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VEGF/VEGFR-2 system exerts neuroprotection against Phoneutria nigriventer spider envenomation through PI3K-AKT-dependent pathway. Toxicon 2020; 185:76-90. [PMID: 32649934 DOI: 10.1016/j.toxicon.2020.06.019] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2019] [Revised: 06/23/2020] [Accepted: 06/23/2020] [Indexed: 01/19/2023]
Abstract
This study was undertaken to elucidate why VEGF/VEGFR-2 is elevated in the hippocampus of rats injected with Phoneutria nigriventer spider venom (PNV). PNV delays Na+ channels inactivation; blocks Ca2+ and K+ channels, increases glutamate release, causes blood-brain breakdown (BBBb), brain edema and severe excitotoxicity. Analytical FT-IR spectroscopy showed profound alteration in molecular biochemical state, with evidences for VEGFR-2 (KDR/Flk-1) signaling mediation. By blocking VEGF/VEGFR-2 binding via pre-treatment with itraconazole we demonstrated that animals' condition was deteriorated soon at 1-2 h post-PNV exposure concurrently with decreased expression of VEGF, BBB-associated proteins, ZO-1, β-catenin, laminin, P-gp (P-glycoprotein), Neu-N (neuron's viability marker) and MAPKphosphorylated-p38, while phosphorylated-ERK and Src pathways were increased. At 5 h and coinciding with incipient signs of animals' recuperation, the proteins associated with protection (HIF-1α, VEGF, VEGFR-1, VEGFR-2, Neu-N, occludin, β-catenin, laminin, P-gp efflux protein, phosphorylated-p38) increased thus indicating p38 pathway activation together with paracellular route strengthening. However, the BBB transcellular trafficking and caspase-3 increased (pro-apoptotic pathway activation). At 24 h, the transcellular route reestablished physiological state but the pro-survival pathway PI3K/(p-Akt) dropped in animals underwent VEGF/VEGFR-2 binding inhibition, whereas it was significantly activated at matched interval in PNV group without prior itraconazole; these results demonstrate impaired VEGF' survival effects at 24 h. The inhibition of VEGF/VEGFR-2 binding identified 5 h as turning point at which multi-level dynamic interplay was elicited to reverse hippocampal damage. Collectively, the data confirmed VEGFR-2 signaling via serine-threonine kinase Akt as neuroprotective pathway against PNV-induced damage. Further studies are needed to elucidate mechanisms underlying PNV effects.
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2
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Harding IC, Mitra R, Mensah SA, Herman IM, Ebong EE. Pro-atherosclerotic disturbed flow disrupts caveolin-1 expression, localization, and function via glycocalyx degradation. J Transl Med 2018; 16:364. [PMID: 30563532 PMCID: PMC6299559 DOI: 10.1186/s12967-018-1721-2] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2018] [Accepted: 12/04/2018] [Indexed: 12/18/2022] Open
Abstract
BACKGROUND Endothelial-dependent atherosclerosis develops in a non-random pattern in regions of vessel bending and bifurcations, where blood flow exhibits disturbed flow (DF) patterns. In contrast, uniform flow (UF), normal endothelium, and healthy vessel walls co-exist within straight vessels. In clarifying how flow protectively or atherogenically regulates endothelial cell behavior, involvement of the endothelial surface glycocalyx has been suggested due to reduced expression in regions of atherosclerosis development. Here, we hypothesized that pro-atherosclerotic endothelial dysfunction occurs as a result of DF-induced reduction in glycocalyx expression and subsequently impairs endothelial sensitivity to flow. Specifically, we propose that glycocalyx degradation can induce pro-atherosclerotic endothelial dysfunction through decreased caveolin-1 and endothelial nitric oxide synthase expression and localization. METHODS We studied endothelial cells in atherosclerotic-prone DF and atherosclerotic-resistant UF conditions in parallel plate flow culture and in C57Bl/6 mice. The effects of flow conditioning on endothelial cell behavior were quantified using immunocytochemistry. The glycocalyx was fluorescently labeled for wheat germ agglutinin, which serves as a general glycocalyx label, and heparan sulfate, a major glycocalyx component. Additionally, mechanosensitivity was assessed by immunocytochemical fluorescence expression and function of caveolin-1, the protein that forms the mechanosignaling caveolar invaginations on the endothelial surface, total endothelial-type nitric oxide synthase (eNOS), which synthesizes nitric oxide, and serine 1177 phosphorylated eNOS (eNOS-pS1177), which is the active form of eNOS. Caveolin function and eNOS expression and activation were correlated to glycocalyx expression. Heparinase III enzyme was used to degrade a major glycocalyx component, HS, to identify the role of the glycocalyx in caveoin-1 and eNOS-pS1177 regulation. RESULTS Results confirmed that DF reduces caveolin-1 expression and abolishes most of its subcellular localization preferences, when compared to the effect of UF. DF down-regulates caveolin-1 mechanosignaling, as indicated by its reduced colocalization with serine 1177 phosphorylated endothelial-type nitric oxide synthase (eNOS-pS1177), a vasoregulatory signaling molecule whose activity is regulated by its residence in caveolae. As expected, DF inhibited glycocalyx expression compared to UF. In the absence of heparan sulfate, a major glycocalyx component, UF-conditioned endothelial cells exhibited near DF-like caveolin-1 expression, localization, and colocalization with eNOS-pS1177. CONCLUSIONS This is the first demonstration of a flow-defined role of the glycocalyx in caveolae expression and function related to vasculoprotective endothelial mechanosensitivity that defends against atherosclerosis. The results suggest that a glycocalyx-based therapeutic targeted to areas of atherosclerosis development could prevent disease initiation and progression.
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Affiliation(s)
- Ian C Harding
- Department of Bioengineering, Northeastern University, Boston, MA, USA
| | - Ronodeep Mitra
- Department of Chemical Engineering, Northeastern University, Boston, MA, 02115, USA
| | - Solomon A Mensah
- Department of Bioengineering, Northeastern University, Boston, MA, USA
| | - Ira M Herman
- Department of Developmental, Molecular, and Chemical Biology, Tufts Sackler School of Graduate Biomedical Sciences, Boston, MA, USA.,Center for Innovations in Wound Healing Research, Tufts University School of Medicine, Boston, MA, USA
| | - Eno E Ebong
- Department of Bioengineering, Northeastern University, Boston, MA, USA. .,Department of Chemical Engineering, Northeastern University, Boston, MA, 02115, USA. .,Department of Neuroscience, Albert Einstein College of Medicine, New York, NY, USA.
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Goonasekara CL, Balse E, Hatem S, Steele DF, Fedida D. Cholesterol and cardiac arrhythmias. Expert Rev Cardiovasc Ther 2014; 8:965-79. [DOI: 10.1586/erc.10.79] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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4
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Prinetti A, Prioni S, Loberto N, Aureli M, Nocco V, Illuzzi G, Mauri L, Valsecchi M, Chigorno V, Sonnino S. Aberrant glycosphingolipid expression and membrane organization in tumor cells: consequences on tumor-host interactions. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2011; 705:643-67. [PMID: 21618134 DOI: 10.1007/978-1-4419-7877-6_34] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Alessandro Prinetti
- Department of Medical Chemistry, Biochemistry and Biotechnology, Center of Excellence on Neurodegenerative Diseases, University of Milan, Via Fratelli Cervi 93, 20090 Segrate, Milano, Italy.
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Xu Y, Henning RH, Sandovici M, van der Want JJ, van Gilst WH, Buikema H. Enhanced myogenic constriction of mesenteric artery in heart failure relates to decreased smooth muscle cell caveolae numbers and altered AT1- and epidermal growth factor-receptor function. Eur J Heart Fail 2009; 11:246-55. [PMID: 19147448 DOI: 10.1093/eurjhf/hfn027] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
AIMS We previously showed that enhanced myogenic constriction (MC) of peripheral resistance arteries involves active AT(1) receptors in chronic heart failure (CHF). Recent data suggest both transactivation of EGF receptors and caveolae-like microdomains to be implicated in the activity of AT(1) receptors. Thus, we assessed their roles in increased MC in mesenteric arteries of CHF rats. METHODS AND RESULTS Male Wistar rats underwent myocardial infarction to induce CHF and were sacrificed after 12 weeks. The number of caveolae in smooth muscle cells (SMC) of mesenteric arteries of CHF rats was decreased by 43.6 +/- 4.0%, this was accompanied by increased MC, which was fully normalized to the level of sham by antagonists of the AT(1)-receptor (losartan) or EGF-receptor (AG1478). Acute disruption of caveolae in sham rats affected caveolae numbers and MC to a similar extent as CHF, however MC was only reversed by the antagonist of the EGF-receptor, but not by the AT(1)-receptor antagonist. Further, in sham rats, MC was increased by a sub-threshold concentration of angiotensin II and reversed by both AT(1)- as well as EGF-receptor inhibition. In contrast, increased MC by a sub-threshold concentration of EGF was only reversed by EGF receptor inhibition. CONCLUSION These findings provide the first evidence that decreased SMC caveolae numbers are involved in enhanced MC in small mesenteric arteries, by affecting AT(1)- and EGF-receptor function. This suggests a novel mechanism involved in increased peripheral resistance in CHF.
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Affiliation(s)
- Ying Xu
- Department of Clinical Pharmacology, Groningen University Institute for Drug Exploration (GUIDE), University Medical Center Groningen, University of Groningen, Groningen, the Netherlands.
