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Fonódi M, Nagy L, Boratkó A. Role of Protein Phosphatases in Tumor Angiogenesis: Assessing PP1, PP2A, PP2B and PTPs Activity. Int J Mol Sci 2024; 25:6868. [PMID: 38999976 PMCID: PMC11241275 DOI: 10.3390/ijms25136868] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2024] [Revised: 06/19/2024] [Accepted: 06/20/2024] [Indexed: 07/14/2024] Open
Abstract
Tumor angiogenesis, the formation of new blood vessels to support tumor growth and metastasis, is a complex process regulated by a multitude of signaling pathways. Dysregulation of signaling pathways involving protein kinases has been extensively studied, but the role of protein phosphatases in angiogenesis within the tumor microenvironment remains less explored. However, among angiogenic pathways, protein phosphatases play critical roles in modulating signaling cascades. This review provides a comprehensive overview of the involvement of protein phosphatases in tumor angiogenesis, highlighting their diverse functions and mechanisms of action. Protein phosphatases are key regulators of cellular signaling pathways by catalyzing the dephosphorylation of proteins, thereby modulating their activity and function. This review aims to assess the activity of the protein tyrosine phosphatases and serine/threonine phosphatases. These phosphatases exert their effects on angiogenic signaling pathways through various mechanisms, including direct dephosphorylation of angiogenic receptors and downstream signaling molecules. Moreover, protein phosphatases also crosstalk with other signaling pathways involved in angiogenesis, further emphasizing their significance in regulating tumor vascularization, including endothelial cell survival, sprouting, and vessel maturation. In conclusion, this review underscores the pivotal role of protein phosphatases in tumor angiogenesis and accentuate their potential as therapeutic targets for anti-angiogenic therapy in cancer.
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Affiliation(s)
| | | | - Anita Boratkó
- Department of Medical Chemistry, Faculty of Medicine, University of Debrecen, Egyetem tér 1, H-4032 Debrecen, Hungary; (M.F.); (L.N.)
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Thankam FG, Huynh J, Fang W, Chen Y, Agrawal DK. Exosomal-ribosomal proteins-driven heterogeneity of epicardial adipose tissue derived stem cells under ischemia for cardiac regeneration. J Tissue Eng Regen Med 2022; 16:396-408. [PMID: 35142442 DOI: 10.1002/term.3289] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2021] [Revised: 01/19/2022] [Accepted: 01/31/2022] [Indexed: 12/22/2022]
Abstract
Extracellular ribosomal proteins secreted in exosomes elicit biological/regenerative responses; however, ribosomal proteins contained in the exosomes of ischemia-challenged epicardial adipose tissue-derived stem cells (EATDS) remain unexplored. This study focuses on the identification of ribosomal proteins in the exosomes of ischemia-challenged EATDS and their sub-populations based on the key ribosomal proteins using single-cell genomics. Exosomes were isolated from control, ischemic (ISC), and reperfused (ISC/R) EATDS harvested from hyperlipidemic microswine, and the proteins were detected using Liquid chromatography with tandem mass spectrometry (LC-MS/MS). One hundred ninety-nine proteins and 177 proteins were detected in ISC and ISC/R groups, respectively with significant fold-change compared to controls. Five ribosomal proteins, RPL10A, 40SRPS18, 40SRPS30, 60SRPL14, and 40SRPSA, were significant owing to their abundance based on LC-MS/MS data. Expression of these proteins, except RPL10A, at transcript and protein levels were lower in ISC group compared to the control. scRNAseq analysis revealed EATDS heterogeneity based on the upregulation of 40SRPSA, 40SRPL18, and 40SRPS18. Pro-inflammatory sub-populations upregulated CCL5, anti-inflammatory sub-population upregulated IL-11, proliferative sub-population upregulated cell cycle and DNA replication mediators, and non-proliferative population downregulated the cell cycle and DNA replication mediators. Overall, the functional role of extracellular ribosomal proteins in driving unique phenotypes of EATDS population offers promise for designing effective translational approaches for myocardial regeneration.
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Affiliation(s)
- Finosh G Thankam
- Department of Translational Research, Western University of Health Sciences, Pomona, California, USA
| | - James Huynh
- Department of Translational Research, Western University of Health Sciences, Pomona, California, USA
| | - William Fang
- Department of Translational Research, Western University of Health Sciences, Pomona, California, USA
| | - Yu Chen
- Molecular Instrumentation Center, University of California-Los Angeles, Los Angeles, California, USA
| | - Devendra K Agrawal
- Department of Translational Research, Western University of Health Sciences, Pomona, California, USA
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Quan X, Liu X, Qin X, Wang Y, Sun T, Li Z, Zhu L, Chen J, Zhou Y, Singh S, Dong H, Zhang Z, Zhang H. The role of LR-TIMAP/PP1c complex in the occurrence and development of no-reflow. EBioMedicine 2021; 65:103251. [PMID: 33639401 PMCID: PMC7921471 DOI: 10.1016/j.ebiom.2021.103251] [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: 08/22/2020] [Revised: 02/01/2021] [Accepted: 02/03/2021] [Indexed: 12/22/2022] Open
Abstract
BACKGROUND The presence of no-reflow can increase the risk of major adverse cardiac events and is widely regarded as an important sign of serious prognosis. Previous studies show that laminin receptor (LR) is closely related to the morphology and function of microvessels. However, whether LR is involved in the occurrence and development of no-reflow is still unknown. METHODS In vivo, positron emission tomography (PET) perfusion imaging was performed to detect the effects of intramyocardial gene (LR-AAV and LR-siRNA-AAV) delivery treatment on the degree of no-reflow. In vitro, LC-MS/MS analysis was conducted to identify the LR phosphorylation sites of human cardiac microvascular endothelial cells (HCMECs) treated with oxygen-glucose deprivation (OGD) for 4 h. Western blot analyses were used to evaluate the phosphorylation levels of LR at residues Tyr47 (phospho-Tyr47-LR/pY47-LR) and Thr125 (phospho-Thr125-LR/pT125-LR) and their effects on the phosphorylation of VE-cadherin residue Ser665 (phospho-Ser665-VE-cad). FINDINGS LR over-expression, LRT125A (phosphonull) and LRY47A (phosphonull) treatments were found to reduce the level of phospho-Ser665-VE-cad, and subsequently maintain adherent junctions and endothelial barrier integrity in hypoxic environments. Mechanistically, TIMAP/PP1c can combine with LR on the cell membrane to form a novel LR-TIMAP/PP1c complex. The level of pY47-LR determined the stability of LR-TIMAP/PP1c complex. The binding of TIMAP/PP1c on LR activated the protein phosphatase activity of PP1c and regulated the level of pT125-LR. INTERPRETATION This study demonstrates that low level of phospho-LR reduces no-reflow area through stabilizing the LR-TIMAP/PP1c complex and promoting the stability of adherens junctions, and may help identify new therapeutic targets for the treatment of no-reflow.
