1
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Wu Y, Liu Z, He Z, Yi J, Qiao X, Tan C, Xing Y, Zeng Y, Yang D, Yin J, Fan B, Zeng G. Cantharidin analogue alleviates dextran sulfate sodium-induced colitis in mice by inhibiting the activation of NF-κB signaling. Eur J Med Chem 2023; 260:115731. [PMID: 37643546 DOI: 10.1016/j.ejmech.2023.115731] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2023] [Revised: 07/28/2023] [Accepted: 08/14/2023] [Indexed: 08/31/2023]
Abstract
Ulcerative colitis is a chronic inflammatory disease with a remitting-relapsing clinical course, it has evolved into a global burden given its high incidence worldwide. Cantharidin (CTD) derivatives are a class of compounds whose structures characterized with a 7-oxabicyclo [2.2.1]heptane core. Though potent cytotoxicity CTD and its derivatives showed, their clinical usage as anti-cancer drugs was limited by the toxicity in organs. In order to find new CTD analogues with good activity and lower toxicity, 21 CTD analogues with or without alkynyl substitution at C5 position of 7-oxabicyclo [2.2.1]heptane core were synthesized, some compounds showed better in vitro anti-inflammatory activity compared to CTD and norcantharidin (NCTD). Based on the structure-activity relationship results of in vitro experiment, analogue 3i was chosen for further study. Results from the acute toxicity in mice showed that 3i was hypotoxic with the single-dose MTD (maximum tolerated dose) for oral administration is over 1852 mg/kg, at least 35-fold lower than that of NCTD. Mechanism study indicated that 3i could potently inhibit TNF-α induced activation of NF-κB signaling by down-regulation the expression levels of phosphor- IKK, IκBα, and NF-κB p65, and alleviated dextran sulfate sodium-induced colitis in mice. This study indicated that CTD analogues with alkynyl substitution at C5 position of 7-oxabicyclo [2.2.1]heptane core is a kind of new compounds with good anti-inflammatory activity and lower toxicity in vivo, and might be used as therapeutic agents for inflammatory diseases.
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Affiliation(s)
- Yihang Wu
- Key Laboratory of Chemistry in Ethnic Medicinal Resources, State Ethnic Affairs Commission and Ministry of Education, Yunnan Minzu University, Kunming 650504, China
| | - Zixiu Liu
- Key Laboratory of Chemistry in Ethnic Medicinal Resources, State Ethnic Affairs Commission and Ministry of Education, Yunnan Minzu University, Kunming 650504, China
| | - Zhenxiu He
- Key Laboratory of Chemistry in Ethnic Medicinal Resources, State Ethnic Affairs Commission and Ministry of Education, Yunnan Minzu University, Kunming 650504, China
| | - Jumei Yi
- Key Laboratory of Chemistry in Ethnic Medicinal Resources, State Ethnic Affairs Commission and Ministry of Education, Yunnan Minzu University, Kunming 650504, China
| | - Xingfang Qiao
- Chongqing Key Laboratory of Traditional Chinese Medicine Health, Chongqing Academy of Chinese Materia Medica, Chongqing 400065, China
| | - Chunbin Tan
- Chongqing Key Laboratory of Traditional Chinese Medicine Health, Chongqing Academy of Chinese Materia Medica, Chongqing 400065, China
| | - Yajing Xing
- Chongqing Key Laboratory of Traditional Chinese Medicine Health, Chongqing Academy of Chinese Materia Medica, Chongqing 400065, China
| | - Yaobo Zeng
- Chongqing Key Laboratory of Traditional Chinese Medicine Health, Chongqing Academy of Chinese Materia Medica, Chongqing 400065, China
| | - Dajian Yang
- Chongqing Key Laboratory of Traditional Chinese Medicine Health, Chongqing Academy of Chinese Materia Medica, Chongqing 400065, China.
| | - Junlin Yin
- Key Laboratory of Chemistry in Ethnic Medicinal Resources, State Ethnic Affairs Commission and Ministry of Education, Yunnan Minzu University, Kunming 650504, China
| | - Baomin Fan
- Key Laboratory of Chemistry in Ethnic Medicinal Resources, State Ethnic Affairs Commission and Ministry of Education, Yunnan Minzu University, Kunming 650504, China.
| | - Guangzhi Zeng
- Key Laboratory of Chemistry in Ethnic Medicinal Resources, State Ethnic Affairs Commission and Ministry of Education, Yunnan Minzu University, Kunming 650504, China.
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Zhang Y, Lv M, Jiang H, Li H, Li R, Yang C, Huang Y, Zhou H, Mei Y, Gao J, Cao X. Mitotic defects lead to unreduced sperm formation in cdk1 -/- mutants. Int J Biol Macromol 2023:125171. [PMID: 37271265 DOI: 10.1016/j.ijbiomac.2023.125171] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2023] [Revised: 05/03/2023] [Accepted: 05/23/2023] [Indexed: 06/06/2023]
Abstract
Unreduced gametes, that are important for species evolution and agricultural development, are generally believed to be formed by meiotic defects. However, we found that male diploid loach (Misgurnus anguillicaudatus) could produce not only haploid sperms, but also unreduced sperms, after cyclin-dependent kinase 1 gene (cdk1, one of the most important kinases in regulating cell mitosis) deletion. Observations on synaptonemal complexes of spermatocyte in prophase of meiosis and spermatogonia suggested that the number of chromosomes in some spermatogonia of cdk1-/- loach doubled, leading to unreduced diploid sperm production. Then, transcriptome analysis revealed aberrant expressions of some cell cycle-related genes (such as ppp1c and gadd45) in spermatogonia of cdk1-/- loach relative to wild-type loach. An in vitro and in vivo experiment further validated that Cdk1 deletion in diploid loach resulted in mitotic defects, leading to unreduced diploid sperm formation. In addition, we found that cdk1-/- zebrafish could also produce unreduced diploid sperms. This study provides important information on revealing the molecular mechanisms behind unreduced gamete formation through mitotic defects, and lays the foundation for a novel strategy for fish polyploidy creation by using cdk1 mutants to produce unreduced sperms, which can then be used to obtain polyploidy, proposed to benefit aquaculture.
