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Steagall RJ, Yao F, Shaikh SR, Abdel-Rahman AA. Estrogen receptor α activation enhances its cell surface localization and improves myocardial redox status in ovariectomized rats. Life Sci 2017; 182:41-49. [PMID: 28599865 PMCID: PMC5535783 DOI: 10.1016/j.lfs.2017.06.005] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Revised: 05/19/2017] [Accepted: 06/05/2017] [Indexed: 12/16/2022]
Abstract
AIMS Little is known about the role of subcellular trafficking of estrogen receptor (ER) subtypes in the acute estrogen (E2)-mediated alleviation of oxidative stress. We tested the hypothesis that ERα migration to the cardiac myocyte membrane mediates the acute E2-dependent improvement of cellular redox status. MAIN METHODS Myocardial distribution of subcellular ERα, ERβ and G-protein coupled estrogen receptor (GPER) was determined in proestrus sham-operated (SO) and in ovariectomized (OVX) rats, acutely treated with E2 (1μg/kg) or a selective ERα (PPT), ERβ (DPN) or GPER (G1) agonist (10μg/kg), by immunofluorescence and Western blot. We measured ROS and malondialdehyde (MDA) levels, and catalase and superoxide dismutase (SOD) activities to evaluate myocardial antioxidant/redox status. KEY FINDINGS Compared with SO, OVX rats exhibited higher myocardial ROS and MDA levels, reduced catalase and SOD activities, along with diminished ERα, and enhanced ERβ and GPER, localization at cardiomyocyte membrane. Acute E2 or an ERα (PPT), but not ERβ (DPN) or GPER (G1), agonist reversed these responses in OVX rats and resulted in higher ERα/ERβ and ERα/GPER ratios at the cardiomyocytes membrane. PPT or DPN enhanced myocardial Akt phosphorylation. We present the first evidence that preferential aggregation of ERα at the cardiomyocytes plasma membrane is ERα-dependent, and underlies E2-mediated reduction in oxidative stress, at least partly, via the enhancements of myocardial catalase and SOD activities in OVX rats. SIGNIFICANCE The findings highlight ERα agonists as potential therapeutics for restoring the myocardial redox status following E2 depletion in postmenopausal women.
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Affiliation(s)
- Rebecca J Steagall
- Department of Pharmacology and Toxicology, Brody School of Medicine, East Carolina University, Greenville, NC 27834, USA
| | - Fanrong Yao
- Department of Pharmacology and Toxicology, Brody School of Medicine, East Carolina University, Greenville, NC 27834, USA
| | - Saame Raza Shaikh
- Department of Biochemistry and Molecular Biology, East Carolina Diabetes & Obesity Institute, Brody School of Medicine, East Carolina University, Greenville, NC 27834, USA
| | - Abdel A Abdel-Rahman
- Department of Pharmacology and Toxicology, Brody School of Medicine, East Carolina University, Greenville, NC 27834, USA.
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Jana S, Patel D, Patel S, Upadhyay K, Thadani J, Mandal R, Das S, Devkar R. Anthocyanin rich extract of Brassica oleracea L. alleviates experimentally induced myocardial infarction. PLoS One 2017; 12:e0182137. [PMID: 28763488 PMCID: PMC5538674 DOI: 10.1371/journal.pone.0182137] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2017] [Accepted: 07/12/2017] [Indexed: 11/18/2022] Open
Abstract
Cardioprotective potential of anthocyanin rich red cabbage extract (ARCE) was assessed in H2O2 treated rat neonatal cardiomyoblasts (H9c2 cells) and isoproterenol (ISO) induced rodent model of myocardial infarction. H2O2 treated H9c2 cells recorded cytotoxicity (48–50%) and apoptosis (57.3%), the same were reduced in presence of ARCE (7–10% & 12.3% respectively). Rats pretreated with ARCE for 30 days followed by ISO treatment recorded favourable heart: body weight ratio as compared to ISO treated group. Also, the mRNA levels of enzymatic antioxidants (sod and catalase) and apoptotic genes (bax and bcl-2) in ARCE+ISO treated group were similar to the control group suggesting that ARCE pretreatment prevents ISO induced depletion of enzymatic antioxidants and apoptosis. Histoarchitecture of ventricular tissue of ISO treated group was marked by infracted areas (10%) and derangement of myocardium whereas, ARCE+ISO treated group (4.5%) recorded results comparable to control (0%). ARCE+ISO treated group accounted for upregulation of caveolin-3 and SERCA2a expression as compared to the ISO treated group implying towards ARCE mediated reduction in membrane damage and calcium imbalance. Molecular docking scores and LigPlot analysis of cyanidin-3-glucoside (-8.7 Kcal/mol) and delphinidin-3-glucoside (-8.5 Kcal/mol) showed stable hydrophobic and electrostatic interactions with β1 adrenergic receptor. Overall this study elucidates the mechanism of ARCE mediated prevention of experimentally induced myocardial damage.
