title: Identification of a novel Ser/Thr protein phosphatase Ppq1 as a negative regulator of mating MAP kinase pathway in Saccharomyces cerevisiae.
abstract: The specificity and efficiency of cell signaling is largely governed by the complex formation of signaling proteins. The precise spatio-temporal control of the complex assembly is crucial for proper signaling and cell survival. Protein phosphorylation is a key mechanism of signal processing in most of cell signaling networks. Phosphatases, along with kinases, control the phosphorylation state of many proteins and thus play a critical role in the precise regulation of signaling at each stage such as activation, propagation, and adaptation. Identification and functional analysis of pathway-specific phosphatase is, therefore, crucial for the understanding of cell signaling mechanisms. Here, we have developed a novel screening strategy to identify pathway-specific phosphatases, in which the entire repertoire of cell's phosphatases was tethered to a signaling complex and the changes in signaling response were monitored. As a model target, we have chosen the mating MAP kinase pathway in the budding yeast, which is composed of three kinases and Ste5 scaffold protein. Using this strategy, a putative Ser/Thr phosphatase, Ppq1, was identified to be mating-specific. Results show that Ppq1 down-regulates mating signaling by targeting at or upstream of the terminal MAP kinase Fus3 in the cascade. The catalytic activity of Ppq1 as a phosphatase was confirmed in vitro and is necessary for its function in the regulation of mating signaling. Overall, the data suggest that Ppq1 functions as a negative regulator of mating MAPK pathway by dephosphorylating target pathway protein(s) and plays a key role in the control of the background signaling noise.
authors.affiliation: Department of Biological Sciences and Research Center for Functional Cellulomics, Seoul National University, Seoul 151-742, Republic of Korea.
authors.forename: Eunyeong
authors.initials: E
authors.lastname: Shim
authors.affiliation: Department of Biological Sciences and Research Center for Functional Cellulomics, Seoul National University, Seoul 151-742, Republic of Korea. Electronic address: biopark@snu.ac.kr.
authors.forename: Sang-Hyun
authors.initials: SH
authors.lastname: Park
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D002384:Catalysis; D017353:Gene Deletion; D049770:Genes, Mating Type, Fungal; D020935:MAP Kinase Signaling System; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D010749:Phosphoprotein Phosphatases / Q000235:genetics / Q000502:physiology*; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C080321:STE5 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; C075580:FUS3 protein, S cerevisiae; D020928:Mitogen-Activated Protein Kinases; C091992:PPQ1 protein, S cerevisiae; D010749:Phosphoprotein Phosphatases
keywords: MAP kinase pathway; MAPK; MAPKK; MAPKKK; Mating; PP1; Phosphatase; Phosphoprotein phosphatase 1; Ppq1; Scaffold; Yeast; mitogen-activated protein kinase; mitogen-activated protein kinase kinase; mitogen-activated protein kinase kinase kinase; p-nitrophenyl phosphate; pNPP; yEGFP; yeast enhanced green fluorescent protein