Glutathionylation of beta-actin via a cysteinyl sulfenic acid intermediary.
BACKGROUND
Cysteinyl residues in actin are glutathionylated, ie. form a mixed disulfide with glutathione, even in the absence of exogenous oxidative stress. Glutathionylation inhibits actin polymerization and reversible actin glutathionylation is a redox dependent mechanism for regulation of the cytoskeleton structure. The molecular mechanism that mediates actin glutathionylation in vivo is unclear.


RESULTS
We have studied glutathionylation of alpha- and beta-actin in vitro using an enzyme-linked immunosorbant assay with a monoclonal anti-glutathione antibody. alpha- and beta-actin were both glutathionylated when incubated with reduced glutathione (GSH) combined with diamide as a thiol oxidant. However, beta-actin was also glutathionylated by both glutathione disulfide (GSSG) and GSH in the absence of diamide whereas alpha-actin was poorly glutathionylated by GSH or GSSG. Glutathionylation of beta-actin by GSSG is likely to be mediated by a thiol-exchange mechanism whereas glutathionylation by GSH requires thiol oxidation. beta-actin glutathionylation by GSH was inhibited by arsenite and dimedone suggesting that the mechanism involved formation of a cysteinyl sulfenic acid residue in beta-actin.


CONCLUSIONS
We conclude that glutathionylation of beta-actin may occur via spontaneous oxidation of a cysteinyl residue to a sulfenic acid that readily reacts with GSH to form a mixed disulfide. We also show that the reactivity and oxidation to a reactive protein thiol intermediary differ between different actin isoforms.
Johansson
Magnus
M
Karolinska Institute, Department of Laboratory Medicine, Division for Clinical Microbiology, Karolinska University Hospital at Huddinge, S-141 86 Stockholm, Sweden. magnus.johansson@ki.se
Lundberg
Mathias
M
D000199:Actins / Q000737:chemistry / Q000378:metabolism; D000818:Animals; D000911:Antibodies, Monoclonal; D018053:Arsenites / Q000037:antagonists & inhibitors; D003545:Cysteine / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D005978:Glutathione / Q000737:chemistry / Q000378:metabolism*; D019803:Glutathione Disulfide / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D010084:Oxidation-Reduction; D020033:Protein Isoforms / Q000737:chemistry / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D011817:Rabbits; D013434:Sulfenic Acids / Q000737:chemistry*
D000199:Actins; D000911:Antibodies, Monoclonal; D018053:Arsenites; D020033:Protein Isoforms; D013434:Sulfenic Acids; D005978:Glutathione; D003545:Cysteine; D019803:Glutathione Disulfide