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Affiliation(s)
- Yunbang Zhang
- College of Fisheries, Engineering Research Center of Green Development for Conventional Aquatic Biological Industry in the Yangtze River Economic Belt, Ministry of Education, Huazhong Agricultural University, Wuhan 430070, China; Hubei Provincial Engineering Laboratory for Pond Aquaculture, Hubei, China
| | - Meiqi Lv
- College of Fisheries, Engineering Research Center of Green Development for Conventional Aquatic Biological Industry in the Yangtze River Economic Belt, Ministry of Education, Huazhong Agricultural University, Wuhan 430070, China
| | - Hanjun Jiang
- College of Fisheries, Engineering Research Center of Green Development for Conventional Aquatic Biological Industry in the Yangtze River Economic Belt, Ministry of Education, Huazhong Agricultural University, Wuhan 430070, China
| | - Hui Li
- College of Fisheries, Engineering Research Center of Green Development for Conventional Aquatic Biological Industry in the Yangtze River Economic Belt, Ministry of Education, Huazhong Agricultural University, Wuhan 430070, China
| | - Rongyun Li
- College of Fisheries, Engineering Research Center of Green Development for Conventional Aquatic Biological Industry in the Yangtze River Economic Belt, Ministry of Education, Huazhong Agricultural University, Wuhan 430070, China
| | - Chuang Yang
- College of Fisheries, Engineering Research Center of Green Development for Conventional Aquatic Biological Industry in the Yangtze River Economic Belt, Ministry of Education, Huazhong Agricultural University, Wuhan 430070, China
| | - Yuwei Huang
- College of Fisheries, Engineering Research Center of Green Development for Conventional Aquatic Biological Industry in the Yangtze River Economic Belt, Ministry of Education, Huazhong Agricultural University, Wuhan 430070, China
| | - He Zhou
- College of Fisheries and Life Science, Dalian Ocean University, Dalian 116023, China
| | - Yihui Mei
- College of Fisheries, Engineering Research Center of Green Development for Conventional Aquatic Biological Industry in the Yangtze River Economic Belt, Ministry of Education, Huazhong Agricultural University, Wuhan 430070, China
| | - Jian Gao
- College of Fisheries, Engineering Research Center of Green Development for Conventional Aquatic Biological Industry in the Yangtze River Economic Belt, Ministry of Education, Huazhong Agricultural University, Wuhan 430070, China; Hubei Provincial Engineering Laboratory for Pond Aquaculture, Hubei, China.
| | - Xiaojuan Cao
- College of Fisheries, Engineering Research Center of Green Development for Conventional Aquatic Biological Industry in the Yangtze River Economic Belt, Ministry of Education, Huazhong Agricultural University, Wuhan 430070, China; Hubei Provincial Engineering Laboratory for Pond Aquaculture, Hubei, China.
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3
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Insight into the Molecular Mechanism for the Discrepant Inhibition of Microcystins (MCLR, LA, LF, LW, LY) on Protein Phosphatase 2A. Toxins (Basel) 2022; 14:toxins14060390. [PMID: 35737051 PMCID: PMC9227578 DOI: 10.3390/toxins14060390] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2022] [Revised: 05/29/2022] [Accepted: 06/01/2022] [Indexed: 12/20/2022] Open
Abstract
Microcystins (MCs) exhibit diversified inhibition effects on protein phosphatases (PPs) due to their structural differences. To fully evaluate the potential mechanism for the discrepant inhibition effects, the five most frequent MCs with varying residues at position Z4 were selected as the tested toxins. Their inhibition sequence on PP2A was detected as follows: MCLR > MCLW > MCLA > MCLF > MCLY. Combined with homology modeling and molecular docking technology, the major interaction parameters between the MCs and PP2A were obtained. The correlation analysis for the major interaction parameters and inhibition effects showed that the hydrophobicity of Z4 had an important influence on the interaction of the MCs to PP2A. The introduction of hydrophobic Z4 directly weakened hydrogen bonds Z4→Pro213 and Z4←Arg214, indirectly weakened hydrogen bonds Adda5←Asn117, Glu6←Arg89, and MeAsp3←Arg89, but indirectly enhanced ionic bonds Glu6←Arg89, Glu6-Mn12+, and Glu6-Mn22+. In this way, the combination of the MCs with PP2A was blocked, and thus, the interactions between PP2A and the Mn2+ ions (in the catalytic center) were further affected; metal bonds Asp85-Mn12+ and Asp85-Mn22+ were weakened, while metal bond His241-Mn12+ was enhanced. As a result, the interactions in the catalytic center were inhibited to varying degrees, resulting in the reduced toxicity of MCs.
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Ying KE, Feng W, Ying WZ, Li X, Xing D, Sun Y, Chen Y, Sanders PW. Dietary salt initiates redox signaling between endothelium and vascular smooth muscle through NADPH oxidase 4. Redox Biol 2022; 52:102296. [PMID: 35378363 PMCID: PMC8980891 DOI: 10.1016/j.redox.2022.102296] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2022] [Accepted: 03/16/2022] [Indexed: 11/19/2022] Open
Abstract
Prevention of phenotype switching of vascular smooth muscle cells is an important determinant of normal vascular physiology. Hydrogen peroxide (H2O2) promotes osteogenic differentiation of vascular smooth muscle cells through expression of Runt related transcription factor 2 (Runx2). In this study, an increase in dietary NaCl increased endothelial H2O2 generation through NOX4, a NAD(P)H oxidase. The production of H2O2 was sufficient to increase Runx2, osteopontin and osteocalcin in adjacent vascular smooth muscle cells from control littermate mice but was inhibited in mice lacking endothelial Nox4. A vascular smooth muscle cell culture model confirmed the direct involvement of the activation of protein kinase B (Akt) with inactivation of FoxO1 and FoxO3a observed in the control mice on the high NaCl diet. The present study also showed a reduction of catalase activity in aortas during high NaCl intake. The findings demonstrated an interesting cell-cell communication in the vascular wall that was initiated with H2O2 production by endothelium and was regulated by dietary NaCl intake. A better understanding of how dietary salt intake alters vascular biology may improve treatment of vascular disease that involves activation of Runx2.