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Xu Y, Buikema H, van Gilst WH, Henning RH. Caveolae and endothelial dysfunction: filling the caves in cardiovascular disease. Eur J Pharmacol 2008; 585:256-60. [PMID: 18423600 DOI: 10.1016/j.ejphar.2008.02.086] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2008] [Revised: 02/04/2008] [Accepted: 02/13/2008] [Indexed: 11/27/2022]
Abstract
Discovery in the early 1990s of caveolin-1, the structural protein responsible for maintaining the ohm shape of caveolae, greatly enhanced investigations to elucidate the role of these little caves in the plasma membrane. Perhaps one of the most important realizations concerning caveolae and caveolin is that these elements play an important functional role in the modulation of cell signal transduction pathways, including those involved in endothelial nitric oxide synthase (eNOS) function. Their role was confirmed by studies with caveolin-1 knockout mice which lack caveolae and display abnormal endothelial function responses. One limitation of these knockout models, however, is that absence of the caveolin protein not only results in the lack of caveolae as a structure but also in the lack of interaction/modulation of enzymes/molecules (e.g. eNOS) to which caveolin binds (whether in- or outside caveolae). In contrast to caveolin knockout models, recent experimental findings suggest that in certain cardiovascular diseases caveolin may dissociate from caveolae to the cytosol, hence decreasing the number of caveolae without a change in the total amount of caveolin. Therefore, as the importance of defining the role of caveolins both in caveolae and in cellular regions is being highlighted, it seems also important at the same time to further define the role of caveolae per se being present in the plasma membrane as a structural entity. The objective of this review is to make an explorative tour on the role of caveolae in vascular endothelial function based on existing literature together with some preliminary experimental findings. Evidence and arguments are put forward that alterations in endothelial caveolae do occur in cardiovascular disease and may contribute to the observed endothelial dysfunction in these conditions.
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Affiliation(s)
- Ying Xu
- Department of Clinical Pharmacology, Groningen University Institute for Drug Exploration (GUIDE), University Medical Center Groningen, University of Groningen, The Netherlands
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Korade Z, Kenworthy AK. Lipid rafts, cholesterol, and the brain. Neuropharmacology 2008; 55:1265-73. [PMID: 18402986 DOI: 10.1016/j.neuropharm.2008.02.019] [Citation(s) in RCA: 221] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2007] [Revised: 02/15/2008] [Accepted: 02/26/2008] [Indexed: 01/11/2023]
Abstract
Lipid rafts are specialized membrane microdomains that serve as organizing centers for assembly of signaling molecules, influence membrane fluidity and trafficking of membrane proteins, and regulate different cellular processes such as neurotransmission and receptor trafficking. In this article, we provide an overview of current methods for studying lipid rafts and models for how lipid rafts might form and function. Next, we propose a potential mechanism for regulating lipid rafts in the brain via local control of cholesterol biosynthesis by neurotrophins and their receptors. Finally, we discuss evidence that altered cholesterol metabolism and/or lipid rafts play a critical role in the pathophysiology of multiple CNS disorders, including Smith-Lemli-Opitz syndrome, Huntington's, Alzheimer's, and Niemann-Pick Type C diseases.
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Affiliation(s)
- Zeljka Korade
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
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8
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Prinetti A, Prioni S, Loberto N, Aureli M, Chigorno V, Sonnino S. Regulation of tumor phenotypes by caveolin-1 and sphingolipid-controlled membrane signaling complexes. Biochim Biophys Acta Gen Subj 2007; 1780:585-96. [PMID: 17889439 DOI: 10.1016/j.bbagen.2007.08.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2007] [Revised: 07/26/2007] [Accepted: 08/02/2007] [Indexed: 12/11/2022]
Abstract
Aberrant (glyco)sphingolipid expression deeply affects several properties of tumor cells that are involved in tumor progression and metastasis formation: cell adhesion (to the extracellular matrix or to the endothelium of blood vessels), motility, recognition and invasion of host tissues. In particular, (glyco)sphingolipids might contribute to the modulation of integrin-dependent interactions of tumor cells (determining their adhesion, motility and invasiveness) with the extracellular matrix as well as with host cells present in the stromal compartment of the tumor. A model based on solid experimental evidence has been proposed: (glyco)sphingolipids at the cell surface interact with plasma membrane receptors (e.g., integrin receptors and growth factor receptors) and adapter molecules (including tetraspanins) forming signaling complexes that are able to influence the activity of signal transduction molecules oriented at the cytosolic surface of the plasma membrane (mainly the Src kinases pathway members). The function of these signaling complexes appears to be strictly dependent on their (glyco)sphingolipid composition, and likely on specific sphingolipid-protein interactions. From this point of view, particularly intriguing is the connection between (glyco)sphingolipids and caveolin-1, a membrane protein that plays multiple roles as a suppressor of tumor growth and metastasis in ovarian, breast and colon human carcinomas.
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Affiliation(s)
- Alessandro Prinetti
- Center of Excellence on Neurodegenerative Diseases, Department of Medical Chemistry, Biochemistry and Biotechnology, University of Milan, 20090 Segrate, Italy.
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9
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Xiao Z, Schmitz F, Pricolo VE, Biancani P, Behar J. Role of caveolae in the pathogenesis of cholesterol-induced gallbladder muscle hypomotility. Am J Physiol Gastrointest Liver Physiol 2007; 292:G1641-9. [PMID: 17307729 DOI: 10.1152/ajpgi.00495.2006] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Muscle cells from human gallbladders (GB) with cholesterol stones (ChS) exhibit a defective contraction, excess cholesterol (Ch) in the plasma membrane, and lower binding of CCK-1 receptors. These abnormalities improved after muscle cells were incubated with Ch-free liposomes that remove the excess Ch from the plasma membrane. The present studies were designed to investigate the role of caveolin-3 proteins (Cav-3) in the pathogenesis of these abnormalities. Muscle cells from GB with ChS exhibit higher Ch levels in the plasma membrane that were mostly localized in caveolae and associated with parallel increases in the expression of Cav-3 in the caveolae compared with that in GB with pigment stones (PS). The overall number of CCK-1 receptors in the plasma membrane was not different between muscle cells from GB with ChS and PS, but they were increased in the caveolae in muscle cells from GB with ChS. Treatment of muscle cells from GB with ChS with a Galpha(i3) protein fragment increased the total binding of CCK-1 receptors (from 8.3 to 11.2%) and muscle contraction induced by CCK-8 (from 11.2 to 17.3% shortening). However, Galpha(q/11) protein fragment had no such effect. Moreover, neither fragment had any effect on muscle cells from GB with PS. We conclude that the defective contraction of muscle cells with excessive Ch levels in the plasma membrane is due to an increased expression of Cav-3 that results in the sequestration of CCK-1 receptors in the caveolae, probably by inhibiting the functions of Galpha(i3) proteins.
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Affiliation(s)
- Zuoliang Xiao
- Division of Gastroenterology, APC 406, Rhode Island Hospital/Brown Univ. Medical School, 593 Eddy St., Providence, RI 02903, USA.
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10
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Akpovi CD, Yoon SR, Vitale ML, Pelletier RM. The predominance of one of the SR-BI isoforms is associated with increased esterified cholesterol levels not apoptosis in mink testis. J Lipid Res 2006; 47:2233-47. [PMID: 16861621 DOI: 10.1194/jlr.m600162-jlr200] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Scavenger receptor class B type I (SR-BI) contributes to HDL-mediated cellular cholesterol efflux and is a phagocytosis-inducing phospholipid phosphatidylserine receptor in rat Sertoli cells, whereas the spliced variant of the SR-B gene, SR-BII, is implicated in the efflux of free cholesterol in macrophages. This study aimed to assess whether spontaneous autoimmune orchitis (AIO), which causes impaired clearance of apoptotic germ cells and spermatogenic arrest, involves SR-BI, SR-BII, and/or cholesterol. The levels measured during development and the annual reproductive cycle in normal mink were compared with those in mink with spontaneous AIO. Time periods with lowest tubular esterified cholesterol (EC) levels showed maximal SR-BI and SR-BII levels, and the periods when one or the other SR-BI isoform predominated showed increased EC levels and spermatogenic arrest in normal mink seminiferous tubules. In tubules with AIO, the predominance of only one or the other SR-BI isoform was the reverse of that measured in normal tubules, and it was associated with an increase in EC levels but not with apoptosis levels. SR-BI and SR-BII levels were not correlated with serum testosterone levels. SR-BI mainly localized to the Leydig cell, germ cell, and Sertoli cell surface, where its distribution was stage-specific. SR-BII was principally intracellular. Tubules from testes with AIO showed a deregulation of cholesterol homeostasis and SR-BI expression but relatively unchanged apoptosis levels. These results suggest that the expression of both SR-BI isoforms is required for the maintenance of low EC levels and that the predominance of only one isoform is associated with the accumulation of EC but not with apoptosis in the tubules.
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Affiliation(s)
- Casimir D Akpovi
- Département de Pathologie et Biologie Cellulaire, Faculté de Médecine, Université de Montréal, Montréal, Québec, Canada
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11
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Sonnino S, Prinetti A, Mauri L, Chigorno V, Tettamanti G. Dynamic and Structural Properties of Sphingolipids as Driving Forces for the Formation of Membrane Domains. Chem Rev 2006; 106:2111-25. [PMID: 16771445 DOI: 10.1021/cr0100446] [Citation(s) in RCA: 138] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Sandro Sonnino
- Center of Excellence on Neurodegenerative Diseases, Department of Medical Chemistry, Biochemistry and Biotechnology, University of Milan, 20090 Segrate (MI), Italy.