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Affiliation(s)
- Sarmita Jana
- Phytotherapeutics and Metabolic Endocrinology Division, Department of Zoology, Faculty of Science, The M.S. University of Baroda, Vadodara, India
| | - Dipak Patel
- Phytotherapeutics and Metabolic Endocrinology Division, Department of Zoology, Faculty of Science, The M.S. University of Baroda, Vadodara, India
- Ecotoxicology lab, Jai Research Foundation, Vapi, India
| | - Shweta Patel
- Phytotherapeutics and Metabolic Endocrinology Division, Department of Zoology, Faculty of Science, The M.S. University of Baroda, Vadodara, India
| | - Kapil Upadhyay
- Phytotherapeutics and Metabolic Endocrinology Division, Department of Zoology, Faculty of Science, The M.S. University of Baroda, Vadodara, India
| | - Jaymesh Thadani
- Phytotherapeutics and Metabolic Endocrinology Division, Department of Zoology, Faculty of Science, The M.S. University of Baroda, Vadodara, India
| | - Rahul Mandal
- Biomedical Informatics centre, National Institute of Cholera and Enteric Diseases, Kolkata, India
| | - Santasabuj Das
- Biomedical Informatics centre, National Institute of Cholera and Enteric Diseases, Kolkata, India
| | - Ranjitsinh Devkar
- Phytotherapeutics and Metabolic Endocrinology Division, Department of Zoology, Faculty of Science, The M.S. University of Baroda, Vadodara, India
- * E-mail:
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Murfitt L, Whiteley G, Iqbal MM, Kitmitto A. Targeting caveolin-3 for the treatment of diabetic cardiomyopathy. Pharmacol Ther 2015; 151:50-71. [PMID: 25779609 DOI: 10.1016/j.pharmthera.2015.03.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2015] [Accepted: 03/09/2015] [Indexed: 12/21/2022]
Abstract
Diabetes is a global health problem with more than 550 million people predicted to be diabetic by 2030. A major complication of diabetes is cardiovascular disease, which accounts for over two-thirds of mortality and morbidity in diabetic patients. This increased risk has led to the definition of a diabetic cardiomyopathy phenotype characterised by early left ventricular dysfunction with normal ejection fraction. Here we review the aetiology of diabetic cardiomyopathy and explore the involvement of the protein caveolin-3 (Cav3). Cav3 forms part of a complex mechanism regulating insulin signalling and glucose uptake, processes that are impaired in diabetes. Further, Cav3 is key for stabilisation and trafficking of cardiac ion channels to the plasma membrane and so contributes to the cardiac action potential shape and duration. In addition, Cav3 has direct and indirect interactions with proteins involved in excitation-contraction coupling and so has the potential to influence cardiac contractility. Significantly, both impaired contractility and rhythm disturbances are hallmarks of diabetic cardiomyopathy. We review here how changes to Cav3 expression levels and altered relationships with interacting partners may be contributory factors to several of the pathological features identified in diabetic cardiomyopathy. Finally, the review concludes by considering ways in which levels of Cav3 may be manipulated in order to develop novel therapeutic approaches for treating diabetic cardiomyopathy.
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Affiliation(s)
- Lucy Murfitt
- Institute of Cardiovascular Sciences, Faculty of Medical and Human Sciences, University of Manchester, M13 9NT, UK
| | - Gareth Whiteley
- Institute of Cardiovascular Sciences, Faculty of Medical and Human Sciences, University of Manchester, M13 9NT, UK
| | - Mohammad M Iqbal
- Institute of Cardiovascular Sciences, Faculty of Medical and Human Sciences, University of Manchester, M13 9NT, UK
| | - Ashraf Kitmitto
- Institute of Cardiovascular Sciences, Faculty of Medical and Human Sciences, University of Manchester, M13 9NT, UK.
