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Sager RA, Backe SJ, Dunn DM, Heritz JA, Ahanin E, Dushukyan N, Panaretou B, Bratslavsky G, Woodford MR, Bourboulia D, Mollapour M. SUMOylation of protein phosphatase 5 regulates phosphatase activity and substrate release. EMBO Rep 2024:10.1038/s44319-024-00250-2. [PMID: 39304777 DOI: 10.1038/s44319-024-00250-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2024] [Revised: 08/16/2024] [Accepted: 08/20/2024] [Indexed: 09/22/2024] Open
Abstract
The serine/threonine protein phosphatase 5 (PP5) regulates hormone and stress-induced signaling networks. Unlike other phosphoprotein phosphatases, PP5 contains both regulatory and catalytic domains and is further regulated through post-translational modifications (PTMs). Here we identify that SUMOylation of K430 in the catalytic domain of PP5 regulates phosphatase activity. Additionally, phosphorylation of PP5-T362 is pre-requisite for SUMOylation, suggesting the ordered addition of PTMs regulates PP5 function in cells. Using the glucocorticoid receptor, a well known substrate for PP5, we demonstrate that SUMOylation results in substrate release from PP5. We harness this information to create a non-SUMOylatable K430R mutant as a 'substrate trap' and globally identified novel PP5 substrate candidates. Lastly, we generated a consensus dephosphorylation motif using known substrates, and verified its presence in the new candidate substrates. This study unravels the impact of cross talk of SUMOylation and phosphorylation on PP5 phosphatase activity and substrate release in cells.
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Affiliation(s)
- Rebecca A Sager
- Department of Urology, SUNY Upstate Medical University, 750 E. Adams St., Syracuse, NY, 13210, USA
- Upstate Cancer Center, SUNY Upstate Medical University, 750 E. Adams St., Syracuse, NY, 13210, USA
| | - Sarah J Backe
- Department of Urology, SUNY Upstate Medical University, 750 E. Adams St., Syracuse, NY, 13210, USA
- Upstate Cancer Center, SUNY Upstate Medical University, 750 E. Adams St., Syracuse, NY, 13210, USA
| | - Diana M Dunn
- Department of Urology, SUNY Upstate Medical University, 750 E. Adams St., Syracuse, NY, 13210, USA
- Upstate Cancer Center, SUNY Upstate Medical University, 750 E. Adams St., Syracuse, NY, 13210, USA
| | - Jennifer A Heritz
- Department of Urology, SUNY Upstate Medical University, 750 E. Adams St., Syracuse, NY, 13210, USA
- Upstate Cancer Center, SUNY Upstate Medical University, 750 E. Adams St., Syracuse, NY, 13210, USA
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, 750 E. Adams St., Syracuse, NY, 13210, USA
| | - Elham Ahanin
- Department of Urology, SUNY Upstate Medical University, 750 E. Adams St., Syracuse, NY, 13210, USA
- Upstate Cancer Center, SUNY Upstate Medical University, 750 E. Adams St., Syracuse, NY, 13210, USA
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, 750 E. Adams St., Syracuse, NY, 13210, USA
| | - Natela Dushukyan
- Department of Urology, SUNY Upstate Medical University, 750 E. Adams St., Syracuse, NY, 13210, USA
- Upstate Cancer Center, SUNY Upstate Medical University, 750 E. Adams St., Syracuse, NY, 13210, USA
| | - Barry Panaretou
- School of Cancer and Pharmaceutical Sciences, Institute of Pharmaceutical Science, King's College London, London, SE1 9NQ, UK
| | - Gennady Bratslavsky
- Department of Urology, SUNY Upstate Medical University, 750 E. Adams St., Syracuse, NY, 13210, USA
- Upstate Cancer Center, SUNY Upstate Medical University, 750 E. Adams St., Syracuse, NY, 13210, USA
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, 750 E. Adams St., Syracuse, NY, 13210, USA
| | - Mark R Woodford
- Department of Urology, SUNY Upstate Medical University, 750 E. Adams St., Syracuse, NY, 13210, USA
- Upstate Cancer Center, SUNY Upstate Medical University, 750 E. Adams St., Syracuse, NY, 13210, USA
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, 750 E. Adams St., Syracuse, NY, 13210, USA
| | - Dimitra Bourboulia
- Department of Urology, SUNY Upstate Medical University, 750 E. Adams St., Syracuse, NY, 13210, USA
- Upstate Cancer Center, SUNY Upstate Medical University, 750 E. Adams St., Syracuse, NY, 13210, USA
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, 750 E. Adams St., Syracuse, NY, 13210, USA
| | - Mehdi Mollapour
- Department of Urology, SUNY Upstate Medical University, 750 E. Adams St., Syracuse, NY, 13210, USA.
- Upstate Cancer Center, SUNY Upstate Medical University, 750 E. Adams St., Syracuse, NY, 13210, USA.
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, 750 E. Adams St., Syracuse, NY, 13210, USA.
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Jaime-Garza M, Nowotny CA, Coutandin D, Wang F, Tabios M, Agard DA. Hsp90 provides a platform for kinase dephosphorylation by PP5. Nat Commun 2023; 14:2197. [PMID: 37069154 PMCID: PMC10110553 DOI: 10.1038/s41467-023-37659-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2022] [Accepted: 03/23/2023] [Indexed: 04/19/2023] Open
Abstract
The Hsp90 molecular chaperone collaborates with the phosphorylated Cdc37 cochaperone for the folding and activation of its many client kinases. As with many kinases, the Hsp90 client kinase CRaf is activated by phosphorylation at specific regulatory sites. The cochaperone phosphatase PP5 dephosphorylates CRaf and Cdc37 in an Hsp90-dependent manner. Although dephosphorylating Cdc37 has been proposed as a mechanism for releasing Hsp90-bound kinases, here we show that Hsp90 bound kinases sterically inhibit Cdc37 dephosphorylation indicating kinase release must occur before Cdc37 dephosphorylation. Our cryo-EM structure of PP5 in complex with Hsp90:Cdc37:CRaf reveals how Hsp90 both activates PP5 and scaffolds its association with the bound CRaf to dephosphorylate phosphorylation sites neighboring the kinase domain. Thus, we directly show how Hsp90's role in maintaining protein homeostasis goes beyond folding and activation to include post translationally modifying its client kinases.
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Affiliation(s)
- Maru Jaime-Garza
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA, 94143, USA
| | - Carlos A Nowotny
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA, 94143, USA
| | - Daniel Coutandin
- Novartis Institutes for BioMedical Research, San Diego, CA, 92121, USA
| | - Feng Wang
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA, 94143, USA
| | - Mariano Tabios
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA, 94143, USA
| | - David A Agard
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA, 94143, USA.
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Plk4 Is a Novel Substrate of Protein Phosphatase 5. Int J Mol Sci 2023; 24:ijms24032033. [PMID: 36768356 PMCID: PMC9917060 DOI: 10.3390/ijms24032033] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Revised: 01/13/2023] [Accepted: 01/17/2023] [Indexed: 01/21/2023] Open
Abstract
The conserved Ser/Thr protein phosphatase 5 (PP5) is involved in the regulation of key cellular processes, including DNA damage repair and cell division in eukaryotes. As a co-chaperone of Hsp90, PP5 has been shown to modulate the maturation and activity of numerous oncogenic kinases. Here, we identify a novel substrate of PP5, the Polo-like kinase 4 (Plk4), which is the master regulator of centriole duplication in animal cells. We show that PP5 specifically interacts with Plk4, and is able to dephosphorylate the kinase in vitro and in vivo, which affects the interaction of Plk4 with its partner proteins. In addition, we provide evidence that PP5 and Plk4 co-localize to the centrosomes in Drosophila embryos and cultured cells. We demonstrate that PP5 is not essential; the null mutant flies are viable without a severe mitotic phenotype; however, its loss significantly reduces the fertility of the animals. Our results suggest that PP5 is a novel regulator of the Plk4 kinase in Drosophila.
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Multi-Level Control of the ATM/ATR-CHK1 Axis by the Transcription Factor E4F1 in Triple-Negative Breast Cancer. Int J Mol Sci 2022; 23:ijms23169217. [PMID: 36012478 PMCID: PMC9409040 DOI: 10.3390/ijms23169217] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2022] [Revised: 08/10/2022] [Accepted: 08/12/2022] [Indexed: 12/01/2022] Open
Abstract
E4F1 is essential for early embryonic mouse development and for controlling the balance between proliferation and survival of actively dividing cells. We previously reported that E4F1 is essential for the survival of murine p53-deficient cancer cells by controlling the expression of genes involved in mitochondria functions and metabolism, and in cell-cycle checkpoints, including CHEK1, a major component of the DNA damage and replication stress responses. Here, combining ChIP-Seq and RNA-Seq approaches, we identified the transcriptional program directly controlled by E4F1 in Human Triple-Negative Breast Cancer cells (TNBC). E4F1 binds and regulates a limited list of direct target genes (57 genes) in these cells, including the human CHEK1 gene and, surprisingly, also two other genes encoding post-transcriptional regulators of the ATM/ATR-CHK1 axis, namely, the TTT complex component TTI2 and the phosphatase PPP5C, that are essential for the folding and stability, and the signaling of ATM/ATR kinases, respectively. Importantly, E4F1 also binds the promoter of these genes in vivo in Primary Derived Xenograft (PDX) of human TNBC. Consequently, the protein levels and signaling of CHK1 but also of ATM/ATR kinases are strongly downregulated in E4F1-depleted TNBC cells resulting in a deficiency of the DNA damage and replicative stress response in these cells. The E4F1-depleted cells fail to arrest into S-phase upon treatment with the replication-stalling agent Gemcitabine, and are highly sensitized to this drug, as well as to other DNA-damaging agents, such as Cisplatin. Altogether, our data indicate that in breast cancer cells the ATM/ATR-CHK1 signaling pathway and DNA damage-stress response are tightly controlled at the transcriptional and post-transcriptional level by E4F1.
