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Yang X, Guo J, Li W, Li C, Zhu X, Liu Y, Wu X. PPM1H is down-regulated by ATF6 and dephosphorylates p-RPS6KB1 to inhibit progression of hepatocellular carcinoma. MOLECULAR THERAPY. NUCLEIC ACIDS 2023; 33:164-179. [PMID: 37456776 PMCID: PMC10345229 DOI: 10.1016/j.omtn.2023.06.013] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/05/2023] [Accepted: 06/15/2023] [Indexed: 07/18/2023]
Abstract
We have shown previously that polymorphism of activating transcription factor 6 (ATF6) is associated with susceptibility to hepatocellular carcinoma (HCC). Therefore, genes down-regulated by ATF6 might play a tumor-suppressing role. In the present study, we identified that expression of protein phosphatase magnesium- or manganous-dependent 1H (PPM1H) mRNA and protein can be inhibited by ATF6 in hepatoma cells and mice with liver Atf6 knockdown. Tumor tissues from 134 HCC patients were analyzed by immunohistochemistry, and PPM1H exhibited higher expression levels in adjacent para-cancer tissues than in HCC tissues. Therefore, patients with higher expression of PPM1H had a better prognosis. PPM1H inhibited proliferation, migration, and invasion of hepatoma cells. In addition, PPM1H inhibited induced HCC nodule formation as well as tumor xenograft growth in diethylnitrosamine/CCl4-induced HCC mouse model and nude mouse tumorigenicity assay, respectively. A 3D model of PPM1H was obtained by homology multi-template modeling, and ribosomal protein S6 kinase B1 (RPS6KB1) in the bone morphogenetic protein (BMP)/transforming growth factor β (TGF-β) pathway was screened out as the potential substrate of PPM1H by Rosetta. PPM1H could directly dephosphorylate p-RPS6KB1. To conclude, we discovered RPS6KB1 as a new PPM1H dephosphorylation substrate. PPM1H exhibited a suppressive effect on HCC progression by dephosphorylating p-RPS6KB1.
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Affiliation(s)
- Xiaoshuang Yang
- State Key Laboratory of Medical Molecular Biology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences, Beijing 100005, P.R. China
- School of Basic Medicine, Peking Union Medical College, Beijing 100005, P.R. China
| | - Jianting Guo
- State Key Laboratory of Medical Molecular Biology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences, Beijing 100005, P.R. China
- School of Basic Medicine, Peking Union Medical College, Beijing 100005, P.R. China
| | - Wei Li
- Department of Interventional Radiology, Affiliated Hospital of Qingdao University, Shandong 266003, P.R. China
| | - Chunrui Li
- Beijing Cloud Computing Key Technique and Application Key Laboratory, Beijing Computing Center, Beijing 100094, P.R. China
| | - Xilin Zhu
- State Key Laboratory of Medical Molecular Biology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences, Beijing 100005, P.R. China
- School of Basic Medicine, Peking Union Medical College, Beijing 100005, P.R. China
| | - Ying Liu
- State Key Laboratory of Medical Molecular Biology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences, Beijing 100005, P.R. China
- School of Basic Medicine, Peking Union Medical College, Beijing 100005, P.R. China
| | - Xiaopan Wu
- State Key Laboratory of Medical Molecular Biology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences, Beijing 100005, P.R. China
- School of Basic Medicine, Peking Union Medical College, Beijing 100005, P.R. China
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2
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Genome-wide association study on 13,167 individuals identifies regulators of blood CD34+ cell levels. Blood 2022; 139:1659-1669. [PMID: 35007327 DOI: 10.1182/blood.2021013220] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2021] [Accepted: 12/11/2021] [Indexed: 11/20/2022] Open