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Affiliation(s)
- Xiaoyu Quan
- Thoracic Surgery Laboratory, the First College of Clinical Medicine, Xuzhou Medical University, Xuzhou, Jiangsu 221006, China
| | - Xiucheng Liu
- Thoracic Surgery Laboratory, the First College of Clinical Medicine, Xuzhou Medical University, Xuzhou, Jiangsu 221006, China; Department of Thoracic Surgery, Affifiliated Hospital of Xuzhou Medical University, 99 West Huaihai Road, Xuzhou, Jiangsu 221006, China
| | - Xichun Qin
- Thoracic Surgery Laboratory, the First College of Clinical Medicine, Xuzhou Medical University, Xuzhou, Jiangsu 221006, China; Department of Thoracic Surgery, Affifiliated Hospital of Xuzhou Medical University, 99 West Huaihai Road, Xuzhou, Jiangsu 221006, China
| | - Yuzhuo Wang
- Department of Thoracic Surgery, Affifiliated Hospital of Xuzhou Medical University, 99 West Huaihai Road, Xuzhou, Jiangsu 221006, China
| | - Teng Sun
- Thoracic Surgery Laboratory, the First College of Clinical Medicine, Xuzhou Medical University, Xuzhou, Jiangsu 221006, China; Department of Thoracic Surgery, Affifiliated Hospital of Xuzhou Medical University, 99 West Huaihai Road, Xuzhou, Jiangsu 221006, China
| | - Zhimin Li
- Department of Thoracic Surgery, Affifiliated Hospital of Xuzhou Medical University, 99 West Huaihai Road, Xuzhou, Jiangsu 221006, China
| | - Lidong Zhu
- Department of Thoracic Surgery, Affifiliated Hospital of Xuzhou Medical University, 99 West Huaihai Road, Xuzhou, Jiangsu 221006, China
| | - Jiali Chen
- Department of Thoracic Surgery, Affifiliated Hospital of Xuzhou Medical University, 99 West Huaihai Road, Xuzhou, Jiangsu 221006, China
| | - Yeqing Zhou
- Department of Thoracic Surgery, Affifiliated Hospital of Xuzhou Medical University, 99 West Huaihai Road, Xuzhou, Jiangsu 221006, China
| | - Sandeep Singh
- School of International Education, Xuzhou Medical University, 209 Tongshan Road, Xuzhou, Jiangsu 221004, China
| | - Hongyan Dong
- Morphological Research Experiment Center, Xuzhou Medical University, 209 Tongshan Road, Xuzhou, Jiangsu 221004, China
| | - Zhongming Zhang
- Department of Thoracic Surgery, Affifiliated Hospital of Xuzhou Medical University, 99 West Huaihai Road, Xuzhou, Jiangsu 221006, China.
| | - Hao Zhang
- Thoracic Surgery Laboratory, the First College of Clinical Medicine, Xuzhou Medical University, Xuzhou, Jiangsu 221006, China; Department of Thoracic Surgery, Affifiliated Hospital of Xuzhou Medical University, 99 West Huaihai Road, Xuzhou, Jiangsu 221006, China.
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Wang X, Obeidat M, Li L, Pasarj P, Aburahess S, Holmes CFB, Ballermann BJ. TIMAP inhibits endothelial myosin light chain phosphatase by competing with MYPT1 for the catalytic protein phosphatase 1 subunit PP1cβ. J Biol Chem 2019; 294:13280-13291. [PMID: 31315927 PMCID: PMC6737228 DOI: 10.1074/jbc.ra118.006075] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2018] [Revised: 06/17/2019] [Indexed: 11/06/2022] Open
Abstract
Transforming growth factor-β membrane associated protein (TIMAP) is an endothelial cell (EC)-predominant PP1 regulatory subunit and a member of the myosin phosphatase target (MYPT) protein family. The MYPTs preferentially bind the catalytic protein phosphatase 1 subunit PP1cβ, forming myosin phosphatase holoenzymes. We investigated whether TIMAP/PP1cβ could also function as a myosin phosphatase. Endogenous PP1cβ, myosin light chain 2 (MLC2), and myosin IIA heavy chain coimmunoprecipitated from EC lysates with endogenous TIMAP, and endogenous MLC2 colocalized with TIMAP in EC projections. Purified recombinant GST-TIMAP interacted directly with purified recombinant His-MLC2. However, TIMAP overexpression in EC enhanced MLC2 phosphorylation, an effect not observed with a TIMAP mutant that does not bind PP1cβ. Conversely, MLC2 phosphorylation was reduced in lung lysates from TIMAP-deficient mice and upon silencing of endogenous TIMAP expression in ECs. Ectopically expressed TIMAP slowed the rate of MLC2 dephosphorylation, an effect requiring TIMAP-PP1cβ interaction. The association of MYPT1 with PP1cβ was profoundly reduced in the presence of excess TIMAP, leading to proteasomal MYPT1 degradation. In the absence of TIMAP, MYPT1-associated PP1cβ readily bound immobilized microcystin-LR, an active-site inhibitor of PP1c. By contrast, TIMAP-associated PP1cβ did not interact with microcystin-LR, indicating that the active site of PP1cβ is blocked when it is bound to TIMAP. Thus, TIMAP inhibits myosin phosphatase activity in ECs by competing with MYPT1 for PP1cβ and blocking the PP1cβ active site.
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Affiliation(s)
- Xin Wang
- Department of Medicine, University of Alberta, Edmonton, Alberta T6G 2G3, Canada
| | - Marya Obeidat
- Department of Medicine, University of Alberta, Edmonton, Alberta T6G 2G3, Canada
| | - Laiji Li
- Department of Medicine, University of Alberta, Edmonton, Alberta T6G 2G3, Canada
| | - Phuwadet Pasarj
- Department of Biochemistry, University of Alberta, Edmonton, Alberta T6G 2G3, Canada
| | - Salah Aburahess
- Department of Medicine, University of Alberta, Edmonton, Alberta T6G 2G3, Canada
| | - Charles F B Holmes
- Department of Biochemistry, University of Alberta, Edmonton, Alberta T6G 2G3, Canada
| | - Barbara J Ballermann
- Department of Medicine, University of Alberta, Edmonton, Alberta T6G 2G3, Canada.
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Boratkó A, Csortos C. TIMAP, the versatile protein phosphatase 1 regulator in endothelial cells. IUBMB Life 2017; 69:918-928. [DOI: 10.1002/iub.1695] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2017] [Accepted: 10/26/2017] [Indexed: 01/28/2023]
Affiliation(s)
- Anita Boratkó
- Department of Medical Chemistry; Faculty of Medicine, University of Debrecen, Egyetem tér 1; Debrecen Hungary
| | - Csilla Csortos
- Department of Medical Chemistry; Faculty of Medicine, University of Debrecen, Egyetem tér 1; Debrecen Hungary
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PKC mediated phosphorylation of TIMAP regulates PP1c activity and endothelial barrier function. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2017; 1864:431-439. [DOI: 10.1016/j.bbamcr.2016.12.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2016] [Revised: 11/10/2016] [Accepted: 12/04/2016] [Indexed: 12/17/2022]
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Yang J, Yin S, Bi F, Liu L, Qin T, Wang H, Cao W. TIMAP repression by TGFβ and HDAC3-associated Smad signaling regulates macrophage M2 phenotypic phagocytosis. J Mol Med (Berl) 2016; 95:273-285. [PMID: 27709267 DOI: 10.1007/s00109-016-1479-z] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2016] [Revised: 08/23/2016] [Accepted: 09/26/2016] [Indexed: 11/30/2022]
Abstract
TIMAP (TGFβ-inhibited membrane-associated protein) is an endothelium-enriched TGFβ downstream protein and structurally belongs to the targeting subunit of myosin phosphatase; however, the mechanism of TGFβ repressing TIMAP and its functional relevance to TGFβ bioactivity remain largely unknown. Here, we report that TIMAP is reduced in TGFβ-elevated mouse fibrotic kidney and highly expressed in macrophages. TGFβ repression of TIMAP is associated with HDAC3 upregulation and its recruitment by Smad2/3 at the Smad binding element on TIMAP promoter, whereas specific HDAC3 inhibition reversed the TIMAP repression, suggesting that TGFβ transcriptionally downregulates TIMAP through HDAC3-associated Smad signaling. Further investigation showed that TIMAP over-expression interrupted TGFβ-associated Smad signaling and TIMAP repression by TGFβ correlated with TGFβ-induced macrophage M2 polarization markers, migration, and phagocytosis-the processes promoted by phosphorylation of the putative TIMAP substrate myosin light chain (MLC). Consistently, TIMAP dephosphorylated MLC in macrophages and TGFβ induced macrophage migration and phagocytosis in TIMAP- and MLC phosphorylation-dependent manners, suggesting that TIMAP dephosphorylation of MLC constitutes an essential regulatory loop mitigating TGFβ-associated macrophage M2 phenotypic activities. Given that hyperactive TGFβ often causes excessive macrophage phagocytic activities potentially leading to various chronic disorders, the strategies targeting HDAC3/TIMAP axis might improve TGFβ-associated pathological processes. KEY MESSAGE TIMAP is enriched in the endothelium and highly expressed in macrophages. TIMAP is suppressed by TGFβ via HDAC3-associated Smad signaling. TIMAP inhibits TGFβ signaling and TGFβ-associated macrophage M2 polarization. TIMAP dephosphorylation of MLC counteracts TGFβ-induced macrophage phagocytosis.