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12
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Withers S, Cartwright EJ, Neyses L. Sperm phenotype of mice carrying a gene deletion for the plasma membrane calcium/calmodulin dependent ATPase 4. Mol Cell Endocrinol 2006; 250:93-7. [PMID: 16442703 DOI: 10.1016/j.mce.2005.12.028] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The sarcolemmal calcium pumps (PMCA for plasma membrane calcium/calmodulin dependent ATPase) are a family of 10 transmembrane domain proteins ejecting calcium from the cytosol. They are encoded by four independent genes and at least 21 splice variants have been described. Isoforms 1 and 4 are ubiquitous, whereas isoforms 2 and 3 are confined to neurons and few other cells (e.g. isoform 2 in the myocardium). In non-excitable cells they are thought to be the only calcium ejection systems and their function as governors of calcium balance is hence intuitive since cells cannot survive in a state of calcium overload. Differences in the affinity of the various isoforms for calcium, ATP and calmodulin have been described, but it is unclear whether the pumps have specialized functions over and above their 'housekeeping' role. In particular, in excitable cells, most calcium is ejected by the sodium/calcium exchanger suggesting that the PMCAs may have evolved into a specialized role. Recently, our group has identified a number of specialized functions of the PMCAs, notably a prominent regulatory role of PMCA4 (splice variant b) for neuronal NO synthase as well as for the Ras pathway. In addition, mice carrying a genetic deletion of the PMCA4 gene showed normal female, but completely infertile male animals. This is due to a highly specific defect in sperm motility, which is reduced to zero, with normal fertilization capacity. Overall, a scenario emerges where the plasma membrane calcium pumps fulfil roles far beyond the traditional housekeeping function, notably in cell signaling, sperm motility, and potentially in cell division. Consequently, we are currently exploring their potential as future drug targets for a variety of conditions, as well as their potential use in the development of a male contraception.
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Affiliation(s)
- Sarah Withers
- Division of Cardiology, University of Manchester, Room 1.302 Stopford Building, Oxford Road, Manchester M13 9PT, UK
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13
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Millán J, Hewlett L, Glyn M, Toomre D, Clark P, Ridley AJ. Lymphocyte transcellular migration occurs through recruitment of endothelial ICAM-1 to caveola- and F-actin-rich domains. Nat Cell Biol 2006; 8:113-23. [PMID: 16429128 DOI: 10.1038/ncb1356] [Citation(s) in RCA: 310] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2005] [Accepted: 11/28/2005] [Indexed: 01/13/2023]
Abstract
During inflammation, leukocytes bind to the adhesion receptors ICAM-1 and VCAM-1 on the endothelial surface before undergoing transendothelial migration, also called diapedesis. ICAM-1 is also involved in transendothelial migration, independently of its role in adhesion, but the molecular basis of this function is poorly understood. Here we demonstrate that, following clustering, apical ICAM-1 translocated to caveolin-rich membrane domains close to the ends of actin stress fibres. In these F-actin-rich areas, ICAM-1 was internalized and transcytosed to the basal plasma membrane through caveolae. Human T-lymphocytes extended pseudopodia into endothelial cells in caveolin- and F-actin-enriched areas, induced local translocation of ICAM-1 and caveolin-1 to the endothelial basal membrane and transmigrated through transcellular passages formed by a ring of F-actin and caveolae. Reduction of caveolin-1 levels using RNA interference (RNAi) specifically decreased lymphocyte transcellular transmigration. We propose that the translocation of ICAM-1 to caveola- and F-actin-rich domains links the sequential steps of lymphocyte adhesion and transendothelial migration and facilitates lymphocyte migration through endothelial cells from capillaries into surrounding tissue.
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Affiliation(s)
- Jaime Millán
- Ludwig Institute for Cancer Research, Royal Free and University College School of Medicine, 91 Riding House Street, London W1W 7BS, UK
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Tosi MR, Tugnoli V. Cholesteryl esters in malignancy. Clin Chim Acta 2005; 359:27-45. [PMID: 15939411 DOI: 10.1016/j.cccn.2005.04.003] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2005] [Revised: 03/31/2005] [Accepted: 04/04/2005] [Indexed: 01/23/2023]
Abstract
Cholesteryl esters, formed by the esterification of cholesterol with long-chain fatty acids, on one hand, are the means by which cholesterol is transported through the blood by lipoproteins, on the other, the way cholesterol itself can be accumulated in the cells. Therefore, these important molecules play an active part in metabolic pathways that form the basis of cholesterol trafficking and homeostasis. The role of different regulatory mechanisms in cholesterol homeostasis in physiologic and neoplastic conditions with emphasis on intracellular content of cholesteryl esters is here reviewed. Numerous studies carried out on tumor cell lines, experimental tumors, and human tumors have shown an abnormal cholesterol metabolism that is reflected by an increase in intracellular cholesteryl esters due to an alteration in all the mechanisms that form the basis of regulation, in particular: cholesterol de novo biosynthesis; uptake of exogenous cholesterol LDL receptor mediated; cholesterol esterification mediated by the ACAT activity; cholesterol efflux HDL receptor mediated. The most recent analytic-spectroscopic applications that permit cholesteryl ester determination on tumor lipidic extracts and directly in vivo are also reported. This review gives an overview of cholesterol homeostasis in physiological and pathological conditions where cholesteryl esters are over-expressed.
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Affiliation(s)
- Maria R Tosi
- ITOI-CNR, presso IOR, via di Barbiano 1/10, 40136, Bologna, Italy.
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15
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Ramos M, Lamé MW, Segall HJ, Wilson DW. The BMP type II receptor is located in lipid rafts, including caveolae, of pulmonary endothelium in vivo and in vitro. Vascul Pharmacol 2005; 44:50-9. [PMID: 16271518 DOI: 10.1016/j.vph.2005.09.007] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2005] [Revised: 08/23/2005] [Accepted: 09/28/2005] [Indexed: 11/21/2022]
Abstract
Polymorphic mutations in the Bone Morphogenetic Protein type II receptor (BMPrII) gene have been implicated in the development of familial primary pulmonary hypertension (PPH) however, the role BMPrII mutations play in the development of PH has not yet been elucidated. Endothelial caveolae are an important domain of hemodynamics containing eNOS, the serotonin transporter, and endothelin receptors. In this study we show by standard immunohistochemistry (IHC) that BMPrII is widely distributed in the vasculature of the rat lung, and more specifically distributed to both apical and basal membranes of the arteriolar endothelium by fluorescent IHC. We also examined compartmentalization of BMPrII in lipid fractions of plasma membranes isolated by silica based extraction from human pulmonary artery endothelial cells and rat lung endothelium. Density gradient centrifugation demonstrated BMPrII in separate caveolin-1 (cav-1) and non-cav-1 lipid rich fractions. Electron microscopy co-localized cav-1 and BMPrII in flask shaped membrane fragments. Three-dimensional fluorescence microscopy demonstrated BMPrII in discrete membrane foci, a portion of which were co-localized with cav-1, as well as in Golgi. Our findings indicate that BMPrII is located within lipid-dense fractions of pulmonary endothelial cell membranes with a portion present in caveolae suggesting potential dynamic regulatory structural relationships.
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Affiliation(s)
- M Ramos
- Department of Veterinary Medicine: Pathology, Immunology, Microbiology, One Shields Avenue, 1044 Haring Hall, University of California, Davis, Davis, California 95616-8617, United States.
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Chao WT, Tsai SH, Lin YC, Lin WW, Yang VC. Cellular localization and interaction of ABCA1 and caveolin-1 in aortic endothelial cells after HDL incubation. Biochem Biophys Res Commun 2005; 332:743-9. [PMID: 15907796 DOI: 10.1016/j.bbrc.2005.05.019] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2005] [Accepted: 05/02/2005] [Indexed: 01/27/2023]
Abstract
The goal of this study was to investigate the cellular localization and the interaction between caveolin-1 and ABCA1 in cholesterol-loaded aortic endothelial cells after HDL incubation. Immunofluorescence confocal microscopy showed that ABCA1 was found primarily on the cell surface, whereas caveolin-1 was revealed on the cell surface and in the cytoplasm. The HDL appeared to colocalize with ABCA1 and caveolin-1 on the cell surface. No free HDL was revealed in the cytoplasm. The HDL was colocalized neither with early endosome marker (CD71) nor with late endosome marker (LAMP2). The chemical cross-linking and immunoprecipitation analysis revealed that ABCA1 binds directly to both HDL and caveolin-1, whereas HDL does not bind directly to caveolin-1. The studies provide evidence for a direct interaction between ABCA1 and HDL, ABCA1 and caveolin-1, but not HDL and caveolin-1, indicating that ABCA1 may act as a structural platform between HDL and caveolin-1 on the cell surface during cellular cholesterol efflux.
