G-PROTEIN SUBUNITS EXPRESSED IN CATFISH OLFACTORY RECEPTOR NEURONS

Olfactory signal transduction in a number of species has been shown to be mediated by heterotrimeric GTP-binding proteins (G-proteins). The expression of different C-proteins in channel catfish (Ictalurus punct atus) olfactory epithelium was investigated using antibodies to both t he alpha and beta subunits of G-proteins. Based on Western blotting an d immunohistochemical data, the following G-protein subunits were iden tified in the olfactory epithelium: G(s)/G(olf), G(i1), G(i2), G(q) an d G(beta). Immunohistochemical results indicated that all of these G-p roteins, encompassing three G-protein subfamilies, were expressed in t he dendrites and cilia of olfactory receptor neurons. These findings s uggest that different G-protein subunits may mediate multiple signal t ransduction pathways in the catfish olfactory system, i.e. G(olf)/G(s) , may mediate odorant activation of adenylyl cyclase while G(i) and G( beta) may mediate odorant activation of phospholipase C.