Lobster G-protein coupled receptor kinase that associates with membranes and G(beta) in response to odorants and neurotransmitters

A cDNA clone (lobGRK2) encoding a protein of 690 amino acids with significa nt similarity to the GRK2 subfamily of G-protein coupled receptor kinases w as isolated. lobGRK2 was widely expressed as a 9-kb major transcript and a protein of 80 kDa. It was most abundant in the brain and the olfactory orga n but was absent in the eye/eyestalk. Immunocytochemistry revealed lobGRK2 immunoreactivity in the outer dendritic segments of the olfactory receptor neurons, the site of olfactory transduction. LobGRK2 immunoreactivity was o bserved in most neuronal structures in the brain, although with varying int ensity. It was strongest in neuropil, especially the olfactory and accessor y lobes but was also detectable in neuronal cell bodies. Stimulation of bra in homogenates with a mixture of neurotransmitters increased the associatio n of lobGRK2 with membranes and with Gp. Similarly, stimulation of olfactor y dendrite homogenates with an odorant mixture caused lobGRK2 to associate with Gp. These results support the conclusion that lobGRK2 responds to odor ants and to neurotransmitters and may act to initiate desensitization by ph osphorylating G-protein-coupled receptors in the olfactory organ and the br ain, respectively. (C) 1999 Wiley-Liss, Inc.