Abstract
Stem cell transplantation is a cornerstone in the treatment of blood malignancies. The most common method to harvest stem cells for transplantation is by leukapheresis, requiring mobilization of CD34+ hematopoietic stem and progenitor cells (HSPC) from the bone marrow into the blood. Identifying the genetic factors that control blood CD34+ cell levels could expose new drug targets for HSPC mobilization. Here, we report the first large-scale genome-wide association study on blood CD34+ cell levels. Across 13,167 individuals, we identify 9 significant and 2 suggestive associations, accounted for by 8 loci (PPM1H, CXCR4, ENO1-RERE, ITGA9, ARHGAP45, CEBPA, TERT and MYC). Notably, 4 of the identified associations map to CXCR4, demonstrating that bona fide regulators of blood CD34+ cell levels can be identified through genetic variation. Further, the most significant association maps to PPM1H, encoding a serine/threonine phosphatase never previously implicated in HSPC biology. PPM1H is expressed in HSPCs, and the allele that confers higher blood CD34+ cell levels downregulates PPM1H. Through functional fine-mapping, we find that this downregulation is caused by the variant rs772557-A, which abrogates a MYB transcription factor binding site in PPM1H intron 1 that is active in specific HSPC subpopulations, including hematopoietic stem cells, and interacts with the promoter by chromatin looping. Furthermore, PPM1H knockdown increases the proportion of CD34+ and CD34+90+ cells in cord blood assays. Our results provide first large-scale analysis of the genetic architecture of blood CD34+ cell levels, and warrant further investigation of PPM1H as a potential inhibition target for stem cell mobilization.
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Metal dependent protein phosphatase PPM family in cardiac health and diseases. Cell Signal 2021; 85:110061. [PMID: 34091011 PMCID: PMC9107372 DOI: 10.1016/j.cellsig.2021.110061] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Revised: 05/31/2021] [Accepted: 06/02/2021] [Indexed: 12/20/2022]
Abstract
Protein phosphorylation and dephosphorylation is central to signal transduction in nearly every aspect of cellular function, including cardiovascular regulation and diseases. While protein kinases are often regarded as the molecular drivers in cellular signaling with high specificity and tight regulation, dephosphorylation mediated by protein phosphatases is also gaining increasing appreciation as an important part of the signal transduction network essential for the robustness, specificity and homeostasis of cell signaling. Metal dependent protein phosphatases (PPM, also known as protein phosphatases type 2C, PP2C) belong to a highly conserved family of protein phosphatases with unique biochemical and molecular features. Accumulating evidence also indicates important and specific functions of individual PPM isoform in signaling and cellular processes, including proliferation, senescence, apoptosis and metabolism. At the physiological level, abnormal PPM expression and activity have been implicated in major human diseases, including cancer, neurological and cardiovascular disorders. Finally, inhibitors for some of the PPM members have been developed as a potential therapeutic strategy for human diseases. In this review, we will focus on the background information about the biochemical and molecular features of major PPM family members, with emphasis on their demonstrated or potential roles in cardiac pathophysiology. The current challenge and potential directions for future investigations will also be highlighted.
