Normal Function of the Yeast TOR Pathway Requires the Type 2C Protein Phosphatase Ptc1

González, Asier; Ruiz, Amparo; Casamayor, Antonio; Ariño, Joaquı́n

doi:10.1128/mcb.01740-08

Cited by 40 publications

(53 citation statements)

References 78 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…In this regard, it has been recently shown that Ptc1 is required for normal TOR signaling, possibly by regulating a step upstream of the type 2A-related Ser/Thr phosphatase Sit4 in a way independent of the HOG pathway (28). This finding provides the first evidence that a PP2C is linked to this important and conserved pathway.…”

supporting

confidence: 51%

Type 2C Protein Phosphatases in Fungi

2011

Self Cite

View full text Add to dashboard Cite

Type 2C Ser/Thr phosphatases are a remarkable class of protein phosphatases, which are conserved in eukaryotes and involved in a large variety of functional processes. Unlike in other Ser/Thr phosphatases, the catalytic polypeptide is not usually associated with regulatory subunits, and functional specificity is achieved by encoding multiple isoforms. For fungi, most information comes from the study of type 2C protein phosphatase (PP2C) enzymes in Saccharomyces cerevisiae, where seven PP2C-encoding genes (PTC1 to -7) with diverse functions can be found. More recently, data on several Candida albicans PP2C proteins became available, suggesting that some of them can be involved in virulence. In this work we review the available literature on fungal PP2Cs and explore sequence databases to provide a comprehensive overview of these enzymes in fungi.Reversible phosphorylation of proteins is a major mechanism regulating many biological processes such as metabolism, gene transcription, or cell cycle. It is an extremely common event in signal transduction, and it is considered the main mechanism of posttranslational modification leading, for instance, to a change in enzyme activity. The phosphorylation state of a protein results from the balance of protein kinases and protein phosphatases activities. Alterations in the phosphorylation state of proteins are a cause of various diseases, such as cancer, diabetes, rheumatoid arthritis, or hypertension. The importance of this regulatory mechanism is evident when it is considered that it affects around 30% of the proteome of Saccharomyces cerevisiae (72) and that the number of genes encoding phosphatases and kinases represents 2 to 4% of all genes in a typical eukaryotic genome (60).Most phosphorylation events in eukaryotes involve transfer of phosphate to Ser and Thr residues. Removal of this phosphate is catalyzed by Ser/Thr protein phosphatases. Members of this large family of enzymes were initially classified, using enzymological criteria, as type 1 (PP1) and type 2 (PP2) phosphatases. PP2 enzymes were subsequently divided into three groups on the basis of the requirements for metal ions: 2A (not requiring metal ions), 2B (activated by calcium), and 2C (Mg 2ϩ dependent) (10). The molecular cloning of a number of cDNAs and genes from diverse organisms allowed the establishment of three major subfamilies: PPP (phosphoprotein phosphatases), including type 1, 2A, and 2B phosphatases, among others; PPM (metal-dependent protein phosphatases), including type 2C enzymes (PP2C), which are the subject of this review; and the catalytically Asp-based subfamily, represented by HAD and FCP/SCP (see reference 89 for a review).Although PP2C proteins are distantly related in primary sequence to PPP enzymes, their tridimensional structure and catalytic mechanisms appear to be quite similar. Type 2C phosphatases are widely represented in bacteria, fungi, plants, insects, and mammals (83), suggesting that they are involved in key cellular processes, such as proliferation, metabolism, and cell...

show abstract

supporting

confidence: 51%

Type 2C Protein Phosphatases in Fungi

2011

Self Cite

View full text Add to dashboard Cite

show abstract

“…This induction is decreased in the ptc1 mutant (Gonzalez et al 2009) (Figure S1). We tested, by using transcriptional fusions of the promoters to the lacZ reporter gene, whether further deletion of MKK1 or MKK2 would rescue normal gene expression.…”

Section: Resultsmentioning

confidence: 98%

“…Cells carrying plasmids pGAP1 and pMEP1 (Gonzalez et al 2009), pKC201 (Alepuz et al 1997), pMLP1-LacZ (Garcia et al 2009), and pAMS366 (Stathopoulos and Cyert 1997) were grown to saturation on synthetic medium lacking uracil or, in the case of pMEP2 (Marini et al 1997), lacking leucine and then inoculated into 5 ml of YPD medium up to an OD 660 of 0.2. Growth was resumed until an OD 660 of 0.8 was reached.…”

Section: B-galactosidase Reporter Assaysmentioning

confidence: 99%

“…A link between Ptc1 and the targetof-rapamycin (TOR) pathway was suggested by the increased sensitivity of ptc1 cells to rapamycin, an inhibitor of the TORC1 complex (Parsons et al 2004;Xie et al 2005). Subsequent work demonstrated that Ptc1 is required for normal TOR signaling by regulating, in a HOG-independent manner, a step upstream of the Sit4 phosphatase (Gonzalez et al 2009). Recently, Ptc1 has been shown to dephosphorylate the Snf1 protein kinase at Thr 210 in vivo (Ruiz et al 2013).…”

mentioning

confidence: 99%

See 1 more Smart Citation

Wide-Ranging Effects of the Yeast Ptc1 Protein Phosphatase Acting Through the MAPK Kinase Mkk1