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Barrientos G, Llanos P, Hidalgo J, Bolaños P, Caputo C, Riquelme A, Sánchez G, Quest AFG, Hidalgo C. Cholesterol removal from adult skeletal muscle impairs excitation-contraction coupling and aging reduces caveolin-3 and alters the expression of other triadic proteins. Front Physiol 2015; 6:105. [PMID: 25914646 PMCID: PMC4392612 DOI: 10.3389/fphys.2015.00105] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2015] [Accepted: 03/16/2015] [Indexed: 12/30/2022] Open
Abstract
Cholesterol and caveolin are integral membrane components that modulate the function/location of many cellular proteins. Skeletal muscle fibers, which have unusually high cholesterol levels in transverse tubules, express the caveolin-3 isoform but its association with transverse tubules remains contentious. Cholesterol removal impairs excitation–contraction (E–C) coupling in amphibian and mammalian fetal skeletal muscle fibers. Here, we show that treating single muscle fibers from adult mice with the cholesterol removing agent methyl-β-cyclodextrin decreased fiber cholesterol by 26%, altered the location pattern of caveolin-3 and of the voltage dependent calcium channel Cav1.1, and suppressed or reduced electrically evoked Ca2+ transients without affecting membrane integrity or causing sarcoplasmic reticulum (SR) calcium depletion. We found that transverse tubules from adult muscle and triad fractions that contain ~10% attached transverse tubules, but not SR membranes, contained caveolin-3 and Cav1.1; both proteins partitioned into detergent-resistant membrane fractions highly enriched in cholesterol. Aging entails significant deterioration of skeletal muscle function. We found that triad fractions from aged rats had similar cholesterol and RyR1 protein levels compared to triads from young rats, but had lower caveolin-3 and glyceraldehyde 3-phosphate dehydrogenase and increased Na+/K+-ATPase protein levels. Both triad fractions had comparable NADPH oxidase (NOX) activity and protein content of NOX2 subunits (p47phox and gp91phox), implying that NOX activity does not increase during aging. These findings show that partial cholesterol removal impairs E–C coupling and alters caveolin-3 and Cav1.1 location pattern, and that aging reduces caveolin-3 protein content and modifies the expression of other triadic proteins. We discuss the possible implications of these findings for skeletal muscle function in young and aged animals.
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Affiliation(s)
- Genaro Barrientos
- Physiology and Biophysics Program, Institute of Biomedical Sciences, School of Medicine, University of Chile Santiago, Chile
| | - Paola Llanos
- Institute for Research in Dental Sciences, Faculty of Dentistry, University of Chile Santiago, Chile
| | - Jorge Hidalgo
- Physiology and Biophysics Program, Institute of Biomedical Sciences, School of Medicine, University of Chile Santiago, Chile
| | - Pura Bolaños
- Centre of Biophysics and Biochemistry, Venezuelan Institute for Scientific Research Caracas, Venezuela
| | - Carlo Caputo
- Centre of Biophysics and Biochemistry, Venezuelan Institute for Scientific Research Caracas, Venezuela
| | - Alexander Riquelme
- Biomedical Neuroscience Institute, School of Medicine, University of Chile Santiago, Chile
| | - Gina Sánchez
- Biomedical Neuroscience Institute, School of Medicine, University of Chile Santiago, Chile ; Pathophysiology Program, Institute of Biomedical Sciences, School of Medicine, University of Chile Santiago, Chile ; Center for Molecular Studies of the Cell, School of Medicine, University of Chile Santiago, Chile
| | - Andrew F G Quest
- Center for Molecular Studies of the Cell, School of Medicine, University of Chile Santiago, Chile ; Laboratory of Cell Communication, Program in Cell and Molecular Biology, Institute of Biomedical Sciences, School of Medicine, University of Chile Santiago, Chile ; Advanced Center for Chronic Diseases and Network for Metabolic Stress Signaling, University of Chile Santiago, Chile
| | - Cecilia Hidalgo
- Physiology and Biophysics Program, Institute of Biomedical Sciences, School of Medicine, University of Chile Santiago, Chile ; Biomedical Neuroscience Institute, School of Medicine, University of Chile Santiago, Chile ; Center for Molecular Studies of the Cell, School of Medicine, University of Chile Santiago, Chile
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Vitadello M, Gherardini J, Gorza L. The stress protein/chaperone Grp94 counteracts muscle disuse atrophy by stabilizing subsarcolemmal neuronal nitric oxide synthase. Antioxid Redox Signal 2014; 20:2479-96. [PMID: 24093939 PMCID: PMC4025603 DOI: 10.1089/ars.2012.4794] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