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Affiliation(s)
- Jun Yang
- Nanjing University School of Medicine, Jiangsu Key Laboratory of Molecular Medicine, 22 Hankou Road, Room 209, Science & Technology Building, Nanjing, 210093, China
| | - Shasha Yin
- Nanjing University School of Medicine, Jiangsu Key Laboratory of Molecular Medicine, 22 Hankou Road, Room 209, Science & Technology Building, Nanjing, 210093, China
| | - Fangfang Bi
- Nanjing University School of Medicine, Jiangsu Key Laboratory of Molecular Medicine, 22 Hankou Road, Room 209, Science & Technology Building, Nanjing, 210093, China
| | - Lin Liu
- Nanjing University School of Medicine, Jiangsu Key Laboratory of Molecular Medicine, 22 Hankou Road, Room 209, Science & Technology Building, Nanjing, 210093, China
| | - Tian Qin
- Nanjing University School of Medicine, Jiangsu Key Laboratory of Molecular Medicine, 22 Hankou Road, Room 209, Science & Technology Building, Nanjing, 210093, China
| | - Hongwei Wang
- Nanjing University School of Medicine, Jiangsu Key Laboratory of Molecular Medicine, 22 Hankou Road, Room 209, Science & Technology Building, Nanjing, 210093, China
| | - Wangsen Cao
- Nanjing University School of Medicine, Jiangsu Key Laboratory of Molecular Medicine, 22 Hankou Road, Room 209, Science & Technology Building, Nanjing, 210093, China.
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Boratkó A, Veréb Z, Petrovski G, Csortos C. TIMAP-protein phosphatase 1-complex controls endothelin-1 production via ECE-1 dephosphorylation. Int J Biochem Cell Biol 2016; 73:11-18. [DOI: 10.1016/j.biocel.2016.01.016] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2015] [Revised: 01/16/2016] [Accepted: 01/20/2016] [Indexed: 01/13/2023]
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Elongation factor-1A1 is a novel substrate of the protein phosphatase 1-TIMAP complex. Int J Biochem Cell Biol 2015; 69:105-13. [PMID: 26497934 DOI: 10.1016/j.biocel.2015.10.021] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2015] [Revised: 10/18/2015] [Accepted: 10/19/2015] [Indexed: 01/08/2023]
Abstract
TIMAP (TGF-β inhibited membrane associated protein) is a protein phosphatase 1 (PP1) regulatory subunit highly abundant in endothelial cells and it is involved in the maintenance of pulmonary endothelial barrier function. It localizes mainly in the plasma membrane, but it is also present in the nuclei and cytoplasm. Direct interaction of TIMAP with the eukaryotic elongation factor 1 A1 (eEF1A1) is shown by pull-down, LC-MS/MS, Far-Western and immunoprecipitations. In connection with the so called moonlighting functions of the elongation factor, eEF1A is thought to establish protein-protein interactions through a transcription-dependent nuclear export motif, TD-NEM, and to aid nuclear export of TD-NEM containing proteins. We found that a TD-NEM-like motif of TIMAP has a critical role in its specific binding to eEF1A1. However, eEF1A1 is not or not exclusively responsible for the nuclear export of TIMAP. On the contrary, TIMAP seems to regulate membrane localization of eEF1A1 as the elongation factor co-localized with TIMAP in the plasma membrane fraction of control endothelial cells, but it has disappeared from the membrane in TIMAP depleted cells. It is demonstrated that membrane localization of eEF1A1 depends on the phosphorylation state of its Thr residue(s); and ROCK phosphorylated eEF1A1 is a novel substrate for TIMAP-PP1 underlining the complex regulatory role of TIMAP in the endothelium. The elongation factor seems to be involved in the regulation of endothelial cell attachment and spreading as silencing of eEF1A1 positively affected these processes which were monitored by transendothelial resistance measurements.
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DiGiacomo V, Meruelo D. Looking into laminin receptor: critical discussion regarding the non-integrin 37/67-kDa laminin receptor/RPSA protein. Biol Rev Camb Philos Soc 2015; 91:288-310. [PMID: 25630983 DOI: 10.1111/brv.12170] [Citation(s) in RCA: 94] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2013] [Revised: 12/04/2014] [Accepted: 12/08/2014] [Indexed: 02/06/2023]
Abstract
The 37/67-kDa laminin receptor (LAMR/RPSA) was originally identified as a 67-kDa binding protein for laminin, an extracellular matrix glycoprotein that provides cellular adhesion to the basement membrane. LAMR has evolutionary origins, however, as a 37-kDa RPS2 family ribosomal component. Expressed in all domains of life, RPS2 proteins have been shown to have remarkably diverse physiological roles that vary across species. Contributing to laminin binding, ribosome biogenesis, cytoskeletal organization, and nuclear functions, this protein governs critical cellular processes including growth, survival, migration, protein synthesis, development, and differentiation. Unsurprisingly given its purview, LAMR has been associated with metastatic cancer, neurodegenerative disease and developmental abnormalities. Functioning in a receptor capacity, this protein also confers susceptibility to bacterial and viral infection. LAMR is clearly a molecule of consequence in human disease, directly mediating pathological events that make it a prime target for therapeutic interventions. Despite decades of research, there are still a large number of open questions regarding the cellular biology of LAMR, the nature of its ability to bind laminin, the function of its intrinsically disordered C-terminal region and its conversion from 37 to 67 kDa. This review attempts to convey an in-depth description of the complexity surrounding this multifaceted protein across functional, structural and pathological aspects.
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Affiliation(s)
- Vincent DiGiacomo
- Department of Pathology, New York University School of Medicine, 180 Varick Street, New York, NY 10014, U.S.A
| | - Daniel Meruelo
- Department of Pathology, New York University School of Medicine, 180 Varick Street, New York, NY 10014, U.S.A.,NYU Cancer Institute, 550 First Avenue, New York, NY 10016, U.S.A.,NYU Gene Therapy Center, 550 First Avenue, New York, NY 10016, U.S.A
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11
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Korrodi-Gregório L, Esteves SLC, Fardilha M. Protein phosphatase 1 catalytic isoforms: specificity toward interacting proteins. Transl Res 2014; 164:366-91. [PMID: 25090308 DOI: 10.1016/j.trsl.2014.07.001] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/23/2014] [Revised: 06/26/2014] [Accepted: 07/01/2014] [Indexed: 01/21/2023]
Abstract
The coordinated and reciprocal action of serine-threonine protein kinases and protein phosphatases produces transitory phosphorylation, a fundamental regulatory mechanism for many biological processes. Phosphoprotein phosphatase 1 (PPP1), a major serine-threonine phosphatase, in particular, is ubiquitously distributed and regulates a broad range of cellular functions, including glycogen metabolism, cell cycle progression, and muscle relaxation. PPP1 has evolved effective catalytic machinery but in vitro lacks substrate specificity. In vivo, its specificity is achieved not only by the existence of different PPP1 catalytic isoforms, but also by binding of the catalytic moiety to a large number of regulatory or targeting subunits. Here, we will address exhaustively the existence of diverse PPP1 catalytic isoforms and the relevance of their specific partners and consequent functions.