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MESH Headings
- ATP Binding Cassette Transporter 1
- ATP-Binding Cassette Transporters/metabolism
- Animals
- Aorta, Thoracic/cytology
- Aorta, Thoracic/drug effects
- Aorta, Thoracic/metabolism
- Biological Transport, Active
- Caveolin 1
- Caveolins/metabolism
- Cell Membrane/metabolism
- Cells, Cultured
- Cholesterol/metabolism
- Endosomes/metabolism
- Endothelium, Vascular/drug effects
- Endothelium, Vascular/metabolism
- Lipoproteins, HDL/metabolism
- Lipoproteins, HDL/pharmacology
- Models, Biological
- Protein Binding
- Rats
- Subcellular Fractions/metabolism
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Affiliation(s)
- Wei-Ting Chao
- Department of Life Science, Life Science Research Center, Tunghai University, Taichung, Taiwan, ROC
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17
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Islam KK, Knight BL, Frayn KN, Patel DD, Gibbons GF. Deficiency of PPARα disturbs the response of lipogenic flux and of lipogenic and cholesterogenic gene expression to dietary cholesterol in mouse white adipose tissue. Biochim Biophys Acta Mol Cell Biol Lipids 2005; 1734:259-68. [PMID: 15878692 DOI: 10.1016/j.bbalip.2005.03.009] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2005] [Revised: 03/31/2005] [Accepted: 03/31/2005] [Indexed: 10/25/2022]
Abstract
PPARalpha-deficiency in mice fed a high-carbohydrate, low-cholesterol diet was associated with a decreased weight of epididymal adipose tissue and an increased concentration of adipose tissue cholesterol. Consumption of a high (2% w/w) cholesterol diet resulted in a further increase in the concentration of cholesterol and a further decrease in epididymal fat pad weight in PPARalpha-null mice, but had no effect in the wild-type. These reductions in fat pad weight were associated with an increase in hepatic triacylglycerol content, indicating that both PPARalpha-deficiency and cholesterol altered the distribution of triacylglycerol in the body. Adipose tissue de novo lipogenesis was increased in PPARalpha-null mice and was further enhanced when they were fed a cholesterol-rich diet; no such effect was observed in the wild-type mice. The increased lipogenesis in the chow-fed PPARalpha-null mice was accompanied paradoxically by lower mRNA expression of SREBP-1c and its target genes, acetyl-CoA carboxylase and fatty acid synthase. Consumption of a high-cholesterol diet increased the mRNA expression of these genes in the PPARalpha-deficient mice but not in the wild-type. De novo cholesterol synthesis was not detectable in the adipose tissue of either genotype despite a relatively high expression of the mRNA's encoding SREBP-2 and 3-hydroxy-3-methylglutaryl Coenzyme A reductase. The mRNA expression of these genes and of the LDL-receptor in adipose tissue of the PPARalpha-deficient mice was lower than that of the wild-type and was not downregulated by cholesterol feeding. The results suggest that PPARalpha plays a role in adipose tissue cholesterol and triacylglycerol homeostasis and prevents cholesterol-mediated changes in de novo lipogenesis.
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Affiliation(s)
- K K Islam
- Metabolic Research Laboratory, OCDEM, Churchill Hospital, Oxford OX3 7LJ, UK
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18
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Yang XR, Lin MJ, Yip KP, Jeyakumar LH, Fleischer S, Leung GPH, Sham JSK. Multiple ryanodine receptor subtypes and heterogeneous ryanodine receptor-gated Ca2+ stores in pulmonary arterial smooth muscle cells. Am J Physiol Lung Cell Mol Physiol 2005; 289:L338-48. [PMID: 15863441 DOI: 10.1152/ajplung.00328.2004] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Ryanodine receptors (RyRs) of pulmonary arterial smooth muscle cells (PASMCs) play important roles in major physiological processes such as hypoxic pulmonary vasoconstriction and perinatal pulmonary vasodilatation. Recent studies show that three subtypes of RyRs are coexpressed and RyR-gated Ca2+ stores are distributed heterogeneously in systemic vascular myocytes. However, the molecular identity and subcellular distribution of RyRs have not been examined in PASMCs. In this study we detected mRNA and proteins of all three subtypes in rat intralobar PASMCs using RT-PCR and Western blot. Quantitative real-time RT-PCR showed that RyR2 mRNA was most abundant, approximately 15-20 times more than the other two subtypes. Confocal fluorescence microscopy revealed that RyRs labeled with BODIPY TR-X ryanodine were localized in the peripheral and perinuclear regions and were colocalized with sarcoplasmic reticulum labeled with Fluo-5N. Immunostaining showed that the subsarcolemmal regions exhibited clear signals of RyR1 and RyR2, whereas the perinuclear compartments contained mainly RyR1 and RyR3. Ca2+ sparks were recorded in both regions, and their activities were enhanced by a subthreshold concentration of caffeine or by endothelin-1, indicating functional RyR-gated Ca2+ stores. Moreover, 18% of the perinuclear sparks were prolonged [full duration/half-maximum (FDHM) = 193.3 +/- 22.6 ms] with noninactivating kinetics, in sharp contrast to the typical fast inactivating Ca2+ sparks (FDHM = 44.6 +/- 3.2 ms) recorded in the same PASMCs. In conclusion, multiple RyR subtypes are expressed differentially in peripheral and perinuclear RyR-gated Ca2+ stores; the molecular complexity and spatial heterogeneity of RyRs may facilitate specific Ca2+ regulation of cellular functions in PASMCs.
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Affiliation(s)
- Xiao-Ru Yang
- Div. of Pulmonary and Critical Care Medicine, Johns Hopkins Asthma and Allergy Center, 5501 Hopkins Bayview Cir., Baltimore, MD 21224, USA
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19
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Arnulphi C, Sánchez SA, Tricerri MA, Gratton E, Jonas A. Interaction of human apolipoprotein A-I with model membranes exhibiting lipid domains. Biophys J 2005; 89:285-95. [PMID: 15849246 PMCID: PMC1366526 DOI: 10.1529/biophysj.104.047480] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Several mechanisms for cell cholesterol efflux have been proposed, including membrane microsolubilization, suggesting that the existence of specific domains could enhance the transfer of lipids to apolipoproteins. In this work isothermal titration calorimetry, circular dichroism spectroscopy, and two-photon microscopy are used to study the interaction of lipid-free apolipoprotein A-I (apoA-I) with small unilamellar vesicles (SUVs) of 1-palmitoyl, 2-oleoyl phosphatidylcholine (POPC) and sphingomyelin (SM), with and without cholesterol. Below 30 degrees C the calorimetric results show that apoA-I interaction with POPC/SM SUVs produces an exothermic reaction, characterized as nonclassical hydrophobic binding. The heat capacity change (DeltaCp degrees ) is small and positive, whereas it was larger and negative for pure POPC bilayers, in the absence of SM. Inclusion of cholesterol in the membranes induces changes in the observed thermodynamic pattern of binding and counteracts the formation of alpha-helices in the protein. Above 30 degrees C the reactions are endothermic. Giant unilamellar vesicles (GUVs) of identical composition to the SUVs, and two-photon fluorescence microscopy techniques, were utilized to further characterize the interaction. Fluorescence imaging of the GUVs indicates coexistence of lipid domains under 30 degrees C. Binding experiments and Laurdan generalized-polarization measurements suggest that there is no preferential binding of the labeled apoA-I to any particular domain. Changes in the content of alpha-helix, binding, and fluidity data are discussed in the framework of the thermodynamic parameters.
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Affiliation(s)
- Cristina Arnulphi
- Department of Biochemistry, and Laboratory for Fluorescence Dynamics, University of Illinois at Urbana-Champaign, Champaign, Illinois, USA .
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20
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Gojova A, Barakat AI. Vascular endothelial wound closure under shear stress: role of membrane fluidity and flow-sensitive ion channels. J Appl Physiol (1985) 2005; 98:2355-62. [PMID: 15705727 DOI: 10.1152/japplphysiol.01136.2004] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Sufficiently rapid healing of vascular endothelium following injury is essential for preventing further pathological complications. Recent work suggests that fluid dynamic shear stress regulates endothelial cell (EC) wound closure. Changes in membrane fluidity and activation of flow-sensitive ion channels are among the most rapid endothelial responses to flow and are thought to play an important role in EC responsiveness to shear stress. The goal of the present study was to probe the role of these responses in bovine aortic EC (BAEC) wound closure under shear stress. BAEC monolayers were mechanically wounded and subsequently subjected to either "high" (19 dyn/cm(2)) or "low" (3 dyn/cm(2)) levels of steady shear stress. Image analysis was used to quantify cell migration and spreading under both flow and static control conditions. Our results demonstrate that, under static conditions, BAECs along both wound edges migrate at similar velocities to cover the wounded area. Low shear stress leads to significantly lower BAEC migration velocities, whereas high shear stress results in cells along the upstream edge of the wound migrating significantly more rapidly than those downstream. The data also show that reducing BAEC membrane fluidity by enriching the cell membrane with exogenous cholesterol significantly slows down both cell spreading and migration under flow and hence retards wound closure. Blocking flow-sensitive K and Cl channels reduces cell spreading under flow but has no impact on cell migration. These findings provide evidence that membrane fluidity and flow-sensitive ion channels play distinct roles in regulating EC wound closure under flow.
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Affiliation(s)
- Andrea Gojova
- Dept. of Mechanical and Aeronautical Engineering, University of California-Davis, One Shields Avenue, Davis, CA 95616, USA.