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Metal-dependent Ser/Thr protein phosphatase PPM family: Evolution, structures, diseases and inhibitors. Pharmacol Ther 2020; 215:107622. [PMID: 32650009 DOI: 10.1016/j.pharmthera.2020.107622] [Citation(s) in RCA: 49] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Accepted: 06/29/2020] [Indexed: 02/06/2023]
Abstract
Protein phosphatases and kinases control multiple cellular events including proliferation, differentiation, and stress responses through regulating reversible protein phosphorylation, the most important post-translational modification. Members of metal-dependent protein phosphatase (PPM) family, also known as PP2C phosphatases, are Ser/Thr phosphatases that bind manganese/magnesium ions (Mn2+/Mg2+) in their active center and function as single subunit enzymes. In mammals, there are 20 isoforms of PPM phosphatases: PPM1A, PPM1B, PPM1D, PPM1E, PPM1F, PPM1G, PPM1H, PPM1J, PPM1K, PPM1L, PPM1M, PPM1N, ILKAP, PDP1, PDP2, PHLPP1, PHLPP2, PP2D1, PPTC7, and TAB1, whereas there are only 8 in yeast. Phylogenetic analysis of the DNA sequences of vertebrate PPM isoforms revealed that they can be divided into 12 different classes: PPM1A/PPM1B/PPM1N, PPM1D, PPM1E/PPM1F, PPM1G, PPM1H/PPM1J/PPM1M, PPM1K, PPM1L, ILKAP, PDP1/PDP2, PP2D1/PHLPP1/PHLPP2, TAB1, and PPTC7. PPM-family members have a conserved catalytic core region, which contains the metal-chelating residues. The different isoforms also have isoform specific regions within their catalytic core domain and terminal domains, and these regions may be involved in substrate recognition and/or functional regulation of the phosphatases. The twenty mammalian PPM phosphatases are involved in regulating diverse cellular functions, such as cell cycle control, cell differentiation, immune responses, and cell metabolism. Mutation, overexpression, or deletion of the PPM phosphatase gene results in abnormal cellular responses, which lead to various human diseases. This review focuses on the structures and biological functions of the PPM-phosphatase family and their associated diseases. The development of specific inhibitors against the PPM phosphatase family as a therapeutic strategy will also be discussed.
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CTL0511 from Chlamydia trachomatis Is a Type 2C Protein Phosphatase with Broad Substrate Specificity. J Bacteriol 2016; 198:1827-1836. [PMID: 27114464 DOI: 10.1128/jb.00025-16] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2016] [Accepted: 04/15/2016] [Indexed: 12/26/2022] Open
Abstract
UNLABELLED Protein phosphorylation has become increasingly recognized for its role in regulating bacterial physiology and virulence. Chlamydia spp. encode two validated Hanks'-type Ser/Thr protein kinases, which typically function with cognate protein phosphatases and appear capable of global protein phosphorylation. Consequently, we sought to identify a Ser/Thr protein phosphatase partner for the chlamydial kinases. CTL0511 from Chlamydia trachomatis L2 434/Bu, which has homologs in all sequenced Chlamydia spp., is a predicted type 2C Ser/Thr protein phosphatase (PP2C). Recombinant maltose-binding protein (MBP)-tagged CTL0511 (rCTL0511) hydrolyzed p-nitrophenyl phosphate (pNPP), a generic phosphatase substrate, in a MnCl2-dependent manner at physiological pH. Assays using phosphopeptide substrates revealed that rCTL0511 can dephosphorylate phosphorylated serine (P-Ser), P-Thr, and P-Tyr residues using either MnCl2 or MgCl2, indicating that metal usage can alter substrate preference. Phosphatase activity was unaffected by PP1, PP2A, and PP3 phosphatase inhibitors, while mutation of conserved PP2C residues significantly inhibited activity. Finally, phosphatase activity was detected in elementary body (EB) and reticulate body (RB) lysates, supporting a role for protein dephosphorylation in chlamydial development. These findings support that CTL0511 is a metal-dependent protein phosphatase with broad substrate specificity, substantiating a reversible phosphorylation network in C. trachomatis IMPORTANCE Chlamydia spp. are obligate intracellular bacterial pathogens responsible for a variety of diseases in humans and economically important animal species. Our work demonstrates that Chlamydia spp. produce a PP2C capable of dephosphorylating P-Thr, P-Ser, and P-Tyr and that Chlamydia trachomatis EBs and RBs possess phosphatase activity. In conjunction with the chlamydial Hanks'-type kinases Pkn1 and PknD, validation of CTL0511 fulfills the enzymatic requirements for a reversible phosphoprotein network. As protein phosphorylation regulates important cellular processes, including metabolism, differentiation, and virulence, in other bacterial pathogens, these results set the stage for elucidating the role of global protein phosphorylation in chlamydial physiology and virulence.
