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Abbineni PS, Coorssen JR. Application of High-Throughput Assays to Examine Phospho-Modulation of the Late Steps of Regulated Exocytosis. High Throughput 2017; 6:ht6040017. [PMID: 29479054 PMCID: PMC5748596 DOI: 10.3390/ht6040017] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2017] [Revised: 11/01/2017] [Accepted: 11/06/2017] [Indexed: 01/19/2023] Open
Abstract
Abstract: Regulated exocytosis enables a range of physiological functions including neurotransmission, and the late steps (i.e., docking, priming and Ca2+-triggered membrane fusion) are modulated by a highly conserved set of proteins and lipids. Many of the molecular components and biochemical interactions required have been identified; the precise mechanistic steps they modulate and the biochemical interactions that need to occur across steps are still the subject of intense investigation. Particularly, although the involvement of phosphorylation in modulating exocytosis has been intensively investigated over the past three decades, it is unclear which phosphorylation events are a conserved part of the fundamental fusion mechanism and/or serve as part of the physiological fusion machine (e.g., to modulate Ca2+ sensitivity). Here, the homotypic fusion of cortical vesicles was monitored by utilizing new high-throughput, cost-effective assays to assess the influence of 17 small molecule phospho-modulators on docking/priming, Ca2+ sensitivity and membrane fusion. Specific phosphatases and casein kinase 2 are implicated in modulating the Ca2+ sensitivity of fusion, whereas sphingosine kinase is implicated in modulating the ability of vesicles to fuse. These results indicate the presence of multiple kinases and phosphatases on the vesicles and critical phosphorylation sites on vesicle membrane proteins and lipids that directly influence late steps of regulated exocytosis.
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Affiliation(s)
- Prabhodh S Abbineni
- Department of Molecular Physiology, and the WSU Molecular Medicine Research Group, School of Medicine, Western Sydney University, Campbelltown, NSW 2560, Australia.
| | - Jens R Coorssen
- Faculty of Applied Health Sciences and Faculty of Mathematics and Science, Brock University, St. Catharines, ON L2S 3A1, Canada.
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Angiotensin II induces connective tissue growth factor expression in human hepatic stellate cells by a transforming growth factor β-independent mechanism. Sci Rep 2017; 7:7841. [PMID: 28798388 PMCID: PMC5552744 DOI: 10.1038/s41598-017-08334-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2017] [Accepted: 07/11/2017] [Indexed: 02/06/2023] Open
Abstract
Angiotensin II (Ang II) promotes hepatic fibrosis by increasing extracellular matrix (ECM) synthesis. Connective tissue growth factor (CTGF) plays a crucial role in the pathogenesis of hepatic fibrosis and emerges as downstream of the profibrogenic cytokine transforming growth factor-β (TGF-β). We aimed to investigate the molecular events that lead from the Ang II receptor to CTGF upregulation in human hepatic stellate cells, a principal fibrogenic cell type. Ang II produced an early, AT1 receptor-dependent stimulation of CTGF expression and induced a rapid activation of PKC and its downstream p38 MAPK, thereby activating a nuclear factor-κB (NF-κB) and Smad2/3 cross-talk pathway. Chemical blockade of NF-κB and Smad2/3 signaling synergistically diminished Ang II-mediated CTGF induction and exhibited an additive effect in abrogating the ECM accumulation caused by Ang II. Furthermore, we demonstrated that CTGF expression was essential for Ang II-mediated ECM synthesis. Interestingly, the ability of dephosphorylated, but not phosphorylated JNK to activate Smad2/3 signaling revealed a novel role of JNK in Ang II-mediated CTGF overexpression. These results suggest that Ang II induces CTGF expression and ECM accumulation through a special TGF-β-independent interaction between the NF-κB and Smad2/3 signals elicited by the AT1/PKCα/p38 MAPK pathway.