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21
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Abstract
Change in the intracellular concentration of osmolytes or the extracellular tonicity results in a rapid transmembrane water flow in mammalian cells until intracellular and extracellular tonicities are equilibrated. Most cells respond to the osmotic cell swelling by activation of volume-sensitive flux pathways for ions and organic osmolytes to restore their original cell volume. Taurine is an important organic osmolyte in mammalian cells, and taurine release via a volume-sensitive taurine efflux pathway is increased and the active taurine uptake via the taurine specific taurine transporter TauT decreased following osmotic cell swelling. The cellular signaling cascades, the second messengers profile, the activation of specific transporters, and the subsequent time course for the readjustment of the cellular content of osmolytes and volume vary from cell type to cell type. Using Ehrlich ascites tumor cells, NIH3T3 mouse fibroblasts and HeLa cells as biological systems, it is revealed that phospholipase A2-mediated mobilization of arachidonic acid from phospholipids and subsequent oxidation of the fatty acid via lipoxygenase systems to potent eicosanoids are essential elements in the signaling cascade that is activated by cell swelling and leads to release of osmolytes. The cellular signaling cascade and the activity of the volume-sensitive taurine efflux pathway are modulated by elements of the cytoskeleton, protein tyrosine kinases/phosphatases, GTP-binding proteins, Ca2+/calmodulin, and reactive oxygen species and nucleotides. Serine/threonine phosphorylation of the active taurine uptake system TauT or a putative regulator, as well as change in the membrane potential, are important elements in the regulation of TauT activity. A model describing the cellular sequence, which is activated by cell swelling and leads to activation of the volume-sensitive efflux pathway, is presented at the end of the review.
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Affiliation(s)
- Ian Henry Lambert
- The August Krogh Institute, Biochemical Department, Universitetsparken 13, DK-2100, Copenhagen O, Denmark.
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22
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van der Wouden JM, Maier O, van IJzendoorn SCD, Hoekstra D. Membrane dynamics and the regulation of epithelial cell polarity. INTERNATIONAL REVIEW OF CYTOLOGY 2004; 226:127-64. [PMID: 12921237 DOI: 10.1016/s0074-7696(03)01003-9] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Plasma membranes of epithelial cells consist of two domains, an apical and a basolateral domain, the surfaces of which differ in composition. The separation of these domains by a tight junction and the fact that specific transport pathways exist for intracellular communication between these domains and distinct intracellular compartments relevant to cell polarity development, have triggered extensive research on issues that focus on how the polarity is generated and maintained. Apart from proper assembly of tight junctions, their potential functioning as landmark for the transport machinery, cell-cell adhesion is obviously instrumental in barrier formation. In recent years, distinct endocytic compartments, defined as subapical compartment or common endosome, were shown to play a prominent role in regulating membrane trafficking to and from polarized membrane domains. Sorting devices remain to be determined but likely include distinct rab proteins, and evidence is accumulating to indicate that signaling events may direct intracellular membrane transport, intimately involved in the biogenesis and maintenance of polarized membrane domains and hence the development of cell polarity.
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Affiliation(s)
- Johanna M van der Wouden
- Department of Membrane Cell Biology, University of Groningen, Antonius Deusinglaan 1, 9713AV Groningen, The Netherlands
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23
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Mulcahy JV, Riddell DR, Owen JS. Human scavenger receptor class B type II (SR-BII) and cellular cholesterol efflux. Biochem J 2004; 377:741-7. [PMID: 14570588 PMCID: PMC1223905 DOI: 10.1042/bj20030307] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2003] [Revised: 09/12/2003] [Accepted: 10/21/2003] [Indexed: 11/17/2022]
Abstract
Although studies in recombinant cells indicate that scavenger receptor class B, type I (SR-BI) can promote cholesterol efflux, investigations in transgenic mice overexpressing or deficient in SR-BI endorse its physiological function as selectively sequestering cholesteryl esters from high-density lipoproteins (HDLs). Less clear is the role of SR-BII, a splice variant of the SR-B gene that differs only in the C-terminal cytoplasmic domain. Here, we identify several putative signalling motifs in the C-terminus of human SR-BII, which are absent from SR-BI, and hypothesize that these motifs interact with signalling molecules to mobilize stored cholesteryl esters and/or promote the efflux of intracellular free cholesterol. 'Pull-down' assays using a panel of tagged SH3 (Src homology 3) domains showed that cytoplasmic SR-BII, but not cytoplasmic SR-BI, bound the SH3 domain of phospholipase C-gamma1; this interaction was not, however, detected under more physiological conditions. Specific anti-peptide antisera identified SR-BII in human monocyte/macrophage THP-1 cells and, in recombinant cells, revealed receptor localization to caveolae, a plasma membrane microdomain that concentrates signal-transducer molecules and acts as a conduit for cholesterol flux between cells and lipoproteins. Consistent with its caveolar localization, expression of human SR-BII in recombinant Chinese hamster ovary cells (CHO-SR-BII) was associated with increased HDL-mediated cholesterol efflux. Nevertheless, when CHO-SR-BII cells were pre-loaded with cholesteryl [(3)H]oleate and incubated with HDL, cholesteryl ester stores were not reduced compared with control cells. We conclude that although human SR-BII is expressed by macrophages, contains cytoplasmic signalling motifs and localizes to caveolae, its ability to stimulate cholesterol efflux does not reflect enhanced hydrolysis of stored cholesteryl esters.
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Affiliation(s)
- Jane V Mulcahy
- Department of Medicine, Royal Free, University College Medical School, University College London, Royal Free Campus, London NW3 2PF, U.K
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24
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Moreno M, Molina H, Amigo L, Zanlungo S, Arrese M, Rigotti A, Miquel JF. Hepatic overexpression of caveolins increases bile salt secretion in mice. Hepatology 2003; 38:1477-88. [PMID: 14647059 DOI: 10.1016/j.hep.2003.09.011] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Caveolins are cholesterol-binding proteins involved in the regulation of several intracellular processes, including cholesterol transport. Because hepatocytes express caveolin-1 and caveolin-2, these proteins might modulate hepatic lipid metabolism and biliary lipid secretion. Our aim was to investigate the potential physiologic role of caveolins in hepatic cholesterol and bile salt (BS) metabolism and transport using adenoviral gene transfer. C57BL/6 mice were infected with recombinant human caveolin-1 and caveolin-2 adenoviruses. Mice infected with adenovirus lacking the transgene were used as controls. Hepatic caveolin expression was evaluated by immunochemical methods. Reverse-transcription polymerase chain reaction (RT-PCR) and immunoblotting were used to assess messenger RNA (mRNA) levels and protein mass of BS transporters (sodium taurocholate cotransporting polypeptide [Ntcp] and bile salt export pump [Bsep]). Serum, liver, biliary, and fecal biochemical determinations and BS maximal secretory rate (SRm) were performed by standard methods. Ad.Cav-1- and Ad.Cav-2-infected mice exhibited a 10- and 7-fold increase in hepatic caveolin-1 and caveolin-2 protein expression, respectively. Caveolin-1-overexpressing mice had a significant increase in plasma high-density lipoprotein (HDL) cholesterol and hepatic free cholesterol content, whereas total plasma cholesterol and triglyceride levels remained unchanged. Hepatic caveolin-1 and/or caveolin-2 overexpression significantly increased bile flow and secretion of all biliary lipids. Caveolin-1-overexpressing mice showed a 2.5-fold increase in taurocholate (TC) SRm, indicating increased canalicular BS transport capacity. BS pool size and fecal BS excretion remained within the normal range in mice with Cav-1 overexpression. No changes were seen in the protein mass of BS transporters Ntcp and Bsep. In conclusion, our findings indicate that caveolins may play an important role in regulating hepatic BS and cholesterol metabolism.
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Affiliation(s)
- Mauricio Moreno
- Departamento de Gastroenterología, Pontificia Universidad Católica de Chile, Santiago, Chile
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25
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Buhagiar KA, Hansen PS, Kong BY, Clarke RJ, Fernandes C, Rasmussen HH. Dietary cholesterol alters Na+/K+ selectivity at intracellular Na+/K+ pump sites in cardiac myocytes. Am J Physiol Cell Physiol 2003; 286:C398-405. [PMID: 14522815 DOI: 10.1152/ajpcell.00016.2003] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
A modest diet-induced increase in serum cholesterol in rabbits increases the sensitivity of the sarcolemmal Na+/K+ pump to intracellular Na+, whereas a large increase in cholesterol levels decreases the sensitivity to Na+. To examine the mechanisms, we isolated cardiac myocytes from controls and from rabbits with diet-induced increases in serum cholesterol. The myocytes were voltage clamped with the use of patch pipettes that contained osmotically balanced solutions with Na+ in a concentration of 10 mM and K+ in concentrations ([K+]pip) ranging from 0 to 140 mM. There was no effect of dietary cholesterol on electrogenic Na+/K+ current (Ip) when pipette solutions were K+ free. A modest increase in serum cholesterol caused a [K+]pip-dependent increase in Ip, whereas a large increase caused a [K+]pip-dependent decrease in Ip. Modeling suggested that pump stimulation with a modest increase in serum cholesterol can be explained by a decrease in the microscopic association constant KK describing the backward reaction E1 + 2K+ --> E2(K+)2, whereas pump inhibition with a large increase in serum cholesterol can be explained by an increase in KK. Because hypercholesterolemia upregulates angiotensin II receptors and because angiotensin II regulates the Na+/K+ pump in cardiac myocytes in a [K+]pip-dependent manner, we blocked angiotensin synthesis or angiotensin II receptors in vivo in cholesterol-fed rabbits. This abolished cholesterol-induced pump inhibition. Because the epsilon-isoform of protein kinase C (epsilonPKC) mediates effects of angiotensin II on the pump, we included specific epsilonPKC-blocking peptide in patch pipette filling solutions. The peptide reversed cholesterol-induced pump inhibition.