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Affiliation(s)
- Luís Korrodi-Gregório
- Laboratório de Transdução de Sinais, Departamento de Biologia, Secção Autónoma de Ciências de Saúde, Centro de Biologia Celular, Universidade de Aveiro, Aveiro, Portugal
| | - Sara L C Esteves
- Laboratório de Transdução de Sinais, Departamento de Biologia, Secção Autónoma de Ciências de Saúde, Centro de Biologia Celular, Universidade de Aveiro, Aveiro, Portugal
| | - Margarida Fardilha
- Laboratório de Transdução de Sinais, Departamento de Biologia, Secção Autónoma de Ciências de Saúde, Centro de Biologia Celular, Universidade de Aveiro, Aveiro, Portugal.
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Obeidat M, Li L, Ballermann BJ. TIMAP promotes angiogenesis by suppressing PTEN-mediated Akt inhibition in human glomerular endothelial cells. Am J Physiol Renal Physiol 2014; 307:F623-33. [PMID: 25007873 DOI: 10.1152/ajprenal.00070.2014] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
The function of TIMAP, an endothelial cell (EC)-predominant protein phosphatase 1-regulatory subunit, is poorly understood. We explored the potential role of TIMAP in the Akt-dependent regulation of glomerular EC proliferation, survival, and in vitro angiogenesis. To deplete TIMAP, the EC were transfected with TIMAP-specific or nonspecific small interfering (si) RNA. The rate of electrical impedance development across subconfluent EC monolayers, a measure of the time-dependent increase in EC number, was 93 ± 2% lower in TIMAP-depleted than in control EC. This effect on cell proliferation was associated with reduced DNA synthesis and increased apoptosis: TIMAP silencing reduced 5-ethynyl-2'-deoxyuridine incorporation by 38 ± 2% during the exponential phase of EC proliferation, and cleaved caspase 3 as well as caspase 3 activity increased in TIMAP-depleted relative to control cells. Furthermore, TIMAP depletion inhibited the formation of angiogenic sprouts by glomerular EC in three-dimensional culture. TIMAP depletion strongly diminished growth factor-stimulated Akt phosphorylation without altering ERK1/2 phosphorylation, suggesting a specific effect on the PI3K/Akt/PTEN pathway. Endogenous TIMAP and PTEN colocalized in EC and coimmunoprecipitated from EC lysates. The inhibitory PTEN phosphorylation on S370 was significantly reduced in TIMAP-depleted compared with control EC, while phosphorylation of PTEN on the S380/T382/T383 cluster remained unchanged. Finally, the PTEN inhibitor bpV(phen) fully reversed the suppressive effect of TIMAP depletion on Akt phosphorylation. The data indicate that in growing EC, TIMAP is necessary for Akt-dependent EC proliferation, survival, and angiogenic sprout formation and that this effect of TIMAP is mediated by inhibition of the tumor suppressor PTEN.
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Affiliation(s)
- Marya Obeidat
- Department of Medicine, University of Alberta, Edmonton, Alberta, Canada
| | - Laiji Li
- Department of Medicine, University of Alberta, Edmonton, Alberta, Canada
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Tovar-Mendez A, Miernyk JA, Hoyos E, Randall DD. A functional genomic analysis of Arabidopsis thaliana PP2C clade D. PROTOPLASMA 2014; 251:265-271. [PMID: 23832523 DOI: 10.1007/s00709-013-0526-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/03/2013] [Accepted: 06/24/2013] [Indexed: 06/02/2023]
Abstract
In the reference dicot plant Arabidopsis thaliana, the PP2C family of P-protein phosphatases includes the products of 80 genes that have been separated into ten multi-protein clades plus six singletons. Clade D includes the products of nine genes distributed among three chromosomes (APD1, At3g12620; APD2, At3g17090; APD3, At3g51370; APD4, At3g55050; APD5, At4g33920; APD6, At4g38520; APD7, At5g02760; APD8, At5g06750; and APD9, At5g66080). As part of a functional genomics analysis of protein phosphorylation, we retrieved expression data from public databases and determined the subcellular protein localization of the members of clade D. While the nine proteins have been grouped together based upon primary sequence alignments, we observed no obvious common patterns in expression or localization. We found chimera with the GFP associated with the nucleus, plasma membrane, the endomembrane system, and mitochondria in transgenic plants.
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Shopik MJ, Li L, Luu HA, Obeidat M, Holmes CFB, Ballermann BJ. Multi-directional function of the protein phosphatase 1 regulatory subunit TIMAP. Biochem Biophys Res Commun 2013; 435:567-73. [PMID: 23685145 DOI: 10.1016/j.bbrc.2013.05.012] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2013] [Accepted: 05/04/2013] [Indexed: 11/19/2022]
Abstract
TIMAP is an endothelial-cell predominant member of the MYPT family of PP1c regulatory subunits. This study explored the TIMAP-PP1c interaction and substrate specificity in vitro. TIMAP associated with all three PP1c isoforms, but endogenous endothelial cell TIMAP preferentially co-immunoprecipitated with PP1cβ. Structural modeling of the TIMAP/PP1c complex predicts that the PP1c C-terminus is buried in the TIMAP ankyrin cluster, and that the PP1c active site remains accessible. Consistent with this model, C-terminal PP1c phosphorylation by cdk2-cyclinA was masked by TIMAP, and PP1c bound TIMAP when the active site was occupied by the inhibitor microcystin. TIMAP inhibited PP1c activity toward phosphorylase a in a concentration-dependent manner, with half-maximal inhibition in the 0.4-1.2 nM range, an effect modulated by the length, and by Ser333/Ser337 phosphomimic mutations of the TIMAP C-terminus. TIMAP-bound PP1cβ effectively dephosphorylated MLC2 and TIMAP itself. By contrast, TIMAP inhibited the PP1cβ activity toward the putative substrate LAMR1, and instead masked LAMR1 PKA- and PKC-phosphorylation sites. This is direct evidence that MLC2 is a TIMAP/PP1c substrate. The data also indicate that TIMAP can modify protein phosphorylation independent of its function as a PP1c regulatory subunit, namely by masking phosphorylation sites of binding partners like PP1c and LAMR1.
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Affiliation(s)
- Micheal J Shopik
- Department of Biochemistry, University of Alberta, Edmonton, AB, Canada
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15
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Boratkó A, Gergely P, Csortos C. RACK1 is involved in endothelial barrier regulation via its two novel interacting partners. Cell Commun Signal 2013; 11:2. [PMID: 23305203 PMCID: PMC3560227 DOI: 10.1186/1478-811x-11-2] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2012] [Accepted: 01/07/2013] [Indexed: 01/17/2023] Open
Abstract
Background RACK1, receptor for activated protein kinase C, serves as an anchor in multiple signaling pathways. TIMAP, TGF-β inhibited membrane-associated protein, is most abundant in endothelial cells with a regulatory effect on the endothelial barrier function. The interaction of TIMAP with protein phosphatase 1 (PP1cδ) was characterized, yet little is known about its further partners. Results We identified two novel interacting partners of RACK1, namely, TGF-β inhibited membrane-associated protein, TIMAP, and farnesyl transferase. TIMAP is most abundant in endothelial cells where it is involved in the regulation of the barrier function. WD1-4 repeats of RACK1 were identified as critical regions of the interaction both with TIMAP and farnesyl transferase. Phosphorylation of TIMAP by activation of the cAMP/PKA pathway reduced the amount of TIMAP-RACK1 complex and enhanced translocation of TIMAP to the cell membrane in vascular endothelial cells. However, both membrane localization of TIMAP and transendothelial resistance were attenuated after RACK1 depletion. Farnesyl transferase, the enzyme responsible for prenylation and consequent membrane localization of TIMAP, is present in the RACK1-TIMAP complex in control cells, but it does not co-immunoprecipitate with TIMAP after RACK1 depletion. Conclusions Transient parallel linkage of TIMAP and farnesyl transferase to RACK1 could ensure prenylation and transport of TIMAP to the plasma membrane where it may attend in maintaining the endothelial barrier as a phosphatase regulator.