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Affiliation(s)
- Kai Er Ying
- Department of Medicine, University of Alabama at Birmingham, Birmingham, AL, 35294-0007, USA
| | - Wenguang Feng
- Department of Medicine, University of Alabama at Birmingham, Birmingham, AL, 35294-0007, USA
| | - Wei-Zhong Ying
- Department of Medicine, University of Alabama at Birmingham, Birmingham, AL, 35294-0007, USA
| | - Xingsheng Li
- Department of Urology, University of Alabama at Birmingham, Birmingham, AL, 35294-0007, USA
| | - Dongqi Xing
- Department of Medicine, University of Alabama at Birmingham, Birmingham, AL, 35294-0007, USA
| | - Yong Sun
- Department of Pathology, University of Alabama at Birmingham, Birmingham, AL, 35294-0007, USA
| | - Yabing Chen
- Department of Pathology, University of Alabama at Birmingham, Birmingham, AL, 35294-0007, USA; Birmingham Department of Veterans Affairs Health Care System, Birmingham, AL, 35233, USA
| | - Paul W Sanders
- Department of Medicine, University of Alabama at Birmingham, Birmingham, AL, 35294-0007, USA; Department of Cell, Developmental and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL, 35294-0007, USA; Birmingham Department of Veterans Affairs Health Care System, Birmingham, AL, 35233, USA.
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5
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Fréville A, Gnangnon B, Khelifa AS, Gissot M, Khalife J, Pierrot C. Deciphering the Role of Protein Phosphatases in Apicomplexa: The Future of Innovative Therapeutics? Microorganisms 2022; 10:microorganisms10030585. [PMID: 35336160 PMCID: PMC8949495 DOI: 10.3390/microorganisms10030585] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2022] [Revised: 03/04/2022] [Accepted: 03/05/2022] [Indexed: 12/10/2022] Open
Abstract
Parasites belonging to the Apicomplexa phylum still represent a major public health and world-wide socioeconomic burden that is greatly amplified by the spread of resistances against known therapeutic drugs. Therefore, it is essential to provide the scientific and medical communities with innovative strategies specifically targeting these organisms. In this review, we present an overview of the diversity of the phosphatome as well as the variety of functions that phosphatases display throughout the Apicomplexan parasites’ life cycles. We also discuss how this diversity could be used for the design of innovative and specific new drugs/therapeutic strategies.
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Affiliation(s)
- Aline Fréville
- Univ. Lille, CNRS, Inserm, CHU Lille, Institut Pasteur de Lille, U1019-UMR 9017-CIIL-Centre d’Infection et d’Immunité de Lille, 59000 Lille, France; (B.G.); (A.S.K.); (M.G.); (J.K.)
- Department of Infection Biology, Faculty of Infectious and Tropical Diseases, London School of Tropical Medicine and Hygiene, Keppel Street, London WC1E 7HT, UK
- Correspondence: (A.F.); (C.P.)
| | - Bénédicte Gnangnon
- Univ. Lille, CNRS, Inserm, CHU Lille, Institut Pasteur de Lille, U1019-UMR 9017-CIIL-Centre d’Infection et d’Immunité de Lille, 59000 Lille, France; (B.G.); (A.S.K.); (M.G.); (J.K.)
- Department of Epidemiology, Center for Communicable Diseases Dynamics, Harvard TH Chan School of Public Health, Boston, MA 02115, USA
| | - Asma S. Khelifa
- Univ. Lille, CNRS, Inserm, CHU Lille, Institut Pasteur de Lille, U1019-UMR 9017-CIIL-Centre d’Infection et d’Immunité de Lille, 59000 Lille, France; (B.G.); (A.S.K.); (M.G.); (J.K.)
| | - Mathieu Gissot
- Univ. Lille, CNRS, Inserm, CHU Lille, Institut Pasteur de Lille, U1019-UMR 9017-CIIL-Centre d’Infection et d’Immunité de Lille, 59000 Lille, France; (B.G.); (A.S.K.); (M.G.); (J.K.)
| | - Jamal Khalife
- Univ. Lille, CNRS, Inserm, CHU Lille, Institut Pasteur de Lille, U1019-UMR 9017-CIIL-Centre d’Infection et d’Immunité de Lille, 59000 Lille, France; (B.G.); (A.S.K.); (M.G.); (J.K.)
| | - Christine Pierrot
- Univ. Lille, CNRS, Inserm, CHU Lille, Institut Pasteur de Lille, U1019-UMR 9017-CIIL-Centre d’Infection et d’Immunité de Lille, 59000 Lille, France; (B.G.); (A.S.K.); (M.G.); (J.K.)
- Correspondence: (A.F.); (C.P.)
