Differential regulation of FUS3 MAP kinase by tyrosine-specific phosphatases PTP2/PTP3 and dual-specificity phosphatase MSG5 in Saccharomyces cerevisiae.

Abstract

The Saccharomyces cerevisiae mating pheromone response is mediated by activation of a MAP kinase (Fus3p and Ksslp) signaling pathway. Pheromone stimulation causes cell cycle arrest. Therefore, inactivation of the Fus3p and Ksslp MAP kinases is required during recovery phase for the resumption of cell growth. We have isolated a novel protein tyrosine phosphatase gene, PTP3, as a negative regulator of this pathway. Ptp3p directly dephosphorylates and inactivates Fus3p MAP kinase in vitro. Multicopy PTP3 represses pheromone-induced transcription and promotes recovery. In contrast, disruption of PTP3 in combination with its homolog PTP2 results in constitutive tyrosine phosphorylation, enhanced kinase activity of Fus3p MAP kinase on stimulation, and delayed recovery from the cell cycle arrest. Both tyrosine phosphorylation and kinase activity of Fus3p are further increased by disruption of PTP3 and PTP2 in combination with MSG5, which encodes a dual-specificity phosphatase. Cells deleted for all three of the phosphatases (ptp2~ptp3Amsg5~) are hypersensitive to pheromone and exhibit a severe defect in recovery from pheromone-induced growth arrest. Our data indicate that Ptp3p is the major phosphatase responsible for tyrosine dephosphorylation of Fus3p to maintain a low basal activity; it also has important roles, along with Msg5p, in inactivation of Fus3p following pheromone stimulation. These data present the first evidence for a coordinated regulation of MAP kinase function through differential actions of protein tyrosine phosphatases and a dual-specificity phosphatase.[Key Words: FUS3 MAP kinase; protein tyrosine phosphatase; pheromone response pathway; PTP2; PTP3; MSGS]

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

“…Protein tyrosine phosphatases and dual specificity phosphatases are known to affect MAPKs activity in yeast. For instance, Ptp2 and Ptp3 affect localization of the Hog1 MAPK, but are also known to regulate Fus3 and Slt2 (Mattison & Ota, 2000;Mattison, Spencer, Kresge, Lee, & Ota, 1999;Zhan, Deschenes, & Guan, 1997). The upper part of the Ste/MAPK cascade is shared between the pseudohyphal/invasive growth pathway and the mating pheromone response pathway and Kss1, the MAPK of the pseudohyphae/invasive growth module, has been indicated as a bona fide component of the mating pathway (Breitkreutz & Tyers, 2002).…”

A walk-through of the yeast mating pheromone response pathway

“…For example, the tyrosine phosphatases Ptp2 and Ptp3, and the dual-specificity phosphatase Msg5, act on Fus3 MAPK and Kss1 MAPK [34,155]. Many of these phosphatase activities are constitutive, but Msg5 is positively regulated at the transcriptional level by pheromone.…”

Pheromone induction promotes Ste11 degradation through a MAPK feedback and ubiquitin-dependent mechanism

“…Further, this outcome establishes that Ste11 is subject to different modes of regulation in the two pathways. This phenomenon occurs through several desensitization or adaptation mechanisms that impinge on different components of the signaling pathway (37)(38)(39)(40)(41)(42)(43)(44)(45). The feedback and ubiquitindependent degradation of Ste11 could be an additional mechanism that contributes to desensitization.…”