Identification of the monomeric G-protein, Rhes, as an efaroxan-regulated protein in the pancreatic beta-cell.

Efaroxan induces membrane depolarization by interaction with the pore forming subunit of the ATP-sensitive potassium channel, Kir6.2. However, this effect is not responsible for its full secretory activity. In this study we have used an anti-idiotypic approach to generate antibodies that recognize additional proteins that may be regulated by efaroxan in pancreatic beta-cells. Using these antisera in an expression cloning strategy we have identified a monomeric GTP-binding protein, Rhes, as a potential target for regulation by imidazoline ligands. Rhes is shown to be expressed in beta-cells and its expression is regulated by efaroxan under conditions when a structurally related molecule, KU14R, is ineffective. The results reveal that beta-cells express Rhes and suggest that changes in the expression of this molecule may regulate the sensitivity of beta-cells to imidazoline secretagogues.