Novel molecular mediators in the pathway connecting G-protein-coupled receptors to MAP kinase cascades

The family of receptors coupled to heterotrimeric GTP-binding proteins (G p roteins) constitutes the largest group of integral membrane proteins involv ed in signal transduction. These receptors participate in many important bi ological functions, ranging from photoreception to neurotransmission and ex ocytosis, as well as in processes such as embryogenesis, angiogenesis, tiss ue regeneration and normal and aberrant cell growth. Initial studies addres sing the functioning of these receptors had focused primarily on second mes senger-generating systems. Here, the authors survey the current knowledge o n how this family of receptors transduces signals to the nucleus through an intricate network of nucleotide exchange factors, small GTPases, and cytop lasmic kinases which, in turn, control gene expression by phosphorylating n uclear regulatory molecules.