Abstract #83B

Conserved Actin Cysteine Residues: Oxidative Stress Sensors That Can Regulate Programmed Cell Death in Yeast. Michelle E. Farah, David C. Amberg. Biochemistry, Upstate Medical University, Syracuse, NY.
   The actin cytoskeleton of eukaryotic cells is a participant in diverse cellular processes. Because of its broad range of involvement, actin is also a likely target of oxidative stress. We have previously shown that in the absence of the long-studied oxidoreductase Oye2p, S. cerevisiae actin is also subject to the same form of oxidation on co-conserved cysteines 285 and 374 [1]. Importantly, actin hyperstabilization and oxidative sensitivity of oye2D cells are suppressed in the presence of act1^C285A and act1^C374A mutations, suggesting that actin’s cysteines are a crucial target of oxidation in the cell. It has been shown that hyperstabilization of actin triggers an apoptotic phenotype in yeast[2]. However, the connection between actin oxidation and programmed cell death has not been defined. We will present data to show that hallmark indicators of programmed cell death are elevated in old yellow enzyme-lacking cells and these correlate with a dramatic reduction in chronological life span. The cell death phenotype of OYE2-lacking cells can be completely suppressed by removing the potential for formation of the actin C285-C374 disulfide bond. We will further show that the clinically important antioxidant N-acetylcysteine can suppress the oye2D cytoskeletal and cell death phenotype. This highlights the critical role that oxidation of actin’s C285 and C374 plays during aging and programmed cell death. Collectively, our data favor a model where the actin cytoskeleton is a sensor that can initiate cell death in response to oxidative load. 1.Haarer, B.K. and D.C. Amberg, Old yellow enzyme protects the actin cytoskeleton from oxidative stress. Mol Biol Cell, 2004. 15(10): p. 4522-31. 2.Gourlay, C.W., et al., A role for the actin cytoskeleton in cell death and aging in yeast. J Cell Biol, 2004. 164(6): p. 803-9.

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