001; Nishiguchi et al., 2004) while Ric-8B a putative GEF for Gαolf that is abundant in olfactory sensory neurons amplifi es odorant receptor signaling (Von Dannecker et al., 2005, 2006). Ric-8B has one other known mammalian homologue, Ric-8A, which was shown to enhance Gαq-mediated ERK activation by GPCRs (Nishimura et al., 2006) as well as interact and display GEF activity for Gαi1, Gαq and Gαo but not Gαs in vitro (Tall et al., 2003). The GEF activity of Ric-8A on the Gαι subunit has been extensively studied in receptor-independent G-protein-mediated events regulating microtubules pulling forces during cell division (Tall and Gilman, 2005). In this system the action of Ric-8A is similar to that of a GPCR while the GDI activity of GPR/GoLoco motif-containing proteins resemble that of Gβγ subunits (Thomas et al., 2008). In gustation, RGS21 has been reported to be expressed specifically in taste cells and to play a role in gustducin signaling (von Buchholtz et al., 2004); however, no reports of GEFs further controlling this system have been made. To study whether GEFs are involved in the transduction of the signal downstream of the taste GPCRs we investigated the expression of Ric-8A and Ric-8B in mouse taste cells and their interaction with G-protein subunits found in taste buds.