Signal transduction in the vomeronasal organ of garter snakes: ligand-receptor binding-mediated protein phosphorylation.
The vomeronasal (VN) system of garter snakes plays an important role in several species-typical behaviors, such as prey recognition and responding to courtship pheromones. We (X.C. Jiang et al., J. Biol. Chem. 265 (1990) 8736-8744 and Y. Luo et al., J. Biol. Chem. 269 (1994) 16867-16877) have demonstrated previously that in the snake VN sensory epithelium, the chemoattractant ES20, a 20-kDa glycoprotein derived from electric shock-induced earthworm secretion, binds to its receptor which is coupled to PTX-sensitive G-proteins. Such binding results in elevated levels of IP3. We now report that ES20-receptor binding regulates the phosphorylation of two membrane-bound proteins with molecular masses of 42- and 44-kDa (p42/44) in both intact and cell-free preparations of the VN sensory epithelium. ES20 and DAG regulate the phosphorylation of p42/44 in a similar manner. ES20-receptor binding-mediated phosphorylation of p42/44 is rapid and transient, reaching a peak value within 40 seconds and decaying thereafter. Phosphorylation of p42/44 appears to be regulated by the countervailing actions of a specific membrane-bound protein kinase and a protein phosphatase. The phosphorylation of these membrane-bound proteins significantly reduces the activity of G-proteins as evidenced by a decrease in GTPase activity, but has little effect on ligand-receptor binding. These findings suggest that p42/44 play a role in modulating the signal transduction induced by ES20 in the vomeronasal system.
Department of Biochemistry, SUNY Health Science Center at Brooklyn, 450 Clarkson Avenue, Brooklyn, NY 11203, USA.
J
J
Liu
P
P
Chen
D
D
Wang
M
M
Halpern
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D017812:Colubridae / Q000502:physiology*; D004075:Diglycerides / Q000494:pharmacology; D004848:Epithelium / Q000378:metabolism; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D019204:GTP-Binding Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D006023:Glycoproteins / Q000494:pharmacology; D036341:Intercellular Signaling Peptides and Proteins; D008565:Membrane Proteins / Q000378:metabolism; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors / Q000378:metabolism; D010766:Phosphorylation; D011984:Sensory Receptor Cells / Q000187:drug effects / Q000502:physiology*; D015398:Signal Transduction; D019147:Vomeronasal Organ / Q000378:metabolism*
D004075:Diglycerides; C108946:ES20 protein, Lumbricus terrestris; D006023:Glycoproteins; D036341:Intercellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D010749:Phosphoprotein Phosphatases; D019204:GTP-Binding Proteins; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D002118:Calcium