Novel RGS polypeptides, proteins, and nucleic acid molecules are disclosed. In addition to isolated, full-length RGS proteins, the invention further provides isolated RGS fusion proteins, antigenic peptides, and anti-RGS antibodies. The invention also provides RGS nucleic acid molecules, recombinant expression vectors containing a nucleic acid molecule of the invention, host cells into which the expression vectors have been introduced, and nonhuman transgenic animals in which an RGS gene has been introduced or disrupted. Diagnostic, screening, and therapeutic methods utilizing compositions of the invention are also provided.