AIMS Redox and growth-factor imbalance fosters muscle disuse atrophy. Since the endoplasmic-reticulum chaperone Grp94 is required for folding insulin-like growth factors (IGFs) and for antioxidant cytoprotection, we investigated its involvement in muscle mass loss due to inactivity. RESULTS Rat soleus muscles were transfected in vivo and analyzed after 7 days of hindlimb unloading, an experimental model of muscle disuse atrophy, or standard caging. Increased muscle protein carbonylation and decreased Grp94 protein levels (p<0.05) characterized atrophic unloaded solei. Recombinant Grp94 expression significantly reduced atrophy of transfected myofibers, compared with untransfected and empty-vector transfected ones (p<0.01), and decreased the percentage of carbonylated myofibers (p=0.001). Conversely, expression of two different N-terminal deleted Grp94 species did not attenuate myofiber atrophy. No change in myofiber trophism was detected in transfected ambulatory solei. The absence of effects on atrophic untransfected myofibers excluded a major role for IGFs folded by recombinant Grp94. Immunoprecipitation and confocal microscopy assays to investigate chaperone interaction with muscle atrophy regulators identified 160 kDa neuronal nitric oxide synthase (nNOS) as a new Grp94 partner. Unloading was demonstrated to untether nNOS from myofiber subsarcolemma; here, we show that such nNOS localization, revealed by means of NADPH-diaphorase histochemistry, appeared preserved in unloaded myofibers expressing recombinant Grp94, compared to those transfected with the empty vector or deleted Grp94 cDNA (p<0.02). INNOVATION Grp94 interacts with nNOS and prevents its untethering from sarcolemma in unloaded myofibers. CONCLUSION Maintenance of Grp94 expression is sufficient to counter unloading atrophy and oxidative stress by mechanistically stabilizing nNOS-multiprotein complex at the myofiber sarcolemma.
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Whiteley G, Collins RF, Kitmitto A. Characterization of the molecular architecture of human caveolin-3 and interaction with the skeletal muscle ryanodine receptor. J Biol Chem 2012; 287:40302-16. [PMID: 23071107 PMCID: PMC3504746 DOI: 10.1074/jbc.m112.377085] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Caveolin-3 (cav-3), an integral membrane protein, is a building block of caveolae as well as a regulator of a number of physiological processes by facilitating the formation of multiprotein signaling complexes. We report that the expression of cav-3 in insect (Sf9) cells induces caveola formation, comparable in size with those observed in native tissue. We have also purified the recombinant cav-3 determining that it forms an oligomer of ∼220 kDa. We present the first three-dimensional structure for cav-3 (using transmission electron microscopy and single particle analysis methods) and show that nine cav-3 monomers assemble to form a complex that is toroidal in shape, ∼16.5 nm in diameter and ∼ 5.5 nm in height. Labeling experiments and reconstitution of the purified cav-3 into liposomes have allowed a proposal for the orientation of the protein with respect to the membrane. We have identified multiple caveolin-binding motifs within the ryanodine receptor (RyR1) sequence employing a bioinformatic analysis. We have then shown experimentally that there is a direct interaction between recombinant cav-3 nonamers and purified RyR1 homotetramers that would imply that at least one of the predicted cav-3-binding sites is exposed within the fully assembled RyR1 structure. The cav-3 three-dimensional model provides new insights as to how a cav-3 oligomer can bind multiple partners in close proximity to form signaling complexes. Furthermore, a direct interaction with RyR1 suggests a possible role for cav-3 as a modifier of muscle excitation-contraction coupling and/or for localization of the receptor to regions of the sarcoplasmic reticulum.
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Affiliation(s)
- Gareth Whiteley
- School of Biomedicine, Cardiovascular Group, Faculty of Medical and Human Sciences, University of Manchester, Manchester M13 9NT, UK
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Dolganiuc A. Role of lipid rafts in liver health and disease. World J Gastroenterol 2011; 17:2520-35. [PMID: 21633657 PMCID: PMC3103810 DOI: 10.3748/wjg.v17.i20.2520] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/06/2011] [Revised: 02/24/2011] [Accepted: 03/03/2011] [Indexed: 02/06/2023] Open
Abstract
Liver diseases are an increasingly common cause of morbidity and mortality; new approaches for investigation of mechanisms of liver diseases and identification of therapeutic targets are emergent. Lipid rafts (LRs) are specialized domains of cellular membranes that are enriched in saturated lipids; they are small, mobile, and are key components of cellular architecture, protein partition to cellular membranes, and signaling events. LRs have been identified in the membranes of all liver cells, parenchymal and non-parenchymal; more importantly, LRs are active participants in multiple physiological and pathological conditions in individual types of liver cells. This article aims to review experimental-based evidence with regard to LRs in the liver, from the perspective of the liver as a whole organ composed of a multitude of cell types. We have gathered up-to-date information related to the role of LRs in individual types of liver cells, in liver health and diseases, and identified the possibilities of LR-dependent therapeutic targets in liver diseases.
