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The plasma membrane ferrireductase activity of Saccharomyces cerevisiae is partially controlled by cyclic AMP
E Lesuisse1, B Horion, P Labbe
1Laboratoire de Biochimie des Porphyrines, Université Paris, France.
Abstract:
The plasma-membrane-bound ferrireductase activity of ras1 and ras2 mutants of Saccharomyces cerevisiae is not induced in response to iron limitation. This phenotype was suppressed by the bcy1 mutation in ras2 but not in ras1 mutants. The cellular haem content of ras-1-bearing strains decreased dramatically when cells were grown in semi-synthetic medium (low yeast extract content), which could account for their very low ferrireductase activity. The ferrireductase activity of cdc25 and cdc35 mutants dropped when the cells were shifted to a non-permissive temperature. This drop was prevented in the double mutant cdc35 sra5 by adding cyclic AMP to the growth medium. We propose that ferrireductase activity is under the control of a cyclic AMP-dependent protein phosphorylation.
Insights
Ras1 and Ras2 proteins in Saccharomyces cerevisiae are crucial for iron uptake. Their mutations impair ferrireductase activity, essential for iron assimilation, suggesting a link to cyclic AMP signaling pathways.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Ferrireductase activity is vital for iron uptake in Saccharomyces cerevisiae.
- Ras1 and Ras2 proteins are involved in cellular signaling pathways.
- Iron limitation is a key environmental factor influencing cellular processes.
Purpose of the Study:
- To investigate the role of Ras1 and Ras2 proteins in regulating plasma-membrane-bound ferrireductase activity.
- To explore the relationship between Ras proteins, iron metabolism, and cyclic AMP signaling.
- To elucidate the mechanisms controlling ferrireductase activity in yeast.
Main Methods:
- Analysis of ferrireductase activity in Saccharomyces cerevisiae mutants (ras1, ras2, bcy1, cdc25, cdc35, sra5).
- Measurement of cellular haem content in different mutant strains.
- Manipulation of growth conditions, including iron limitation and cyclic AMP supplementation.
Main Results:
- Ras1 and Ras2 mutants exhibited impaired ferrireductase activity, not induced by iron limitation.
- The bcy1 mutation suppressed the ras2 phenotype but not the ras1 phenotype.
- Cellular haem content decreased in ras1 mutants, correlating with reduced ferrireductase activity.
- Ferrireductase activity in cdc25 and cdc35 mutants decreased at non-permissive temperatures.
- Cyclic AMP addition prevented the drop in ferrireductase activity in cdc35 sra5 double mutants.
Conclusions:
- Plasma-membrane-bound ferrireductase activity in Saccharomyces cerevisiae is regulated by Ras1 and Ras2 proteins.
- Ferrireductase activity appears to be under the control of a cyclic AMP-dependent protein phosphorylation pathway.
- These findings highlight a novel connection between Ras signaling, iron homeostasis, and cyclic AMP pathways in yeast.