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You T, Fan Y, Li Q, Gao Y, Yang Y, Zhao Z, Wang C. Increased SSeCKS expression in rat hepatic stellate cells upon activation in vitro and in vivo. Inflammation 2014; 36:1415-23. [PMID: 23925424 DOI: 10.1007/s10753-013-9681-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Recent reports suggest that src suppressed c kinase substrates (SSeCKS) are early inflammatory response protein. However, there is only scarce knowledge on the functional role of SSeCKS in liver under conditions of acute inflammation. In the present study, we investigated SSeCKS expression in liver after administration of carbon tetrachloride (CCl4) in rats and in isolated primary hepatic stellate cells (HSCs) upon activation on a plastic dish. We found that SSeCKS mRNA was hardly detectable in healthy liver tissue and further increased in carbon tetrachloride-mediated acute liver failure. SSeCKS protein expression was mainly found in hepatic stellate cells. In vitro, SSeCKS expression in activated rat HSCs was dramatically increased. The upregulation of SSeCKS protein expression in rat HSCs during activation in vitro and in vivo suggested the possibility of SSeCKS, an important part of function of the activated HSCs, perhaps through modulation of liver regeneration or formation of liver fibrosis after various injuries.
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Affiliation(s)
- Tiangeng You
- Department of General Surgery, Shanghai East Hospital, Tongji University School of Medicine, Shanghai, 200120, People's Republic of China
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Sun WY, Song Y, Hu SS, Wang QT, Wu HX, Chen JY, Wei W. Depletion of β-arrestin2 in hepatic stellate cells reduces cell proliferation via ERK pathway. J Cell Biochem 2013. [PMID: 23192415 DOI: 10.1002/jcb.24458] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
β-Arrestins are multifunctional adaptor proteins. Recently, some new roles of β-arrestins in regulating intracellular signaling networks have been discovered, which regulate cell growth, proliferation, and apoptosis. Though, the role of β-arrestins expression in the pathology of hepatic fibrosis remains unclear. In this study, the possible relationship between the expression of β-arrestins with the experimental hepatic fibrosis and the proliferation of hepatic stellate cells (HSCs) were investigated. Porcine serum induced liver fibrosis was established in this study. At five time points, the dynamic expression of β-arrestin1, β-arrestin2, and α-smooth muscle actin (α-SMA) in rat liver tissues, was measured by immunohistochemical staining, double immunofluorescent staining, and Western blotting. This study showed that aggravation of hepatic fibrosis with gradually increasing expression of β-arrestin2 in the hepatic tissues, but not β-arrestin1. Further, as hepatic fibrosis worsens, β-arrestin2-expressing activated HSCs accounts for an increasingly larger percentage of all activated HSCs. And the expression of β-arrestin2 had a significant positive correlation with the expression of α-SMA, an activated HSCs marker. In vitro studies, the dynamic expression of β-arrestin1 and β-arrestin2 in platelet derived growth factor-BB (PDGF-BB) stimulated HSCs was assessed by Western blotting. The expression of β-arrestin2 was remarkably increased in PDGF-BB stimulated HSCs. Furthermore, the small interfering RNA (siRNA) technique was used to explore the effect of β-arrestins on the proliferation of HSCs and the activation of ERK1/2. Transfection of siRNA targeting β-arrestin2 mRNA (siβ-arrestin2) into HSCs led to a 68% and 70% reduction of β-arrestin2 mRNA and protein expression, respectively. siβ-arrestin2 abolished the effect of PDGF-BB on the proliferation of HSCs. In addition, siβ-arrestin2 exerted the inhibition of the activation of ERK1/2 in HSCs. The present study provided strong evidence for the participation of the β-arrestin2 in the pathogenesis of hepatic fibrosis. The β-arrestin2 depletion diminishes HSCs ERK1/2 signaling and proliferation stimulated by PDGF-BB. Selective targeting of β-arrestin2 inhibitors to HSCs might present as a novel strategy for the treatment of hepatic fibrosis.