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Affiliation(s)
- Anita Boratkó
- Department of Medical Chemistry, University of Debrecen Medical and Health Science Center, Egyetem tér 1, Debrecen, H 4032, Hungary.
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16
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The folded and disordered domains of human ribosomal protein SA have both idiosyncratic and shared functions as membrane receptors. Biosci Rep 2012; 33:113-24. [PMID: 23137297 PMCID: PMC4098866 DOI: 10.1042/bsr20120103] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The human RPSA [ribosomal protein SA; also known as LamR1(laminin receptor 1)] belongs to the
ribosome but is also a membrane receptor for laminin, growth factors, prion, pathogens and the
anticarcinogen EGCG (epigallocatechin-gallate). It contributes to the crossing of the
blood–brain barrier by neurotropic viruses and bacteria, and is a biomarker of metastasis.
RPSA includes an N-terminal domain, which is folded and homologous to the prokaryotic RPS2, and a
C-terminal extension, which is intrinsically disordered and conserved in vertebrates. We used
recombinant derivatives of RPSA and its N- and C-domains to quantify its interactions with ligands
by in-vitro immunochemical and spectrofluorimetric methods. Both N- and C-domains
bound laminin with KD (dissociation constants) of 300 nM. Heparin
bound only to the N-domain and competed for binding to laminin with the negatively charged C-domain,
which therefore mimicked heparin. EGCG bound only to the N-domain with a
KD of 100 nM. Domain 3 of the envelope protein from yellow fever
virus and serotypes-1 and -2 of dengue virus bound preferentially to the C-domain whereas that from
West Nile virus bound only to the N-domain. Our quantitative in-vitro approach
should help clarify the mechanisms of action of RPSA, and ultimately fight against cancer and
infectious agents.
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Ould-Abeih MB, Petit-Topin I, Zidane N, Baron B, Bedouelle H. Multiple Folding States and Disorder of Ribosomal Protein SA, a Membrane Receptor for Laminin, Anticarcinogens, and Pathogens. Biochemistry 2012; 51:4807-21. [DOI: 10.1021/bi300335r] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Mohamed B. Ould-Abeih
- Institut Pasteur, Unit of Molecular Prevention and
Therapy of Human Diseases, Department
of Infection and Epidemiology, rue du Dr. Roux, F-75015 Paris, France
- CNRS, URA3012, rue du Dr. Roux, F-75015 Paris, France
- Université Paris Diderot, Sorbonne Paris Cité, Cellule Pasteur,
rue du Dr. Roux, F-75015 Paris, France
| | - Isabelle Petit-Topin
- Institut Pasteur, Unit of Molecular Prevention and
Therapy of Human Diseases, Department
of Infection and Epidemiology, rue du Dr. Roux, F-75015 Paris, France
- CNRS, URA3012, rue du Dr. Roux, F-75015 Paris, France
| | - Nora Zidane
- Institut Pasteur, Unit of Molecular Prevention and
Therapy of Human Diseases, Department
of Infection and Epidemiology, rue du Dr. Roux, F-75015 Paris, France
- CNRS, URA3012, rue du Dr. Roux, F-75015 Paris, France
| | - Bruno Baron
- Institut Pasteur, Plate-forme
de Biophysique des Macromolécules et de leurs
Interactions, Department of Structural Biology and Chemistry, rue
du Dr. Roux, F-75015 Paris, France
- CNRS, UMR3528, rue du Dr. Roux, 75015
Paris, France
| | - Hugues Bedouelle
- Institut Pasteur, Unit of Molecular Prevention and
Therapy of Human Diseases, Department
of Infection and Epidemiology, rue du Dr. Roux, F-75015 Paris, France
- CNRS, URA3012, rue du Dr. Roux, F-75015 Paris, France
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18
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Yu W, Li J, Wang M, Quan Y, Chen J, Nie Z, Lv Z, Zhang Y. The screening and functional study of proteins binding with the BmNPV polyhedrin promoter. Virol J 2012; 9:90. [PMID: 22559085 PMCID: PMC3422170 DOI: 10.1186/1743-422x-9-90] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2011] [Accepted: 04/20/2012] [Indexed: 11/10/2022] Open
Abstract
Background The polyhedrin gene promoter has an essential role in regulating foreign gene expression in baculovirus expression vector systems (BEVS); however, the high-level transcription mechanism is still unknown. One-hybrid screening in yeast is a powerful way of identifying rapidly heterologous transcription factors that can interact with the polyhedrin promoter DNA sequence. In the current study, total RNA was extracted from the fat bodies of fifth-instar silkworm larvae that had been infected with Bombyx mori nuclear polyhedrosis virus (BmNPV) for 5 days; complementary DNA (cDNA) was then generated using reverse-transcription (RT)-PCR to construct a silkworm gene expression library. Key polyhedrin promoter bait sequences were synthesized to generate a bait yeast strain, which was used to screen the one-hybrid cDNA library. Results In total, 12 positive yeast colonies were obtained from the SD/-Leu/AbA plates; sequencing analysis showed that they belong to two different protein cDNA colonies. Positive colonies underwent bioinformatics analysis, which revealed one colony to be ribosomal proteins [B. mori ribosomal protein SA (BmRPSA)] and the other to be NPV DNA-binding proteins (DBP). To further verify the regulatory function of these two protein groups, transient expression vectors (pSK-IE-dbp and pSK-IE-BmRPSA) were constructed. The recombinant plasmids were then transfected into cultured B. mori N (BmN) cells, which had been infected with a recombinant bacmid containing the gene encoding luciferase (luc). The results showed that overexpression of either dbp or BmRPSA upregulated the polh promoter-driven transcription of luc in BmN cells. In addition, dbp or BmRPSA RNA interference (RNAi) resulted in the downregulation of luciferase reporter expression in BmN cells, demonstrating that DBP and BmRPSA are important for luc transcription. EMSA results further confirmed that DBP could directly bind to the conserved single-stranded polh promoter region in intro. However, EMSA assay also showed that BmRPSA did not bind to this region, precluding a direct DNA association. Conclusions Both DBP and BmRPSA are important for polh transcription. DBP can regulate polh promoter activity by direct binding to the conserved single-stranded polh promoter region, BmRPSA may regulate polh promoter activity by indirect binding to this region.
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Affiliation(s)
- Wei Yu
- Institute of Biochemistry, Zhejiang Sci-Tech University, Hangzhou, China.
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19
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Poirier C, Gorshkov BA, Zemskova MA, Bogatcheva NV, Verin AD. TIMAP protects endothelial barrier from LPS-induced vascular leakage and is down-regulated by LPS. Respir Physiol Neurobiol 2011; 179:334-7. [PMID: 21907835 DOI: 10.1016/j.resp.2011.08.012] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2011] [Revised: 08/19/2011] [Accepted: 08/22/2011] [Indexed: 10/17/2022]
Abstract
TIMAP is a regulatory subunit of protein phosphatase 1, whose role remains largely unknown. Our recent data suggested that TIMAP is involved in the regulation of barrier function in cultured pulmonary endothelial monolayers [Csortos et al., 2008. Am. J. Physiol. Lung Cell. Mol. Physiol. 295, L440-L450]. Here we showed that TIMAP depletion exacerbates lipopolysaccharide (LPS)-induced vascular leakage in murine lung, suggesting that TIMAP has a barrier-protective role in vivo. Real-Time RT PCR analysis revealed that treatment with LPS significantly suppressed Timap mRNA level. This suppression was not achieved via the down-regulation of Timap promoter activity, suggesting that LPS decreased Timap mRNA stability. Pretreatment with protein kinase A (PKA) inhibitor H-89 reduced TIMAP mRNA level, whereas pretreatment with PKA activator, bnz-cAMP, increased this level and attenuated LPS-induced decrease in TIMAP mRNA. Altogether, these data confirmed the barrier-protective role of TIMAP and suggested that barrier-disruptive and barrier-protective agents may employ modulation of TIMAP expression as a mechanism affecting barrier permeability.
