Rho GTPase activating proteins in cancer phenotypes.

Rho proteins belong to the Ras superfamily of small GTPases and function as binary switches that shuttle between active and inactive states based on the nature of bound guanine nucleotide. Three sets of regulatory proteins, namely, guanine dissociation inhibitors, guanine exchange factors, and GTPase activating proteins (GAPs) control the balance between active and inactive Rho proteins. There are more than 70 RhoGAPs encoded in the human genome. The RhoGAP family is distinguished by the presence of the RhoGAP domain. However, the majority of RhoGAPs contain multiple additional domains. There are as many as eight domains in some of these proteins. The modular structure of GAPs is important for their interaction with other proteins. A significant number of RhoGAPs have been shown to be present in altered abundance in a variety of human cancers or cell lines. The ability of RhoGAPs to modulate Rho mediated signaling pathways may lend themselves as targets for small molecule therapeutic agents against cancer.