Protein phosphatase 2C, encoded by ptc1+, is important in the heat shock response of Schizosaccharomyces pombe.

Abstract

Protein phosphatase 2C (PP2C), an Mg2e-dependent enzyme that dephosphorylates serine and threonine residues, defines one of the three major families of structurally unrelated eukaryotic protein phosphatases. Members Eukaryotic protein phosphatases have traditionally been classified into five broad classes on the basis of substrate amino acid specificity and cofactor requirements (2). However, gene cloning and sequencing studies have revealed that there are in fact three major evolutionary families of eukaryotic protein phosphatases. One family includes members that dephosphorylate exclusively tyrosine together with the more recently recognized dual-specificity phosphatases such as Cdc25 that dephosphorylate tyrosine and threonine in vivo (reviewed in reference 25). This is a highly divergent family, but all of its members share a conserved active site that includes a cysteine residue that is the phosphate acceptor in the dephosphorylation reaction. The second major family consists of type 1 (PP1), type 2A (PP2A), and type 2B (PP2B) serine/threonine phosphatases (2). These enzymes share -40% identity of amino acid sequence in their catalytic domains, show sensitivity to certain phosphatase inhibitors such as okadaic acid, and do not require Mg" for enzymatic activity (2). A number of new phosphatase genes whose protein products have a structural similarity to this family have been identified in a variety of species (4), and the family continues to expand.The third major protein phosphatase family is made up of type 2C enzymes (PP2C). Like the second family, these enzymes predominantly dephosphorylate serine and threonine residues, but their activity is Mg2+ dependent and resistant to okadaic acid (2). These enzymes are ubiquitous in eukaryotes; PP2C activity has been detected in a variety of species, and PP2C genes have been cloned in rats (35,36), rabbits, humans (19), and most recently in the budding yeast Saccharomyces cerevisiae (18). PP2C enzymes share -25% identity in their catalytic domains, but they have no detectable sequence similarity to the phosphatases from the other families.Genetic studies have been instrumental in unraveling the biological functions of various members of the tyrosine phosphatases and PP1/PP2A/PP2B serine/threonine phosphatases. * Corresponding author. Phone: (619) 554-6165.In addition to functions in basic processes of cellular metabolism, these phosphatases have important roles in cell cycle control, as well as regulation of cell proliferation and differentiation. In contrast, very little is known about physiological functions of PP2C, mainly because of a lack of genetic studies or a specific inhibitor of PP2C. Here we report the cloning and characterization of a PP2C gene in Schizosaccharomyces pombe. This gene, ptcl +, was isolated as a multicopy suppressor of swol-26, a temperature-sensitive mutation of a gene encoding an 82-kDa protein that is closely related to the stress protein hsp9O. ptcl + mRNA is heat inducible, and ptcl deletion mutant cells are highly sensitive to ...

The Specificity of Extracellular Signal-regulated Kinase 2 Dephosphorylation by Protein Phosphatases

“…In contrast, PP2C has been suggested as a negative regulator of p38 and JNK kinases involved in stress responses (57)(58)(59)(60)(61). However, it is not clear whether PP2C or other Ser/Thr protein phosphatases are also responsible for ERK2 inactivation.…”

Protein Phosphatase 2C Acts Independently of Stress-activated Kinase Cascade to Regulate the Stress Response in Fission Yeast

“…graphic properties of Ptc1 established in previous studies (15,16). Interestingly, overexpression of ptc1 ϩ leads to a decrease in cell length, 15.1 Ϯ 0.9 m for control cells and 12.8 Ϯ 1 m for pART1-ptc1 ϩ -transformed cells, respectively (Fig.…”

“…ptc1 ϩ Expression Is Regulated by Spc1 and Atf1-Heat shock leads to phosphorylation and the activation of Spc1 and increased expression of ptc1 ϩ mRNA (10,15). These observations prompted us to explore whether ptc1 ϩ mRNA expression is responsive to other forms of stress that are known to activate Spc1 kinase, such as high osmolarity, and whether the activation of Spc1 and increased expression of ptc1 ϩ are causally related.…”

“…Analysis of PP2C Activity-Fractionation of S. pombe crude lysates by Mono Q chromatography was performed as described (15,16). Preparation of 32 P-labeled casein and the procedures of the PP2C phosphatase assay were as described by McGowan and Cohen (24).…”

“…Independent evidence for a role of PP2C in the negative regulation of stress-activated kinase cascades came from studies of S. pombe. In S. pombe the genes ptc1 ϩ , ptc2 ϩ , and ptc3 ϩ account for ϳ90% of the total PP2C activity (15,16). Mutants carrying deletions of two or three of these genes are hypersensitive to increased levels of calcium.…”