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Affiliation(s)
- Christophe Poirier
- Vascular Biology Center, Georgia Health Sciences University, Augusta, GA 30912, USA.
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20
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Characterization of the effect of TIMAP phosphorylation on its interaction with protein phosphatase 1. Biochimie 2011; 93:1139-45. [PMID: 21466834 DOI: 10.1016/j.biochi.2011.03.011] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2010] [Accepted: 03/28/2011] [Indexed: 12/15/2022]
Abstract
TIMAP, TGF-β inhibited, membrane-associated protein, is highly abundant in endothelial cells (EC). We have shown earlier the involvement of TIMAP in PKA-mediated ERM (ezrin-radixin-moesin) dephosphorylation as part of EC barrier protection by TIMAP (Csortos et al., 2008). Emerging data demonstrate the regulatory role of TIMAP on protein phosphatase 1 (PP1) activity. We provide here evidence for specific interaction (K(a) = 1.80 × 10(6) M(-1)) between non-phosphorylated TIMAP and the catalytic subunit of PP1 (PP1c) by surface plasmon resonance based binding studies. Thiophosphorylation of TIMAP by PKA, or sequential thiophosphorylation by PKA and GSK3β slightly modifies the association constant for the interaction of TIMAP with PP1c and decreases the rate of dissociation. However, dephosphorylation of phospho-moesin substrate by PP1cβ is inhibited to different extent in the presence of non- (~60% inhibition), mono- (~50% inhibition) or double-thiophosphorylated (<10% inhibition) form of TIMAP. Our data suggest that double-thiophosphorylation of TIMAP has minor effect on its binding ability to PP1c, but considerably attenuates its inhibitory effect on the activity of PP1c. PKA activation by forskolin treatment of EC prevented thrombin evoked barrier dysfunction and ERM phosphorylation at the cell membrane (Csortos et al., 2008). With the employment of specific GSK3β inhibitor it is shown here that PKA activation is followed by GSK3β activation in bovine pulmonary EC and both of these activations are required for the rescuing effect of forskolin in thrombin treated EC. Our results suggest that the forskolin induced PKA/GSK3β activation protects the EC barrier via TIMAP-mediated decreasing of the ERM phosphorylation level.
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21
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Grassie ME, Moffat LD, Walsh MP, MacDonald JA. The myosin phosphatase targeting protein (MYPT) family: a regulated mechanism for achieving substrate specificity of the catalytic subunit of protein phosphatase type 1δ. Arch Biochem Biophys 2011; 510:147-59. [PMID: 21291858 DOI: 10.1016/j.abb.2011.01.018] [Citation(s) in RCA: 181] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2010] [Revised: 01/22/2011] [Accepted: 01/26/2011] [Indexed: 12/23/2022]
Abstract
The mammalian MYPT family consists of the products of five genes, denoted MYPT1, MYPT2, MBS85, MYPT3 and TIMAP, which function as targeting and regulatory subunits to confer substrate specificity and subcellular localization on the catalytic subunit of type 1δ protein serine/threonine phosphatase (PP1cδ). Family members share several conserved domains, including an RVxF motif for PP1c binding and several ankyrin repeats that mediate protein-protein interactions. MYPT1, MYPT2 and MBS85 contain C-terminal leucine zipper domains involved in dimerization and protein-protein interaction, whereas MYPT3 and TIMAP are targeted to membranes via a C-terminal prenylation site. All family members are regulated by phosphorylation at multiple sites by various protein kinases; for example, Rho-associated kinase phosphorylates MYPT1, MYPT2 and MBS85, resulting in inhibition of phosphatase activity and Ca(2+) sensitization of smooth muscle contraction. A great deal is known about MYPT1, the myosin targeting subunit of myosin light chain phosphatase, in terms of its role in the regulation of smooth muscle contraction and, to a lesser extent, non-muscle motile processes. MYPT2 appears to be the key myosin targeting subunit of myosin light chain phosphatase in cardiac and skeletal muscles. MBS85 most closely resembles MYPT2, but little is known about its physiological function. Little is also known about the physiological role of MYPT3, although it is likely to target myosin light chain phosphatase to membranes and thereby achieve specificity for substrates involved in regulation of the actin cytoskeleton. MYPT3 is regulated by phosphorylation by cAMP-dependent protein kinase. TIMAP appears to target PP1cδ to the plasma membrane of endothelial cells where it serves to dephosphorylate proteins involved in regulation of the actin cytoskeleton and thereby control endothelial barrier function. With such a wide range of regulatory targets, MYPT family members have been implicated in diverse pathological events, including hypertension, Parkinson's disease and cancer.
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Affiliation(s)
- Michael E Grassie
- Smooth Muscle Research Group, Department of Biochemistry and Molecular Biology, University of Calgary, AB, Canada
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22
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Mendrysa SM, Akagi K, Roayaei J, Lien WH, Copeland NG, Jenkins NA, Eisenman RN. An Integrated Genetic-Genomic Approach for the Identification of Novel Cancer Loci in Mice Sensitized to c-Myc-Induced Apoptosis. Genes Cancer 2010; 1:465-479. [PMID: 20927200 DOI: 10.1177/1947601910374875] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Deregulated c-Myc is associated with a wide range of human cancers. In many cell types, overexpression of c-Myc potently promotes cell growth and proliferation concomitant with the induction of apoptosis. Secondary genetic events that shift this balance either by increasing growth and proliferation or limiting apoptosis are likely to cooperate with c-Myc in tumorigenesis. Here, the authors have performed large-scale insertional mutagenesis in Eμ-c-myc mice that, through mdm2 loss of function mutations, are sensitized to apoptosis. The authors chose to use this genetic background based on the hypothesis that the high level of apoptosis induced by c-Myc overexpression in MDM2-deficient mice would act as a rate-limiting barrier for lymphoma development. As a result, it was predicted that the spectrum of retroviral insertions would be shifted toward loci that harbor antiapoptotic genes. Nine novel common insertion sites (CISs) specific to mice with this sensitized genetic background were identified, suggesting the presence of novel antiapoptotic cancer genes. Moreover, cross-comparing the data to the Retroviral Tagged Cancer Gene Database, the authors identified an additional 23 novel CISs. Here, evidence is presented that 2 genes, ppp1r16b and hdac6, identified at CISs, are bona fide cellular oncogenes. This study highlights the power of combining unique sensitized genetic backgrounds with large-scale mutagenesis as an approach for identifying novel cancer genes.
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Affiliation(s)
- Susan M Mendrysa
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA, USA
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23
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Cui YF, Shi L, Qin H, Liu S. Research progress in mechanisms of the anticancer effects of green tea polyphenol (-)-epigallocatechin-3-gallate. Shijie Huaren Xiaohua Zazhi 2009; 17:229-235. [DOI: 10.11569/wcjd.v17.i3.229] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Green tea is a worldwide popular beverage, which is found to have a broad anticancer activity. Polyphenol, one of the major constituents of green tea, is composed of catechins, mainly (-)-epigallocatechin-3-gallate (EGCG). It is known anticancer effects of green tea are associated with this component. It has been well established that EGCG has strong anticancer effects. Studies have shown that the mechanisms through which EGCG exerts its anticarcinogenesis potential are very complex, such as cell division, apoptosis induction, angiogenesis inhibition, and so on. Recently, many new findings have been reported, like the action on 67 kDa Laminin receptors and AKT signaling pathway, which are not well covered by the previous researches. The mechanisms of its anticancer effects are becoming clear. In this paper we mainly discussed the mechanisms of anticancer effects of EGCG, based on the latest findings and proved conclusions, in hope of providing rationale for future cancer managements and giving enlightenment to the design of next-generation chemotherapeutics.