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Structural and Biochemical Characterization of a Cyanobacterial PP2C Phosphatase Reveals Insights into Catalytic Mechanism and Substrate Recognition. Catalysts 2016. [DOI: 10.3390/catal6050060] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
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Sierecki E, Newton AC. Biochemical characterization of the phosphatase domain of the tumor suppressor PH domain leucine-rich repeat protein phosphatase. Biochemistry 2014; 53:3971-81. [PMID: 24892992 PMCID: PMC4072346 DOI: 10.1021/bi500428j] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
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PH domain leucine-rich repeat protein
phosphatase (PHLPP) directly
dephosphorylates and inactivates Akt and protein kinase C and is therefore
a prime target for pharmacological intervention of two key signaling
pathways, the phosphatidylinositol 3-kinase and diacylglycerol signaling
pathways. Here we report on the first biochemical characterization
of the phosphatase domain of a PHLPP family member. The human PHLPP1
and PHLPP2 phosphatase domains were expressed and purified from bacteria
or insect cells and their activities compared to that of full-length
proteins immunoprecipitated from mammalian cells. Biochemical analyses
reveal that the PHLPP phosphatase domain effectively dephosphorylates
synthetic and peptidic substrates, that its activity is modulated
by metals and lipophilic compounds, and that it has relatively high
thermal stability. Mutational analysis of PHLPP2 reveals an unusual
active site architecture compared to the canonical architecture of
PP2C phosphatases and identifies key acidic residues (Asp 806, Glu
989, and Asp 1024) and bulky aromatic residues (Phe 783 and Phe 808)
whose mutation impairs activity. Consistent with a unique active site
architecture, we identify inhibitors that discriminate between PHLPP2
and PP2Cα. These data establish PHLPP as a member of the PP2C
family of phosphatases with a unique active site architecture.
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Affiliation(s)
- Emma Sierecki
- Department of Pharmacology, University of California San Diego , La Jolla, California 92093, United States
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8
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Tanoue K, Miller Jenkins LM, Durell SR, Debnath S, Sakai H, Tagad HD, Ishida K, Appella E, Mazur SJ. Binding of a third metal ion by the human phosphatases PP2Cα and Wip1 is required for phosphatase activity. Biochemistry 2013; 52:5830-43. [PMID: 23906386 DOI: 10.1021/bi4005649] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The PPM phosphatases require millimolar concentrations of Mg²⁺ or Mn²⁺ to activate phosphatase activity in vitro. The human phosphatases PP2Cα (PPM1A) and Wip1 (PPM1D) differ in their physiological function, substrate specificity, and apparent metal affinity. A crystallographic structure of PP2Cα shows only two metal ions in the active site. However, recent structural studies of several bacterial PP2C phosphatases have indicated three metal ions in the active site. Two residues that coordinate the third metal ion are highly conserved, suggesting that human PP2C phosphatases may also bind a third ion. Here, isothermal titration calorimetry analysis of Mg²⁺ binding to PP2Cα distinguished binding of two ions to high affinity sites from the binding of a third ion with a millimolar affinity, similar to the apparent metal affinity required for catalytic activity. Mutational analysis indicated that Asp239 and either Asp146 or Asp243 was required for low-affinity binding of Mg²⁺, but that both Asp146 and Asp239 were required for catalysis. Phosphatase activity assays in the presence of MgCl₂, MnCl₂, or mixtures of the two, demonstrate high phosphatase activity toward a phosphopeptide substrate when Mg²⁺ was bound to the low-affinity site, whether Mg²⁺ or Mn²⁺ ions were bound to the high affinity sites. Mutation of the corresponding putative third metal ion-coordinating residues of Wip1 affected catalytic activity similarly both in vitro and in human cells. These results suggest that phosphatase activity toward phosphopeptide substrates by PP2Cα and Wip1 requires the binding of a Mg²⁺ ion to the low-affinity site.
