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Published on: November 8, 2006
Suppression of the profilin-deficient phenotype by the RHO2 signaling pathway in Saccharomyces cerevisiae
N Marcoux1, S Cloutier, E Zakrzewska
1Pavillon Charles-Eugène Marchand, Laval University, Ste-Foy, Quebec G1K 7P4, Canada.
Abstract:
Profilin plays an important role in actin organization in all eukaryotic cells through mechanisms that are still poorly understood. We had previously shown that Mid2p, a transmembrane protein and a potential cell wall sensor, is an effective multicopy suppressor of the profilin-deficient phenotype in Saccharomyces cerevisiae. To better understand the role of Mid2p in the organization of the actin cytoskeleton, we isolated five additional multicopy suppressors of pfy1Delta cells that are Rom1p, Rom2p, Rho2p, Smy1p, and the previously uncharacterized protein Syp1p. The problems of caffeine and NaCl sensitivity, growth defects at 30 degrees and 37 degrees, the accumulation of intracellular vesicular structures, and a random budding pattern in pfy1Delta cells are corrected by all the suppressors tested. This is accompanied by a partial repolarization of the cortical actin patches without the formation of visible actin cables. The overexpression of Mid2p, Rom2p, and Syp1p, but not the overexpression of Rho2p and Smy1p, results in an abnormally thick cell wall in wild-type and pfy1Delta cells. Since none of the suppressors, except Rho2p, can correct the phenotype of the pfy1-111/rho2Delta strain, we propose a model in which the suppressors act through the Rho2p signaling pathway to repolarize cortical actin patches.
Insights
Profilin is crucial for actin organization. Researchers identified new suppressors, including Syp1p, that help correct defects in profilin-deficient yeast cells, suggesting a role in actin cytoskeleton regulation.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Profilin is essential for actin organization in eukaryotic cells, but its precise mechanisms remain unclear.
- Mid2p, a transmembrane protein, was previously identified as a suppressor of profilin deficiency in yeast.
- Understanding the role of Mid2p and other suppressors in actin cytoskeleton regulation is critical.
Purpose of the Study:
- To identify and characterize additional multicopy suppressors of profilin deficiency (pfy1Δ) in Saccharomyces cerevisiae.
- To investigate the role of these suppressors in correcting actin cytoskeleton defects.
- To elucidate the signaling pathways involved in actin organization and cell wall integrity.
Main Methods:
- Genetic screening for multicopy suppressors of pfy1Δ.
- Phenotypic analysis of yeast mutants, including growth assays, caffeine and NaCl sensitivity tests, and budding pattern analysis.
- Microscopic examination of actin cytoskeleton organization and cell wall thickness.
Main Results:
- Five additional multicopy suppressors were identified: Rom1p, Rom2p, Rho2p, Smy1p, and Syp1p.
- All identified suppressors corrected various defects in pfy1Δ cells, including sensitivity to caffeine and NaCl, growth issues, and abnormal budding.
- Suppression was associated with partial repolarization of cortical actin patches.
- Overexpression of Mid2p, Rom2p, and Syp1p led to increased cell wall thickness.
Conclusions:
- The identified suppressors, acting through the Rho2p signaling pathway, can restore actin cytoskeleton organization in profilin-deficient cells.
- These findings provide new insights into the complex regulation of the actin cytoskeleton and cell wall integrity.
- Syp1p represents a novel factor involved in actin organization and cell polarity.
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