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Fielder SM, Rosenfeld JA, Burrage LC, Emrick L, Lalani S, Attali R, Bembenek JN, Hoang H, Baldridge D, Silverman GA, Schedl T, Pak SC. Functional analysis of a novel de novo variant in PPP5C associated with microcephaly, seizures, and developmental delay. Mol Genet Metab 2022; 136:65-73. [PMID: 35361529 DOI: 10.1016/j.ymgme.2022.03.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/11/2022] [Accepted: 03/13/2022] [Indexed: 11/27/2022]
Abstract
We describe a proband evaluated through the Undiagnosed Diseases Network (UDN) who presented with microcephaly, developmental delay, and refractory epilepsy with a de novo p.Ala47Thr missense variant in the protein phosphatase gene, PPP5C. This gene has not previously been associated with a Mendelian disease, and based on the population database, gnomAD, the gene has a low tolerance for loss-of-function variants (pLI = 1, o/e = 0.07). We functionally evaluated the PPP5C variant in C. elegans by knocking the variant into the orthologous gene, pph-5, at the corresponding residue, Ala48Thr. We employed assays in three different biological processes where pph-5 was known to function through opposing the activity of genes, mec-15 and sep-1. We demonstrated that, in contrast to control animals, the pph-5 Ala48Thr variant suppresses the neurite growth phenotype and the GABA signaling defects of mec-15 mutants, and the embryonic lethality of sep-1 mutants. The Ala48Thr variant did not display dominance and behaved similarly to the reference pph-5 null, indicating that the variant is likely a strong hypomorph or complete loss-of-function. We conclude that pph-5 Ala48Thr is damaging in C. elegans. By extension in the proband, PPP5C p.Ala47Thr is likely damaging, the de novo dominant presentation is consistent with haplo-insufficiency, and the PPP5C variant is likely responsible for one or more of the proband's phenotypes.
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Affiliation(s)
- Sara M Fielder
- Department of Pediatrics, Washington University in St Louis School of Medicine, St Louis, MO 63110, USA
| | - Jill A Rosenfeld
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Lindsay C Burrage
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA; Texas Children's Hospital, Houston, TX 77030, USA
| | - Lisa Emrick
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA; Texas Children's Hospital, Houston, TX 77030, USA
| | - Seema Lalani
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA; Texas Children's Hospital, Houston, TX 77030, USA
| | - Ruben Attali
- Genomic Research Department, Emedgene Technologies, 6744332 Tel Aviv, Israel
| | - Joshua N Bembenek
- Department of Obstetrics and Gynecology, C.S. Mott Center for Human Growth and Development, Wayne State University School of Medicine, Detroit, MI 48201, USA
| | - Hieu Hoang
- Department of Pediatrics, Washington University in St Louis School of Medicine, St Louis, MO 63110, USA
| | - Dustin Baldridge
- Department of Pediatrics, Washington University in St Louis School of Medicine, St Louis, MO 63110, USA
| | - Gary A Silverman
- Department of Pediatrics, Washington University in St Louis School of Medicine, St Louis, MO 63110, USA
| | - Tim Schedl
- Department of Genetics, Washington University in St Louis School of Medicine, St Louis, MO 63110, USA
| | - Stephen C Pak
- Department of Pediatrics, Washington University in St Louis School of Medicine, St Louis, MO 63110, USA.
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Johnson JL. Mutations in Hsp90 Cochaperones Result in a Wide Variety of Human Disorders. Front Mol Biosci 2021; 8:787260. [PMID: 34957217 PMCID: PMC8694271 DOI: 10.3389/fmolb.2021.787260] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Accepted: 11/08/2021] [Indexed: 12/19/2022] Open
Abstract
The Hsp90 molecular chaperone, along with a set of approximately 50 cochaperones, mediates the folding and activation of hundreds of cellular proteins in an ATP-dependent cycle. Cochaperones differ in how they interact with Hsp90 and their ability to modulate ATPase activity of Hsp90. Cochaperones often compete for the same binding site on Hsp90, and changes in levels of cochaperone expression that occur during neurodegeneration, cancer, or aging may result in altered Hsp90-cochaperone complexes and client activity. This review summarizes information about loss-of-function mutations of individual cochaperones and discusses the overall association of cochaperone alterations with a broad range of diseases. Cochaperone mutations result in ciliary or muscle defects, neurological development or degeneration disorders, and other disorders. In many cases, diseases were linked to defects in established cochaperone-client interactions. A better understanding of the functional consequences of defective cochaperones will provide new insights into their functions and may lead to specialized approaches to modulate Hsp90 functions and treat some of these human disorders.
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Affiliation(s)
- Jill L Johnson
- Department of Biological Sciences and Center for Reproductive Biology, University of Idaho, Moscow, ID, United States
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Li J, Cui P, Sun Q, Du Z, Chen Z, Li Z, Liu C, Cao Y, Yang Z, Liu R, Luo M. PSPC1 regulates CHK1 phosphorylation through phase separation and participates in mouse oocyte maturation. Acta Biochim Biophys Sin (Shanghai) 2021; 53:1527-1537. [PMID: 34490876 DOI: 10.1093/abbs/gmab123] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2021] [Indexed: 12/21/2022] Open
Abstract
Liquid-liquid phase separation (LLPS) underlies the formation of membraneless compartments in mammal cells. However, there are few reports that focus on the correlation of mouse oocyte maturation with LLPS. Previous studies have reported that paraspeckle component 1 (PSPC1) is related to the occurrence and development of tumors, but whether PSPC1 functions in mouse oocyte maturation is still unclear. Sequence analysis of PSPC1 protein showed that it contains a prion-like domain (PrLD) that is required for phase separation of proteins. In this study, we found that PSPC1 could undergo phase separation. Moreover, the loss of PrLD domain of PSPC1 could greatly weaken its phase separation ability. The immunofluorescence assays showed that PSPC1 is present in mouse oocytes in the germinal vesicle (GV) stage. Knockdown of PSPC1 significantly impeded the maturation of mouse oocytes in vitro. CHK1 has been reported to play important roles in the GV stage of mouse oocytes. Co-IP experiment revealed that PSPC1 could interact with phosphatase serine/threonine-protein phosphatase 5 (PPP5C), which regulates CHK1 phosphorylation. Western blot analysis revealed that PSPC1 could regulate the phosphorylation of CHK1 through PPP5C; however, PSPC1 without PrLD domain was inactive, suggesting that the lack of phase separation ability led to the abnormal function of PSPC1 in regulating CHK1 phosphorylation. Thus, we conclude that PSPC1 may undergo phase separation to regulate the phosphorylation level of CHK1 via PPP5C and participate in mouse oocyte maturation. Our study provides new insights into the mechanism of mouse oocyte maturation.