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Vassilopoulos S, Oddoux S, Groh S, Cacheux M, Fauré J, Brocard J, Campbell KP, Marty I. Caveolin 3 is associated with the calcium release complex and is modified via in vivo triadin modification. Biochemistry 2010; 49:6130-5. [PMID: 20565104 PMCID: PMC2907096 DOI: 10.1021/bi100796v] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The triadin isoforms Trisk 95 and Trisk 51 are both components of the skeletal muscle calcium release complex. To investigate the specific role of Trisk 95 and Trisk 51 isoforms in muscle physiology, we overexpressed Trisk 95 or Trisk 51 using adenovirus-mediated gene transfer in skeletal muscle of newborn mice. Overexpression of either Trisk 95 or Trisk 51 alters the muscle fiber morphology, while leaving unchanged the expression of the ryanodine receptor, the dihydropyridine receptor, and calsequestrin. We also observe an aberrant expression of caveolin 3 in both Trisk 95- and Trisk 51-overexpressing skeletal muscles. Using a biochemical approach, we demonstrate that caveolin 3 is associated with the calcium release complex in skeletal muscle. Taking advantage of muscle and non-muscle cell culture models and triadin null mouse skeletal muscle, we further dissect the molecular organization of the caveolin 3-containing calcium release complex. Our data demonstrate that the association of caveolin 3 with the calcium release complex occurs via a direct interaction with the transmembrane domain of the ryanodine receptor. Taken together, these data suggest that caveolin 3-containing membrane domains and the calcium release complex are functionally linked and that Trisk 95 and Trisk 51 are instrumental to the regulation of this interaction, the integrity of which may be crucial for muscle physiology.
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Affiliation(s)
- Stéphane Vassilopoulos
- INSERM U836, Grenoble Institut des Neurosciences, Equipe Muscle et Pathologies, Grenoble, France
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Wang J, Wu G, Miyagi T, Lu ZH, Ledeen RW. Sialidase occurs in both membranes of the nuclear envelope and hydrolyzes endogenous GD1a. J Neurochem 2009; 111:547-54. [DOI: 10.1111/j.1471-4159.2009.06339.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
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Kaakinen M, Papponen H, Metsikkö K. Microdomains of endoplasmic reticulum within the sarcoplasmic reticulum of skeletal myofibers. Exp Cell Res 2007; 314:237-45. [PMID: 17999928 DOI: 10.1016/j.yexcr.2007.10.009] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2007] [Revised: 09/14/2007] [Accepted: 10/06/2007] [Indexed: 10/22/2022]
Abstract
The relationship between the endoplasmic reticulum (ER) and the sarcoplasmic reticulum (SR) of skeletal muscle cells has remained obscure. In this study, we found that ER- and SR-specific membrane proteins exhibited diverse solubility properties when extracted with mild detergents. Accordingly, the major SR-specific protein Ca(2+)-ATPase (SERCA) remained insoluble in Brij 58 and floated in sucrose gradients while typical ER proteins were partially or fully soluble. Sphingomyelinase treatment rendered SERCA soluble in Brij 58. Immunofluorescence staining for resident ER proteins revealed dispersed dots over I bands contrasting the continuous staining pattern of SERCA. Infection of isolated myofibers with enveloped viruses indicated that interfibrillar protein synthesis occurred. Furthermore, we found that GFP-tagged Dad1, able to incorporate into the oligosaccharyltransferase complex, showed the dot-like structures but the fusion protein was also present in membranes over the Z lines. This behaviour mimics that of cargo proteins that accumulated over the Z lines when blocked in the ER. Taken together, the results suggest that resident ER proteins comprised Brij 58-soluble microdomains within the insoluble SR membrane. After synthesis and folding in the ER-microdomains, cargo proteins and non-incorporated GFP-Dad1 diffused into the Z line-flanking compartment which likely represents the ER exit sites.
