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 proteins) constitutes the largest group of integral membrane proteins involved in signal transduction. These receptors participate in many important biological functions, ranging from photoreception to neurotransmission and exocytosis, as well as in processes such as embryogenesis, angiogenesis, tissue regeneration and normal and aberrant cell growth. Initial studies addressing the functioning of these receptors had focused primarily on second messenger-generating systems. Here, the authors survey the current knowledge on how this family of receptors transduces signals to the nucleus through an intricate network of nucleotide exchange factors, small GTPases, and cytoplasmic kinases which, in turn, control gene expression by phosphorylating nuclear regulatory molecules.