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Torices S, Daire L, Simon S, Naranjo O, Mendoza L, Teglas T, Fattakhov N, Adesse D, Toborek M. Occludin: a gatekeeper of brain Infection by HIV-1. Fluids Barriers CNS 2023; 20:73. [PMID: 37840143 PMCID: PMC10577960 DOI: 10.1186/s12987-023-00476-7] [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: 08/05/2023] [Accepted: 10/09/2023] [Indexed: 10/17/2023] Open
Abstract
Compromised structure and function of the blood-brain barrier (BBB) is one of the pathological hallmarks of brain infection by HIV-1. BBB damage during HIV-1 infection has been associated with modified expression of tight junction (TJ) proteins, including occludin. Recent evidence indicated occludin as a redox-sensitive, multifunctional protein that can act as both an NADH oxidase and influence cellular metabolism through AMPK kinase. One of the newly identified functions of occludin is its involvement in regulating HIV-1 infection. Studies suggest that occludin expression levels and the rate of HIV-1 infection share a reverse, bidirectional relationship; however, the mechanisms of this relationship are unclear. In this review, we describe the pathways involved in the regulation of HIV-1 infection by occludin. We propose that occludin may serve as a potential therapeutic target to control HIV-1 infection and to improve the lives of people living with HIV-1.
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Affiliation(s)
- Silvia Torices
- Department of Biochemistry and Molecular Biology, University of Miami School of Medicine, 528E Gautier Bldg. 1011 NW 15th Street Miami, Miami, FL, 11336, USA
| | - Leah Daire
- Department of Biochemistry and Molecular Biology, University of Miami School of Medicine, 528E Gautier Bldg. 1011 NW 15th Street Miami, Miami, FL, 11336, USA
| | - Sierra Simon
- Department of Biochemistry and Molecular Biology, University of Miami School of Medicine, 528E Gautier Bldg. 1011 NW 15th Street Miami, Miami, FL, 11336, USA
| | - Oandy Naranjo
- Department of Biochemistry and Molecular Biology, University of Miami School of Medicine, 528E Gautier Bldg. 1011 NW 15th Street Miami, Miami, FL, 11336, USA
| | - Luisa Mendoza
- Department of Biochemistry and Molecular Biology, University of Miami School of Medicine, 528E Gautier Bldg. 1011 NW 15th Street Miami, Miami, FL, 11336, USA
| | - Timea Teglas
- Department of Biochemistry and Molecular Biology, University of Miami School of Medicine, 528E Gautier Bldg. 1011 NW 15th Street Miami, Miami, FL, 11336, USA
| | - Nikolai Fattakhov
- Department of Biochemistry and Molecular Biology, University of Miami School of Medicine, 528E Gautier Bldg. 1011 NW 15th Street Miami, Miami, FL, 11336, USA
| | - Daniel Adesse
- Department of Biochemistry and Molecular Biology, University of Miami School of Medicine, 528E Gautier Bldg. 1011 NW 15th Street Miami, Miami, FL, 11336, USA
- Laboratório de Biologia Estrutural, Instituto Oswaldo Cruz, Fiocruz, Rio de Janeiro, Brazil
| | - Michal Toborek
- Department of Biochemistry and Molecular Biology, University of Miami School of Medicine, 528E Gautier Bldg. 1011 NW 15th Street Miami, Miami, FL, 11336, USA.