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Affiliation(s)
- Jiong Li
- Hubei Provincial Key Laboratory of Developmentally Originated Disease, Department of Tissue and Embryology, School of Basic Medical Sciences, Wuhan University, Wuhan 430062, China
| | - Peng Cui
- Hubei Provincial Key Laboratory of Developmentally Originated Disease, Department of Tissue and Embryology, School of Basic Medical Sciences, Wuhan University, Wuhan 430062, China
| | - Qi Sun
- Hubei Provincial Key Laboratory of Developmentally Originated Disease, Department of Tissue and Embryology, School of Basic Medical Sciences, Wuhan University, Wuhan 430062, China
| | - Ziye Du
- Hubei Provincial Key Laboratory of Developmentally Originated Disease, Department of Tissue and Embryology, School of Basic Medical Sciences, Wuhan University, Wuhan 430062, China
| | - Zhen Chen
- Hubei Provincial Key Laboratory of Developmentally Originated Disease, Department of Tissue and Embryology, School of Basic Medical Sciences, Wuhan University, Wuhan 430062, China
| | - Zejia Li
- Hubei Provincial Key Laboratory of Developmentally Originated Disease, Department of Tissue and Embryology, School of Basic Medical Sciences, Wuhan University, Wuhan 430062, China
| | - Cong Liu
- Hubei Provincial Key Laboratory of Developmentally Originated Disease, Department of Tissue and Embryology, School of Basic Medical Sciences, Wuhan University, Wuhan 430062, China
| | - Yuming Cao
- Hubei Provincial Key Laboratory of Developmentally Originated Disease, Department of Tissue and Embryology, School of Basic Medical Sciences, Wuhan University, Wuhan 430062, China
| | - Zhe Yang
- College of Life Science, Liaoning University, Shenyang 110036, China
| | - Rong Liu
- Hubei Provincial Key Laboratory of Developmentally Originated Disease, Department of Tissue and Embryology, School of Basic Medical Sciences, Wuhan University, Wuhan 430062, China
| | - Mengcheng Luo
- Hubei Provincial Key Laboratory of Developmentally Originated Disease, Department of Tissue and Embryology, School of Basic Medical Sciences, Wuhan University, Wuhan 430062, China
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Neumann J, Boknik P, Kirchhefer U, Gergs U. The role of PP5 and PP2C in cardiac health and disease. Cell Signal 2021; 85:110035. [PMID: 33964402 DOI: 10.1016/j.cellsig.2021.110035] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Revised: 04/16/2021] [Accepted: 05/03/2021] [Indexed: 02/08/2023]
Abstract
Protein phosphatases are important, for example, as functional antagonists of β-adrenergic stimulation of the mammalian heart. While β-adrenergic stimulations increase the phosphorylation state of regulatory proteins and therefore force of contraction in the heart, these phosphorylations are reversed and thus force is reduced by the activity of protein phosphatases. In this context the role of PP5 and PP2C is starting to unravel. They do not belong to the same family of phosphatases with regard to sequence homology, many similarities with regard to location, activation by lipids and putative substrates have been worked out over the years. We also suggest which pathways for regulation of PP5 and/or PP2C described in other tissues and not yet in the heart might be useful to look for in cardiac tissue. Both phosphatases might play a role in signal transduction of sarcolemmal receptors in the heart. Expression of PP5 and PP2C can be increased by extracellular stimuli in the heart. Because PP5 is overexpressed in failing animal and human hearts, and because overexpression of PP5 or PP2C leads to cardiac hypertrophy and KO of PP5 leads to cardiac hypotrophy, one might argue for a role of PP5 and PP2C in heart failure. Because PP5 and PP2C can reduce, at least in vitro, the phosphorylation state of proteins thought to be relevant for cardiac arrhythmias, a role of these phosphatases for cardiac arrhythmias is also probable. Thus, PP5 and PP2C might be druggable targets to treat important cardiac diseases like heart failure, cardiac hypertrophy and cardiac arrhythmias.
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Affiliation(s)
- Joachim Neumann
- Institut für Pharmakologie und Toxikologie, Medizinische Fakultät, Martin-Luther-Universität Halle-Wittenberg, Magdeburger Str. 4, D-06097 Halle, Germany.
| | - Peter Boknik
- Institut für Pharmakologie und Toxikologie, Medizinische Fakultät, Westfälische Wilhelms-Universität, Domagkstraße 12, D-48149 Münster, Germany.
| | - Uwe Kirchhefer
- Institut für Pharmakologie und Toxikologie, Medizinische Fakultät, Westfälische Wilhelms-Universität, Domagkstraße 12, D-48149 Münster, Germany.
| | - Ulrich Gergs
- Institut für Pharmakologie und Toxikologie, Medizinische Fakultät, Martin-Luther-Universität Halle-Wittenberg, Magdeburger Str. 4, D-06097 Halle, Germany.
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Zhang X, Wang J, Pan Y, Zhao J, Pan Y, Yan Y, Shen Z. MicroRNA-365b-3p represses the proliferation and promotes the apoptosis of non-small cell lung cancer cells by targeting PPP5C. Oncol Lett 2021; 21:389. [PMID: 33777212 PMCID: PMC7988734 DOI: 10.3892/ol.2021.12650] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2019] [Accepted: 05/13/2020] [Indexed: 12/25/2022] Open
Abstract
MicroRNA (miR)-365b-3p has been recently reported to induce cell cycle arrest and apoptosis in retinoblastoma; however, its expression pattern and biological function in non-small cell lung cancer (NSCLC) remain unknown. The present study aimed to investigate the functional role of miR-365b-3p in NSCLC. The results demonstrated that miR-365b-3p expression level was significantly decreased in NSCLC tissues and cell lines compared with controls using reverse transcriptase quantitative PCR. Furthermore, miR-365b-3p expression level was overexpressed by miR-365b-3p mimics transfection in A549 cells, whereas it was downregulated following H1299 cell transfection with miR-365b-3p inhibitor. Restoration of miR-365b-3p inhibited cell proliferation, induced cell cycle G0/G1 arrest and stimulated apoptosis in A549 cells using CCK-8 assay, colony formation and flow cytometry assay. However, miR-365b-3p inhibitor had the opposite effects in H1299 cells. Furthermore, results from bioinformatics analysis and luciferase reporter assay confirmed that serine/threonine protein phosphatase 5 (PPP5C) was a direct target of miR-365b-3p. In addition, online Kaplan-Meier plotter software demonstrated that high PPP5C expression level was associated with lower overall survival and disease-free survival in patients with NSCLC. Furthermore, PPP5C knockdown imitated the effects of miR-365b-3p mimics on A549 cell proliferation, cell cycle distribution and apoptosis, whereas its overexpression rescued the effects of miR-365b-3p mimics on A549 cell proliferation, cell cycle distribution and apoptosis. In conclusion, the findings from the present study suggested that miR-365b-3p may partly suppress NSCLC cell behaviors by targeting PPP5C, which may represent a promising therapeutic target for patients with NSCLC.
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Affiliation(s)
- Xiaomiao Zhang
- Department of Cardiovascular Surgery, The First Affiliated Hospital of Soochow University, Suzhou 215006, P.R. China
- Department of Thoracic Surgery, Shanghai General Hospital, Shanghai Jiao Tong University, Shanghai 200080, P.R. China
| | - Jin Wang
- Department of Thoracic Surgery, Shanghai General Hospital, Shanghai Jiao Tong University, Shanghai 200080, P.R. China
| | - Yuqin Pan
- Nursing Department, Shanghai General Hospital, Shanghai Jiao Tong University, Shanghai 200080, P.R. China
| | - Jun Zhao
- Nursing Department, Shanghai General Hospital, Shanghai Jiao Tong University, Shanghai 200080, P.R. China
| | - Yingge Pan
- Nursing Department, Shanghai General Hospital, Shanghai Jiao Tong University, Shanghai 200080, P.R. China
| | - Yunqi Yan
- Nursing Department, Shanghai General Hospital, Shanghai Jiao Tong University, Shanghai 200080, P.R. China
| | - Zhenya Shen
- Department of Cardiovascular Surgery, The First Affiliated Hospital of Soochow University, Suzhou 215006, P.R. China
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10
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Sager RA, Dushukyan N, Woodford M, Mollapour M. Structure and function of the co-chaperone protein phosphatase 5 in cancer. Cell Stress Chaperones 2020; 25:383-394. [PMID: 32239474 PMCID: PMC7193036 DOI: 10.1007/s12192-020-01091-3] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2020] [Revised: 03/04/2020] [Accepted: 03/12/2020] [Indexed: 12/12/2022] Open
Abstract
Protein phosphatase 5 (PP5) is a serine/threonine protein phosphatase that regulates many cellular functions including steroid hormone signaling, stress response, proliferation, apoptosis, and DNA repair. PP5 is also a co-chaperone of the heat shock protein 90 molecular chaperone machinery that assists in regulation of cellular signaling pathways essential for cell survival and growth. PP5 plays a significant role in survival and propagation of multiple cancers, which makes it a promising target for cancer therapy. Though there are several naturally occurring PP5 inhibitors, none is specific for PP5. Here, we review the roles of PP5 in cancer progression and survival and discuss the unique features of the PP5 structure that differentiate it from other phosphoprotein phosphatase (PPP) family members and make it an attractive therapeutic target.
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Affiliation(s)
- Rebecca A Sager
- Department of Urology, SUNY Upstate Medical University, Syracuse, NY, 13210, USA
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY, 13210, USA
- Upstate Cancer Center, SUNY Upstate Medical University, Syracuse, NY, 13210, USA
- College of Medicine, SUNY Upstate Medical University, Syracuse, NY, 13210, USA
| | - Natela Dushukyan
- Department of Urology, SUNY Upstate Medical University, Syracuse, NY, 13210, USA
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY, 13210, USA
- Upstate Cancer Center, SUNY Upstate Medical University, Syracuse, NY, 13210, USA
| | - Mark Woodford
- Department of Urology, SUNY Upstate Medical University, Syracuse, NY, 13210, USA
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY, 13210, USA
- Upstate Cancer Center, SUNY Upstate Medical University, Syracuse, NY, 13210, USA
| | - Mehdi Mollapour
- Department of Urology, SUNY Upstate Medical University, Syracuse, NY, 13210, USA.
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY, 13210, USA.
- Upstate Cancer Center, SUNY Upstate Medical University, Syracuse, NY, 13210, USA.
