Recent evidence has suggested that receptor-mediated phosphoinositide turnover, like that of the adenylate cyclase cAMP pathway, is regulated by guanine nucleotides. It is likely that one or more guanine nucleotide-binding proteins (G-proteins) couple calcium-mobilizing receptors to the activation of phosphoinositidase C. Recent studies utilizing various bacterial toxins have strongly suggested the presence of multiple G-proteins in the regulation of receptor-phosphoinositidase C coupling in a variety of cell types.