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Eto M, Katsuki S, Ohashi M, Miyagawa Y, Tanaka Y, Takeya K, Kitazawa T. Possible roles of N- and C-terminal unstructured tails of CPI-17 in regulating Ca<sup>2+</sup> sensitization force of smooth muscle. J Smooth Muscle Res 2022; 58:22-33. [PMID: 35418530 PMCID: PMC9006046 DOI: 10.1540/jsmr.58.22] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
CPI-17 regulates the myosin phosphatase and mediates the agonist-induced contraction of
smooth muscle. PKC and ROCK phosphorylate CPI-17 at Thr38 leading to a conformational
change of the central inhibitory domain (PHIN domain). The N- and C-terminal tails of
CPI-17 are predicted as unstructured loops and their sequences are conserved among
mammals. Here we characterized CPI-17 N- and C-terminal unstructured tails using
recombinant proteins that lack the potions. Recombinant CPI-17 proteins at a physiologic
level (10 µM) were doped into beta-escin-permeabilized smooth muscle strips for
Ca2+ sensitization force measurement. The ectopic full-length CPI-17
augmented the PDBu-induced Ca2+ sensitization force at pCa6.3, indicating
myosin phosphatase inhibition. Deletion of N- and C-terminal tails of CPI-17 attenuated
the extent of PDBu-induced Ca2+-sensitization force. The N-terminal deletion
dampened phosphorylation at Thr38 by protein kinase C (PKC), and the C-terminal truncation
lowered the affinity to the myosin phosphatase. Under the physiologic conditions, PKC and
myosin phosphatase may recognize CPI-17 N-/C-terminal unstructured tails inducing
Ca2+ sensitization force in smooth muscle cells.
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Affiliation(s)
- Masumi Eto
- Biochemistry Unit, Faculty of Veterinary Medicine, Okayama University of Science, 1-3 Ikoino-oka, Imabari, Ehime 794-8555, Japan
| | - Shuichi Katsuki
- Biochemistry Unit, Faculty of Veterinary Medicine, Okayama University of Science, 1-3 Ikoino-oka, Imabari, Ehime 794-8555, Japan
| | - Minami Ohashi
- Biochemistry Unit, Faculty of Veterinary Medicine, Okayama University of Science, 1-3 Ikoino-oka, Imabari, Ehime 794-8555, Japan
| | - Yui Miyagawa
- Biochemistry Unit, Faculty of Veterinary Medicine, Okayama University of Science, 1-3 Ikoino-oka, Imabari, Ehime 794-8555, Japan
| | - Yoshinori Tanaka
- Biochemistry Unit, Faculty of Veterinary Medicine, Okayama University of Science, 1-3 Ikoino-oka, Imabari, Ehime 794-8555, Japan
| | - Kosuke Takeya
- Biochemistry Unit, Faculty of Veterinary Medicine, Okayama University of Science, 1-3 Ikoino-oka, Imabari, Ehime 794-8555, Japan
| | - Toshio Kitazawa
- Department of Mol Physiol & Biophysics, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA
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Chen C, Huang FW, Huang SS, Huang JS. IGFBP-3 and TGF-β inhibit growth in epithelial cells by stimulating type V TGF-β receptor (TβR-V)-mediated tumor suppressor signaling. FASEB Bioadv 2021; 3:709-729. [PMID: 34485840 PMCID: PMC8409558 DOI: 10.1096/fba.2021-00016] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2021] [Revised: 04/06/2021] [Accepted: 04/23/2021] [Indexed: 12/13/2022] Open
Abstract
The TGF-β type V receptor (TβR-V) mediates growth inhibition by IGFBP-3 and TGF-β in epithelial cells and loss of TβR-V expression in these cells leads to development of carcinoma. The mechanisms by which TβR-V mediates growth inhibition (tumor suppressor) signaling remain elusive. Previous studies revealed that IGFBP-3 and TGF-β inhibit growth in epithelial cells by stimulating TβR-V-mediated IRS-1/2-dependent activation and cytoplasm-to-nucleus translocation of IGFBP-3- or TGF-β-stimulated protein phosphatase (PPase), resulting in dephosphorylation of pRb-related proteins (p107, p130) or pRb, and growth arrest. To define the signaling, we characterized/identified the IGFBP-3- and TGF-β-stimulated PPases in cell lysates and nucleus fractions in Mv1Lu cells treated with IGFBP-3 and TGF-β, using a cell-free assay with 32P-labeled casein as a substrate. Both IGFBP-3- and TGF-β-stimulated PPase activities in cell lysates are abolished when cells are co-treated with TGF-β/IGFBP-3 antagonist or RAP (LRP-1/TβR-V antagonist). However, the IGFBP-3-stimulated PPase activity, but not TGF-β-stimulated PPase activity, is sensitive to inhibition by okadaic acid (OA). In addition, OA or PP2Ac siRNA reverses IGFBP-3 growth inhibition, but not TGF-β growth inhibition, in Mv1Lu and 32D cells. These suggest that IGFBP-3- and TGF-β-stimulated PPases are identical to PP2A and PP1, respectively. By Western blot/phosphorimager/immunofluorescence-microscopy analyses, IGFBP-3 and TGF-β stimulate TβR-V-mediated IRS-2-dependent activation and cytoplasm-to-nucleus translocation of PP2Ac and PP1c, resulting in dephosphorylation of p130/p107 and pRb, respectively, and growth arrest. Small molecule TGF-β enhancers, which potentiate TGF-β growth inhibition by enhancing TβR-I-TβR-II-mediated canonical signaling and thus activating TβR-V-mediated tumor suppressor signaling cascade (TβR-V/IRS-2/PP1/pRb), could be used to prevent and treat carcinoma.