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Brunner J, Schvartz D, Gouiller A, Hainard A, Borchard G. Impact of peptide permeation enhancer on tight junctions opening cellular mechanisms. Biochem Biophys Rep 2022; 32:101375. [PMID: 36324528 PMCID: PMC9618981 DOI: 10.1016/j.bbrep.2022.101375] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2022] [Revised: 10/03/2022] [Accepted: 10/24/2022] [Indexed: 11/09/2022] Open
Abstract
The myristoylated pentapeptide, L-R5, contains an amino acid sequence of the zeta inhibitory peptide (ZIP) portion (pseudosubstrate) of protein kinase C zeta (PKC ζ). As PKC ζ is involved in the modulation of epithelial tight junctions (TJs) through the phosphorylation of TJ proteins, L-R5 was suggested to interact with the enzyme resulting in the enhancement of paracellular permeability. This study shows that L-R5 does not bind to the enzyme but interacts directly with TJ proteins. We show here that the binding of PKC ζ to occludin and its successive phosphorylation is prevented by L-R5, which leads to TJ disruption and enhanced epithelial permeability. Although L-R5 did not show any in vitro cytotoxicity, a proteomics study revealed that L-R5 interferes with other regulatory pathways, e.g., apoptosis and immune response. We suggest that structural modification of the peptide may increase the specificity TJ protein-peptide interaction. Microscale thermophoresis (MST) showed robust results for protein bindings. The competitivity of L-R5 peptide for the binding of occludin-PKC zeta was shown. Tight junctions proteins expression was decreased due to L-R5 peptide. Multiple other mechanisms can be explored to use L-R5 for other therapies.
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Affiliation(s)
- Joël Brunner
- School of Pharmaceutical Sciences, University of Geneva, Geneva, Switzerland
| | - Domitille Schvartz
- Proteomics Core Facility, Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Aurélie Gouiller
- School of Pharmaceutical Sciences, University of Geneva, Geneva, Switzerland
| | - Alexandre Hainard
- Proteomics Core Facility, Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Gerrit Borchard
- School of Pharmaceutical Sciences, University of Geneva, Geneva, Switzerland,Corresponding author.
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3
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EMAP II Expression Is Increased on Peripheral Blood Cells from Non-Hodgkin Lymphoma. J Immunol Res 2022; 2022:7219207. [PMID: 36132984 PMCID: PMC9484964 DOI: 10.1155/2022/7219207] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Revised: 06/10/2022] [Accepted: 08/20/2022] [Indexed: 12/02/2022] Open
Abstract
Tumor immune evasion is a lineament of cancer. Endothelial monocyte activating polypeptide-II (EMAP II) has been assumed to impact tumor immune escape significantly. EMAP II was first reported in the murine methylcholanthrene A-induced fibrosarcoma supernatant and identified as a tumor-derived cytokine. This study evaluated EMAP II expression in peripheral blood cells and its association with treatment outcome, lactate dehydrogenase (LDH) levels, and clinical criteria in non-Hodgkin's lymphoma (NHL) patients. EMAP II expression on different blood cells obtained from the peripheral blood of 80 NHL patients was evaluated by two-color flow cytometry. The study reported that EMAP II expression was significantly increased in peripheral blood cells in patients with NHL compared to normal volunteers (P < 0.001). Additionally, EMAP II expression levels on blood cells decreased in complete remission (CR) while they increased in relapse. This study showed coexpression of EMAP II and CD36 on peripheral lymphocytes in NHL patients but not in healthy controls (P < 0.001). EMAP II expression on blood cells was associated with increased serum LDH levels. Furthermore, the percentages of EMAP II+/CD36+ peripheral lymphocytes were significantly higher in relapse than in CR and healthy controls. Analyses revealed that higher percentages of EMAP II+CD36+ cells were positively correlated with hepatomegaly, splenomegaly, and an advanced (intermediate and high risk) NHL stage. The results assume that EMAP II might be involved in NHL development and pathogenesis.