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Abstract
The 67LR (67 kDa laminin receptor) is a cell-surface receptor with high affinity for its primary ligand. Its role as a laminin receptor makes it an important molecule both in cell adhesion to the basement membrane and in signalling transduction following this binding event. The protein also plays critical roles in the metastasis of tumour cells. Isolation of the protein from either normal or cancerous cells results in a product with an approx. molecular mass of 67 kDa. This protein is believed to be derived from a smaller precursor, the 37LRP (37 kDa laminin receptor precursor). However, the precise mechanism by which cytoplasmic 37LRP becomes cell-membrane-embedded 67LR is unclear. The process may involve post-translational fatty acylation of the protein combined with either homo- or hetero-dimerization, possibly with a galectin-3-epitope-containing partner. Furthermore, it has become clear that acting as a receptor for laminin is not the only function of this protein. 67LR also acts as a receptor for viruses, such as Sindbis virus and dengue virus, and is involved with internalization of the prion protein. Interestingly, unmodified 37LRP is a ribosomal component and homologues of this protein are found in all five kingdoms. In addition, it appears to be strongly associated with histones in the eukaryotic cell nucleus, although the precise role of these interactions is not clear. Here we review the current understanding of the structure and function of this molecule, as well as highlighting areas requiring further research.
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25
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Csortos C, Czikora I, Bogatcheva NV, Adyshev DM, Poirier C, Olah G, Verin AD. TIMAP is a positive regulator of pulmonary endothelial barrier function. Am J Physiol Lung Cell Mol Physiol 2008; 295:L440-50. [PMID: 18586956 DOI: 10.1152/ajplung.00325.2007] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
TGF-beta-inhibited membrane-associated protein, TIMAP, is expressed at high levels in endothelial cells (EC). It is regarded as a member of the MYPT (myosin phosphatase target subunit) family of protein phosphatase 1 (PP1) regulatory subunits; however, its function in EC is not clear. In our pull-down experiments, recombinant TIMAP binds preferentially the beta-isoform of the catalytic subunit of PP1 (PP1cbeta) from pulmonary artery EC. As PP1cbeta, but not PP1calpha, binds with MYPT1 into functional complex, these results suggest that TIMAP is a novel regulatory subunit of myosin phosphatase in EC. TIMAP depletion by small interfering RNA (siRNA) technique attenuates increases in transendothelial electrical resistance induced by EC barrier-protective agents (sphingosine-1-phosphate, ATP) and enhances the effect of barrier-compromising agents (thrombin, nocodazole) demonstrating a barrier-protective role of TIMAP in EC. Immunofluorescent staining revealed colocalization of TIMAP with membrane/cytoskeletal protein, moesin. Moreover, TIMAP coimmunoprecipitates with moesin suggesting the involvement of TIMAP/moesin interaction in TIMAP-mediated EC barrier enhancement. Activation of cAMP/PKA cascade by forskolin, which has a barrier-protective effect against thrombin-induced EC permeability, attenuates thrombin-induced phosphorylation of moesin at the cell periphery of control siRNA-treated EC. On the contrary, in TIMAP-depleted EC, forskolin failed to affect the level of moesin phosphorylation at the cell edges. These results suggest the involvement of TIMAP in PKA-mediated moesin dephosphorylation and the importance of this dephosphorylation in TIMAP-mediated EC barrier protection.
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Affiliation(s)
- Csilla Csortos
- Department of Medical Chemistry, Research Center for Molecular Medicine, University of Debrecen, Medical and Health Science Center, Debrecen, Hungary
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26
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Umeda D, Yano S, Yamada K, Tachibana H. Green tea polyphenol epigallocatechin-3-gallate signaling pathway through 67-kDa laminin receptor. J Biol Chem 2007; 283:3050-3058. [PMID: 18079119 DOI: 10.1074/jbc.m707892200] [Citation(s) in RCA: 169] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
(-)-Epigallocatechin-3-gallate (EGCG), the principal polyphenol in green tea, has been shown to be a potent chemopreventive agent. Recently, 67-kDa laminin receptor (67LR) has been identified as a cell surface receptor for EGCG that mediates the anticancer activity of EGCG. Indeed, expression of 67LR confers EGCG responsiveness to tumor cells; however, the molecular basis for the anticancer activity of EGCG in vivo is not entirely understood. Here we show that (i) using a direct genetic screen, eukaryotic translation elongation factor 1A (eEF1A) is identified as a component responsible for the anticancer activity of EGCG; (ii) through both eEF1A and 67LR, EGCG induces the dephosphorylation of myosin phosphatase targeting subunit 1 (MYPT1) at Thr-696 and activates myosin phosphatase; and (iii) silencing of 67LR, eEF1A, or MYPT1 in tumor cells results in abrogation of EGCG-induced tumor growth inhibition in vivo. Additionally, we found that eEF1A is up-regulated by EGCG through 67LR. Overall, these findings implicate both eEF1A and MYPT1 in EGCG signaling for cancer prevention through 67LR.
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Affiliation(s)
- Daisuke Umeda
- Laboratory of Food Chemistry, Division of Applied Biological Chemistry, Department of Bioscience and Biotechnology, Faculty of Agriculture, Kyushu University, Fukuoka 812-8581, Japan
| | - Satomi Yano
- Laboratory of Food Chemistry, Division of Applied Biological Chemistry, Department of Bioscience and Biotechnology, Faculty of Agriculture, Kyushu University, Fukuoka 812-8581, Japan
| | - Koji Yamada
- Laboratory of Food Chemistry, Division of Applied Biological Chemistry, Department of Bioscience and Biotechnology, Faculty of Agriculture, Kyushu University, Fukuoka 812-8581, Japan
| | - Hirofumi Tachibana
- Laboratory of Food Chemistry, Division of Applied Biological Chemistry, Department of Bioscience and Biotechnology, Faculty of Agriculture, Kyushu University, Fukuoka 812-8581, Japan; Laboratory of Functional Food Design, Department of Functional Metabolic Design, Bio-Architecture Center, Kyushu University, Fukuoka 812-8581, Japan.
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27
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Csortos C, Kolosova I, Verin AD. Regulation of vascular endothelial cell barrier function and cytoskeleton structure by protein phosphatases of the PPP family. Am J Physiol Lung Cell Mol Physiol 2007; 293:L843-54. [PMID: 17693486 DOI: 10.1152/ajplung.00120.2007] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Reversible phosphorylation of cytoskeletal and cytoskeleton-associated proteins is a significant element of endothelial barrier function regulation. Therefore, understanding the mechanisms of phosphorylation/dephosphorylation of endothelial cell cytoskeletal proteins is vital to the treatment of severe lung disorders such as high permeability pulmonary edema. In vivo, there is a controlled balance between the activities of protein kinases and phosphatases. Due to various external or internal signals, this balance may be shifted. The actual balances at a given time alter the phosphorylation level of certain proteins with appropriate physiological consequences. The latest information about the structure and regulation of different types of Ser/Thr protein phosphatases participating in the regulation of endothelial cytoskeletal organization and barrier function will be reviewed here.