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Affiliation(s)
- Chun‐Lin Chen
- Department of Biological ScienceNational Sun Yat‐sen UniversityKaohsiungTaiwan
- Departments of Biochemistry and Molecular BiologySaint Louis University School of MedicineSt. LouisMOUSA
| | - Franklin W. Huang
- Division of Hematology and OncologyDepartment of MedicineUniversity of CaliforniaSan FranciscoCAUSA
| | | | - Jung San Huang
- Departments of Biochemistry and Molecular BiologySaint Louis University School of MedicineSt. LouisMOUSA
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8
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Betancor G, Jimenez-Guardeño JM, Lynham S, Antrobus R, Khan H, Sobala A, Dicks MDJ, Malim MH. MX2-mediated innate immunity against HIV-1 is regulated by serine phosphorylation. Nat Microbiol 2021; 6:1031-1042. [PMID: 34282309 PMCID: PMC7611661 DOI: 10.1038/s41564-021-00937-5] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2020] [Accepted: 06/17/2021] [Indexed: 01/24/2023]
Abstract
The antiviral cytokine interferon activates expression of interferon-stimulated genes to establish an antiviral state. Myxovirus resistance 2 (MX2, also known as MxB) is an interferon-stimulated gene that inhibits the nuclear import of HIV-1 and interacts with the viral capsid and cellular nuclear transport machinery. Here, we identified the myosin light chain phosphatase (MLCP) subunits myosin phosphatase target subunit 1 (MYPT1) and protein phosphatase 1 catalytic subunit-β (PPP1CB) as positively-acting regulators of MX2, interacting with its amino-terminal domain. We demonstrated that serine phosphorylation of the N-terminal domain at positions 14, 17 and 18 suppresses MX2 antiviral function, prevents interactions with the HIV-1 capsid and nuclear transport factors, and is reversed by MLCP. Notably, serine phosphorylation of the N-terminal domain also impedes MX2-mediated inhibition of nuclear import of cellular karyophilic cargo. We also found that interferon treatment reduces levels of phosphorylation at these serine residues and outline a homeostatic regulatory mechanism in which repression of MX2 by phosphorylation, together with MLCP-mediated dephosphorylation, balances the deleterious effects of MX2 on normal cell function with innate immunity against HIV-1.
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Affiliation(s)
- Gilberto Betancor
- Department of Infectious Diseases, School of Immunology and Microbial Sciences, King's College London, London, UK.
| | - Jose M Jimenez-Guardeño
- Department of Infectious Diseases, School of Immunology and Microbial Sciences, King's College London, London, UK
| | - Steven Lynham
- Centre of Excellence for Mass Spectrometry, The James Black Centre, King's College London, London, UK
| | - Robin Antrobus
- Cambridge Institute for Medical Research, Department of Medicine, University of Cambridge, Cambridge, UK
| | - Hataf Khan
- Department of Infectious Diseases, School of Immunology and Microbial Sciences, King's College London, London, UK
| | - Andrew Sobala
- Department of Infectious Diseases, School of Immunology and Microbial Sciences, King's College London, London, UK
| | - Matthew D J Dicks
- Department of Infectious Diseases, School of Immunology and Microbial Sciences, King's College London, London, UK
| | - Michael H Malim
- Department of Infectious Diseases, School of Immunology and Microbial Sciences, King's College London, London, UK.
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9
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Shiravand Y, Walter U, Jurk K. Fine-Tuning of Platelet Responses by Serine/Threonine Protein Kinases and Phosphatases-Just the Beginning. Hamostaseologie 2021; 41:206-216. [PMID: 34192779 DOI: 10.1055/a-1476-7873] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
Comprehensive proteomic analyses of human and murine platelets established an extraordinary intracellular repertoire of signaling components, which control crucial functions. The spectrum of platelet serine/threonine protein kinases (more than 100) includes the AGC family (protein kinase A, G, C [PKA, PKG, PKC]), the mitogen-activated protein kinases (MAPKs), and others. PKA and PKG have multiple significantly overlapping substrates in human platelets, which possibly affect functions with clear "signaling nodes" of regulation by multiple protein kinases/phosphatases. Signaling nodes are intracellular Ca2+ stores, the contractile system (myosin light chains), and other signaling components such as G-proteins, protein kinases, and protein phosphatases. An example for this fine-tuning is the tyrosine kinase Syk, a crucial component of platelet activation, which is controlled by several serine/threonine and tyrosine protein kinases as well as phosphatases. Other protein kinases including PKA/PKG modulate protein phosphatase 2A, which may be a master regulator of MAPK signaling in human platelets. Protein kinases and in particular MAPKs are targeted by an increasing number of clinically used inhibitors. However, the precise regulation and fine-tuning of these protein kinases and their effects on other signaling components in platelets are only superficially understood-just the beginning. However, promising future approaches are in sight.
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Affiliation(s)
- Yavar Shiravand
- Department of Molecular Medicine and Medical Biotechnology, University of Naples Federico II, Naples, Italy
| | - Ulrich Walter
- Center for Thrombosis and Hemostasis (CTH), University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany
| | - Kerstin Jurk
- Center for Thrombosis and Hemostasis (CTH), University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany
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George MJ, Litvinov J, Aroom K, Spangler LJ, Caplan H, Wade CE, Cox CS, Gill BS. Microelectromechanical System Measurement of Platelet Contraction: Direct Interrogation of Myosin Light Chain Phosphorylation. Int J Mol Sci 2021; 22:ijms22126448. [PMID: 34208643 PMCID: PMC8234414 DOI: 10.3390/ijms22126448] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2021] [Revised: 06/11/2021] [Accepted: 06/12/2021] [Indexed: 12/16/2022] Open
Abstract
Myosin Light Chain (MLC) regulates platelet contraction through its phosphorylation by Myosin Light Chain Kinase (MLCK) or dephosphorylation by Myosin Light Chain Phosphatase (MLCP). The correlation between platelet contraction force and levels of MLC phosphorylation is unknown. We investigate the relationship between platelet contraction force and MLC phosphorylation using a novel microelectromechanical (MEMS) based clot contraction sensor (CCS). The MLCK and MLCP pair were interrogated by inhibitors and activators of platelet function. The CCS was fabricated from silicon using photolithography techniques and force was validated over a range of deflection for different chip spring constants. The force of platelet contraction measured by the clot contraction sensor (CCS) was compared to the degree of MLC phosphorylation by Western Blotting (WB) and ELISA. Stimulators of MLC phosphorylation produced higher contraction force, higher phosphorylated MLC signal in ELISA and higher intensity bands in WB. Inhibitors of MLC phosphorylation produced the opposite. Contraction force is linearly related to levels of phosphorylated MLC. Direct measurements of clot contractile force are possible using a MEMS sensor platform and correlate linearly with the degree of MLC phosphorylation during coagulation. Measured force represents the mechanical output of the actin/myosin motor in platelets regulated by myosin light chain phosphorylation.