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Pan R, Liu W, Liu KJ. MMP-2/9-cleaved occludin promotes endothelia cell death in ischemic stroke. BRAIN HEMORRHAGES 2021. [DOI: 10.1016/j.hest.2021.01.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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5
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Li C, Ma W, Zhao Y, Wang H. Changes in the expression of endothelial monocyte‑activating polypeptide II in the rat hippocampus following status epilepticus. Int J Mol Med 2020; 47:699-707. [PMID: 33416103 PMCID: PMC7797450 DOI: 10.3892/ijmm.2020.4808] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2020] [Accepted: 11/10/2020] [Indexed: 11/08/2022] Open
Abstract
Endothelial monocyte-activating polypeptide II (EMAP II) is a sensitive marker of neurotoxic injury, the expression of which increases significantly under conditions of stress, such as hypoxia or apoptosis. Studies have confirmed the extensive apoptosis of nerve cells in the brain following status epilepticus (SE), and the occurrence of SE can confer a hypoxic state on cells. The purpose of the present study was to observe the changes in the expression of EMAP II, and in the numbers and tight junction protein levels of micro-vascular endothelial cells in the hippocampus of rats with pilocarpine-induced SE. The protein expression levels of EMAP II, CD31, zonula occludens 1 (ZO-1) and occludin in the hippocampus were determined by immunofluorescence and western blot analyses. It was found that almost 75.6% of the rats in the SE group developed Racine stage IV-V seizures at approximately 44.7±18.8 min after the pilocarpine administration, and the 24-h mortality rate was almost 10.4%. The weight of the rats in the SE group was significantly decreased within 24 h following SE. Immunofluorescence staining revealed a low EMAP II expression in the hippo-campus of the rats in the control group; however, the numbers of EMAP II-positive cells were significantly increased in the SE group from 2 h to 21 days. The trend of EMAP II protein expression was consistent with that obtained with immunofluorescence staining. The numbers of CD31-positive microvascular endothelial cells were significantly increased from 24 h to 21 days compared with the levels in the control group. The protein expression of ZO-1 and occludin was most significantly decreased in the SE group. On the whole, the present study demonstrated that the expression of EMAP II in the rat hippocampus was upregulated in the SE model, which may promote angiogenesis and alter the TJ integrity of brain microvascular endothelial cells, with an increased number of CD31-positive microvascular endothelial cells and a decreased expression of ZO-1 and occludin.
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Affiliation(s)
- Chun Li
- Department of Pediatrics, Shengjing Hospital of China Medical University, Shenyang, Liaoning 110004, P.R. China
| | - Weining Ma
- Department of Neurosurgery, Shengjing Hospital of China Medical University, Shenyang, Liaoning 110022, P.R. China
| | - Yajuan Zhao
- Department of Pediatrics, Shengjing Hospital of China Medical University, Shenyang, Liaoning 110004, P.R. China
| | - Hua Wang
- Department of Pediatrics, Shengjing Hospital of China Medical University, Shenyang, Liaoning 110004, P.R. China
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Roles of aminoacyl-tRNA synthetase-interacting multi-functional proteins in physiology and cancer. Cell Death Dis 2020; 11:579. [PMID: 32709848 PMCID: PMC7382500 DOI: 10.1038/s41419-020-02794-2] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2020] [Revised: 07/03/2020] [Accepted: 07/06/2020] [Indexed: 12/15/2022]
Abstract
Aminoacyl-tRNA synthetases (ARSs) are an important class of enzymes with an evolutionarily conserved mechanism for protein synthesis. In higher eukaryotic systems, eight ARSs and three ARS-interacting multi-functional proteins (AIMPs) form a multi-tRNA synthetase complex (MSC), which seems to contribute to cellular homeostasis. Of these, AIMPs are generally considered as non-enzyme factors, playing a scaffolding role during MSC assembly. Although the functions of AIMPs are not fully understood, increasing evidence indicates that these scaffold proteins usually exert tumor-suppressive activities. In addition, endothelial monocyte-activating polypeptide II (EMAP II), as a cleavage product of AIMP1, and AIMP2-DX2, as a splice variant of AIMP2 lacking exon 2, also have a pivotal role in regulating tumorigenesis. In this review, we summarize the biological functions of AIMP1, EMAP II, AIMP2, AIMP2-DX2, and AIMP3. Also, we systematically introduce their emerging roles in cancer, aiming to provide new ideas for the treatment of cancer.
