Use of adenoviruses to study isoform specificity of G-protein-receptor-coupled Ca2+ signaling in intact epithelial cells

It is firmly established that the activation of many heptahelical receptors by extracellular agonists leads to the activation of effectors such as phospholipase Cbeta (PLCbeta), the subsequent production of inositol-1,4,5-trisphosphate (IP3), and a resultant increase in intracellular free Ca2+. Heterotrimeric G-Proteins have a critical role in transducing the signal from the heptahelical receptor to PLCbeta and in determining the specificity and duration of the cellular responses. There remain, however, a number of areas of uncertainty regarding the exact mechanisms involved in regulating G-protein-mediated receptor-effector coupling in different cell types. For example, the molecular identity of the G-protein involved and the degree of isoform specificity among G-proteins of the same family and their receptors remains unclear. It is also not known in many cell types whether it is the alpha- or the betagamma-subunits of these G-proteins that activate PLCbeta. In order to address these issues, we have used replication-deficient adenoviruses as a tool to deliver, into intact epithelial cells, transgenes coding for proteins involved in G-protein-coupled receptor signaling pathways.