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Affiliation(s)
- Mitchell J. George
- Department of Surgery, McGovern Medical School at The University of Texas Health Science Center, Houston, TX 77030, USA; (K.A.); (C.E.W.); (C.S.C.J.); (B.S.G.)
- Correspondence:
| | - Julia Litvinov
- Department of Pediatric Surgery, McGovern Medical School at The University of Texas Health Science Center, Houston, TX 77030, USA; (J.L.); (H.C.)
| | - Kevin Aroom
- Department of Surgery, McGovern Medical School at The University of Texas Health Science Center, Houston, TX 77030, USA; (K.A.); (C.E.W.); (C.S.C.J.); (B.S.G.)
| | | | - Henry Caplan
- Department of Pediatric Surgery, McGovern Medical School at The University of Texas Health Science Center, Houston, TX 77030, USA; (J.L.); (H.C.)
| | - Charles E. Wade
- Department of Surgery, McGovern Medical School at The University of Texas Health Science Center, Houston, TX 77030, USA; (K.A.); (C.E.W.); (C.S.C.J.); (B.S.G.)
| | - Charles S. Cox
- Department of Surgery, McGovern Medical School at The University of Texas Health Science Center, Houston, TX 77030, USA; (K.A.); (C.E.W.); (C.S.C.J.); (B.S.G.)
- Department of Pediatric Surgery, McGovern Medical School at The University of Texas Health Science Center, Houston, TX 77030, USA; (J.L.); (H.C.)
| | - Brijesh S. Gill
- Department of Surgery, McGovern Medical School at The University of Texas Health Science Center, Houston, TX 77030, USA; (K.A.); (C.E.W.); (C.S.C.J.); (B.S.G.)
- Department of Pediatric Surgery, McGovern Medical School at The University of Texas Health Science Center, Houston, TX 77030, USA; (J.L.); (H.C.)
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11
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Latifah SY, Gopalsamy B, Abdul Rahim R, Manaf Ali A, Haji Lajis N. Anticancer Potential of Damnacanthal and Nordamnacanthal from Morinda elliptica Roots on T-lymphoblastic Leukemia Cells. Molecules 2021; 26:molecules26061554. [PMID: 33808969 PMCID: PMC7998966 DOI: 10.3390/molecules26061554] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Revised: 02/01/2021] [Accepted: 02/02/2021] [Indexed: 12/24/2022] Open
Abstract
Background: This study reports on the cytotoxic properties of nordamnacanthal and damnacanthal, isolated from roots of Morinda elliptica on T-lymphoblastic leukaemia (CEM-SS) cell lines. Methods: MTT assay, DNA fragmentation, ELISA and cell cycle analysis were carried out. Results: Nordamnacanthal and damnacanthal at IC50 values of 1.7 μg/mL and10 μg/mL, respectively. At the molecular level, these compounds caused internucleosomal DNA cleavage producing multiple 180–200 bp fragments that are visible as a “ladder” on the agarose gel. This was due to the activation of the Mg2+/Ca2+-dependent endonuclease. The induction of apoptosis by nordamnacanthal was different from the one induced by damnacanthal, in a way that it occurs independently of ongoing transcription process. Nevertheless, in both cases, the process of dephosphorylation of protein phosphates 1 and 2A, the ongoing protein synthesis and the elevations of the cytosolic Ca2+ concentration were not needed for apoptosis to take place. Nordamnacanthal was found to have a cytotoxic effect by inducing apoptosis, while damnacanthal caused arrest at the G0/G1 phase of the cell cycle. Conclusion: Damnacanthal and nordamnacanthal have anticancer properties, and could act as potential treatment for T-lymphoblastic leukemia.
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Affiliation(s)
- Saiful Yazan Latifah
- Department of Biomedical Sciences, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia, Serdang 43400 UPM, Selangor, Malaysia;
- Correspondence: ; Tel.: +603-89472308
| | - Banulata Gopalsamy
- Department of Biomedical Sciences, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia, Serdang 43400 UPM, Selangor, Malaysia;
| | - Raha Abdul Rahim
- Department of Cell and Molecular Biology, Faculty of Biotechnology and Biomolecular Sciences, Universiti Putra Malaysia, Serdang 43400 UPM, Selangor, Malaysia;
| | - Abdul Manaf Ali
- Faculty of Bioresources and Food Industry, Universiti Sultan Zainal Abidin (UniSZA), Kuala 20300, Terengganu, Malaysia;
| | - Nordin Haji Lajis
- Laboratory of Natural Products, Institute of Bioscience, Universiti Putra Malaysia, Serdang 43400 UPM, Selangor, Malaysia;
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12
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Abstract
Tau, a microtubule-associated protein, plays a critical role in the pathophysiology of neurons. However, whether tau protein is expressed in smooth muscle cells is unknown. Thus, we tested the hypothesis that tau protein is expressed in the primary cultures of smooth muscle cells. Here, we report that tau protein is expressed and constitutively phosphorylated at threonine 181 in various smooth muscle cell types, including human pulmonary artery smooth muscle cells, bronchial airway smooth muscle cells, and cerebral artery smooth muscle cells. Immunofluorescence staining revealed that phosphorylated tau at threonine 181 is more organized in the cell than is total tau protein. A protein phosphatase inhibitor, calyculin A, induced the formation of higher molecular weight species of phosphorylated tau, as visualized by Western blotting, indicating the occurrence of tau aggregation. Immunofluorescence analysis also showed that calyculin A caused the aggregation of phosphorylated tau and disrupted the cytoskeletal organization. These results demonstrate the existence of tau protein in smooth muscle cells, and that smooth muscle tau is susceptible to protein phosphorylation and aggregation. Lung smooth muscle tau may therefore play an important role in pulmonary pathophysiology.