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Affiliation(s)
- Wu-Yi Sun
- Institute of Clinical Pharmacology, Anhui Medical University, Key Laboratory of Anti-inflammatory and Immunopharmacology, Ministry of Education, Engineering Technology Research Center of Anti-inflammatory and Immunodrugs in Anhui Province, Hefei, Anhui Province 230032, China
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Hattori T, Ara T, Fujinami Y. Pharmacological evidences for the stimulation of calcium-sensing receptors by nifedipine in gingival fibroblasts. J Pharmacol Pharmacother 2011; 2:30-5. [PMID: 21701644 PMCID: PMC3117567 DOI: 10.4103/0976-500x.77111] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
Abstract
OBJECTIVE To investigate pharmacologically whether CaSRs are involved in the Ca(2+) antagonist-induced [Ca(2+)]i elevation in gingival fibroblasts. MATERIALS AND METHODS Gin-1 cells, normal human gingival fibroblasts, were used as the material. The [Ca(2+)] i was measured with fura-2/AM, a Ca(2+)-sensitive fluorescent dye. RESULTS At first, we confirmed the existence of CaSRs in these cells by showing that [Ca(2+)] i was elevated by high concentrations of extracellular Ca(2+) and by prototypic agonists of the CaSR such as gentamicin. The action of gentamicin was antagonized by inhibitors of phospholipase C (PLC), inositol trisphosphate (IP(3)) receptors, NSCCs, and, importantly, by the CaSR antagonist, NPS2390. Furthermore, the action of gentamicin was potentiated by activators of PLC and protein kinase C (PKC). This confirmed the pathway components mediating Ca(2+) responses to a known agonist of the CaSR. We then investigated whether nifedipine (an L-type Ca(2+) channel blocker) stimulates CaSRs to elevate [Ca(2+)] i via a similar mechanism. Nifedipine Ca(2+) responses were dose-dependently blocked by NPS2390 and by the same inhibitors of PLC, IP(3) receptors, and NSCCs that disrupted the action of gentamicin. Calphostin C (a PKC inhibitor) and TMB-8 (an inhibitor of Ca(2+) release from stores) also inhibited the nifedipine-induced [Ca(2+)] i elevation. CONCLUSION These findings suggest that CaSRs are involved in the nifedipine-induced [Ca(2+)] i elevation in gingival fibroblasts.
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Affiliation(s)
- Toshimi Hattori
- Department of Dental Pharmacology, Matsumoto Dental University, Shiojiri 399-0781, Japan
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Ma J, Li F, Liu L, Cui D, Wu X, Jiang X, Jiang H. Raf kinase inhibitor protein inhibits cell proliferation but promotes cell migration in rat hepatic stellate cells. Liver Int 2009; 29:567-74. [PMID: 19323783 DOI: 10.1111/j.1478-3231.2009.01981.x] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
AIM Hepatic stellate cells (HSCs) play an important role in the pathogenesis of liver fibrosis and cirrhosis. Raf kinase inhibitor protein (RKIP), an inhibitor of extracellular signal-regulated kinases (ERK)/mitogen-activated protein kinase (MAPK) signalling pathway, has been proved to suppress tumor metastasis. Interestingly, RKIP promotes cell migration in Madin-Darby canine kidney epithelial cells. However, the effects of RKIP on HSC behaviours are unknown. The purpose of the present study is to investigate the role of RKIP in HSC proliferation, apoptosis and migration. METHODS Two types of cells, freshly isolated HSC and HSC-T6 cell line, were used in this study. The amount of RKIP, the phosphorylation of RKIP, Raf and ERK (pRKIP, pRaf and pERK) were analysed in quiescent and activated HSCs by Western blots. HSC-T6 cells were transfected with RKIP-expressing plasmid or treated with locostatin, a RKIP inhibitor. HSC proliferation, apoptosis and migration were evaluated with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labelling (TUNEL) staining and Transwell cell migration assay respectively. RESULTS In activated HSCs, RKIP protein expression was downregulated whereas pRKIP, pRaf and pERK were upregulated. RKIP overexpression significantly mitigated the phosphorylation of RKIP, Raf and ERK. This in turn inhibited HSC proliferation. Locostatin not only inhibited RKIP protein expression but also, to some extent, reversed the RKIP-inhibited phosphorylation of RKIP, Raf and ERK. RKIP augmented HSC migration and enhanced wound closure. Locostatin reversed the effects of RKIP. CONCLUSION Raf kinase inhibitor protein inhibits ERK/MAPK signalling and this inhibition impedes HSC proliferation. RKIP promotes HSC migration and wound closure.
