Mitogen‐activated protein kinase Mkp1 of Pneumocystis carinii complements the slt2Δ defect in the cell integrity pathway of Saccharomyces cerevisiae

Fox, D.; Ag, Smulian

doi:10.1046/j.1365-2958.1999.01606.x

Cited by 32 publications

(25 citation statements)

References 37 publications

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“…Although evidences exist that hydrogen peroxide activates p44/p42 MAPK in mammalian cells, our results show for the first time activation of p44/p42 MAPK by hydrogen peroxide in the yeast S. cerevisiae (Hannken et al, 2000;Nguyen et al, 2004;van Rossum et al, 2004). Interestingly Mkp1, a Pneumocystis carinii homologue of Mpk1, has been found to be activated by the same oxidant (Fox and Smulian, 1999).…”

Section: Discussionmentioning

confidence: 44%

Oxidative Stress ActivatesFUS1andRLM1Transcription in the YeastSaccharomyces cerevisiaein an Oxidant-dependent Manner

Staleva

Hall

Orlow

2004

MBoC

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Mating in haploid Saccharomyces cerevisiae occurs after activation of the pheromone response pathway. Biochemical components of this pathway are involved in other yeast signal transduction networks. To understand more about the coordination between signaling pathways, we used a "chemical genetic" approach, searching for compounds that would activate the pheromone-responsive gene FUS1 and RLM1, a reporter for the cell integrity pathway. We found that catecholamines (L-3,4-hydroxyphenylalanine [L-dopa], dopamine, adrenaline, and noradrenaline) elevate FUS1 and RLM1 transcription. N-Acetyl-cysteine, a powerful antioxidant in yeast, completely reversed this effect, suggesting that FUS1 and RLM1 activation in response to catecholamines is a result of oxidative stress. The oxidant hydrogen peroxide also was found to activate transcription of an RLM1 reporter. Further genetic analysis combined with immunoblotting revealed that Kss1, one of the mating mitogen-activated protein kinases (MAPKs), and Mpk1, an MAPK of the cell integrity pathway, participated in L-dopa-induced stimulation of FUS1 and RLM1 transcription. We also report that Mpk1 and Hog1, the high osmolarity MAPK, were phosphorylated upon induction by hydrogen peroxide. Together, our results demonstrate that cells respond to oxidative stress via different signal transduction machinery dependent upon the nature of the oxidant. INTRODUCTIONIn the haploid cells of the yeast Saccharomyces cerevisiae, four essential MAPK cascades (Figure 1) respond to different external signals to mediate specific responses. The mating pathway is activated by peptide pheromones and induces cell-cycle arrest and the morphological changes required for mating (Elion, 1998;Gustin et al., 1998). The invasive growth pathway is activated by starvation and induces foraging into the agar substratum. The high osmolarity glycerol (HOG) pathway increases intracellular glycerol levels in response to hypertonic stress, whereas the cell integrity pathway is activated by hypotonic stress, heat shock, or impaired cell wall synthesis. Recently, an additional MAPK cascade has been described: the Kss1 vegetative growth pathway (Lee and Elion, 1999). The Kss1 pathway may be activated by cell wall stress or changes in osmolarity (Cullen et al., 2000).The mating pathway is the most studied cellular response to an external signal. As a relatively simple G protein-coupled cascade, it is a widely used model to study mammalian G protein-coupled receptors. The mating cascade includes pheromone receptors (Ste2 and Ste3), G proteins (Gpa1, Ste4, and Ste18), the p21 activating protein kinase Ste20, a mitogen-activated protein kinase kinase kinase (MAPKKK) Ste11, a mitogen-activated protein kinase kinase (MAPKK) Ste7, a scaffolding protein Ste5 and two MAPKs (Fus3 and Kss1) (Gustin et al., 1998;Madhani and Fink, 1998;Farley et al., 1999). Targets of the terminal MAPK include Ste12, a factor required for transcription of pheromone-responsive genes, and Far1, a bifunctional protein required for polarization and G1...

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Section: Discussionmentioning

confidence: 44%

Oxidative Stress ActivatesFUS1andRLM1Transcription in the YeastSaccharomyces cerevisiaein an Oxidant-dependent Manner

Staleva

Hall

Orlow

2004

MBoC

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“…PHR class genes have been implicated in cell wall generation, cross-linking, and stability under adverse conditions. Heterologous expression of P. carinii genes in culturable fungal species has recently proven a useful experimental approach to infer P. carinii gene function (10,17,36). Accordingly, we evaluated the ability of P. carinii PHR1 to growth complement an S. cerevisiae mutant strain deficient in the PHR1 analogue GAS1 in the presence of a potent osmotic destabilizing agent, SDS (38).…”

Section: Resultsmentioning

confidence: 99%

Characterization ofPneumocystis carinii PHR1, a pH-Regulated Gene Important for Cell Wall Integrity

