Bcl-x Complements Saccharomyces cerevisiae Genes That Facilitate the Switch from Glycolytic to Oxidative Metabolism

Abstract

All eukaryotic organisms have mechanisms to adapt to changing metabolic conditions. The mammalian cell survival gene Bcl-x L enables cells to adapt to changes in cellular metabolism. To identify genes whose function can be substituted by Bcl-x L in a unicellular eukaryote, a genetic screen was performed using the yeast Saccharomyces cerevisiae. S. cerevisiae grows by anaerobic glycolysis when glucose is available, switching to oxidative phosphorylation when carbohydrate in the media becomes limiting (diauxic shift). Given that Bcl-x L appears to facilitate the switch from glycolytic to oxidative metabolism in mammalian cells, a library of yeast mutants was tested for the ability to efficiently undergo diauxic shift in the presence and absence of Bcl-x L . Several mutants were identified that have a defect in growth when switched from a fermentable to a nonfermentable carbon source that is corrected by the expression of Bcl-x L . These genes include the mitochondrial chaperonin TCM62, as well as previously uncharacterized genes. One of these uncharacterized genes, SVF1, promotes cell survival in mammalian cells in response to multiple apoptotic stimuli. The finding that TCM62 and the analogous human prohibitin gene also inhibit mammalian cell death following growth factor withdrawal implicates mitochondrial chaperones as regulators of apoptosis. Further characterization of the genes identified in this screen may enhance our understanding of Bcl-x L function in mammalian cells, and of cell survival pathways in general.

The Adaptive Response to Intestinal Oxidative Stress in Mammalian Hibernation

“…Studies in yeast suggest that Bcl-x L expression may promote mitochondrial physiology by allowing for continued oxidative phosphorylation and maintenance of cellular ATP levels despite events such as decreased glycolysis (12). The greater expression of Bcl-x L during the hibernation season strengthens our hypothesis that the intestine of hibernating squirrels responds to stress stimuli that might lead to cell death by increased expression of anti-apoptotic pathways.…”

Androgens target prohibitin to regulate proliferation of prostate cancer cells

“…It is possible that this mitochondrial function is regulated in response to cell growth, as prohibitin protein levels appear to increase in differentiated cells (Thompson et al, 2001). It has also been suggested that prohibitin may protect against apoptosis at times of metabolic stress in both yeast and mammalian cells, a function possibly related to its localization in the mitochondria (Vander Heiden et al, 2002). The cell-cycle function of prohibitin is less well understood and there is some dispute over the precise role of the protein (Coates et al, 2001).…”

SVF1 Regulates Cell Survival by Affecting Sphingolipid Metabolism in Saccharomyces cerevisiae

“…An SVF1-null strain marked with the HIS3 gene was generated in the wild-type parental strain by homologous replacement using methods previously described (Bahler et al 1998). In the W303 background, replacement of the coding region of SVF1 with the HIS3 and kanamycin resistance gene was performed as described (Bahler et al 1998;Vander Heiden et al 2002). All genomic deletions were confirmed by PCR to regions surrounding the deletion as well as phenotypic confirmation after tetrad dissection.…”

“…We identified SVF1 in a screen for yeast factors regulating cell survival that could be partially complemented by expression of mammalian Bcl-x L (Vander Heiden et al 2002). We have shown that while Svf1p and Bcl-x L have distinct functional properties, Svf1p functions to regulate survival under a variety of stress conditions.…”

“…We have shown that while Svf1p and Bcl-x L have distinct functional properties, Svf1p functions to regulate survival under a variety of stress conditions. In particular, cells lacking SVF1 are defective in responding to the metabolic changes that occur during the diauxic shift (Vander Heiden et al 2002) and are hypersensitive to cold stress, H 2 O 2 , menadione, and acetic acid, conditions that elevate production of, or exposure to, reactive oxidative species (Brace et al 2005). The mechanism of action of Svf1p has not been defined.…”