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Cong X, Kong W. Endothelial tight junctions and their regulatory signaling pathways in vascular homeostasis and disease. Cell Signal 2019; 66:109485. [PMID: 31770579 DOI: 10.1016/j.cellsig.2019.109485] [Citation(s) in RCA: 128] [Impact Index Per Article: 25.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2019] [Revised: 11/21/2019] [Accepted: 11/21/2019] [Indexed: 12/13/2022]
Abstract
Endothelial tight junctions (TJs) regulate the transport of water, ions, and molecules through the paracellular pathway, serving as an important barrier in blood vessels and maintaining vascular homeostasis. In endothelial cells (ECs), TJs are highly dynamic structures that respond to multiple external stimuli and pathological conditions. Alterations in the expression, distribution, and structure of endothelial TJs may lead to many related vascular diseases and pathologies. In this review, we provide an overview of the assessment methods used to evaluate endothelial TJ barrier function both in vitro and in vivo and describe the composition of endothelial TJs in diverse vascular systems and ECs. More importantly, the direct phosphorylation and dephosphorylation of TJ proteins by intracellular kinases and phosphatases, as well as the signaling pathways involved in the regulation of TJs, including and the protein kinase C (PKC), PKA, PKG, Ras homolog gene family member A (RhoA), mitogen-activated protein kinase (MAPK), phosphatidylinositol 3-kinase (PI3K)/Akt, and Wnt/β-catenin pathways, are discussed. With great advances in this area, targeting endothelial TJs may provide novel treatment for TJ-related vascular pathologies.
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Affiliation(s)
- Xin Cong
- Department of Physiology and Pathophysiology, Peking University School of Basic Medical Sciences, Key Laboratory of Molecular Cardiovascular Sciences, Ministry of Education, Beijing Key Laboratory of Cardiovascular Receptors Research, Beijing 100191, China.
| | - Wei Kong
- Department of Physiology and Pathophysiology, Peking University School of Basic Medical Sciences, Key Laboratory of Molecular Cardiovascular Sciences, Ministry of Education, Beijing Key Laboratory of Cardiovascular Receptors Research, Beijing 100191, China.
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Liu J, Liu L, Chao S, Liu Y, Liu X, Zheng J, Chen J, Gong W, Teng H, Li Z, Wang P, Xue Y. The Role of miR-330-3p/PKC-α Signaling Pathway in Low-Dose Endothelial-Monocyte Activating Polypeptide-II Increasing the Permeability of Blood-Tumor Barrier. Front Cell Neurosci 2017; 11:358. [PMID: 29311822 PMCID: PMC5742213 DOI: 10.3389/fncel.2017.00358] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2017] [Accepted: 10/27/2017] [Indexed: 12/13/2022] Open
Abstract
This study was performed to determine whether EMAP II increases the permeability of the blood-tumor barrier (BTB) by affecting the expression of miR-330-3p as well as its possible mechanisms. We determined the over-expression of miR-330-3p in glioma microvascular endothelial cells (GECs) by Real-time PCR. Endothelial monocyte-activating polypeptide-II (EMAP-II) significantly decreased the expression of miR-330-3p in GECs. Pre-miR-330-3p markedly decreased the permeability of BTB and increased the expression of tight junction (TJ) related proteins ZO-1, occludin and claudin-5, however, anti-miR-330-3p had the opposite effects. Anti-miR-330-3p could enhance the effect of EMAP-II on increasing the permeability of BTB, however, pre-miR-330-3p partly reversed the effect of EMAP-II on that. Similarly, anti-miR-330-3p improved the effects of EMAP-II on increasing the expression levels of PKC-α and p-PKC-α in GECs and pre-miR-330-3p partly reversed the effects. MiR-330-3p could target bind to the 3′UTR of PKC-α. The results of in vivo experiments were similar to those of in vitro experiments. These suggested that EMAP-II could increase the permeability of BTB through inhibiting miR-330-3p which target negative regulation of PKC-α. Pre-miR-330-3p and PKC-α inhibitor decreased the BTB permeability and up-regulated the expression levels of ZO-1, occludin and claudin-5 while anti-miR-330-3p and PKC-α activator brought the reverse effects. Compared with EMAP-II, anti-miR-330-3p and PKC-α activator alone, the combination of the three combinations significantly increased the BTB permeability. EMAP-II combined with anti-miR-330-3p and PKCα activator could enhance the DOX’s effects on inhibiting the cell viabilities and increasing the apoptosis of U87 glioma cells. Our studies suggest that low-dose EMAP-II up-regulates the expression of PKC-α and increases the activity of PKC-α by inhibiting the expression of miR-330-3p, reduces the expression of ZO-1, occludin and claudin-5, and thereby increasing the permeability of BTB. The results can provide a new strategy for the comprehensive treatment of glioma.