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Affiliation(s)
- Csilla Csortos
- Department of Medicine, Division of Biological Sciences, The University of Chicago, Chicago, Illinois, USA
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28
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Li L, Kozlowski K, Wegner B, Rashid T, Yeung T, Holmes C, Ballermann BJ. Phosphorylation of TIMAP by glycogen synthase kinase-3beta activates its associated protein phosphatase 1. J Biol Chem 2007; 282:25960-9. [PMID: 17609201 DOI: 10.1074/jbc.m703532200] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
TIMAP (TGF-beta1 inhibited, membrane-associated protein) is a prenylated, endothelial cell-predominant protein phosphatase 1 (PP1c) regulatory subunit that localizes to the plasma membrane of filopodia. Here, we determined whether phosphorylation regulates TIMAP-associated PP1c function. Phosphorylation of TIMAP was observed in cells metabolically labeled with [32P]orthophosphate and was reduced by inhibitors of protein kinase A (PKA) and glycogen synthase kinase-3 (GSK-3). In cell-free assays, immunopurified TIMAP was phosphorylated by PKA and, after PKA priming, by GSK-3beta. Site-specific Ser to Ala substitution identified amino acid residues Ser333/Ser337 as the likely PKA/GSK-3beta phosphorylation site. Substitution of Ala for Val and Phe in the KVSF motif of TIMAP (TIMAPV64A/F66A) abolished PP1c binding and TIMAP-associated PP1c activity. TIMAPV64A/F66A was hyper-phosphorylated in cells, indicating that TIMAP-associated PP1c auto-dephosphorylates TIMAP. Constitutively active GSK-3beta stimulated phosphorylation of TIMAPV64A/F66A, but not wild-type TIMAP, suggesting that the PKA/GSK-3beta site may be subject to dephosphorylation by TIMAP-associated PP1c. Substitution of Asp or Glu for Ser at amino acid residues 333 and 337 to mimic phosphorylation reduced the PP1c association with TIMAP. Conversely, GSK-3 inhibitors augmented PP1c association with TIMAP-PP1c in cells. The 333/337 phosphomimic mutations also increased TIMAP-associated PP1c activity in vitro and against the non-integrin laminin receptor 1 in cells. Finally, TIMAP mutants with reduced PP1c activity strongly stimulated endothelial cell filopodia formation, an effect mimicked by the GSK-3 inhibitor LiCl. We conclude that TIMAP is a target for PKA-primed GSK-3beta-mediated phosphorylation. This phosphorylation controls TIMAP association and activity of PP1c, in turn regulating extension of filopodia in endothelial cells.
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Affiliation(s)
- Laiji Li
- Department of Medicine, University of Alberta, Edmonton, Alberta T5R 0B7, Canada
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29
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Browne G, Fardilha M, Oxenham S, Wu W, Helps N, da Cruz E Silva O, Cohen P, Cruz E Silva E. SARP, a new alternatively spliced protein phosphatase 1 and DNA interacting protein. Biochem J 2007; 402:187-96. [PMID: 17123353 PMCID: PMC1783986 DOI: 10.1042/bj20060600] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
PP1 (protein phosphatase 1) is a ubiquitously expressed serine/threonine-specific protein phosphatase whose activity towards different substrates appears to be mediated via binding to specific proteins that play critical regulatory and targeting roles. In the present paper we report the cloning and characterization of a new protein, termed SARP (several ankyrin repeat protein), which is shown to interact with all isoforms of PP1 by a variety of techniques. A region encompassing a consensus PP1-binding motif in SARP (K354VHF357) modulates endogenous SARP-PP1 activity in mammalian cells. This SARP-PP1 interaction motif lies partially within the first ankyrin repeat in contrast with other proteins [53BP2 (p53 binding protein 2), MYPT1/M(110)/MBS (myosin binding protein of PP1) and TIMAP (transforming growth factor beta inhibited, membrane-associated protein)], where a PP1-binding motif precedes the ankyrin repeats. Alternative mRNA splicing produces several isoforms of SARP from a single human gene at locus 11q14. SARP1 and/or SARP2 (92-95 kDa) are ubiquitously expressed in all tissues with high levels in testis and sperm, where they are shown to interact with both PP1gamma1 and PP1gamma2. SARP3 (65 kDa) is most abundant in brain where SARP isoforms interact with both PP1alpha and PP1gamma1. SARP is highly abundant in the nucleus of mammalian cells, consistent with the putative nuclear localization signal at the N-terminus. The presence of a leucine zipper near the C-terminus of SARP1 and SARP2, and the binding of mammalian DNA to SARP2, suggests that SARP1 and SARP2 may be transcription factors or DNA-associated proteins that modulate gene expression.
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Affiliation(s)
- Gareth J. Browne
- *Medical Research Council Protein Phosphorylation Unit, School of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, U.K
| | - Margarida Fardilha
- †Laboratório de Transdução de Sinais, Universidade de Aveiro, 3810-193 Aveiro, Portugal
| | - Senga K. Oxenham
- *Medical Research Council Protein Phosphorylation Unit, School of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, U.K
| | - Wenjuan Wu
- †Laboratório de Transdução de Sinais, Universidade de Aveiro, 3810-193 Aveiro, Portugal
| | - Nicholas R. Helps
- *Medical Research Council Protein Phosphorylation Unit, School of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, U.K
| | - Odete A. B. da Cruz E Silva
- ‡Laboratório de Neurociências, Centro de Biologia Celular, Universidade de Aveiro, 3810-193 Aveiro, Portugal
| | - Patricia T. W. Cohen
- *Medical Research Council Protein Phosphorylation Unit, School of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, U.K
- To whom correspondence should be addressed (email )
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Selleri C, Ragno P, Ricci P, Visconte V, Scarpato N, Carriero MV, Rotoli B, Rossi G, Montuori N. The metastasis-associated 67-kDa laminin receptor is involved in G-CSF–induced hematopoietic stem cell mobilization. Blood 2006; 108:2476-84. [PMID: 16788104 DOI: 10.1182/blood-2005-11-012625] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
AbstractThe 67-kDa laminin receptor (67LR) is a nonintegrin cell-surface receptor with high affinity for laminin, which plays a key role in tumor invasion and metastasis. We investigated the role of 67LR in granulocyte colony-stimulating factor (G-CSF)–induced mobilization of CD34+ hematopoietic stem cells (HSCs) from 35 healthy donors. G-CSF–mobilized HSCs, including CD34+/CD38– cells, showed increased 67LR expression as compared with unstimulated marrow HSCs; noteworthy, also, is the fact that the level of 67LR expression in G-CSF–mobilized HSCs correlated significantly with mobilization efficiency. During G-CSF–induced HSC mobilization, the expression of laminin receptors switched from α6 integrins, which mediated laminin-dependent adhesion of steady-state human marrow HSCs, to 67LR, responsible for G-CSF–mobilized HSC adhesion and migration toward laminin. In vitro G-CSF treatment, alone or combined with exposure to marrow-derived endothelial cells, induced 67LR up-regulation in marrow HSCs; moreover, anti-67LR antibodies significantly inhibited transendothelial migration of G-CSF–stimulated marrow HSCs. Finally, G-CSF–induced mobilization in mice was associated with 67LR up-regulation both in circulating and marrow CD34+ cells, and anti-67LR antibodies significantly reduced HSC mobilization, providing the first in vivo evidence for 67LR involvement in stem-cell egress from bone marrow after G-CSF administration. In conclusion, 67LR up-regulation in G-CSF–mobilized HSCs correlates with their successful mobilization and reflects its increase in marrow HSCs, which contributes to the egress from bone marrow by mediating laminin-dependent cell adhesion and transendothelial migration.
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Affiliation(s)
- Carmine Selleri
- Department of Biochemistry and Medical Biotechnology, Institute of Experimental Endocrinology and Oncology (IEOS), National Research Council (CNR), Via S Pansini 5, 80131, Naples, Italy
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