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13
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Makhoul S, Kumm E, Zhang P, Walter U, Jurk K. The Serine/Threonine Protein Phosphatase 2A (PP2A) Regulates Syk Activity in Human Platelets. Int J Mol Sci 2020; 21:ijms21238939. [PMID: 33255747 PMCID: PMC7728356 DOI: 10.3390/ijms21238939] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2020] [Revised: 11/14/2020] [Accepted: 11/19/2020] [Indexed: 12/21/2022] Open
Abstract
Distinct membrane receptors activate platelets by Src-family-kinase (SFK)-, immunoreceptor-tyrosine-based-activation-motif (ITAM)-dependent stimulation of spleen tyrosine kinase (Syk). Recently, we reported that platelet activation via glycoprotein (GP) VI or GPIbα stimulated the well-established Syk tyrosine (Y)-phosphorylation, but also stoichiometric, transient protein kinase C (PKC)-mediated Syk serine(S)297 phosphorylation in the regulatory interdomain-B, suggesting possible feedback inhibition. The transient nature of Syk S297 phosphorylation indicated the presence of an unknown Syk pS297 protein phosphatase. In this study, we hypothesize that the S-protein phosphatase 2A (PP2A) is responsible for Syk pS297 dephosphorylation, thereby affecting Syk Y-phosphorylation and activity in human washed platelets. Using immunoblotting, we show that specific inhibition of PP2A by okadaic acid (OA) alone leads to stoichiometric Syk S297 phosphorylation, as analyzed by Zn2+-Phos-tag gels, without affecting Syk Y-phosphorylation. Pharmacological inhibition of Syk by PRT060318 or PKC by GF109203X only minimally reduced OA-induced Syk S297 phosphorylation. PP2A inhibition by OA preceding GPVI-mediated platelet activation induced by convulxin extended Syk S297 phosphorylation but inhibited Syk Y-phosphorylation. Our data demonstrate a novel biochemical and functional link between the S-protein phosphatase PP2A and the Y-protein kinase Syk in human platelets, and suggest that PP2A represents a potential enhancer of GPVI-mediated Syk activity caused by Syk pS297 dephosphorylation.
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Affiliation(s)
- Stephanie Makhoul
- Center for Thrombosis and Hemostasis (CTH), University Medical Center Mainz of the Johannes Gutenberg University Mainz, D-55131 Mainz, Germany; (S.M.); (E.K.); (P.Z.)
| | - Elena Kumm
- Center for Thrombosis and Hemostasis (CTH), University Medical Center Mainz of the Johannes Gutenberg University Mainz, D-55131 Mainz, Germany; (S.M.); (E.K.); (P.Z.)
| | - Pengyu Zhang
- Center for Thrombosis and Hemostasis (CTH), University Medical Center Mainz of the Johannes Gutenberg University Mainz, D-55131 Mainz, Germany; (S.M.); (E.K.); (P.Z.)
- Leibniz-Institut für Analytische Wissenschaften, D-44227 Dortmund, Germany
| | - Ulrich Walter
- Center for Thrombosis and Hemostasis (CTH), University Medical Center Mainz of the Johannes Gutenberg University Mainz, D-55131 Mainz, Germany; (S.M.); (E.K.); (P.Z.)
- Correspondence: (U.W.); (K.J.)
| | - Kerstin Jurk
- Center for Thrombosis and Hemostasis (CTH), University Medical Center Mainz of the Johannes Gutenberg University Mainz, D-55131 Mainz, Germany; (S.M.); (E.K.); (P.Z.)
- Correspondence: (U.W.); (K.J.)
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14
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Identification of peptides interfering with the LRRK2/PP1 interaction. PLoS One 2020; 15:e0237110. [PMID: 32790695 PMCID: PMC7425875 DOI: 10.1371/journal.pone.0237110] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Accepted: 07/20/2020] [Indexed: 01/17/2023] Open
Abstract
Serine/threonine phosphatases are responsible for modulating the activities of the protein kinases implicated in the development of several pathologies. Here we identified by a PEP-scan approach a peptide of LRRK2, a Parkinson's disease associated protein, interacting with the phosphatase PP1. In order to study its biological activity, the peptide was fused via its N-terminal to an optimized cell penetrating peptide. We synthesized from the original peptide five interfering peptides and identified two (Mut3DPT-LRRK2-Short and Mut3DPT-LRRK2-Long) able to disrupt the LRRK2/PP1 interaction by competition in anti-LRRK2 immunoprecipitates. Using FITC-labelled peptides, we confirmed their internalization into cell lines as well as into primary cells obtained from healthy or ill human donors. We confirmed by ELISA test the association of Mut3DPT-LRRK2-Long peptide to purified PP1 protein. The peptides Mut3DPT-LRRK2-5 to 8 with either N or C-terminal deletions were not able to disrupt the association LRRK2/PP1 nor to associate with purified PP1 protein. The interfering sequences blocking the PP1/LRRK2 interaction were also fused to a shuttle peptide able to cross the blood brain barrier and showed that the newly generated peptides BBB-LRRK2-Short and BBB-LRRK2-Long were highly resistant to protease degradation. Furthermore, they blocked PP1/LRRK2 interaction and they penetrated into cells. Hence, these newly generated peptides can be employed as new tools in the investigation of the role of the LRRK2/PP1 interaction in normal and pathological conditions.
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15
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Naraki Y, Watanabe M, Takeya K. Inhibitory effects of rubratoxin A, a potent inhibitor of protein phosphatase 2, on the Ca 2+-dependent contraction of skinned carotid artery from guinea pig. J Smooth Muscle Res 2020; 55:14-22. [PMID: 31006724 PMCID: PMC6473161 DOI: 10.1540/jsmr.55.14] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Rubratoxin A, a potent inhibitor of PP2A, is known to suppress smooth muscle contraction.