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Affiliation(s)
- Mika Kaakinen
- Department of Anatomy and Cell Biology, P.O. Box 5000 (Aapistie 7), FIN-90014 University of Oulu, Finland
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Nagata J, Guerra MT, Shugrue CA, Gomes DA, Nagata N, Nathanson MH. Lipid rafts establish calcium waves in hepatocytes. Gastroenterology 2007; 133:256-67. [PMID: 17631147 PMCID: PMC2825880 DOI: 10.1053/j.gastro.2007.03.115] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/10/2007] [Accepted: 03/22/2007] [Indexed: 01/09/2023]
Abstract
BACKGROUND & AIMS Polarity is critical for hepatocyte function. Ca(2+) waves are polarized in hepatocytes because the inositol 1,4,5-trisphosphate receptor (InsP3R) is concentrated in the pericanalicular region, but the basis for this localization is unknown. We examined whether pericanalicular localization of the InsP3R and its action to trigger Ca(2+) waves depends on lipid rafts. METHODS Experiments were performed using isolated rat hepatocyte couplets and pancreatic acini, plus SkHep1 cells as nonpolarized controls. The cholesterol depleting agent methyl-beta-cyclodextrin (mbetaCD) was used to disrupt lipid rafts. InsP3R isoforms were examined by immunoblot and immunofluorescence. Ca(2+) waves were examined by confocal microscopy. RESULTS Type II InsP3Rs initially were localized to only some endoplasmic reticulum fractions in hepatocytes, but redistributed into all fractions in mbetaCD-treated cells. This InsP3R isoform was concentrated in the pericanalicular region, but redistributed throughout the cell after mbetaCD treatment. Vasopressin-induced Ca(2+) signals began as apical-to-basal Ca(2+) waves, and mbetaCD slowed the wave speed and prolonged the rise time. MbetaCD had a similar effect on Ca(2+) waves in acinar cells but did not affect Ca(2+) signals in SkHep1 cells, suggesting that cholesterol depletion has similar effects among polarized epithelia, but this is not a nonspecific effect of mbetaCD. CONCLUSIONS Lipid rafts are responsible for the pericanalicular accumulation of InsP3R in hepatocytes, and for the polarized Ca(2+) waves that result. Signaling microdomains exist not only in the plasma membrane, but also in the nearby endoplasmic reticulum, which in turn, helps establish and maintain structural and functional polarity.
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Affiliation(s)
- Jun Nagata
- Section of Digestive Diseases, Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut 06520-8019, USA
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Krasteva G, Pfeil U, Filip AM, Lips KS, Kummer W, König P. Caveolin-3 and eNOS colocalize and interact in ciliated airway epithelial cells in the rat. Int J Biochem Cell Biol 2006; 39:615-25. [PMID: 17123860 DOI: 10.1016/j.biocel.2006.10.019] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2006] [Revised: 10/11/2006] [Accepted: 10/16/2006] [Indexed: 12/21/2022]
Abstract
In ciliated airway epithelial cells endothelial nitric oxide synthase as well as several other membrane bound proteins are located in the apical cell pole. To date, mechanisms that serve to target and to keep these proteins in this region are unknown. Endothelial nitric oxide synthase is known to target to caveolae by interaction with caveolin-1 or caveolin-3. Since caveolin-1 is found only in a subpopulation of ciliated cells at the basolateral cell membrane, we examined if caveolin-3 could be responsible for the apical localization of endothelial nitric oxide synthase in ciliated cells. We used real-time RT-PCR, laser-assisted microdissection, Western blotting and double-labeling immunohistochemistry to examine the presence of caveolin-3 in the airway epithelium of the rat. Indeed, we found caveolin-3-mRNA as well as protein in ciliated cells throughout the trachea and the bronchial tree. Caveolin-3-immunoreactivity was confined to the apical region and was colocalized with endothelial nitric oxide synthase and the high affinity choline transporter in a compartment distinct from the plasma membrane at the light microscopic level. No caveolae were found in the apical plasma membrane of ciliated cells but a tubulovesicular network was present in the apical region that reached up to the basal bodies of the cilia and was in close contact with mitochondria. Co-immunoprecipitation of caveolin-3 with endothelial nitric oxide synthase verified that both proteins interact in airway ciliated cells. These findings indicate that caveolin-3 is responsible to keep endothelial nitric oxide synthase in a membrane compartment in the apical region of ciliated cells.
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Affiliation(s)
- Gabriela Krasteva
- Institut für Anatomie und Zellbiologie, Justus-Liebig-Universität Giessen, Germany
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