1
|
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.
Collapse
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.)
| |
Collapse
|
2
|
Fonódi M, Thalwieser Z, Csortos C, Boratkó A. TIMAP, a Regulatory Subunit of Protein Phosphatase 1, Inhibits In Vitro Neuronal Differentiation. Int J Mol Sci 2023; 24:17360. [PMID: 38139189 PMCID: PMC10744335 DOI: 10.3390/ijms242417360] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2023] [Revised: 12/06/2023] [Accepted: 12/07/2023] [Indexed: 12/24/2023] Open
Abstract
TIMAP (TGF-β-inhibited membrane associated protein) is abundant in endothelial cells, and it has been regarded as a member of the myosin phosphatase targeting protein (MYPT) family. Our workgroup previously identified several interacting protein partners of TIMAP and proved its regulatory subunit role for protein phosphatase 1 catalytic subunit (PP1c). TIMAP is also expressed in neuronal cells, but details of its function have not been studied yet. Therefore, we aimed to explore the role of TIMAP in neuronal cells, especially during differentiation. Expression of TIMAP was proved both at mRNA and protein levels in SH-SY5Y human neuroblastoma cells. Differentiation of SH-SY5Y cells was optimized and proved by the detection of neuronal differentiation markers, such as β3-tubulin, nestin and inhibitor of differentiation 1 (ID1) using qPCR and Western blot. We found downregulation of TIMAP during differentiation. In accordance with this, overexpression of recombinant TIMAP attenuated the differentiation of neuronal cells. Moreover, the subcellular localization of TIMAP has changed during differentiation as it translocated from the plasma membrane into the nucleus. The nuclear interactome of TIMAP revealed more than 50 proteins, offering the possibility to further investigate the role of TIMAP in several key physiological pathways of neuronal cells.
Collapse
Affiliation(s)
| | | | | | - Anita Boratkó
- Department of Medical Chemistry, Faculty of Medicine, University of Debrecen, Egyetem Tér 1, H-4032 Debrecen, Hungary; (M.F.); (Z.T.); (C.C.)
| |
Collapse
|
3
|
Patil RS, Kovacs-Kasa A, Gorshkov BA, Fulton DJR, Su Y, Batori RK, Verin AD. Serine/Threonine Protein Phosphatases 1 and 2A in Lung Endothelial Barrier Regulation. Biomedicines 2023; 11:1638. [PMID: 37371733 PMCID: PMC10296329 DOI: 10.3390/biomedicines11061638] [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: 05/04/2023] [Revised: 05/28/2023] [Accepted: 06/02/2023] [Indexed: 06/29/2023] Open
Abstract
Vascular barrier dysfunction is characterized by increased permeability and inflammation of endothelial cells (ECs), which are prominent features of acute lung injury (ALI), acute respiratory distress syndrome (ARDS), and sepsis, and a major complication of the SARS-CoV-2 infection and COVID-19. Functional impairment of the EC barrier and accompanying inflammation arises due to microbial toxins and from white blood cells of the lung as part of a defensive action against pathogens, ischemia-reperfusion or blood product transfusions, and aspiration syndromes-based injury. A loss of barrier function results in the excessive movement of fluid and macromolecules from the vasculature into the interstitium and alveolae resulting in pulmonary edema and collapse of the architecture and function of the lungs, and eventually culminates in respiratory failure. Therefore, EC barrier integrity, which is heavily dependent on cytoskeletal elements (mainly actin filaments, microtubules (MTs), cell-matrix focal adhesions, and intercellular junctions) to maintain cellular contacts, is a critical requirement for the preservation of lung function. EC cytoskeletal remodeling is regulated, at least in part, by Ser/Thr phosphorylation/dephosphorylation of key cytoskeletal proteins. While a large body of literature describes the role of phosphorylation of cytoskeletal proteins on Ser/Thr residues in the context of EC barrier regulation, the role of Ser/Thr dephosphorylation catalyzed by Ser/Thr protein phosphatases (PPases) in EC barrier regulation is less documented. Ser/Thr PPases have been proposed to act as a counter-regulatory mechanism that preserves the EC barrier and opposes EC contraction. Despite the importance of PPases, our knowledge of the catalytic and regulatory subunits involved, as well as their cellular targets, is limited and under-appreciated. Therefore, the goal of this review is to discuss the role of Ser/Thr PPases in the regulation of lung EC cytoskeleton and permeability with special emphasis on the role of protein phosphatase 1 (PP1) and protein phosphatase 2A (PP2A) as major mammalian Ser/Thr PPases. Importantly, we integrate the role of PPases with the structural dynamics of the cytoskeleton and signaling cascades that regulate endothelial cell permeability and inflammation.