The inhibitory role of PP2A in smooth muscle contraction is still unclear. In order to
clarify the regulatory mechanisms of PP2A on vascular smooth muscle contractility, we
examined the effects of rubratoxin A on the Ca2+-induced contraction of β-escin
skinned carotid artery preparations from guinea pigs. Rubratoxin A at 1 µM and 10 µM
significantly inhibited skinned carotid artery contraction at any Ca2+
concentration. The data fitting to the Hill equation in [Ca2+]-contraction
relationship indicated that rubratoxin A decreased Fmax-Ca2+ and increased
[Ca2+]50, indices of Ca2+ sensitivity for the force and
myosin-actin interaction, respectively. These results suggest that PP2A inhibition causes
downregulation of the myosin light chain phosphorylation and direct interference with
myosin-actin interaction.
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Affiliation(s)
- Yasuyuki Naraki
- Department of Frontier Health Sciences, Graduate School of Human Health Sciences, Tokyo Metropolitan University, 7-2-10 Higashiogu, Arakawa-ku, Tokyo 116-8551, Japan
| | - Masaru Watanabe
- Department of Frontier Health Sciences, Graduate School of Human Health Sciences, Tokyo Metropolitan University, 7-2-10 Higashiogu, Arakawa-ku, Tokyo 116-8551, Japan
| | - Kosuke Takeya
- Department of Veterinary Biochemistry, Faculty of Veterinary Medicine, Okayama University of Science, Imabari-shi, Ehime 794-8555, Japan
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16
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Álvarez-Santos MD, Álvarez-González M, Estrada-Soto S, Bazán-Perkins B. Regulation of Myosin Light-Chain Phosphatase Activity to Generate Airway Smooth Muscle Hypercontractility. Front Physiol 2020; 11:701. [PMID: 32676037 PMCID: PMC7333668 DOI: 10.3389/fphys.2020.00701] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2019] [Accepted: 05/28/2020] [Indexed: 12/21/2022] Open
Abstract
Smooth muscle is a central structure involved in the regulation of airway tone. In addition, it plays an important role in the development of some pathologies generated by alterations in contraction, such as hypercontractility and the airway hyperresponsiveness observed in asthma. The molecular processes associated with smooth muscle contraction are centered around myosin light chain (MLC) phosphorylation, which is controlled by a balance in the activity of myosin light-chain kinase (MLCK) and myosin light-chain phosphatase (MLCP). MLCK activation depends on increasing concentrations of intracellular Ca2+, while MLCP activation is independent of Ca2+. MLCP contains a phosphatase subunit (PP1c) that is regulated through myosin phosphatase target subunit 1 (MYPT1) and other subunits, such as glycogen-associated regulatory subunit and myosin-binding subunit 85 kDa. Interestingly, MLCP inhibition may contribute to exacerbation of smooth muscle contraction by increasing MLC phosphorylation to induce hypercontractility. Many pathways inhibiting MLCP activity in airway smooth muscle have been proposed and are focused on inhibition of PP1c, inhibitory phosphorylation of MYPT1 and dissociation of the PP1c-MYPT1 complex.
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Affiliation(s)
- Mayra D Álvarez-Santos
- Biology Area, Facultad de Ciencias, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | - Marisol Álvarez-González
- Laboratorio de Inmunofarmacología, Instituto Nacional de Enfermedades Respiratorias "Ismael Cosío Villegas", Mexico City, Mexico
| | - Samuel Estrada-Soto
- Facultad de Farmacia, Universidad Autónoma del Estado de Morelos, Cuernavaca, Mexico
| | - Blanca Bazán-Perkins
- Laboratorio de Inmunofarmacología, Instituto Nacional de Enfermedades Respiratorias "Ismael Cosío Villegas", Mexico City, Mexico.,Tecnológico de Monterrey, Escuela de Medicina y Ciencias de la Salud, Monterrey, Mexico
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The Cell Cycle Checkpoint System MAST(L)-ENSA/ARPP19-PP2A is Targeted by cAMP/PKA and cGMP/PKG in Anucleate Human Platelets. Cells 2020; 9:cells9020472. [PMID: 32085646 PMCID: PMC7072724 DOI: 10.3390/cells9020472] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2020] [Revised: 02/14/2020] [Accepted: 02/14/2020] [Indexed: 12/13/2022] Open
Abstract
The cell cycle is controlled by microtubule-associated serine/threonine kinase-like (MASTL), which phosphorylates the cAMP-regulated phosphoproteins 19 (ARPP19) at S62 and 19e/α-endosulfine (ENSA) at S67and converts them into protein phosphatase 2A (PP2A) inhibitors. Based on initial proteomic data, we hypothesized that the MASTL-ENSA/ARPP19-PP2A pathway, unknown until now in platelets, is regulated and functional in these anucleate cells. We detected ENSA, ARPP19 and various PP2A subunits (including seven different PP2A B-subunits) in proteomic studies of human platelets. ENSA-S109/ARPP19–S104 were efficiently phosphorylated in platelets treated with cAMP- (iloprost) and cGMP-elevating (NO donors/riociguat) agents. ENSA-S67/ARPP19-S62 phosphorylations increased following PP2A inhibition by okadaic acid (OA) in intact and lysed platelets indicating the presence of MASTL or a related protein kinase in human platelets. These data were validated with recombinant ENSA/ARPP19 and phospho-mutants using recombinant MASTL, protein kinase A and G. Both ARPP19 phosphorylation sites S62/S104 were dephosphorylated by platelet PP2A, but only S62-phosphorylated ARPP19 acted as PP2A inhibitor. Low-dose OA treatment of platelets caused PP2A inhibition, diminished thrombin-stimulated platelet aggregation and increased phosphorylation of distinct sites of VASP, Akt, p38 and ERK1/2 MAP kinases. In summary, our data establish the entire MASTL(like)–ENSA/ARPP19–PP2A pathway in human platelets and important interactions with the PKA, MAPK and PI3K/Akt systems.
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