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Activation mechanism of Gi and Go by reactive oxygen species.

Nishida M, Schey KL, Takagahara S, Kontani K, Katada T, Urano Y, Nagano T, Nagao T, Kurose H
J Biol Chem. 2002 277 (11): 9036-42

PMID: 11781308 · DOI:10.1074/jbc.M107392200

Reactive oxygen species are proposed to work as intracellular mediators. One of their target proteins is the alpha subunit of heterotrimeric GTP-binding proteins (Galpha(i) and Galpha(o)), leading to activation. H(2)O(2) is one of the reactive oxygen species and activates purified Galpha(i2). However, the activation requires the presence of Fe(2+), suggesting that H(2)O(2) is converted to more reactive species such as c*OH. The analysis with mass spectrometry shows that seven cysteine residues (Cys(66), Cys(112), Cys(140), Cys(255), Cys(287), Cys(326), and Cys(352)) of Galpha(i2) are modified by the treatment with *OH. Among these cysteine residues, Cys(66), Cys(112), Cys(140), Cys(255), and Cys(352) are not involved in *OH-induced activation of Galpha(i2). Although the modification of Cys(287) but not Cys(326) is required for subunit dissociation, the modification of both Cys(287) and Cys(326) is necessary for the activation of Galpha(i2) as determined by pertussis toxin-catalyzed ADP-ribosylation, conformation-dependent change of trypsin digestion pattern or guanosine 5'-3-O-(thio)triphosphate binding. Wild type Galpha(i2) but not Cys(287)- or Cys(326)-substituted mutants are activated by UV light, singlet oxygen, superoxide anion, and nitric oxide, indicating that these oxidative stresses activate Galpha(i2) by the mechanism similar to *OH-induced activation. Because Cys(287) exists only in G(i) family, this study explains the selective activation of G(i)/G(o) by oxidative stresses.

MeSH Terms (12)

Adenosine Diphosphate Ribose Amino Acid Sequence Animals GTP-Binding Protein alpha Subunits, Gi-Go Guanosine 5'-O-(3-Thiotriphosphate) Heterotrimeric GTP-Binding Proteins Hydroxyl Radical Mitogen-Activated Protein Kinases Molecular Sequence Data Rats Rats, Sprague-Dawley Reactive Oxygen Species

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