In Saccharomyces cerevisiae an unbalanced level of tyrosine phosphorylation down-regulates the Ras/PKA pathway

Magherini, Francesca; Busti, Stefano; Gamberi, Tania; Sacco, Elena; Raugei, Giovanni; Manao, Giampaolo; Ramponi, Giampietro; Modesti, Alessandra; Vanoni, Marco

doi:10.1016/j.biocel.2005.10.004

Cited by 10 publications

(6 citation statements)

References 75 publications

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“…It has been known that tyrosine kinase activation initiates the signaling pathway early on to direct the program leading to cell death in cultured cells of plant [29] and human [30]. In yeast, a possible crosstalk between tyrosine phosphorylation and Ras pathways is suggested [31]. As shown in the present study, TICDF was blocked not only by the tyrosine kinase inhibitor (AG18) but also by the farnesyltransferase inhibitor (B581), which specifically blocks Ras activation [32].…”

Section: Discussionsupporting

confidence: 57%

α‐Tomatine, the major saponin in tomato, induces programmed cell death mediated by reactive oxygen species in the fungal pathogen Fusarium oxysporum

Ito¹,

Ihara²,

Tamura³

et al. 2007

FEBS Letters

114

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The tomato saponin a-tomatine has been proposed to kill sensitive cells by binding to cell membranes followed by leakage of cell components. However, details of the modes of action of the compound on fungal cells are poorly understood. In the present study, mechanisms involved in a-tomatine-induced cell death of fungi were examined using a filamentous pathogenic fungus Fusarium oxysporum. a-Tomatine-induced cell death of F. oxysporum (TICDF) occurred only under aerobic conditions and was blocked by the mitochondrial F 0 F 1 -ATPase inhibitor oligomycin, the caspase inhibitor D-VAD-fmk, and protein synthesis inhibitor cycloheximide. Fungal cells exposed to a-tomatine showed TUNEL-positive nuclei, depolarization of transmembrane potential of mitochondria, and reactive oxygen species (ROS) accumulation. These results suggest that TICDF occurs through a programmed cell death process in which mitochondria play a pivotal role. Pharmacological studies using inhibitors suggest that a-tomatine activates phosphotyrosine kinase and monomeric G-protein signaling pathways leading to Ca 2+ elevation and ROS burst in F. oxysporum cells.

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Section: Discussionsupporting

confidence: 57%

α‐Tomatine, the major saponin in tomato, induces programmed cell death mediated by reactive oxygen species in the fungal pathogen Fusarium oxysporum

Ito¹,

Ihara²,

Tamura³

et al. 2007

FEBS Letters

114

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“…The yeast S. cerevisiae has two RasGAP proteins, Ira1 and Ira2. In addition to regulating Ras, previous reports have pointed out that Ira1 and Ira2 can independently regulate different biological pathways (23,28). Gpb1 might target Ira2, whereas Gpb2 might target Ira1.…”

Section: Discussionmentioning

confidence: 99%

The RasGAP Proteins Ira2 and Neurofibromin Are Negatively Regulated by Gpb1 in Yeast and ETEA in Humans

Phan

Ding

et al. 2010

Molecular and Cellular Biology

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The neurofibromatosis type 1 (NF1) gene encodes the GTPase-activating protein (GAP) neurofibromin, which negatively regulates Ras activity. The yeast Saccharomyces cerevisiae has two neurofibromin homologs, Ira1 and Ira2. To understand how these proteins are regulated, we utilized an unbiased proteomics approach to identify Ira2 and neurofibromin binding partners. We demonstrate that the Gpb1/Krh2 protein binds and negatively regulates Ira2 by promoting its ubiquitin-dependent proteolysis. We extended our findings to show that in mammalian cells, the ETEA/UBXD8 protein directly interacts with and negatively regulates neurofibromin. ETEA contains both UBA and UBX domains. Overexpression of ETEA downregulates neurofibromin in human cells. Purified ETEA, but not a mutant of ETEA that lacks the UBX domain, ubiquitinates the neurofibromin GAP-related domain in vitro. Silencing of ETEA expression increases neurofibromin levels and downregulates Ras activity. These findings provide evidence for conserved ubiquitination pathways regulating the RasGAP proteins Ira2 (in yeast) and neurofibromin (in humans).

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“…Finally to confirm the inability of cells lacking active Ras2 in the nucleus to perform invasive growth, we made a fusion between the Ras2 protein and the Rev NES sequence in the strain Tlys86 commonly used to test this phenotype [27] , generating strain Tlys86-NES-RAS2. Also in this background, expression of NES-Ras2 resulted in a polypeptide of the correct size ( Figure 7A ), the mutant strain grew in minimal medium containing glucose at a rate comparable to that of the wild-type strain ( Figure 7B ) and the insertion of the Rev NES sequence completely excluded the NES-Ras2 protein from the nucleus ( Figure 7C ).…”

Section: Resultsmentioning

confidence: 99%

Nuclear Ras2-GTP Controls Invasive Growth in Saccharomyces cerevisiae

2013

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Using an eGFP-RBD3 probe, which specifically binds Ras-GTP, we recently showed that the fluorescent probe was localized to the plasma membrane and to the nucleus in wild type cells growing exponentially on glucose medium, indicating the presence of active Ras in these cellular compartments. To investigate the nuclear function of Ras-GTP, we generated a strain where Ras2 is fused to the nuclear export signal (NES) from the HIV virus, in order to exclude this protein from the nucleus. Our results show that nuclear active Ras2 is required for invasive growth development in haploid yeast, while the expression of the NES-Ras2 protein does not cause growth defects either on fermentable or non-fermentable carbon sources and does not influence protein kinase A (PKA) activity related phenotypes analysed. Moreover, we show that the cAMP/PKA pathway controls invasive growth influencing the localization of active Ras. In particular, we show that PKA activity plays a role in the localization of active Ras and influences the ability of the cells to invade the agar: high PKA activity leads to a predominant nuclear accumulation of active Ras and induces invasive growth, while low PKA activity leads to plasma membrane localization of active Ras and to a defective invasive growth phenotype.

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In Saccharomyces cerevisiae an unbalanced level of tyrosine phosphorylation down-regulates the Ras/PKA pathway

Cited by 10 publications

References 75 publications

α‐Tomatine, the major saponin in tomato, induces programmed cell death mediated by reactive oxygen species in the fungal pathogen Fusarium oxysporum

α‐Tomatine, the major saponin in tomato, induces programmed cell death mediated by reactive oxygen species in the fungal pathogen Fusarium oxysporum

The RasGAP Proteins Ira2 and Neurofibromin Are Negatively Regulated by Gpb1 in Yeast and ETEA in Humans

Nuclear Ras2-GTP Controls Invasive Growth in Saccharomyces cerevisiae

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