Kottom¹,

Thomas²,

Limper

2001

J Bacteriol

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Pneumocystis carinii remains an important opportunistic fungal pathogen causing life-threatening pneumonia in patients with AIDS and malignancy. Currently, little is known about how the organism adapts to environmental stresses and maintains its cellular integrity. We recently discovered an open reading frame approximately 600 bp downstream of the region coding GSC-1, a gene mediating ␤-glucan cell wall synthesis in P. carinii. The predicted amino acid sequence of this new gene, termed P. carinii PHR1, exhibited 38% homology to Saccharomyces cerevisiae GAS1, a glycosylphosphatidylinositol-anchored protein essential to maintaining cell wall integrity, and 37% homology to Candida albicans PHR1/PHR2, pH-responsive genes encoding proteins recently implicated in cross-linking ␤-1,3-and ␤-1,6-glucans. In view of its homology to these related fungal genes, the pH-dependent expression of P. carinii PHR1 was examined. As in C. albicans, P. carinii PHR1 expression was repressed under acidic conditions but induced at neutral and more alkaline pH. PHR1-related proteins have been implicated in glucan cell wall stability under various environmental conditions. Although difficulties with P. carinii culture and transformation have traditionally limited assessment of gene function in the organism itself, we have successfully used heterologous expression of P. carinii genes in related fungi to address functional correlates of P. carinii-encoded proteins. Therefore, the potential role of P. carinii PHR1 in cell wall integrity was examined by assessing its ability to rescue an S. cerevisiae gas1 mutant with absent endogenous Phr1p-like activity. Interestingly, P. carinii PHR1 DNA successfully restored proliferation of S. cerevisiae gas1 mutants under lethal conditions of cell wall stress. These results indicate that P. carinii PHR1 encodes a protein responsive to environmental pH and capable of mediating fungal cell wall integrity.Pneumocystis carinii remains an important fungal agent causing life-threatening pneumonia in patients with impaired immunity (19). Other fungi such as Aspergillus nidulans and Candida albicans alter gene expression as an adaptive response to environmental pH changes in order to maintain cell wall integrity and promote viability under various conditions (6,11,21,23,(32)(33)(34)(35). Specifically, it has been demonstrated that C. albicans expresses a unique family of pH-regulated genes required for virulence. These genes nominally include PHR1, a gene expressed maximally at pH 5.5 to 8.0 which encodes a protein promoting systemic infection of mice. Alternatively, C. albicans also expresses PHR2, whose transcription is greatest at acidic pH (4 to 5) values (24). If PHR2 is rendered inactive, C. albicans mutants exhibit decreased pathogenesis in a mouse model of vaginal infection (6,24,32).Recent studies indicate that Phr1p and Phr2p act on ␤-1,3-glucans of the C. albicans cell walls, elongating the ␤-1,3 polysaccharide backbone and potentially mediating the attachment of ␤-1,6 glucosyl side chains and ␤-1,6-...

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“…We could not detect significant changes in H 2 O 2 induction of SLT2 in hog1⌬ and PTP2 induction in slt2⌬ or hog1⌬ strains (data not shown). It has been shown that Mkp1, an Slt2 homologue of Pneumocystis carinii, can be activated by H 2 O 2 in vitro (39). However, it remains to be ascertained whether Slt2 can be activated by H 2 O 2 and whether this activation is responsible for H 2 O 2 induction of PTP2 and SLT2.…”

Section: Differential Expression Of Slt2 and Phosphatase Genes In Resmentioning

confidence: 99%

Regulation of the Saccharomyces cerevisiae Slt2 Kinase Pathway by the Stress-inducible Sdp1 Dual Specificity Phosphatase

Hahn

Thiele

2002

Journal of Biological Chemistry

112

117

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The Slt2/Mpk1 mitogen-activated protein kinase (MAPK) cell integrity pathway is involved in maintenance of cell shape and integrity during vegetative growth and mating in Saccharomyces cerevisiae. Slt2 is activated by dual phosphorylation of a threonine and tyrosine residue in response to several environmental stresses that perturb cell integrity. Negative regulation of Slt2 is achieved via dephosphorylation by two protein-tyrosine phosphatases, Ptp2 and Ptp3, and a dual specificity phosphatase, Msg5. In this study, we provide genetic and biochemical evidence that the stress-inducible dual specificity phosphatase, Sdp1, negatively regulates Slt2 by direct dephosphorylation. Deletion of SDP1 exacerbated growth defects due to overexpression of Mkk1 p386 , a constitutively active mutant of Slt2 MAPK kinase, whereas overexpression of Sdp1 suppressed lethality caused by Mkk1 p386 overexpression. The heat shock-induced phosphorylation level of Slt2 was elevated in an sdp1⌬ strain compared with that of the wild type, and heat shock-activated phospho-Slt2 was dephosphorylated by recombinant Sdp1 in vitro. Under normal growth conditions, an Sdp1-GFP fusion protein was localized to both the nucleus and cytoplasm. However, the Sdp1-GFP protein translocated to punctate spots throughout the cell after heat shock. SDP1 transcription was induced by several stress conditions in an Msn2/4-dependent manner but independent of the Rlm1 transcription factor, a downstream target activated by Slt2. Induction of SLT2 by high osmolarity was dependent on Rlm1 transcription factor and Hog1 kinase, suggesting cross-talk between Slt2 and Hog1 MAPK pathways. These studies demonstrate regulation of Slt2 activity and gene expression in coordination with other stress signaling pathways.

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Mitogen‐activated protein kinase Mkp1 of Pneumocystis carinii complements the slt2Δ defect in the cell integrity pathway of Saccharomyces cerevisiae

Cited by 32 publications

References 37 publications

Oxidative Stress ActivatesFUS1andRLM1Transcription in the YeastSaccharomyces cerevisiaein an Oxidant-dependent Manner

Oxidative Stress ActivatesFUS1andRLM1Transcription in the YeastSaccharomyces cerevisiaein an Oxidant-dependent Manner

Characterization ofPneumocystis carinii PHR1, a pH-Regulated Gene Important for Cell Wall Integrity

Regulation of the Saccharomyces cerevisiae Slt2 Kinase Pathway by the Stress-inducible Sdp1 Dual Specificity Phosphatase

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