ABSTRACT
This chapter explores the signal transduction mechanisms that may be important for cellular volume regulation. When a ligand binds to its receptor on the cell surface, the resulting conformational change in the receptor initiates a series of intracellular events that culminate in a characteristic response by the cell. A large number of agonists bind to a second class of receptors that are linked to guanine nucleotide-binding regulatory proteins. G protein-coupled receptors have a variably sized ligand-binding domain, a common seven-transmembrane-spanning configuration and a variable-length cytoplasmic tail. The best-studied families of the large group of small-molecular-weight G proteins are the ras, rho, and rab families. The rho family, which also includes Rac, has been shown recently to play a critical role in serum and growth factor-induced actin cytoskeletal reorganization. A number of exchange proteins and GTPase-activating proteins have been identified, but whether and how their activity is modulated by activated growth factor receptors remains unclear.
