Clostridial toxins: Molecular probes of Rho-dependent signaling and apoptosis

The Rho family small GTPases are members of the Ras superfamily of small GT Pases. Rho proteins were first determined to act as key regulators of many types of actin cytoskeletal-dependent cellular functions. Recent work by se veral investigators indicates that Rho GTPases are also critical modulators of several important intracellular and nuclear signal transduction pathway s. Certain clostridial toxins and exoenzymes covalently modify, and thereby inactivate, specific types of Rho family GTPases. As such, these microbial enzymes have proven invaluable in helping to identify structural and funct ional attributes of Rho GTPases.