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Affiliation(s)
- Kan Tanoue
- Laboratory of Cell Biology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, United States
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Chen Y, Tascón I, Neunuebel MR, Pallara C, Brady J, Kinch LN, Fernández-Recio J, Rojas AL, Machner MP, Hierro A. Structural basis for Rab1 de-AMPylation by the Legionella pneumophila effector SidD. PLoS Pathog 2013; 9:e1003382. [PMID: 23696742 DOI: 10.1371/journal.ppat.1003382] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2013] [Accepted: 04/08/2013] [Indexed: 12/31/2022] Open
Abstract
The covalent attachment of adenosine monophosphate (AMP) to proteins, a process called AMPylation (adenylylation), has recently emerged as a novel theme in microbial pathogenesis. Although several AMPylating enzymes have been characterized, the only known virulence protein with de-AMPylation activity is SidD from the human pathogen Legionella pneumophila. SidD de-AMPylates mammalian Rab1, a small GTPase involved in secretory vesicle transport, thereby targeting the host protein for inactivation. The molecular mechanisms underlying Rab1 recognition and de-AMPylation by SidD are unclear. Here, we report the crystal structure of the catalytic region of SidD at 1.6 Å resolution. The structure reveals a phosphatase-like fold with additional structural elements not present in generic PP2C-type phosphatases. The catalytic pocket contains a binuclear metal-binding site characteristic of hydrolytic metalloenzymes, with strong dependency on magnesium ions. Subsequent docking and molecular dynamics simulations between SidD and Rab1 revealed the interface contacts and the energetic contribution of key residues to the interaction. In conjunction with an extensive structure-based mutational analysis, we provide in vivo and in vitro evidence for a remarkable adaptation of SidD to its host cell target Rab1 which explains how this effector confers specificity to the reaction it catalyses.
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Affiliation(s)
- Yang Chen
- Cell Biology and Metabolism Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland, United States of America
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10
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Lee-Hoeflich ST, Pham TQ, Dowbenko D, Munroe X, Lee J, Li L, Zhou W, Haverty PM, Pujara K, Stinson J, Chan SM, Eastham-Anderson J, Pandita A, Seshagiri S, Hoeflich KP, Turashvili G, Gelmon KA, Aparicio SA, Davis DP, Sliwkowski MX, Stern HM. PPM1H is a p27 phosphatase implicated in trastuzumab resistance. Cancer Discov 2011; 1:326-37. [PMID: 22586611 DOI: 10.1158/2159-8290.cd-11-0062] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The HER2 oncogene is overexpressed or amplified in 20% of breast cancers. HER2-positive cancer historically portends a poor prognosis, but the HER2-targeted therapy trastuzumab mitigates this otherwise ominous distinction. Nevertheless, some patients suffer disease recurrence despite trastuzumab, and metastatic disease remains largely incurable due to innate and acquired resistance. Thus, understanding trastuzumab resistance remains an unmet medical need. Through RNA interference screening, we discovered that knockdown of the serine/threonine phosphatase PPM1H confers trastuzumab resistance via reduction in protein levels of the tumor suppressor p27. PPM1H dephosphorylates p27 at threonine 187, thus removing a signal for proteasomal degradation. We further determined that patients whose tumors express low levels of PPM1H trend towards worse clinical outcome on trastuzumab. Identifying PPM1H as a novel p27 phosphatase reveals new insight into how cancer cells destabilize a well-recognized tumor suppressor. Furthermore, low PPM1H expression may identify a subset of HER2-positive tumors that are harder to treat.