Collapse
Affiliation(s)
- Rahul S. Patil
- Vascular Biology Center, Medical College of Georgia, Augusta University, Augusta, GA 30912, USA
| | - Anita Kovacs-Kasa
- Vascular Biology Center, Medical College of Georgia, Augusta University, Augusta, GA 30912, USA
| | - Boris A. Gorshkov
- Vascular Biology Center, Medical College of Georgia, Augusta University, Augusta, GA 30912, USA
| | - David J. R. Fulton
- Vascular Biology Center, Medical College of Georgia, Augusta University, Augusta, GA 30912, USA
- Department of Pharmacology, Medical College of Georgia, Augusta University, Augusta, GA 30912, USA
| | - Yunchao Su
- Department of Pharmacology, Medical College of Georgia, Augusta University, Augusta, GA 30912, USA
| | - Robert K. Batori
- Vascular Biology Center, Medical College of Georgia, Augusta University, Augusta, GA 30912, USA
| | - Alexander D. Verin
- Vascular Biology Center, Medical College of Georgia, Augusta University, Augusta, GA 30912, USA
| |
Collapse
|
4
|
Kaitsuka T, Tomizawa K, Matsushita M. Heat Shock-Induced Dephosphorylation of Eukaryotic Elongation Factor 1BδL by Protein Phosphatase 1. Front Mol Biosci 2021; 7:598578. [PMID: 33521052 PMCID: PMC7841112 DOI: 10.3389/fmolb.2020.598578] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2020] [Accepted: 12/15/2020] [Indexed: 12/04/2022] Open
Abstract
Several variant proteins are produced from EEF1D, including two representative proteins produced via alternative splicing machinery. One protein is the canonical translation eukaryotic elongation factor eEF1Bδ1, and the other is the heat shock-responsive transcription factor eEF1BδL. eEF1Bδ1 is phosphorylated by cyclin-dependent kinase 1 (CDK1), but the machinery controlling eEF1BδL phosphorylation and dephosphorylation has not been clarified. In this study, we found that both proteins were dephosphorylated under heat shock and proteotoxic stress, and this dephosphorylation was inhibited by okadaic acid. Using proteins with mutations at putative phosphorylated residues, we revealed that eEF1Bδ1 and eEF1BδL are phosphorylated at S133 and S499, respectively, and these residues are both CDK1 phosphorylation sites. The eEF1BδL S499A mutant more strongly activated HSPA6 promoter-driven reporter than the wild-type protein and S499D mutant. Furthermore, protein phosphatase 1 (PP1) was co-immunoprecipitated with eEF1Bδ1 and eEF1BδL, and PP1 dephosphorylated both proteins in vitro. Thus, this study clarified the role of phosphorylation/dephosphorylation in the functional regulation of eEF1BδL during heat shock.
Collapse
Affiliation(s)
- Taku Kaitsuka
- Department of Molecular Physiology, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan.,School of Pharmacy in Fukuoka, International University of Health and Welfare, Okawa, Japan
| | - Kazuhito Tomizawa
- Department of Molecular Physiology, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan
| | - Masayuki Matsushita
- Department of Molecular and Cellular Physiology, Graduate School of Medicine, University of the Ryukyus, Okinawa, Japan
| |
Collapse
|
5
|
Zhou Y, Millott R, Kim HJ, Peng S, Edwards RA, Skene-Arnold T, Hammel M, Lees-Miller SP, Tainer JA, Holmes CFB, Glover JNM. Flexible Tethering of ASPP Proteins Facilitates PP-1c Catalysis. Structure 2019; 27:1485-1496.e4. [PMID: 31402222 DOI: 10.1016/j.str.2019.07.012] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2019] [Revised: 06/14/2019] [Accepted: 07/22/2019] [Indexed: 12/15/2022]
Abstract
ASPP (apoptosis-stimulating proteins of p53) proteins bind PP-1c (protein phosphatase 1) and regulate p53 impacting cancer cell growth and apoptosis. Here we determine the crystal structure of the oncogenic ASPP protein, iASPP, bound to PP-1c. The structure reveals a 1:1 complex that relies on interactions of the iASPP SILK and RVxF motifs with PP-1c, plus interactions of the PP-1c PxxPxR motif with the iASPP SH3 domain. Small-angle X-ray scattering analyses suggest that the crystal structure undergoes slow interconversion with more extended conformations in solution. We show that iASPP, and the tumor suppressor ASPP2, enhance the catalytic activity of PP-1c against the small-molecule substrate, pNPP as well as p53. The combined results suggest that PxxPxR binding to iASPP SH3 domain is critical for complex formation, and that the modular ASPP-PP-1c interface provides dynamic flexibility that enables functional binding and dephosphorylation of p53 and other diverse protein substrates.
Collapse
Affiliation(s)
- Yeyun Zhou
- Department of Biochemistry, University of Alberta, Edmonton, AB T6G 2H7, Canada
| | - Robyn Millott
- Department of Biochemistry, University of Alberta, Edmonton, AB T6G 2H7, Canada
| | - Hyeong Jin Kim
- Department of Biochemistry, University of Alberta, Edmonton, AB T6G 2H7, Canada
| | - Shiyun Peng
- Department of Biochemistry, University of Alberta, Edmonton, AB T6G 2H7, Canada
| | - Ross A Edwards
- Department of Biochemistry, University of Alberta, Edmonton, AB T6G 2H7, Canada
| | - Tamara Skene-Arnold
- Department of Biochemistry, University of Alberta, Edmonton, AB T6G 2H7, Canada
| | - Michal Hammel
- Molecular Biophysics & Integrated Bioimaging, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Susan P Lees-Miller
- Department of Biochemistry and Molecular Biology, Arnie Charbonneau Cancer Institute, University of Calgary, Calgary, AB, Canada
| | - John A Tainer
- Molecular Biophysics & Integrated Bioimaging, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA; Department of Molecular and Cellular Oncology, The University of Texas M. D. Anderson Cancer Center, Houston, TX 77030, USA
| | - Charles F B Holmes
- Department of Biochemistry, University of Alberta, Edmonton, AB T6G 2H7, Canada.
| | - J N Mark Glover
- Department of Biochemistry, University of Alberta, Edmonton, AB T6G 2H7, Canada.
| |
Collapse
|
6
|
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.
Collapse
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.
| |
Collapse
|
7
|
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
| |
Collapse
|
8
|
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.
Collapse
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.
| |
Collapse
|
9
|
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]
|
10
|
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.
Collapse
|
11
|
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.
Collapse
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.
| |
Collapse
|
12
|
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.
Collapse
Affiliation(s)
- Marya Obeidat
- Department of Medicine, University of Alberta, Edmonton, Alberta, Canada
| | - Laiji Li
- Department of Medicine, University of Alberta, Edmonton, Alberta, Canada
| | | |
Collapse
|