Two protein-tyrosine phosphatases inactivate the osmotic stress response pathway in yeast by targeting the mitogen-activated protein kinase, Hog1.

Tim Jacoby,Christopher Mattison,Heather Flanagan,Anatole Faykin,Anita G Seto,Irene Ota

doi:10.1074/jbc.272.28.17749

Tim Jacoby, Christopher Mattison + Show 4 more

Open Access

https://doi.org/10.1074/jbc.272.28.17749

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Abstract

Protein phosphatases inactivate mitogen-activated protein kinase (MAPK) signaling pathways by dephosphorylating components of the MAPK cascade. Two genes encoding protein-tyrosine phosphatases, PTP2, and a new phosphatase, PTP3, have been isolated in a genetic selection for negative regulators of an osmotic stress response pathway called HOG, for high osmolarity glycerol, in budding yeast. PTP2 and PTP3 were isolated as multicopy suppressors of a severe growth defect due to hyperactivation of the HOG pathway. Phosphatase activity is required for suppression since mutation of the catalytic Cys residue in Ptp2 and Ptp3, destroys suppressor function and biochemical activity. The substrate of these phosphatases is likely to be the MAPK, Hog1. Catalytically inactive Ptp2 and Ptp3 coprecipitate with Hog1 from yeast extracts. In addition, strains lacking PTP2 and PTP3 do not dephosphorylate Hog1-phosphotyrosine as well as wild type. The latter suggests that PTP2 and PTP3 play a role in adaptation. Consistent with this role, osmotic stress induces expression of PTP2 and PTP3 transcripts in a Hog1-dependent manner. Thus Ptp2 and Ptp3 likely act in a negative feedback loop to inactivate Hog1.

Highlights

MAPK1 signaling is ubiquitous among eukaryotes and regulates a variety of processes
In S. cerevisiae, a putative protein-tyrosine phosphatase encoded by PTP2 [22,23,24] negatively regulates the osmotic stress response pathway, and indirect evidence suggests this occurs by dephosphorylation of Hog1-phosphotyrosine (Hog1-Tyr(P)) [25]
Identification of PTP3 as a Negative Regulator of the HOG mitogen-activated protein kinase (MAPK) Pathway—Protein phosphatases that negatively regulate the S. cerevisiae HOG pathway were isolated by a genetic approach

Summary

Introduction

MAPK1 signaling is ubiquitous among eukaryotes and regulates a variety of processes. In metazoans and in yeast, MAPK pathways regulate growth, development, and the response to stress (reviewed in Refs. 1–5). In S. cerevisiae, a putative protein-tyrosine phosphatase encoded by PTP2 [22,23,24] negatively regulates the osmotic stress response pathway, and indirect evidence suggests this occurs by dephosphorylation of Hog1-phosphotyrosine (Hog1-Tyr(P)) [25]. No obvious differences were observed between ptp2⌬, ptp3⌬, ptp2⌬ ptp3⌬, and wild type strains grown under standard conditions or in high osmolarity media where the HOG pathway would be activated.

Results

Conclusion