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11
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Zhang Z, Zhang W, Bi Y, Han Y, Zong Y, Prusky D. Cuminal Inhibits Trichothecium roseum Growth by Triggering Cell Starvation: Transcriptome and Proteome Analysis. Microorganisms 2020; 8:E256. [PMID: 32075192 PMCID: PMC7074788 DOI: 10.3390/microorganisms8020256] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2019] [Revised: 02/06/2020] [Accepted: 02/11/2020] [Indexed: 12/20/2022] Open
Abstract
Trichothecium roseum is a harmful postharvest fungus causing serious damage, together with the secretion of insidious mycotoxins, on apples, melons, and other important fruits. Cuminal, a predominant component of Cuminum cyminum essential oil has proven to successfully inhibit the growth of T. roseum in vitro and in vivo. Electron microscopic observations revealed cuminal exposure impaired the fungal morphology and ultrastructure, particularly the plasmalemma. Transcriptome and proteome analysis was used to investigate the responses of T. roseum to exposure of cuminal. In total, 2825 differentially expressed transcripts (1516 up and 1309 down) and 225 differentially expressed proteins (90 up and 135 down) were determined. Overall, notable parts of these differentially expressed genes functionally belong to subcellular localities of the membrane system and cytosol, along with ribosomes, mitochondria and peroxisomes. According to the localization analysis and the biological annotation of these genes, carbohydrate and lipids metabolism, redox homeostasis, and asexual reproduction were among the most enriched gene ontology (GO) terms. Biological pathway enrichment analysis showed that lipids and amino acid degradation, ATP-binding cassette transporters, membrane reconstitution, mRNA surveillance pathway and peroxisome were elevated, whereas secondary metabolite biosynthesis, cell cycle, and glycolysis/gluconeogenesis were down regulated. Further integrated omics analysis showed that cuminal exposure first impaired the polarity of the cytoplasmic membrane and then triggered the reconstitution and dysfunction of fungal plasmalemma, resulting in handicapped nutrient procurement of the cells. Consequently, fungal cells showed starvation stress with limited carbohydrate metabolism, resulting a metabolic shift to catabolism of the cell's own components in response to the stress. Additionally, these predicaments brought about oxidative stress, which, in collaboration with the starvation, damaged certain critical organelles such as mitochondria. Such degeneration, accompanied by energy deficiency, suppressed the biosynthesis of essential proteins and inhibited fungal growth.
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Affiliation(s)
- Zhong Zhang
- College of Food Science and Engineering, Gansu Agricultural University, Lanzhou 730070, China
| | - Wenting Zhang
- College of Food Science and Engineering, Gansu Agricultural University, Lanzhou 730070, China
| | - Yang Bi
- College of Food Science and Engineering, Gansu Agricultural University, Lanzhou 730070, China
| | - Ye Han
- College of Food Science and Engineering, Gansu Agricultural University, Lanzhou 730070, China
| | - Yuanyuan Zong
- College of Food Science and Engineering, Gansu Agricultural University, Lanzhou 730070, China
| | - Dov Prusky
- College of Food Science and Engineering, Gansu Agricultural University, Lanzhou 730070, China
- Department of Postharvest Science of Fresh Produce, Agricultural Research Organization, The 12 Volcani Center, Beit Dagan 50200, Israel
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12
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Cell Cycle and DNA Repair Regulation in the Damage Response: Protein Phosphatases Take Over the Reins. Int J Mol Sci 2020; 21:ijms21020446. [PMID: 31936707 PMCID: PMC7014277 DOI: 10.3390/ijms21020446] [Citation(s) in RCA: 49] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2019] [Revised: 12/29/2019] [Accepted: 01/02/2020] [Indexed: 12/14/2022] Open
Abstract
Cells are constantly suffering genotoxic stresses that affect the integrity of our genetic material. Genotoxic insults must be repaired to avoid the loss or inappropriate transmission of the genetic information, a situation that could lead to the appearance of developmental abnormalities and tumorigenesis. To combat this threat, eukaryotic cells have evolved a set of sophisticated molecular mechanisms that are collectively known as the DNA damage response (DDR). This surveillance system controls several aspects of the cellular response, including the detection of lesions, a temporary cell cycle arrest, and the repair of the broken DNA. While the regulation of the DDR by numerous kinases has been well documented over the last decade, the complex roles of protein dephosphorylation have only recently begun to be investigated. Here, we review recent progress in the characterization of DDR-related protein phosphatases during the response to a DNA lesion, focusing mainly on their ability to modulate the DNA damage checkpoint and the repair of the damaged DNA. We also discuss their protein composition and structure, target specificity, and biochemical regulation along the different stages encompassed in the DDR. The compilation of this information will allow us to better comprehend the physiological significance of protein dephosphorylation in the maintenance of genome integrity and cell viability in response to genotoxic stress.
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13
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D'Arcy BM, Swingle MR, Papke CM, Abney KA, Bouska ES, Prakash A, Honkanen RE. The Antitumor Drug LB-100 Is a Catalytic Inhibitor of Protein Phosphatase 2A (PPP2CA) and 5 (PPP5C) Coordinating with the Active-Site Catalytic Metals in PPP5C. Mol Cancer Ther 2019; 18:556-566. [PMID: 30679389 DOI: 10.1158/1535-7163.mct-17-1143] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2017] [Revised: 03/20/2018] [Accepted: 01/11/2019] [Indexed: 12/28/2022]
Abstract
LB-100 is an experimental cancer therapeutic with cytotoxic activity against cancer cells in culture and antitumor activity in animals. The first phase I trial (NCT01837667) evaluating LB-100 recently concluded that safety and efficacy parameters are favorable for further clinical testing. Although LB-100 is widely reported as a specific inhibitor of serine/threonine phosphatase 2A (PP2AC/PPP2CA:PPP2CB), we could find no experimental evidence in the published literature demonstrating the specific engagement of LB-100 with PP2A in vitro, in cultured cells, or in animals. Rather, the premise for LB-100 targeting PP2AC is derived from studies that measure phosphate released from a phosphopeptide (K-R-pT-I-R-R) or inferred from the ability of LB-100 to mimic activity previously reported to result from the inhibition of PP2AC by other means. PP2AC and PPP5C share a common catalytic mechanism. Here, we demonstrate that the phosphopeptide used to ascribe LB-100 specificity for PP2A is also a substrate for PPP5C. Inhibition assays using purified enzymes demonstrate that LB-100 is a catalytic inhibitor of both PP2AC and PPP5C. The structure of PPP5C cocrystallized with LB-100 was solved to a resolution of 1.65Å, revealing that the 7-oxabicyclo[2.2.1]heptane-2,3-dicarbonyl moiety coordinates with the metal ions and key residues that are conserved in both PP2AC and PPP5C. Cell-based studies revealed some known actions of LB-100 are mimicked by the genetic disruption of PPP5C These data demonstrate that LB-100 is a catalytic inhibitor of both PP2AC and PPP5C and suggest that the observed antitumor activity might be due to an additive effect achieved by suppressing both PP2A and PPP5C.
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Affiliation(s)
- Brandon M D'Arcy
- USA Mitchell Cancer Institute, Mobile, Alabama.,Department of Biochemistry and Molecular Biology, University of South Alabama, Mobile, Alabama
| | - Mark R Swingle
- Department of Biochemistry and Molecular Biology, University of South Alabama, Mobile, Alabama
| | - Cinta M Papke
- Department of Biochemistry and Molecular Biology, University of South Alabama, Mobile, Alabama
| | - Kevin A Abney
- Department of Biochemistry and Molecular Biology, University of South Alabama, Mobile, Alabama
| | - Erin S Bouska
- Department of Biochemistry and Molecular Biology, University of South Alabama, Mobile, Alabama
| | - Aishwarya Prakash
- USA Mitchell Cancer Institute, Mobile, Alabama. .,Department of Pharmacology, University of South Alabama, Mobile, Alabama
| | - Richard E Honkanen
- USA Mitchell Cancer Institute, Mobile, Alabama. .,Department of Biochemistry and Molecular Biology, University of South Alabama, Mobile, Alabama
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14
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Wang J, Shen T, Zhu W, Dou L, Gu H, Zhang L, Yang Z, Chen H, Zhou Q, Sánchez ER, Field LJ, Mayo LD, Xie Z, Xiao D, Lin X, Shou W, Yong W. Protein phosphatase 5 and the tumor suppressor p53 down-regulate each other's activities in mice. J Biol Chem 2018; 293:18218-18229. [PMID: 30262665 DOI: 10.1074/jbc.ra118.004256] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2018] [Revised: 09/17/2018] [Indexed: 12/20/2022] Open
Abstract
Protein phosphatase 5 (PP5), a serine/threonine phosphatase, has a wide range of biological functions and exhibits elevated expression in tumor cells. We previously reported that pp5-deficient mice have altered ataxia-telangiectasia mutated (ATM)-mediated signaling and function. However, this regulation was likely indirect, as ATM is not a known PP5 substrate. In the current study, we found that pp5-deficient mice are hypersensitive to genotoxic stress. This hypersensitivity was associated with the marked up-regulation of the tumor suppressor tumor protein p53 and its downstream targets cyclin-dependent kinase inhibitor 1A (p21), MDM2 proto-oncogene (MDM2), and phosphatase and tensin homolog (PTEN) in pp5-deficient tissues and cells. These observations suggested that PP5 plays a role in regulating p53 stability and function. Experiments conducted with p53 +/- pp5 +/- or p53 +/- pp5 -/- mice revealed that complete loss of PP5 reduces tumorigenesis in the p53 +/- mice. Biochemical analyses further revealed that PP5 directly interacts with and dephosphorylates p53 at multiple serine/threonine residues, resulting in inhibition of p53-mediated transcriptional activity. Interestingly, PP5 expression was significantly up-regulated in p53-deficient cells, and further analysis of pp5 promoter activity revealed that p53 strongly represses PP5 transcription. Our results suggest a reciprocal regulatory interplay between PP5 and p53, providing an important feedback mechanism for the cellular response to genotoxic stress.