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Affiliation(s)
- Si Tuen Lee-Hoeflich
- Genentech Research and Early Development, South San Francisco, California 94080, USA
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11
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Sajid A, Arora G, Gupta M, Upadhyay S, Nandicoori VK, Singh Y. Phosphorylation of Mycobacterium tuberculosis Ser/Thr phosphatase by PknA and PknB. PLoS One 2011; 6:e17871. [PMID: 21423706 PMCID: PMC3052367 DOI: 10.1371/journal.pone.0017871] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2010] [Accepted: 02/11/2011] [Indexed: 11/30/2022] Open
Abstract
Background The integrated functions of 11 Ser/Thr protein kinases (STPKs) and one
phosphatase manipulate the phosphorylation levels of critical proteins in
Mycobacterium tuberculosis. In this study, we show that
the lone Ser/Thr phosphatase (PstP) is regulated through phosphorylation by
STPKs. Principal Findings PstP is phosphorylated by PknA and PknB and phosphorylation is influenced by
the presence of Zn2+-ions and inorganic phosphate (Pi). PstP
is differentially phosphorylated on the cytosolic domain with
Thr137, Thr141, Thr174 and
Thr290 being the target residues of PknB while
Thr137 and Thr174 are phosphorylated by PknA. The
Mn2+-ion binding residues Asp38 and
Asp229 are critical for the optimal activity of PstP and
substitution of these residues affects its phosphorylation status. Native
PstP and its phosphatase deficient mutant PstPcD38G
are phosphorylated by PknA and PknB in E. coli and addition
of Zn2+/Pi in the culture conditions affect the
phosphorylation level of PstP. Interestingly, the phosphorylated phosphatase
is more active than its unphosphorylated equivalent. Conclusions and Significance This study establishes the novel mechanisms for regulation of mycobacterial
Ser/Thr phosphatase. The results indicate that STPKs and PstP may regulate
the signaling through mutually dependent mechanisms. Consequently, PstP
phosphorylation may play a critical role in regulating its own activity.
Since, the equilibrium between phosphorylated and non-phosphorylated states
of mycobacterial proteins is still unexplained, understanding the regulation
of PstP may help in deciphering the signal transduction pathways mediated by
STPKs and the reversibility of the phenomena.
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Affiliation(s)
- Andaleeb Sajid
- Institute of Genomics and Integrative Biology
(CSIR), Delhi, India
| | - Gunjan Arora
- Institute of Genomics and Integrative Biology
(CSIR), Delhi, India
| | - Meetu Gupta
- Institute of Genomics and Integrative Biology
(CSIR), Delhi, India
| | - Sandeep Upadhyay
- National Institute of Immunology, Aruna Asaf
Ali Marg, New Delhi, India
| | | | - Yogendra Singh
- Institute of Genomics and Integrative Biology
(CSIR), Delhi, India
- * E-mail:
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Su J, Schlicker C, Forchhammer K. A third metal is required for catalytic activity of the signal-transducing protein phosphatase M tPphA. J Biol Chem 2011; 286:13481-8. [PMID: 21310952 DOI: 10.1074/jbc.m109.036467] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Protein phosphatase M (PPM) regulates key signaling pathways in prokaryotes and eukaryotes. Novel structures of bacterial PPM members revealed three divalent metal ions in their catalytic centers. The function of metal 3 (M3) remained unclear. To reveal its function, we created variants of tPphA from Thermosynechococcus elongatus in all metal-coordinating residues, and multiple variants were created for the M3 coordinating Asp-119 residue. The structures of variants D119A and D193A were resolved, showing loss of M3 binding but unaffected binding of M1 and M2 in the catalytic center of D119A, with the nucleophilic water molecule in the correct place. The catalytic activity of this variant was highly impaired. This and further structure-function analyses showed that M3 is required for catalysis by providing a water molecule as a proton donor during catalysis. Mutation of the homologue Asp residue in human PP2Cα also caused loss of function, suggesting a general requirement of M3 in PPM-catalyzed reactions.
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Affiliation(s)
- Jiyong Su
- Interfaculty Institute of Microbiology and Infection Medicine, Department of Organismic Interactions, University of Tübingen, Auf der Morgenstelle 28, D-72076 Tübingen, Germany
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13
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Maret W. Metalloproteomics, metalloproteomes, and the annotation of metalloproteins. Metallomics 2010; 2:117-25. [DOI: 10.1039/b915804a] [Citation(s) in RCA: 116] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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