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Affiliation(s)
- Junji Ma
- Department of Gastroenterology, The Second Hospital of Hebei Medical University, Hebei Key Laboratory of Gastroenterology, Hebei Institute of Gastroextenology, Hebei, China
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Saksena S, Dwivedi A, Gill RK, Singla A, Alrefai WA, Malakooti J, Ramaswamy K, Dudeja PK. PKC-dependent stimulation of the human MCT1 promoter involves transcription factor AP2. Am J Physiol Gastrointest Liver Physiol 2009; 296:G275-83. [PMID: 19033536 PMCID: PMC2643915 DOI: 10.1152/ajpgi.90503.2008] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Monocarboxylate transporter (MCT1) plays an important role in the absorption of short-chain fatty acids (SCFA) such as butyrate in the human colon. Previous studies from our laboratory have demonstrated that phorbol ester, PMA (1 microM, 24 h), upregulates butyrate transport and MCT1 protein expression in human intestinal Caco-2 cells. However, the molecular mechanisms involved in the transcriptional regulation of MCT1 gene expression by PMA in the intestine are not known. In the present study, we showed that PMA (0.1 microM, 24 h) increased the MCT1 promoter activity (-871/+91) by approximately fourfold. A corresponding increase in MCT1 mRNA abundance in response to PMA was also observed. PMA-induced stimulation of MCT1 promoter activity was observed as early as 1 h and persisted until 24 h, suggesting that the effects of PMA are attributable to initial PKC activation. Kinase inhibitor and phosphorylation studies indicated that these effects may be mediated through activation of the atypical PKC-zeta isoform. 5'-deletion studies demonstrated that the MCT1 core promoter region (-229/+91) is the PMA-responsive region. Site-directed mutagenesis studies showed the predominant involvement of potential activator protein 2 (AP2) binding site in the activation of MCT1 promoter activity by PMA. In addition, overexpression of AP2 in Caco-2 cells significantly increased MCT1 promoter activity in a dose-dependent manner. These findings showing the regulation of MCT1 promoter by PKC and AP2 are of significant importance for an understanding of the molecular regulation of SCFA absorption in the human intestine.
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Affiliation(s)
- Seema Saksena
- Department of Medicine, University of Illinois at Chicago, Chicago, IL 60612, USA.
| | - Alka Dwivedi
- Section of Digestive Diseases and Nutrition, Department of Medicine, University of Illinois at Chicago and Jesse Brown Veterans Affairs Medical Center, Chicago, Illinois
| | - Ravinder K. Gill
- Section of Digestive Diseases and Nutrition, Department of Medicine, University of Illinois at Chicago and Jesse Brown Veterans Affairs Medical Center, Chicago, Illinois
| | - Amika Singla
- Section of Digestive Diseases and Nutrition, Department of Medicine, University of Illinois at Chicago and Jesse Brown Veterans Affairs Medical Center, Chicago, Illinois
| | - Waddah A. Alrefai
- Section of Digestive Diseases and Nutrition, Department of Medicine, University of Illinois at Chicago and Jesse Brown Veterans Affairs Medical Center, Chicago, Illinois
| | - Jaleh Malakooti
- Section of Digestive Diseases and Nutrition, Department of Medicine, University of Illinois at Chicago and Jesse Brown Veterans Affairs Medical Center, Chicago, Illinois
| | - Krishnamurthy Ramaswamy
- Section of Digestive Diseases and Nutrition, Department of Medicine, University of Illinois at Chicago and Jesse Brown Veterans Affairs Medical Center, Chicago, Illinois
| | - Pradeep K. Dudeja
- Section of Digestive Diseases and Nutrition, Department of Medicine, University of Illinois at Chicago and Jesse Brown Veterans Affairs Medical Center, Chicago, Illinois
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McCarthy HS, Williams JH, Davie MW, Marshall MJ. Platelet-derived growth factor stimulates osteoprotegerin production in osteoblastic cells. J Cell Physiol 2009; 218:350-4. [DOI: 10.1002/jcp.21600] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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Rombouts K, Lottini B, Caligiuri A, Liotta F, Mello T, Carloni V, Marra F, Pinzani M. MARCKS is a downstream effector in platelet-derived growth factor-induced cell motility in activated human hepatic stellate cells. Exp Cell Res 2008; 314:1444-54. [DOI: 10.1016/j.yexcr.2008.01.029] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2007] [Revised: 01/30/2008] [Accepted: 01/30/2008] [Indexed: 10/22/2022]
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