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Affiliation(s)
- Kerrie A Buhagiar
- University of Sydney, Department of Cardiology, Royal North Shore Hospital, Pacific Highway, St. Leonards, Sydney, NSW 2065, Australia
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26
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Voldstedlund M, Thuneberg L, Tranum-Jensen J, Vinten J, Christensen EI. Caveolae, caveolin and cav-p60 in smooth muscle and renin-producing cells in the rat kidney. ACTA ACUST UNITED AC 2003; 179:179-88. [PMID: 14510782 DOI: 10.1046/j.1365-201x.2003.01183.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
AIMS In vascular smooth muscle cells caveolae are important for signalling mechanisms regulating vascular contraction. In smooth muscle layer of the renal afferent arteriole juxtaglomerular cells (JG cells) are non-contractile renin producing cells that have the capacity to change their phenotype into smooth muscle cells and back again by metaplastic transformation. Signalling mechanisms in JG cells are not fully understood and we therefore investigated if caveolae were present, and thereby could be involved as integrators of cellular signalling in both of these phenotypes of smooth muscle cells. METHODS Using electron microscopy we compared the number of caveolae in JG cells and smooth muscle cells in the afferent arteriole of the rat kidney. The expression of caveolin and cav-p60 was examined using a combination of immunogold electron microscopy and immunofluorescence microscopy. RESULTS We found that JG cells have sixfold less caveolae per cell surface sectional length than smooth muscle cells. The expression of cavolin-1 and cav-p60 correlated with the number of caveolae. An examination of the general distribution of caveolae, cav-p60 and caveolins in the rat kidney showed that cav-p60, like caveolin-1, is a specific maker of caveolae. CONCLUSION The number of caveolae in JG cells is very low, and this makes it unlikely that caveolae are of major importance for the renin secretion specific for JG cells.
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MESH Headings
- Animals
- Blotting, Western/methods
- Caveolae/metabolism
- Caveolins/analysis
- Immunohistochemistry/methods
- Kidney/cytology
- Kidney/metabolism
- Kidney/ultrastructure
- Male
- Microscopy, Electron/methods
- Microscopy, Fluorescence/methods
- Muscle, Smooth, Vascular/cytology
- Muscle, Smooth, Vascular/metabolism
- Muscle, Smooth, Vascular/ultrastructure
- Rats
- Rats, Wistar
- Renin/biosynthesis
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Affiliation(s)
- M Voldstedlund
- Department of Medical Physiology, University of Copenhagen, Copenhagen, Denmark
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27
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Xie Y, Yang Q, Nelson BD, DePierre JW. The relationship between liver peroxisome proliferation and adipose tissue atrophy induced by peroxisome proliferator exposure and withdrawal in mice. Biochem Pharmacol 2003; 66:749-56. [PMID: 12948855 DOI: 10.1016/s0006-2952(03)00386-1] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
We have previously demonstrated that severe adipose tissue atrophy occurs upon dietary treatment of mice with potent peroxisome proliferators (PPs). This atrophy occurs subsequent to peroxisome proliferation in the liver and may represent a novel addition to the pleiotropic effects exerted by PPs. In the present study we have characterized the recovery of mice from such atrophy following cessation of exposure. Following termination of treatment with perfluorooctanoic acid (PFOA) for 7 days, the adipose tissue atrophy was rapidly reversed, beginning on 2-5 days of recovery and being complete within 10 days. In contrast, hepatic peroxisome proliferation recovered much more slowly, indicating that these processes are not strictly coordinated. Analysis of lipoprotein lipase and hormone-sensitive lipase activities in adipose tissue revealed that the decrease and increase in these activities, respectively, caused by PFOA were both reversed within 10 days of recovery. Overall, these data provide further support for our previous conclusion that the adipose tissue atrophy induced by PFOA is caused, at least in part, by changes in the activities of lipoprotein lipase and hormone-sensitive lipase. The serum level of cholesterol, which increased after termination of PFOA treatment, returned to normal with a time-course similar to the recovery of adipose tissue weight, although hepatic peroxisome proliferation was still present. The possible relationship between the reduction in serum cholesterol and/or in its availability to peripheral tissues and the associated atrophy of adipose tissues caused by PPs is discussed.
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Affiliation(s)
- Yi Xie
- Unit for Biochemical Toxicology, Wallenberg Laboratory, Department of Biochemistry and Biophysics, Stockholm University, S-106 91 Stockholm, Sweden.
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28
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Tobin DJ, Gunin A, Magerl M, Paus R. Plasticity and cytokinetic dynamics of the hair follicle mesenchyme during the hair growth cycle: implications for growth control and hair follicle transformations. J Investig Dermatol Symp Proc 2003; 8:80-6. [PMID: 12895000 DOI: 10.1046/j.1523-1747.2003.12177.x] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Hair fiber production is the macroscopic end-point of a highly complex set of interactions between the hair follicle's epithelial and mesenchymal components. The nature of this relationship is largely set during hair follicle morphogenesis, but is dramatically revisited in the adult during the unique tissue remodeling events required for hair follicle cycling. Whereas significant attention has focused on the fate of the hair follicle epithelium during these events, associated changes in hair follicle fibroblast subpopulations remain unclear. Here, we present a speculative review that represents a critical and innovative synthesis of the current literature and summarizes a recently submitted original study by the authors, on the nature of hair cycle-dependent fibroblast dynamics and on how perturbations thereof may lead to several clinical manifestations of altered human hair growth.
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Affiliation(s)
- Desmond J Tobin
- Department of Biomedical Sciences, School of Life Sciences, University of Bradford, Bradford, West Yorkshire, UK.
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29
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Chao WT, Fan SS, Chen JK, Yang VC. Visualizing caveolin-1 and HDL in cholesterol-loaded aortic endothelial cells. J Lipid Res 2003; 44:1094-9. [PMID: 12639973 DOI: 10.1194/jlr.m300033-jlr200] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Caveolae are vesicular invaginations of the plasma membranes that regulate signal transduction and transcytosis, as well as cellular cholesterol homeostasis. Our previous studies indicated that the removal of cholesterol from aortic endothelial cells and smooth muscle cells in the presence of HDL is associated with plasmalemmal invaginations and plasmalemmal vesicles. The goal of the present study was to investigate the location and distribution of caveolin-1, the main structural protein component of caveolae, in cholesterol-loaded aortic endothelial cells after HDL incubation. Confocal microscopic analysis demonstrated that the caveolin-1 appeared to colocalize with HDL-fluorescein 1,1'-dioctadecyl 3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiI) conjugates on the cell surface. No free HDL-DiI conjugates were revealed in the cytoplasm. Immunoelectron microscopy further demonstrated that caveolin-1 gold (15 nm) conjugates colocalized with HDL gold (10 nm) conjugates in the plasmalemmal invaginations. These morphological results indicated that caveolae are the major membrane domains facilitating the transport of excess cholesterol to HDL on the cell surface of aortic endothelial cells.
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Affiliation(s)
- W T Chao
- Department of Biology and Life Science Research Center, Tunghai University, Taichung, Taiwan, Republic of China
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30
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Tobin DJ, Gunin A, Magerl M, Handijski B, Paus R. Plasticity and cytokinetic dynamics of the hair follicle mesenchyme: implications for hair growth control. J Invest Dermatol 2003; 120:895-904. [PMID: 12787113 DOI: 10.1046/j.1523-1747.2003.12237.x] [Citation(s) in RCA: 118] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The continuously remodeled hair follicle is a uniquely exploitable epithelial-mesenchymal interaction system. In contrast to the cyclical fate of the hair follicle epithelium, the dynamics of the supposedly stable hair follicle mesenchyme remains enigmatic. Here we address this issue using the C57BL/6 hair research model. During hair growth, increase in total follicular papilla size was associated with doubling of papilla cell numbers, much of which occurred before intra-follicular papilla cell proliferation, and subsequent to mitosis in the proximal connective tissue sheath. This indicates that some papilla cells originate in, and migrate from, the proliferating pool of connective tissue sheath fibroblasts. Follicular papilla cell number and total papilla size were maximal by anagen VI, but intriguingly, decreased by 25% during this period of sustained hair production. This cell loss, which continued during catagen, was not associated with intra-follicular papilla apoptosis, strongly indicating that fibroblasts migrate out of the late anagen/early catagen papilla and re-enter the proximal connective tissue sheath. Low-level apoptosis occurred only here, along with the "detachment" of cells from the regressing connective tissue sheath. Thus, the hair follicle mesenchyme exhibits significant hair cycle-associated plasticity. Modulation of these cell interchanges is likely to be important during clinically important hair follicle transformations, e.g. vellus-to-terminal and terminal-to-vellus during androgenetic alopecia.