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Affiliation(s)
- Jun Wang
- From the Comparative Medical Center, Institute of Laboratory Animal Science, Chinese Academy of Medical Sciences, Beijing 100021, China,; School of Life Sciences, Anhui Agricultural University, Hefei, Anhui 230036, China
| | - Tao Shen
- DeBakey Department of Surgery, Baylor College of Medicine, Houston, Texas 77030
| | - Wuqiang Zhu
- Herman B. Wells Center for Pediatric Research, Department of Pediatrics, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Longyu Dou
- From the Comparative Medical Center, Institute of Laboratory Animal Science, Chinese Academy of Medical Sciences, Beijing 100021, China
| | - Hao Gu
- From the Comparative Medical Center, Institute of Laboratory Animal Science, Chinese Academy of Medical Sciences, Beijing 100021, China
| | - Lingling Zhang
- From the Comparative Medical Center, Institute of Laboratory Animal Science, Chinese Academy of Medical Sciences, Beijing 100021, China
| | - Zhenyun Yang
- Herman B. Wells Center for Pediatric Research, Department of Pediatrics, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Hanying Chen
- Herman B. Wells Center for Pediatric Research, Department of Pediatrics, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Qi Zhou
- Herman B. Wells Center for Pediatric Research, Department of Pediatrics, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Edwin R Sánchez
- Department of Physiology and Pharmacology, College of Medicine, University of Toledo, Toledo, Ohio 43614, and
| | - Loren J Field
- Herman B. Wells Center for Pediatric Research, Department of Pediatrics, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Lindsey D Mayo
- Herman B. Wells Center for Pediatric Research, Department of Pediatrics, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Zhongwen Xie
- School of Life Sciences, Anhui Agricultural University, Hefei, Anhui 230036, China
| | - Deyong Xiao
- Fountain Valley Institute of Life Sciences and Fountain Valley Biomedical Technology Company, Dalian Hi-Tech Industrial Zone, Dalian 116023, China
| | - Xia Lin
- DeBakey Department of Surgery, Baylor College of Medicine, Houston, Texas 77030
| | - Weinian Shou
- Herman B. Wells Center for Pediatric Research, Department of Pediatrics, Indiana University School of Medicine, Indianapolis, Indiana 46202,.
| | - Weidong Yong
- From the Comparative Medical Center, Institute of Laboratory Animal Science, Chinese Academy of Medical Sciences, Beijing 100021, China,; Herman B. Wells Center for Pediatric Research, Department of Pediatrics, Indiana University School of Medicine, Indianapolis, Indiana 46202,.
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15
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Huang CY, Hsieh FS, Wang CY, Chen LJ, Chang SS, Tsai MH, Hung MH, Kuo CW, Shih CT, Chao TI, Chen KF. Palbociclib enhances radiosensitivity of hepatocellular carcinoma and cholangiocarcinoma via inhibiting ataxia telangiectasia-mutated kinase-mediated DNA damage response. Eur J Cancer 2018; 102:10-22. [PMID: 30103095 DOI: 10.1016/j.ejca.2018.07.010] [Citation(s) in RCA: 49] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2018] [Revised: 07/12/2018] [Accepted: 07/13/2018] [Indexed: 12/15/2022]
Abstract
AIM Palbociclib is an oral cyclin-dependent kinase 4/6 inhibitor, which is efficacious in treating breast cancer. Currently, there are numerous active clinical trials testing palbociclib alone or in combination with other medications for treating various types of malignancies. Here, we evaluated the anti-cancer effect of palbociclib in combination with radiation therapy (RT) for treating human hepatocellular carcinoma (HCC) and cholangiocarcinoma (CCA) and addressed the molecular mechanism behind the combination therapy. METHODS Immunofluorescence staining of γH2AX or 53BP1 was used to determine the effect of palbociclib on double-strand break (DSB) repair. Clonogenic assays, sphere formation and cell death ELISA were performed to study the sensitising effect of palbociclib on radiation-induced cytotoxicity. Signal alteration in DSB repair pathways was examined by Western blot analysis. Finally, we evaluated the in vivo anti-cancer activity and the associated molecular events of the combination therapy in a preclinical HCC xenograft model. RESULTS Palbociclib affected the kinetics of DNA repair and enhanced the radiation sensitivity of HCC and CCA cells. Importantly, we found that palbociclib inhibits ataxia telangiectasia-mutated (ATM) kinase, the key upstream kinase responding to RT-induced DSBs. Furthermore, we showed that the inhibitory effect of palbociclib on RT-induced ATM kinase activation is mediated by protein phosphatase 5 (PP5). Both in vitro and in vivo investigations revealed that the inhibition of the PP5-ATM axis by palbociclib after DNA damage is responsible for the synergism between palbociclib and RT. CONCLUSION Our findings provide a novel combination strategy against liver cancer cells. Clinical trials using palbociclib as an adjuvant in RT are warranted.
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Affiliation(s)
- Chao-Yuan Huang
- Division of Radiation Oncology, Department of Oncology, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan; Department of Medical Imaging and Radiological Technology, Yuanpei University, Hsinchu, Taiwan
| | - Feng-Shu Hsieh
- Department of Medical Research, National Taiwan University Hospital, Taipei, Taiwan.
| | - Cheng-Yi Wang
- Department of Internal Medicine, Cardinal Tien Hospital, Fu Jen Catholic University, New Taipei City, Taiwan
| | - Li-Ju Chen
- Department of Medical Research, National Taiwan University Hospital, Taipei, Taiwan
| | - Shih-Shin Chang
- Department of Medical Research, National Taiwan University Hospital, Taipei, Taiwan
| | - Ming-Hsien Tsai
- Department of Medical Research, National Taiwan University Hospital, Taipei, Taiwan
| | - Man-Hsin Hung
- Division of Medical Oncology, Department of Oncology, Taipei Veterans General Hospital, Taipei, Taiwan; School of Medicine, National Yang-Ming University, Taipei, Taiwan
| | - Chiung-Wen Kuo
- Department of Medical Imaging and Radiological Technology, Yuanpei University, Hsinchu, Taiwan
| | - Chi-Ting Shih
- Institute of Biopharmaceutical Sciences, National Yang-Ming University, Taipei, Taiwan
| | | | - Kuen-Feng Chen
- Department of Medical Research, National Taiwan University Hospital, Taipei, Taiwan; National Center of Excellence for Clinical Trial and Research, National Taiwan University Hospital, Taipei, Taiwan.
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16
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Zhu J, Ji Y, Yu Y, Jin Y, Zhang X, Zhou J, Chen Y. Knockdown of serine/threonine protein phosphatase 5 enhances gemcitabine sensitivity by promoting apoptosis in pancreatic cancer cells in vitro. Oncol Lett 2018; 15:8761-8769. [PMID: 29805615 DOI: 10.3892/ol.2018.8363] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2016] [Accepted: 09/22/2017] [Indexed: 12/28/2022] Open
Abstract
The targeting protein of serine/threonine protein phosphatase 5 (PPP5C) has been reported to be present in various malignancies. However, its functional role in pancreatic cancer (PC) remains unknown. In the present study, the function of PPP5C in PC cells treated with the first-line drug gemcitabine (GEM) was investigated. Short hairpin (sh)RNA targeting PPP5C was constructed to knockdown PPP5C in PANC-1 cells. Cell cycle and apoptosis analyses were performed in order to investigate the mechanisms underlying the effects induced by PPP5C silencing combined with GEM treatment. Western blot analysis was applied to detect the expression of certain key regulators of cell apoptosis in PANC-1 cells treated with GEM. shRNA against PPP5C effectively suppressed the proliferation of PANC-1 cells treated with GEM. Additionally, cell cycle analysis indicated that PPP5C knockdown resulted in a higher number of PANC-1 cells treated with GEM in G0/G1 phase arrest. Knockdown of PPP5C increased the expression of associated apoptotic markers, including cleaved caspase 3, poly (ADP-ribose) polymerase and phosphorylated (p)-p53. In addition, the combination of treatment with GEM and PPP5C silencing significantly increased the apoptosis of PANC-1 cells by affecting the expression levels of p-c-Jun N-terminal kinases and p-p38. The present study suggests that PPP5C may be a potential target for the treatment of PC and that it may enhance the gemcitabine sensitivity of PC cells.