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Affiliation(s)
- Jiahui Liu
- Department of Neurobiology, College of Basic Medicine, China Medical University, Shenyang, China.,Key Laboratory of Cell Biology, Ministry of Public Health of China, and Key Laboratory of Medical Cell Biology, Ministry of Education of China, China Medical University, Shenyang, China
| | - Libo Liu
- Department of Neurobiology, College of Basic Medicine, China Medical University, Shenyang, China.,Key Laboratory of Cell Biology, Ministry of Public Health of China, and Key Laboratory of Medical Cell Biology, Ministry of Education of China, China Medical University, Shenyang, China
| | - Shuo Chao
- Department of Neurobiology, College of Basic Medicine, China Medical University, Shenyang, China.,Key Laboratory of Cell Biology, Ministry of Public Health of China, and Key Laboratory of Medical Cell Biology, Ministry of Education of China, China Medical University, Shenyang, China
| | - Yunhui Liu
- Department of Neurosurgery, Shengjing Hospital of China Medical University, Shenyang, China.,Liaoning Clinical Medical Research Center in Nervous System Disease, Shenyang, China.,Key Laboratory of Neuro-oncology in Liaoning Province, Shenyang, China
| | - Xiaobai Liu
- Department of Neurosurgery, Shengjing Hospital of China Medical University, Shenyang, China.,Liaoning Clinical Medical Research Center in Nervous System Disease, Shenyang, China.,Key Laboratory of Neuro-oncology in Liaoning Province, Shenyang, China
| | - Jian Zheng
- Department of Neurosurgery, Shengjing Hospital of China Medical University, Shenyang, China.,Liaoning Clinical Medical Research Center in Nervous System Disease, Shenyang, China.,Key Laboratory of Neuro-oncology in Liaoning Province, Shenyang, China
| | - Jiajia Chen
- Department of Neurobiology, College of Basic Medicine, China Medical University, Shenyang, China.,Key Laboratory of Cell Biology, Ministry of Public Health of China, and Key Laboratory of Medical Cell Biology, Ministry of Education of China, China Medical University, Shenyang, China
| | - Wei Gong
- Department of Neurobiology, College of Basic Medicine, China Medical University, Shenyang, China.,Key Laboratory of Cell Biology, Ministry of Public Health of China, and Key Laboratory of Medical Cell Biology, Ministry of Education of China, China Medical University, Shenyang, China
| | - Hao Teng
- Department of Neurosurgery, Shengjing Hospital of China Medical University, Shenyang, China.,Liaoning Clinical Medical Research Center in Nervous System Disease, Shenyang, China.,Key Laboratory of Neuro-oncology in Liaoning Province, Shenyang, China
| | - Zhen Li
- Department of Neurosurgery, Shengjing Hospital of China Medical University, Shenyang, China.,Liaoning Clinical Medical Research Center in Nervous System Disease, Shenyang, China.,Key Laboratory of Neuro-oncology in Liaoning Province, Shenyang, China
| | - Ping Wang
- Department of Neurobiology, College of Basic Medicine, China Medical University, Shenyang, China.,Key Laboratory of Cell Biology, Ministry of Public Health of China, and Key Laboratory of Medical Cell Biology, Ministry of Education of China, China Medical University, Shenyang, China
| | - Yixue Xue
- Department of Neurobiology, College of Basic Medicine, China Medical University, Shenyang, China.,Key Laboratory of Cell Biology, Ministry of Public Health of China, and Key Laboratory of Medical Cell Biology, Ministry of Education of China, China Medical University, Shenyang, China
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Newell-Litwa KA, Horwitz R, Lamers ML. Non-muscle myosin II in disease: mechanisms and therapeutic opportunities. Dis Model Mech 2015; 8:1495-515. [PMID: 26542704 PMCID: PMC4728321 DOI: 10.1242/dmm.022103] [Citation(s) in RCA: 94] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The actin motor protein non-muscle myosin II (NMII) acts as a master regulator of cell morphology, with a role in several essential cellular processes, including cell migration and post-synaptic dendritic spine plasticity in neurons. NMII also generates forces that alter biochemical signaling, by driving changes in interactions between actin-associated proteins that can ultimately regulate gene transcription. In addition to its roles in normal cellular physiology, NMII has recently emerged as a critical regulator of diverse, genetically complex diseases, including neuronal disorders, cancers and vascular disease. In the context of these disorders, NMII regulatory pathways can be directly mutated or indirectly altered by disease-causing mutations. NMII regulatory pathway genes are also increasingly found in disease-associated copy-number variants, particularly in neuronal disorders such as autism and schizophrenia. Furthermore, manipulation of NMII-mediated contractility regulates stem cell pluripotency and differentiation, thus highlighting the key role of NMII-based pharmaceuticals in the clinical success of stem cell therapies. In this Review, we discuss the emerging role of NMII activity and its regulation by kinases and microRNAs in the pathogenesis and prognosis of a diverse range of diseases, including neuronal disorders, cancer and vascular disease. We also address promising clinical applications and limitations of NMII-based inhibitors in the treatment of these diseases and the development of stem-cell-based therapies.