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Affiliation(s)
- Desmond J Tobin
- Department of Biomedical Sciences, University of Bradford, Bradford, UK
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31
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Krotova KY, Zharikov SI, Block ER. Classical isoforms of PKC as regulators of CAT-1 transporter activity in pulmonary artery endothelial cells. Am J Physiol Lung Cell Mol Physiol 2003; 284:L1037-44. [PMID: 12562561 DOI: 10.1152/ajplung.00308.2002] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We examined which isoforms of protein kinase C (PKC) may be involved in the regulation of cationic amino acid transporter-1 (CAT-1) transport activity in cultured pulmonary artery endothelial cells (PAEC). An activator of classical and novel isoforms of PKC, phorbol 12-myristate-13-acetate (PMA; 100 nM), inhibited CAT-1-mediated l-arginine transport in PAEC after a 1-h treatment and activated l-arginine uptake after an 18-h treatment of cells. These changes in l-arginine transport were not related to the changes in the expression of the CAT-1 transporter. The inhibitory effect of PMA on l-arginine transport was accompanied by a translocation of PKCalpha (a classical PKC isoform) from the cytosol to the membrane fraction, whereas the activating effect of PMA on l-arginine transport was accompanied by full depletion of the expression of PKCalpha in PAEC. A selective activator of Ca(2+)-dependent classical isoforms of PKC, thymeleatoxin (Thy; 100 nM; 1-h and 18-h treatments), induced the same changes in l-arginine uptake and PKCalpha translocation and depletion as PMA. The effects of PMA and Thy on l-arginine transport in PAEC were attenuated by a selective inhibitor of classical PKC isoforms Go 6976 (1 micro M). Phosphatidylinositol-3,4,5-triphosphate-dipalmitoyl (PIP; 5 micro M), which activates novel PKC isoforms, did not affect l-arginine transport in PAEC after 1-h and 18-h treatment of cells. PIP (5 micro M; 1 h) induced the translocation of PKCepsilon (a novel PKC isoform) from the cytosolic to the particulate fraction and did not affect the translocation of PKCalpha. These results demonstrate that classical isoforms of PKC are involved in the regulation of CAT-1 transport activity in PAEC. We suggest that translocation of PKCalpha to the plasma membrane induces phosphorylation of the CAT-1 transporter, which leads to inhibition of its transport activity in PAEC. In contrast, depletion of PKCalpha after long-term treatment with PMA or Thy promotes dephosphorylation of the CAT-1 transporter and activation of its activity.
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Affiliation(s)
- Karina Y Krotova
- Department of Medicine, University of Florida College of Medicine; and Research Service, Malcom Randall VA Medical Center, Gainesville, Florida 32610, USA
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Batetta B, Mulas MF, Sanna F, Putzolu M, Bonatesta RR, Gasperi-Campani A, Roncuzzi L, Baiocchi D, Dessì S. Role of cholesterol ester pathway in the control of cell cycle in human aortic smooth muscle cells. FASEB J 2003; 17:746-8. [PMID: 12594184 DOI: 10.1096/fj.02-0396fje] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Cholesterol esterification by acyl-CoA:cholesterol acyltransferase (ACAT) and proliferation of vascular smooth muscle cells (VSMC) are key events in vascular proliferative diseases. Here we performed experiments to ascertain the role of cholesterol ester pathway in the control of human aortic VSMC cycle progression. Results showed that serum-induced VSMC proliferation was preceded by an increased ability of the cells to esterify cholesterol as well as by an increased expression of ACAT and multidrug resistance (MDR1) mRNAs and extracellular related kinases 1/2 (ERK1/2), whereas caveolin-1 levels were markedly decreased. Cell cycle analyses performed in the presence of two inhibitors of cholesterol esterification, directly inhibiting ACAT (Sandoz 58-035) or the transport of cholesterol substrate from plasma membrane to endoplasmic reticulum (progesterone), indicate that each inhibitor suppressed the serum-induced DNA synthesis by accumulation of VSMCs in the G1 phase. The effect was associated with a rapid inhibition of ERK1/2 mitogenic signaling pathway; a down-regulation of cyclin D1, ACAT, and MDR1 mRNA; and an up-regulation of caveolin-1. These data provide a plausible link between cholesterol esterification and control of cell cycle G1/S transition, supporting the hypothesis that cholesterol esterification may accelerate the progression of human vascular proliferative diseases by modulating the rate of the VSMC proliferation.
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MESH Headings
- ATP Binding Cassette Transporter, Subfamily B, Member 1/genetics
- Amides/pharmacology
- Aorta/cytology
- Aorta/drug effects
- Aorta/physiology
- Caveolin 1
- Caveolins/genetics
- Cell Cycle/drug effects
- Cell Cycle/physiology
- Cell Division/drug effects
- Cell Division/physiology
- Cholesterol/metabolism
- Cholesterol Esters/metabolism
- Gene Expression Regulation/drug effects
- Humans
- Muscle, Smooth, Vascular/cytology
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/metabolism
- Organosilicon Compounds/pharmacology
- Progesterone/pharmacology
- RNA, Messenger/drug effects
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Signal Transduction/drug effects
- Signal Transduction/physiology
- Sterol O-Acyltransferase/genetics
- Time Factors
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Affiliation(s)
- Barbara Batetta
- Department of Biomedical Science and Biotechnology, University of Cagliari, Italy
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Chroni A, Liu T, Gorshkova I, Kan HY, Uehara Y, Von Eckardstein A, Zannis VI. The central helices of ApoA-I can promote ATP-binding cassette transporter A1 (ABCA1)-mediated lipid efflux. Amino acid residues 220-231 of the wild-type ApoA-I are required for lipid efflux in vitro and high density lipoprotein formation in vivo. J Biol Chem 2003; 278:6719-30. [PMID: 12488454 DOI: 10.1074/jbc.m205232200] [Citation(s) in RCA: 100] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We have mapped the domains of lipid-free apoA-I that promote cAMP-dependent and cAMP-independent cholesterol and phospholipid efflux. The cAMP-dependent lipid efflux in J774 mouse macrophages was decreased by approximately 80-92% by apoA-I[delta(185-243)], only by 15% by apoA-I[delta(1-41)] or apoA-I[delta(1-59)], and was restored to 75-80% of the wild-type apoA-I control value by double deletion mutants apoA-I[delta(1-41)delta(185-243)] and apoA-I[delta(1-59)delta(185-243)]. Similar results were obtained in HEK293 cells transfected with an ATP-binding cassette transporter A1 (ABCA1) expression plasmid. The double deletion mutant of apoA-I had reduced thermal and chemical stability compared with wild-type apoA-I. Sequential carboxyl-terminal deletions showed that cAMP-dependent cholesterol efflux was diminished in all the mutants tested, except the apoA-I[delta(232-243)] which had normal cholesterol efflux. In cAMP-untreated or in mock-transfected cells, cholesterol efflux was not affected by the amino-terminal deletions, but decreased by 30-40% and 50-65% by the carboxyl-terminal and double deletions, respectively. After adenovirus-mediated gene transfer in apoA-I-deficient mice, wild-type apoA-I and apoA-I[delta(1-41)] formed spherical high density lipoprotein (HDL) particles, whereas apoA-I[delta(1-41)delta(185-243)] formed discoidal HDL. The findings suggest that although the central helices of apoA-I alone can promote ABCA1-mediated lipid efflux, residues 220-231 are necessary to allow functional interactions between the full-length apoA-I and ABCA1 that are required for lipid efflux and HDL biogenesis.
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Affiliation(s)
- Angeliki Chroni
- Section of Molecular Genetics, Whitaker Cardiovascular Institute, Department of Medicine, Boston University School of Medicine, Boston, Massachusetts 02118, USA
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Abstract
The contribution of prolactin (PRL) to the pathogenesis and progression of human breast cancer at the cellular, transgenic, and epidemiological levels is increasingly appreciated. Acting at the endocrine and autocrine/paracrine levels, PRL functions to stimulate the growth and motility of human breast cancer cells. The actions of this ligand are mediated by at least six recognized PRL receptor isoforms found on, or secreted by, human breast epithelium. The PRL/PRL receptor complex associates with and activates several signaling networks that are shared with other members of the cytokine receptor superfamily. Coupled with the recently identified intranuclear function of PRL, these networks are integrated into the in vitro and in vivo actions induced by ligand. These findings indicate that antagonists of PRL/PRL receptor interaction or PRL receptor-associated signal transduction may be of considerable utility in the treatment of human breast cancer.
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Key Words
- cis, cytokine-inducible inhibitor of signaling
- cypb, cyclophilin b
- ecd, extracellular domain
- egf, epidermal growth factor
- ghr, gh receptor
- hprlr, human prlr
- icd, intracellular domain
- jak, janus kinase 2
- jnk, c-jun n-terminal kinase
- pias, peptide inhibitor of activated stat
- pi3k, phosphatidylinositol 3′-kinase
- prl, prolactin
- ptdins, phosphatidylinositol
- prlbp, prl binding protein
- prlr, prl receptor
- shp-2, sh2-containing protein tyrosine phosphatase
- socs, suppressor of cytokine signaling
- stat, signal transducer and activator of transcription
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Affiliation(s)
- Charles V Clevenger
- Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
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Abstract
For three decades, low-density lipoprotein (LDL) dominated research into cholesterol metabolism and atherosclerosis, whereas scant attention was paid to high-density lipoprotein (HDL), an equally important risk factor for cardiovascular disease. This low interest reflected the lack of knowledge about physiological HDL receptors. As a result, our understanding of HDL-cell interactions failed to develop alongside that of LDL, and mechanisms through which atheroprotective HDL promoted clearance of cholesterol from peripheral cells remained poorly-defined. Interest was kindled with the recognition that scavenger receptor class B, type I is the cell-surface protein in hepatocytes and steroidogenic tissues which selectively extracts cholesteryl esters from HDL. Greater impetus still was given by the discovery that mutations in the gene encoding the ATP-binding cassette transporter, class A1 (ABCA1) are the cause of Tangier disease, a rare recessive disorder with near-absent plasma HDL. The ABCA1 transmembrane protein is crucial for efficient efflux of cellular cholesterol and HDL maturation and has emerged as a promising therapeutic target for cardiovascular disease. The hope is that new drugs, regulating ABCA1 activity and HDL homeostasis, will accelerate cholesterol efflux from lipid-laden foam cells and thus promote regression of atherosclerotic lesions.