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Affiliation(s)
- Jinhui Zhu
- Department of General Surgery and Laparoscopic Center, Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou, Zhejiang 310009, P.R. China
| | - Yun Ji
- Department of General Surgery, Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou, Zhejiang 310009, P.R. China
| | - Yuanquan Yu
- Department of General Surgery, Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou, Zhejiang 310009, P.R. China
| | - Yun Jin
- Department of General Surgery, Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou, Zhejiang 310009, P.R. China
| | - Xiaoxiao Zhang
- Department of General Surgery, Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou, Zhejiang 310009, P.R. China
| | - Jiale Zhou
- Department of General Surgery, Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou, Zhejiang 310009, P.R. China
| | - Yan Chen
- Department of General Surgery and Laparoscopic Center, Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou, Zhejiang 310009, P.R. China
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17
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Hamilton CL, Abney KA, Vasauskas AA, Alexeyev M, Li N, Honkanen RE, Scammell JG, Cioffi DL. Serine/threonine phosphatase 5 (PP5C/PPP5C) regulates the ISOC channel through a PP5C-FKBP51 axis. Pulm Circ 2017; 8:2045893217753156. [PMID: 29283027 PMCID: PMC6018905 DOI: 10.1177/2045893217753156] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Pulmonary endothelial cells express a store-operated calcium entry current (Isoc), which contributes to inter-endothelial cell gap formation. Isoc is regulated by a heterocomplex of proteins that includes the immunophilin FKBP51. FKBP51 inhibits Isoc by mechanisms that are not fully understood. In pulmonary artery endothelial cells (PAECs) we have shown that FKBP51 increases microtubule polymerization, an event that is critical for Isoc inhibition by FKBP51. In neurons, FKBP51 promotes microtubule stability through facilitation of tau dephosphorylation. However, FKBP51 does not possess phosphatase activity. Protein phosphatase 5 (PP5C/PPP5C) can dephosphorylate tau, and similar to FKBP51, PP5C possesses tetratricopeptide repeats (TPR) that mediate interaction with heat shock protein-90 (HSP90) chaperone/scaffolding complexes. We therefore tested whether PP5C contributes to FKBP51-mediated inhibition of Isoc. Both siRNA-mediated suppression of PP5C expression in PAECs and genetic disruption of PP5C in HEK293 cells attenuate FKBP51-mediated inhibition of Isoc. Reintroduction of catalytically competent, but not catalytically inactive PP5C, restored FKBP51-mediated inhibition of Isoc. PAEC cell fractionation studies identified both PP5C and the ISOC heterocomplex in the same membrane fractions. Further, PP5C co-precipitates with TRPC4, an essential subunit of ISOC channel. Finally, to determine if PP5C is required for FKBP51-mediated inhibition of calcium entry-induced inter-endothelial cell gap formation, we measured gap area by wide-field microscopy and performed biotin gap quantification assay and electric cell-substrate impedance sensing (ECIS®). Collectively, the data presented indicate that suppression of PP5C expression negates the protective effect of FKBP51. These observations identify PP5C as a novel member of the ISOC heterocomplex that is required for FKBP51-mediated inhibition of Isoc.
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Affiliation(s)
| | | | | | | | - Ni Li
- University of South Alabama
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18
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Chen YL, Hung MH, Chu PY, Chao TI, Tsai MH, Chen LJ, Hsiao YJ, Shih CT, Hsieh FS, Chen KF. Protein phosphatase 5 promotes hepatocarcinogenesis through interaction with AMP-activated protein kinase. Biochem Pharmacol 2017; 138:49-60. [DOI: 10.1016/j.bcp.2017.05.010] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2017] [Accepted: 05/12/2017] [Indexed: 11/27/2022]
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19
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The activity of protein phosphatase 5 towards native clients is modulated by the middle- and C-terminal domains of Hsp90. Sci Rep 2015; 5:17058. [PMID: 26593036 PMCID: PMC4655416 DOI: 10.1038/srep17058] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2015] [Accepted: 10/23/2015] [Indexed: 01/07/2023] Open
Abstract
Protein phosphatase 5 is involved in the regulation of kinases and transcription factors. The dephosphorylation activity is modulated by the molecular chaperone Hsp90, which binds to the TPR-domain of protein phosphatase 5. This interaction is dependent on the C-terminal MEEVD motif of Hsp90. We show that C-terminal Hsp90 fragments differ in their regulation of the phosphatase activity hinting to a more complex interaction. Also hydrodynamic parameters from analytical ultracentrifugation and small-angle X-ray scattering data suggest a compact structure for the Hsp90-protein phosphatase 5 complexes. Using crosslinking experiments coupled with mass spectrometric analysis and structural modelling we identify sites, which link the middle/C-terminal domain interface of C. elegans Hsp90 to the phosphatase domain of the corresponding kinase. Studying the relevance of the domains of Hsp90 for turnover of native substrates we find that ternary complexes with the glucocorticoid receptor (GR) are cooperatively formed by full-length Hsp90 and PPH-5. Our data suggest that the direct stimulation of the phosphatase activity by C-terminal Hsp90 fragments leads to increased dephosphorylation rates. These are further modulated by the binding of clients to the N-terminal and middle domain of Hsp90 and their presentation to the phosphatase within the phosphatase-Hsp90 complex.
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20
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Liu JY, Chen XE, Zhang YL. Insights into the key interactions between human protein phosphatase 5 and cantharidin using molecular dynamics and site-directed mutagenesis bioassays. Sci Rep 2015; 5:12359. [PMID: 26190207 PMCID: PMC4507179 DOI: 10.1038/srep12359] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2015] [Accepted: 05/05/2015] [Indexed: 01/23/2023] Open
Abstract
Serine/threonine protein phosphatase 5 (PP5) is a promising novel target for anticancer therapies. This work aims to uncover the key interactions at the atomic level between PP5 and three inhibitors (cantharidin, norcantharidin and endothall). We found that, unlike previous report, Arg 100 contributes less to PP5-inhibitor binding, and the residues His 69, Asn 128, His 129, Arg 225, His 252 and Arg 250 are of importance to PP5-inhibitor binding. The hydrophobic interactions established between the residues Val 254, Phe 271 and Tyr 276, especially Glu 253, are very important to enhance the inhibitive interaction. We suggested that, to increase the inhibitory activity, the interactions of inhibitor with three negatively charged unfavorable interaction residues, Asp 99, Glu 130 and Asp 213, should be avoided. However, the interactions of inhibitor with favorable interaction residue Arg 250 could enhance the inhibitory activity. The Manganese ion 2 (MN2) unfavorably contribute to the total interaction free energies. The coordination between MN2 and chemical group of inhibitor should be eliminated. This work provides insight into how cantharidin and its analogs bind to PP5c at the atomic level and will facilitate modification of cantharidin-like chemicals to rationally develop more specific and less cytotoxic anti-cancer drugs.
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Affiliation(s)
- Ji-Yuan Liu
- Key Laboratory of Plant Protection Resources &Pest Management of the Ministry of Education, Northwest A&F University, Yangling 712100, Shaanxi, China
| | - Xi-En Chen
- Key Laboratory of Plant Protection Resources &Pest Management of the Ministry of Education, Northwest A&F University, Yangling 712100, Shaanxi, China
| | - Ya-Lin Zhang
- Key Laboratory of Plant Protection Resources &Pest Management of the Ministry of Education, Northwest A&F University, Yangling 712100, Shaanxi, China
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21
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Decreased adipogenesis and adipose tissue in mice with inactivated protein phosphatase 5. Biochem J 2015; 466:163-76. [DOI: 10.1042/bj20140428] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
White adipose tissue levels are decreased and preadipoctye differentiation to adipocytes is retarded in mice with inactivated protein phosphatase 5. Increased phosphate in the glucocorticoid receptor mediates this phenotype by altering expression of several proteins in the pathway of adipogenesis.
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22
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Abstract
We performed quantitative trait locus (QTL) mapping analysis for litter size (total
number of pups born and/or number of pups born alive) in 255 backcross mice derived from
C57BL/6J and RR/Sgn inbred mice. We identified one significant QTL on chromosome 7 and 4
suggestive QTLs on chromosomes 3, 5, 10 and 13. In addition, two suggestive QTLs were
identified on chromosomes 1 and 4 for the number of stillbirth. These results suggested
that both litter size and number of stillbirth were heritable traits, although they were
controlled by distinct genes. The RR allele was associated with reduced litter size and
increased stillbirth at all QTLs. Therefore, RR mothers were observed to have reduced
prolificacy in this particular genetic cross.
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Affiliation(s)
- Jun-ichi Suto
- Agrogenomics Research Center, National Institute of Agrobiological Sciences, Tsukuba, Ibaraki 305-8634, Japan
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23
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Knockdown of PPP5C inhibits growth of hepatocellular carcinoma cells in vitro. Appl Biochem Biotechnol 2014; 175:526-34. [PMID: 25326185 DOI: 10.1007/s12010-014-1281-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2014] [Accepted: 09/30/2014] [Indexed: 02/07/2023]
Abstract
Ser/Thr protein phosphatase 5 (PPP5C) has been reported to participate in tumor progression. However, its functional role in hepatocellular carcinoma (HCC) remains unknown yet. In this study, we firstly evaluated the expression levels of PPP5C in six HCC cell lines by real-time PCR and found that PPP5C was widely expressed in HCC cells. To explore the role of PPP5C in HCC cell growth, lentivirus-mediated short hairpin RNA (shRNA) was employed to silence PPP5C expression in HepG2 and Bel-7404 cells. The expression of PPP5C was significantly downregulated in PPP5C knockdown cells. Knockdown of PPP5C markedly suppressed the proliferation and colony formation ability of HCC cells. Moreover, cell cycle analysis showed that PPP5C depletion in HepG2 cells led to G0/G1 phase and G2/M phase arrest. We demonstrate for the first time that PPP5C is essential for growth of HCC cells, which suggests that inhibition of PPP5C by RNAi may be a potential therapeutic strategy for the treatment of HCC.