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Affiliation(s)
- Karen A Newell-Litwa
- Department of Cell Biology, University of Virginia, Charlottesville, VA 22908, USA
| | - Rick Horwitz
- Department of Cell Biology, University of Virginia, Charlottesville, VA 22908, USA
| | - Marcelo L Lamers
- Department of Morphological Sciences, Institute of Basic Health Science, Federal University of Rio Grande do Sul, Porto Alegre, Rio Grande do Sul 90610-010, Brazil
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Li Z, Liu XB, Liu YH, Xue YX, Wang P, Liu LB, Liu J, Yao YL, Ma J. Roles of Serine/Threonine Phosphatases in Low-Dose Endothelial Monocyte-Activating Polypeptide-II-Induced Opening of Blood-Tumor Barrier. J Mol Neurosci 2015; 57:11-20. [PMID: 26087743 DOI: 10.1007/s12031-015-0604-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2015] [Accepted: 06/10/2015] [Indexed: 12/17/2022]
Abstract
Previous studies have demonstrated that low-dose endothelial monocyte-activating polypeptide-II (EMAP-II) induces blood-tumor barrier (BTB) opening via RhoA/Rho kinase/PKC-α/β signaling pathway. In a recent study, we revealed that low-dose EMAP-II induced significant increases in expression levels of serine/threonine (Ser/Thr) phosphatase (PP)1 and 2A in rat brain microvascular endothelial cells (RBMECs) of BTB model. In addition, PKC-ζ/PP2A signaling pathway is involved in EMAP-II-induced BTB hyperpermeability. The present study further investigated the exact roles of PPs in this process. In an in vitro BTB model, low-dose EMAP-II (0.05 nM) induced a significant increase in PP1 activity in RBMECs. There was an interaction between PKC-α/β and PP1 in RBMECs. Inhibition of PKC-α/β activity with GÖ6976 completely blocked EMAP-II-induced activation of PP1. Conversely, inhibition of PP1 activity with tautomycin had no effect on EMAP-II-induced PKC-α/β activation. Like GÖ6976, tautomycin significantly prevented EMAP-II-induced BTB hyperpermeability and MLC phosphorylation in RBMECs. Also, in this study, EMAP-II induced a marked redistribution of occludin and a significant dephosphorylation of occludin on Ser/Thr residues in RBMECs. Similar with GÖ6976 pretreatment, tautomycin pretreatment dramatically diminished EMAP-II-induced redistribution of occludin. Furthermore, pretreatment with tautomycin significantly inhibited EMAP-II-induced dephosphorylation of occludin on Ser residues. However, pretreatment with okadaic acid (an inhibitor of PP2A) significantly prevented changes in Ser-phosphorylated occludin induced by EMAP-II treatment. Collectively, this study demonstrates that low-dose EMAP-II increases BTB permeability via a RhoA/Rho kinase/PKC-α/β/PP1 signaling pathway and that PP1/PP2A-mediated Ser/Thr dephosphorylation of occludin plays an important role in EMAP-II-induced BTB hyperpermeability.
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Affiliation(s)
- Zhen Li
- Department of Neurosurgery, Shengjing Hospital, China Medical University, Shenyang, Liaoning Province, 110004, People's Republic of China
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