title: Redox regulation of RhoA.
abstract: We have previously shown that redox agents including superoxide anion radical and nitrogen dioxide can react with GXXXXGK(S/T)C motif-containing GTPases (i.e., Rac1, Cdc42, and RhoA) to stimulate guanine nucleotide release. We now show that the reaction of RhoA with redox agents leads to different functional consequences from that of Rac1 and Cdc42 due to the presence of an additional cysteine (GXXXCGK(S/T)C) in the RhoA redox-active motif. While reaction of redox agents with RhoA stimulates guanine nucleotide dissociation, RhoA is subsequently inactivated through formation of an intramolecular disulfide that prevents guanine nucleotide binding thereby causing RhoA inactivation. Thus, redox agents may function to downregulate RhoA activity under conditions that stimulate Rac1 and Cdc42 activity. The opposing functions of these GTPases may be due in part to their differential redox regulation. In addition, the results presented herein suggest that the platinated-chemotherapeutic agent, cisplatin, which is known for targeting nucleic acids, reacts with RhoA to produce a RhoA thiol-cisplatin-thiol adduct, leading to inactivation of RhoA. Similarly, certain arsenic complexes (i.e., arsenate and arsenic trioxide) may inactivate RhoA by bridging the cysteine residues in the GXXXCGK(S/T)C motif. Thus, in addition to redox agents, platinated-chemotherapeutic agents and arsenic complexes may modulate the activity of GTPases containing the GXXXCGK(S/T)C motif (i.e., RhoA and RhoB).
authors.affiliation: Department of Biochemistry and Biophysics, The University of North Carolina, 530 Mary Ellen Jones Building, Chapel Hill, North Carolina 27599-7260, USA.
authors.forename: Jongyun
authors.initials: J
authors.lastname: Heo
authors.forename: Kimberly W
authors.initials: KW
authors.lastname: Raines
authors.forename: Viorel
authors.initials: V
authors.lastname: Mocanu
authors.forename: Sharon L
authors.initials: SL
authors.lastname: Campbell
mesh_terms: D000595:Amino Acid Sequence; D002384:Catalysis; D002945:Cisplatin / Q000494:pharmacology; D006150:Guanine Nucleotides / Q000378:metabolism; D007700:Kinetics; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D009569:Nitric Oxide / Q000737:chemistry / Q000378:metabolism; D010084:Oxidation-Reduction / Q000187:drug effects; D011485:Protein Binding; D020742:rhoA GTP-Binding Protein / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
chemical_list: D006150:Guanine Nucleotides; D009569:Nitric Oxide; D020742:rhoA GTP-Binding Protein; D002945:Cisplatin