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24
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Abstract
The prevalence of diabetes is increasing rapidly worldwide. A cardinal feature of most forms of diabetes is the lack of insulin-producing capability, due to the loss of insulin-producing β-cells, impaired glucose-sensitive insulin secretion from the β-cell, or a combination thereof, the reasons for which largely remain elusive. Reversible phosphorylation is an important and versatile mechanism for regulating the biological activity of many intracellular proteins, which, in turn, controls a variety of cellular functions. For instance, significant changes in protein kinase activities and in protein phosphorylation patterns occur subsequent to the stimulation of insulin release by glucose. Therefore, the molecular mechanisms regulating the phosphorylation of proteins involved in the insulin secretory process by the β-cell have been extensively investigated. However, far less is known about the role and regulation of protein dephosphorylation by various protein phosphatases. Herein, we review extant data implicating serine/threonine and tyrosine phosphatases in various aspects of healthy and diabetic islet biology, ranging from control of hormonal stimulus-secretion coupling to mitogenesis and apoptosis.
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Affiliation(s)
- Henrik Ortsäter
- Biovation Park TelgeSödertälje, SwedenResearch UnitSödertälje Hospital, SE-152 86 Södertälje, SwedenDegenerative Disease ProgramSanford-Burnham Medical Research Institute, Del E. Webb Neuroscience, Aging and Stem Cell Research Center, 10901 North Torrey Pines Road, La Jolla, California 92037, USADepartment of Biochemistry and Molecular BiologyCollege of Medicine, University of South Alabama, Mobile, Alabama 36688, USADepartment of Internal MedicineSödertälje Hospital, Södertälje, SwedenBiovation Park TelgeSödertälje, SwedenResearch UnitSödertälje Hospital, SE-152 86 Södertälje, SwedenDegenerative Disease ProgramSanford-Burnham Medical Research Institute, Del E. Webb Neuroscience, Aging and Stem Cell Research Center, 10901 North Torrey Pines Road, La Jolla, California 92037, USADepartment of Biochemistry and Molecular BiologyCollege of Medicine, University of South Alabama, Mobile, Alabama 36688, USADepartment of Internal MedicineSödertälje Hospital, Södertälje, Sweden
| | - Nina Grankvist
- Biovation Park TelgeSödertälje, SwedenResearch UnitSödertälje Hospital, SE-152 86 Södertälje, SwedenDegenerative Disease ProgramSanford-Burnham Medical Research Institute, Del E. Webb Neuroscience, Aging and Stem Cell Research Center, 10901 North Torrey Pines Road, La Jolla, California 92037, USADepartment of Biochemistry and Molecular BiologyCollege of Medicine, University of South Alabama, Mobile, Alabama 36688, USADepartment of Internal MedicineSödertälje Hospital, Södertälje, Sweden
| | - Richard E Honkanen
- Biovation Park TelgeSödertälje, SwedenResearch UnitSödertälje Hospital, SE-152 86 Södertälje, SwedenDegenerative Disease ProgramSanford-Burnham Medical Research Institute, Del E. Webb Neuroscience, Aging and Stem Cell Research Center, 10901 North Torrey Pines Road, La Jolla, California 92037, USADepartment of Biochemistry and Molecular BiologyCollege of Medicine, University of South Alabama, Mobile, Alabama 36688, USADepartment of Internal MedicineSödertälje Hospital, Södertälje, Sweden
| | - Åke Sjöholm
- Biovation Park TelgeSödertälje, SwedenResearch UnitSödertälje Hospital, SE-152 86 Södertälje, SwedenDegenerative Disease ProgramSanford-Burnham Medical Research Institute, Del E. Webb Neuroscience, Aging and Stem Cell Research Center, 10901 North Torrey Pines Road, La Jolla, California 92037, USADepartment of Biochemistry and Molecular BiologyCollege of Medicine, University of South Alabama, Mobile, Alabama 36688, USADepartment of Internal MedicineSödertälje Hospital, Södertälje, SwedenBiovation Park TelgeSödertälje, SwedenResearch UnitSödertälje Hospital, SE-152 86 Södertälje, SwedenDegenerative Disease ProgramSanford-Burnham Medical Research Institute, Del E. Webb Neuroscience, Aging and Stem Cell Research Center, 10901 North Torrey Pines Road, La Jolla, California 92037, USADepartment of Biochemistry and Molecular BiologyCollege of Medicine, University of South Alabama, Mobile, Alabama 36688, USADepartment of Internal MedicineSödertälje Hospital, Södertälje, SwedenBiovation Park TelgeSödertälje, SwedenResearch UnitSödertälje Hospital, SE-152 86 Södertälje, SwedenDegenerative Disease ProgramSanford-Burnham Medical Research Institute, Del E. Webb Neuroscience, Aging and Stem Cell Research Center, 10901 North Torrey Pines Road, La Jolla, California 92037, USADepartment of Biochemistry and Molecular BiologyCollege of Medicine, University of South Alabama, Mobile, Alabama 36688, USADepartment of Internal MedicineSödertälje Hospital, Södertälje, Sweden
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25
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Fransson L, Rosengren V, Saha TK, Grankvist N, Islam T, Honkanen RE, Sjöholm Å, Ortsäter H. Mitogen-activated protein kinases and protein phosphatase 5 mediate glucocorticoid-induced cytotoxicity in pancreatic islets and β-cells. Mol Cell Endocrinol 2014; 383:126-36. [PMID: 24361515 DOI: 10.1016/j.mce.2013.12.010] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/18/2013] [Revised: 12/15/2013] [Accepted: 12/16/2013] [Indexed: 11/21/2022]
Abstract
Glucocorticoid excess is associated with glucose intolerance and diabetes. In addition to inducing insulin resistance, glucocorticoids impair β-cell function and cause β-cell apoptosis. In this study we show that dexamethasone activates mitogen-activated protein kinases (MAPKs) signaling in MIN6 β-cells, as evident by enhanced phosphorylation of p38 MAPK and c-Jun N-terminal kinase (JNK). In contrast, the integrated stress response pathway was inhibited by dexamethasone. A p38 MAPK inhibitor attenuated dexamethasone-induced apoptosis in β-cells and isolated islets and decreased glucocorticoid receptor phosphorylation at S220. In contrast, a JNK inhibitor augmented DNA fragmentation and dexamethasone-induced formation of cleaved caspase 3. We also show that inhibition of protein phosphatase 5 (PP5) augments apoptosis in dexamethasone-exposed islets and β-cells, with a concomitant activation of p38 MAPK. In conclusion, our data provide evidence that in islets and β-cells, p38 MAPK and JNK phosphorylation work in concert with PP5 to regulate the cytotoxic effects exerted by glucocorticoids.
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Affiliation(s)
- Liselotte Fransson
- Department of Clinical Science and Education, Södersjukhuset, Karolinska Institutet, Stockholm, Sweden
| | - Victoria Rosengren
- Department of Clinical Science and Education, Södersjukhuset, Karolinska Institutet, Stockholm, Sweden
| | - Titu Kumar Saha
- Department of Clinical Science and Education, Södersjukhuset, Karolinska Institutet, Stockholm, Sweden
| | - Nina Grankvist
- Department of Clinical Science and Education, Södersjukhuset, Karolinska Institutet, Stockholm, Sweden
| | - Tohidul Islam
- Department of Clinical Science and Education, Södersjukhuset, Karolinska Institutet, Stockholm, Sweden
| | - Richard E Honkanen
- Department of Clinical Science and Education, Södersjukhuset, Karolinska Institutet, Stockholm, Sweden; Department of Internal Medicine, Södertälje Hospital, SE 152 86 Södertälje, Sweden
| | - Åke Sjöholm
- Department of Internal Medicine, Södertälje Hospital, SE 152 86 Södertälje, Sweden; Department of Biochemistry and Molecular Biology, University of South Alabama, College of Medicine, Mobile, AL, USA
| | - Henrik Ortsäter
- Department of Clinical Science and Education, Södersjukhuset, Karolinska Institutet, Stockholm, Sweden; Research Unit, Södertälje Hospital, SE-152 86 Södertälje, Sweden.
