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 G-proteins in channel catfish (Ictalurus punctatus) olfactory epithelium was investigated using antibodies to both the alpha and beta subunits of G-proteins. Based on Western blotting and immunohistochemical data, the following G-protein subunits were identified in the olfactory epithelium: Gs/G(olf), Gi1, Gi2, Gq and G beta. Immunohistochemical results indicated that all of these G-proteins, encompassing three G-protein subfamilies, were expressed in the dendrites and cilia of olfactory receptor neurons. These findings suggest that different G-protein subunits may mediate multiple signal transduction pathways in the catfish olfactory system, i.e. G(olf)/Gs, may mediate odorant activation of adenylyl cyclase while Gi and G beta may mediate odorant activation of phospholipase C.