et al. 2015

View full text Add to dashboard Cite

The Saccharomyces cerevisiae type 2C protein phosphatase Ptc1 is required for a wide variety of cellular functions, although only a few cellular targets have been identified. A genetic screen in search of mutations in protein kinase-encoding genes able to suppress multiple phenotypic traits caused by the ptc1 deletion yielded a single gene, MKK1, coding for a MAPK kinase (MAPKK) known to activate the cell-wall integrity (CWI) Slt2 MAPK. In contrast, mutation of the MKK1 paralog, MKK2, had a less significant effect. Deletion of MKK1 abolished the increased phosphorylation of Slt2 induced by the absence of Ptc1 both under basal and CWI pathway stimulatory conditions. We demonstrate that Ptc1 acts at the level of the MAPKKs of the CWI pathway, but only the Mkk1 kinase activity is essential for ptc1 mutants to display high Slt2 activation. We also show that Ptc1 is able to dephosphorylate Mkk1 in vitro. Our results reveal the preeminent role of Mkk1 in signaling through the CWI pathway and strongly suggest that hyperactivation of Slt2 caused by upregulation of Mkk1 is at the basis of most of the phenotypic defects associated with lack of Ptc1 function.KEYWORDS synthetic genetic interactions; cell-wall integrity pathway; protein dephosphorylation; Saccharomyces cerevisiae P ROTEIN kinases play an essential role in nearly every aspect of cell physiology, and the activity of these key players is frequently modulated by phosphorylation. Therefore, protein phosphatases (PPases) are important regulators of protein kinases and cellular homeostasis. Among them, type 2C Ser/Thr PPases constitute an evolutionarily conserved group that, in contrast to other PPase families, are monomeric enzymes apparently lacking regulatory subunits. In the yeast Saccharomyces cerevisiae, seven members (Ptc1-Ptc7) have been identified and at least partially characterized [see Arino et al. (2011) for a review].Ptc1 is the closest homolog of human Wip1, a phosphatase involved in the regulation of stress-induced and DNA damage-induced networks in diverse physiologic and pathologic conditions (Le Guezennec and Bulavin 2010;Zhu and Bulavin 2012) and by far the most widely studied yeast isoform. Both the large number of characteristic phenotypes and the specific changes in the transcriptomic profile (Gonzalez et al. 2006) derived from deletion of the gene suggest that this phosphatase is involved in a large variety of cellular processes not shared by other Ptc family members. Early evidence indicated that Ptc1 was involved in the negative regulation of the high-osmolarity glycerol (HOG) pathway (Maeda et al. 1993;Maeda et al. 1994), and subsequent work demonstrated that Ptc1 could dephosphorylate the Hog1 MAPK in vitro and in vivo (Warmka et al. 2001 interacts with the N-terminal domain of Nbp2, an SH3 domaincontaining protein that serves as an adaptor for the recruitment of Ptc1 to the Pbs2-Hog1 complex, and this interaction is necessary for Ptc1 to participate in the regulation of HOGmediated signaling (Uetz et al. 2000;Ito et al. 2001;Ma...

show abstract

“…On a poor N source or in the presence of rapamycin, conditions of low TORC1 activity, Npr1 is weakly phosphorylated and active, whereas in the presence of amino acids, TORC1 is stimulated and promotes Npr1 hyperphosphorylation, causing its inactivation (19,63). Hyperphosphorylation of Npr1 is also observed in mutant cells lacking the TORC1-regulated protein phosphatase 2A (PP2A)-related phosphatase Sit4 (32) or the Ptc1 PP2C phosphatase controlling Sit4 (20). The current model (Fig.…”

mentioning

confidence: 99%

Internal Amino Acids Promote Gap1 Permease Ubiquitylation via TORC1/Npr1/14-3-3-Dependent Control of the Bul Arrestin-Like Adaptors

Ahmad

André

2012

Molecular and Cellular Biology

142

265

View full text Add to dashboard Cite

Ubiquitylation of many plasma membrane proteins promotes their endocytosis followed by degradation in the lysosome. The yeast general amino acid permease, Gap1, is ubiquitylated and downregulated when a good nitrogen source like ammonium is provided to cells growing on a poor nitrogen source. This ubiquitylation requires the Rsp5 ubiquitin ligase and the redundant arrestin-like Bul1 and Bul2 adaptors. Previous studies have shown that Gap1 ubiquitylation involves the TORC1 kinase complex, which inhibits the Sit4 phosphatase. This causes inactivation of the protein kinase Npr1, which protects Gap1 against ubiquitylation. However, the mechanisms inducing Gap1 ubiquitylation after Npr1 inactivation remain unknown. We here show that on a poor nitrogen source, the Bul adaptors are phosphorylated in an Npr1-dependent manner and bound to 14-3-3 proteins that protect Gap1 against downregulation. After ammonium is added and converted to amino acids, the Bul proteins are dephosphorylated, dissociate from the 14-3-3 proteins, and undergo ubiquitylation. Furthermore, dephosphorylation of Bul requires the Sit4 phosphatase, which is essential to Gap1 downregulation. The data support the emerging concept that permease ubiquitylation results from activation of the arrestin-like adaptors of the Rsp5 ubiquitin ligase, this coinciding with their dephosphorylation, dissociation from the inhibitory 14-3-3 proteins, and ubiquitylation.

show abstract

Normal Function of the Yeast TOR Pathway Requires the Type 2C Protein Phosphatase Ptc1

Cited by 40 publications

References 78 publications

Type 2C Protein Phosphatases in Fungi

Type 2C Protein Phosphatases in Fungi

Wide-Ranging Effects of the Yeast Ptc1 Protein Phosphatase Acting Through the MAPK Kinase Mkk1

Internal Amino Acids Promote Gap1 Permease Ubiquitylation via TORC1/Npr1/14-3-3-Dependent Control of the Bul Arrestin-Like Adaptors

Contact Info

Product

Resources

About