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26
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Mazalouskas MD, Godoy-Ruiz R, Weber DJ, Zimmer DB, Honkanen RE, Wadzinski BE. Small G proteins Rac1 and Ras regulate serine/threonine protein phosphatase 5 (PP5)·extracellular signal-regulated kinase (ERK) complexes involved in the feedback regulation of Raf1. J Biol Chem 2013; 289:4219-32. [PMID: 24371145 DOI: 10.1074/jbc.m113.518514] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Serine/threonine protein phosphatase 5 (PP5, PPP5C) is known to interact with the chaperonin heat shock protein 90 (HSP90) and is involved in the regulation of multiple cellular signaling cascades that control diverse cellular processes, such as cell growth, differentiation, proliferation, motility, and apoptosis. Here, we identify PP5 in stable complexes with extracellular signal-regulated kinases (ERKs). Studies using mutant proteins reveal that the formation of PP5·ERK1 and PP5·ERK2 complexes partially depends on HSP90 binding to PP5 but does not require PP5 or ERK1/2 activity. However, PP5 and ERK activity regulates the phosphorylation state of Raf1 kinase, an upstream activator of ERK signaling. Whereas expression of constitutively active Rac1 promotes the assembly of PP5·ERK1/2 complexes, acute activation of ERK1/2 fails to influence the phosphatase-kinase interaction. Introduction of oncogenic HRas (HRas(V12)) has no effect on PP5-ERK1 binding but selectively decreases the interaction of PP5 with ERK2, in a manner that is independent of PP5 and MAPK/ERK kinase (MEK) activity, yet paradoxically requires ERK2 activity. Additional studies conducted with oncogenic variants of KRas4B reveal that KRas(L61), but not KRas(V12), also decreases the PP5-ERK2 interaction. The expression of wild type HRas or KRas proteins fails to reduce PP5-ERK2 binding, indicating that the effect is specific to HRas(V12) and KRas(L61) gain-of-function mutations. These findings reveal a novel, differential responsiveness of PP5-ERK1 and PP5-ERK2 interactions to select oncogenic Ras variants and also support a role for PP5·ERK complexes in regulating the feedback phosphorylation of PP5-associated Raf1.
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Affiliation(s)
- Matthew D Mazalouskas
- From the Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee 37232-6600
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27
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Grankvist N, Honkanen RE, Sjöholm Å, Ortsäter H. Genetic disruption of protein phosphatase 5 in mice prevents high-fat diet feeding-induced weight gain. FEBS Lett 2013; 587:3869-74. [PMID: 24220247 DOI: 10.1016/j.febslet.2013.10.022] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2013] [Revised: 09/30/2013] [Accepted: 10/15/2013] [Indexed: 12/31/2022]
Abstract
The role of serine/threonine protein phosphatase 5 (PP5) in the development of obesity and insulin resistance associated with high-fat diet-feeding (HFD) was examined using PP5-deficient mice (Ppp5c(-/-)). Despite similar caloric intake, Ppp5c(-/-) mice on HFD gained markedly less weight and did not accumulate visceral fat compared to wild-type littermates (Ppp5c(+/+)). On a control diet, Ppp5c(-/-) mice had markedly improved glucose control compared to Ppp5c(+/+) mice, an effect diminished by HFD. However, even after 10 weeks of HFD glucose control in Ppp5c(-/-) mice was similar to that observed in Ppp5c(+/+) mice on the control diet. Thus, PP5 deficiency confers protection against HFD-induced weight gain in mice.
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Affiliation(s)
- N Grankvist
- Department of Clinical Science and Education, Södersjukhuset, Karolinska Institutet, Stockholm, Sweden.
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28
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Shimada M, Nakanishi M. Response to DNA damage: why do we need to focus on protein phosphatases? Front Oncol 2013; 3:8. [PMID: 23386996 PMCID: PMC3560363 DOI: 10.3389/fonc.2013.00008] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2012] [Accepted: 01/09/2013] [Indexed: 01/07/2023] Open
Abstract
Eukaryotic cells are continuously threatened by unavoidable errors during normal DNA replication or various sources of genotoxic stresses that cause DNA damage or stalled replication. To maintain genomic integrity, cells have developed a coordinated signaling network, known as the DNA damage response (DDR). Following DNA damage, sensor molecules detect the presence of DNA damage and transmit signals to downstream transducer molecules. This in turn conveys the signals to numerous effectors, which initiate a large number of specific biological responses, including transient cell cycle arrest mediated by checkpoints, DNA repair, and apoptosis. It is recently becoming clear that dephosphorylation events are involved in keeping DDR factors inactive during normal cell growth. Moreover, dephosphorylation is required to shut off checkpoint arrest following DNA damage and has been implicated in the activation of the DDR. Spatial and temporal regulation of phosphorylation events is essential for the DDR, and fine-tuning of phosphorylation is partly mediated by protein phosphatases. While the role of kinases in the DDR has been well documented, the complex roles of protein dephosphorylation have only recently begun to be investigated. Therefore, it is important to focus on the role of phosphatases and to determine how their activity is regulated upon DNA damage. In this work, we summarize current knowledge on the involvement of serine/threonine phosphatases, especially the protein phosphatase 1, protein phosphatase 2A, and protein phosphatase Mg2+/Mn2+-dependent families, in the DDR.
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Affiliation(s)
- Midori Shimada
- Department of Cell Biology, Graduate School of Medical Sciences, Nagoya City University Nagoya, Japan
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29
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Bruce DL, Macartney T, Yong W, Shou W, Sapkota GP. Protein phosphatase 5 modulates SMAD3 function in the transforming growth factor-β pathway. Cell Signal 2012; 24:1999-2006. [PMID: 22781750 DOI: 10.1016/j.cellsig.2012.07.003] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2012] [Accepted: 07/03/2012] [Indexed: 02/02/2023]
Abstract
Protein phosphatases play a key role in balancing the cellular responses to the transforming growth factor-β (TGFβ) signals. Several protein phosphatases have been attributed roles in the regulation of the TGFβ pathway. Among these, PPM1A is the only phosphatase reported to dephosphorylate SMAD2/3 in the nucleus. However we observed PPM1A exclusively in the cytoplasmic fractions independently of TGFβ treatment in all cells tested. These observations imply that a bona fide nuclear SMAD2/3 phosphatase remains elusive. In this study, we report a role for protein phosphatase 5 (PP5) in the TGFβ pathway. We identified PP5 as an interactor of SMAD2/3. Interestingly, in mouse embryonic fibroblast cells derived from PP5-null mice, TGFβ-induced transcriptional responses were significantly enhanced. Rather surprisingly, this enhancement is due to the increased levels of SMAD3 protein observed in PP5-null MEFs compared to the wild type. No differences in the levels of SMAD3 transcripts were observed between the wild-type and PP5-null MEFs. While PP5 is capable of dephosphorylating SMAD3-tail in overexpression assays, we demonstrate that its activity is essential in controlling SMAD3 protein levels in MEFs. We propose that PP5 regulates the TGFβ pathway in MEFs by regulating the expression of SMAD3 protein levels.
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Affiliation(s)
- David L Bruce
- MRC Protein Phosphorylation Unit, College of Life Sciences, University of Dundee, Dundee, UK
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30
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Grankvist N, Amable L, Honkanen RE, Sjöholm A, Ortsäter H. Serine/threonine protein phosphatase 5 regulates glucose homeostasis in vivo and apoptosis signalling in mouse pancreatic islets and clonal MIN6 cells. Diabetologia 2012; 55:2005-15. [PMID: 22526606 DOI: 10.1007/s00125-012-2541-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/09/2011] [Accepted: 03/02/2012] [Indexed: 01/06/2023]
Abstract
AIMS/HYPOTHESIS During the development of type 2 diabetes mellitus, beta cells are often exposed to a high glucose/hyperlipidaemic environment, in which the levels of reactive oxygen species (ROS) are elevated. In turn, ROS can trigger an apoptotic response leading to beta cell death, by activating mitogen-activated protein kinase (MAPK) signalling cascades. Here we test the hypothesis that serine/threonine protein phosphatase 5 (PP5) acts to suppress proapoptotic c-Jun N-terminal kinase (JNK) signalling in beta cells. METHODS Ppp5c(-/-) and Ppp5c(+/+) mice were subjected to intraperitoneal glucose (IPGTT) or insulin tolerance tests. Pancreatic islets from Ppp5c(-/-) and Ppp5c(+/+) mice or MIN6 cells treated with short-interfering RNA targeting PP5 were exposed to palmitate or H(2)O(2) to activate MAPK signalling. Changes in protein phosphorylation, mRNA expression, apoptosis and insulin secretion were detected by western blot analysis, quantitative RT-PCR or ELISA. RESULTS Ppp5c(-/-) mice weighed less and exhibited reduced fasting glycaemia and improved glucose tolerance during IPGTT, but retained normal insulin sensitivity and islet volume. Comparison of MAPK signalling in islets from Ppp5c(-/-) mice and MIN6 cells revealed that the lack of PP5 was associated with enhanced H(2)O(2)-induced phosphorylation of JNK and c-Jun. Cells with reduced PP5 also showed enhanced JNK phosphorylation and apoptosis after palmitate treatment. PP5 suppression in MIN6 cells correlated with hypersecretion of insulin in response to glucose. CONCLUSIONS/INTERPRETATION PP5 deficiency in mice is associated with reduced weight gain, lower fasting glycaemia, and improved glucose tolerance during IPGTT. At a molecular level, PP5 helps suppress apoptosis in beta cells by a mechanism that involves regulation of JNK phosphorylation.
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Affiliation(s)
- N Grankvist
- Department of Clinical Science and Education, Karolinska Institutet, Södersjukhuset, 118 83 Stockholm, Sweden
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