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Affiliation(s)
- James S Owen
- Department of Medicine, Royal Free and University College Medical School, Royal Free Campus, London NW3 2PF, UK.
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Silva VS, Cordeiro JM, Matos MJ, Oliveira CR, Gonçalves PP. Aluminum accumulation and membrane fluidity alteration in synaptosomes isolated from rat brain cortex following aluminum ingestion: effect of cholesterol. Neurosci Res 2002; 44:181-93. [PMID: 12354633 DOI: 10.1016/s0168-0102(02)00128-1] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In the present work, we studied the effect of cholesterol/phospholipid (CH/PL) molar ratio on aluminum accumulation and aluminum-induced alteration of membrane fluidity in rat brain cortex synaptosomes. We observed that sub-acute (daily supply of 1.00 g of AlCl(3) during 10 days) and chronic (daily supply of 0.03 g of AlCl(3) during 4 months) exposure to dietary aluminum leads to a synaptosomal aluminum enrichment of 45 and 59%, respectively. During chronic exposure to AlCl(3), the enhancement of aluminum content was prevented by administration of colestipol (0.31 g/day), which decreased the synaptosomal membrane CH/PL molar ratio (nmol/nmol) from 1.2 to 0.4. Fluorescence anisotropy analysis, using 1,6-diphenyl-1,3,5-hexatriene (DPH) and 1-(4-(trimethylamino)phenyl)-6-phenylhexa-1,3,5-triene (TMA-DPH), showed that after treatment with colestipol a decrease in membrane order occurs at the level of hydrophilic lipid-water surface and deeper hydrophobic region of the synaptosomal membrane. When the rats were exposed to aluminum, it was observed a significant enhancement of membrane fluidity, which was more pronounced at the level of the membrane hydrophilic regions. Meanwhile, when chronic exposure to dietary AlCl(3) was accompanied by treatment with colestipol, the aluminum-induced decrease in membrane order was negligible when compared to TMA-DPH and DPH anisotropy values measured upon colestipol treatment. In contrast, in vitro incubation of synaptosomes (isolated from control rats) with AlCl(3) induced a concentration-dependent rigidification of this more hydrophilic membrane region. The opposite action of aluminum on synaptosomal membrane fluidity, during in vivo and in vitro experiments, appears to be explained by alteration of synaptosomal CH/PL molar ratio, since a significant reduction (approximately 80%) of this parameter occurs during in vivo exposure to aluminum. In conclusion, during in vivo exposure to aluminum, fluidification of hydrophilic regions and reduction of CH/PL molar ratio of presynaptic membranes accompany the accumulation of this cation, which appear to restrict aluminum retention in brain cortex nerve terminals.
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Affiliation(s)
- Virgília S Silva
- Centro de Estudos do Ambiente e Mar, Departamento de Biologia, Universidade de Aveiro, 3810-193 Aveiro, Portugal
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37
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Abstract
Peroxisomes contain enzymes catalyzing a number of indispensable metabolic functions mainly related to lipid metabolism. The importance of peroxisomes in man is stressed by the existence of genetic disorders in which the biogenesis of the organelle is defective, leading to complex developmental and metabolic phenotypes. The purpose of this review is to emphasize some of the recent findings related to the localization of cholesterol biosynthetic enzymes in peroxisomes and to discuss the impairment of cholesterol biosynthesis in peroxisomal deficiency diseases.
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Affiliation(s)
- Werner J Kovacs
- Department of Biology, San Diego State University, San Diego, CA 92182, USA
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38
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Abstract
Several lines of evidence indicate that the lipids in the plasma membrane of animal cells are inhomogeneously distributed, and that various types of specialized lipid domains play an important role in many biological processes. The characteristics of these domains, such as size, composition and dynamics, are currently under active investigation. It appears that there are many different types of membrane domains in the plasma membrane, and perhaps the entire membrane should be viewed as a mosaic of microdomains.
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Affiliation(s)
- Frederick R Maxfield
- Department of Biochemistry, Weill Medical College of Cornell University, New York, NY 10021, USA.
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39
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Abstract
Caveolae are spherical invaginations of the plasma membrane and associated vesicles that are found at high surface densities in most cells, endothelia included. Their structural framework has been shown to consist of oligomerized caveolin molecules interacting with cholesterol and sphingolipids. Caveolae have been involved in many cellular functions such as endocytosis, signal transduction, mechano-transduction, potocytosis, and cholesterol trafficking. Some confusion still persists in the field with respect to the relationship between caveolae and the lipid rafts, which have been involved in many of the above functions. In addition to all these, endothelial caveolae have been involved in capillary permeability by their participation in the process of transcytosis. This short review will focus on their structure and components, methods used to determine these components, and the role of caveolae in the transendothelial exchanges between blood plasma and the interstitial fluid.
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Affiliation(s)
- Radu-Virgil Stan
- Department of Cellular and Molecular Medicine, University of California San Diego, La Jolla, California 92093-0651, USA.
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40
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Oksvold MP, Skarpen E, Widerberg J, Huitfeldt HS. Fluorescent histochemical techniques for analysis of intracellular signaling. J Histochem Cytochem 2002; 50:289-303. [PMID: 11850432 DOI: 10.1177/002215540205000301] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Intracellular signaling relies on the orchestrated cooperation of signaling proteins and modules, their intracellular localization, and membrane trafficking. Recently, a repertoire of fluorescence-based techniques, which significantly increases our potential for detailed studies of the involved mechanisms, has been introduced. Microscopic techniques with increased resolution have been combined with improved techniques for detection of signaling proteins. Transfections of fluorescently tagged proteins have allowed in vivo microscopy of their trafficking and interactions with other proteins and intracellular structures. We present an overview of general signaling principles and a description of techniques based on fluorescent microscopy suited for studies of signaling mechanisms.
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Affiliation(s)
- Morten P Oksvold
- Center for Cellular Stress Responses, Institute of Pathology, University of Oslo, Oslo, Norway.
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41
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Kranenburg O, Verlaan I, Moolenaar WH. Regulating c-Ras function. cholesterol depletion affects caveolin association, GTP loading, and signaling. Curr Biol 2001; 11:1880-4. [PMID: 11728312 DOI: 10.1016/s0960-9822(01)00582-6] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Cholesterol-rich and caveolin-containing microdomains of the plasma membrane, termed "caveolae," have been implicated in signal transduction. However, the role of caveolae in regulating the Ras-MAP kinase cascade is incompletely understood. The mammalian Ras isoforms (H, N, and K) use different membrane anchors to attach to the plasma membrane and thereby may localize to functionally distinct microdomains, which might explain isoform-specific signaling. Here, we show that, in Cos epithelial cells, endogenous K-Ras colocalizes largely with caveolin, whereas N-Ras localizes to both caveolar and noncaveolar subdomains; H-Ras localization was below detection limits. We find that epidermal growth factor (EGF) activates N-Ras but fails to activate K-Ras in these cells. Extraction of cholesterol with methyl-beta-cyclodextrin disrupts complex formation between caveolin and K- and N-Ras and, strikingly, enables EGF to activate both K-Ras and N-Ras. While cholesterol depletion enhances GTP-loading on total c-Ras, activation of the downstream MEK-MAP kinase cascade by EGF and lysophosphatidic acid but not that by phorbol ester is inhibited. Thus, plasma membrane cholesterol is essential for negative regulation of c-Ras isoforms (complexed to caveolin), as well as for mitogenic signaling downstream of receptor-activated c-Ras.
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Affiliation(s)
- O Kranenburg
- Division of Cellular Biochemistry, The Netherlands Cancer Institute, Center for Biomedical Genetics, Plesmanlaan 121, 1066CX Amsterdam, The Netherlands
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42
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Abstract
Efflux of free cholesterol (FC) continues even when cellular FC mass is unchanged. This reflects a recirculation of preformed FC between cells and extracellular fluids which has multiple functions in cell biology including receptor recycling and signaling as well as cellular FC homeostasis. Total FC efflux is heterogeneous. Simple diffusion to mature high density lipoprotein (HDL), mainly via albumin as intermediate, initiates FC net transport driven by plasma lecithin:cholesterol acyltransferase activity. A second major efflux component reflects protein-facilitated transport from cell surface domains (caveolae, rafts) driven by FC binding to lipid-poor, pre-beta-migrating HDL (pre-beta-HDL). Facilitated efflux from caveolae, unlike simple diffusion, is highly regulated. Neither ABC1 (the protein defective in Tangier disease) nor other ATP-dependent transporters now appear likely to contribute directly to FC efflux. Their role is limited to the initial formation of a particle precursor to circulating pre-beta-HDL, which recycles without further lipid input from ATP-dependent transporter proteins. Lipid-free apolipoprotein A-I, previously considered a surrogate for pre-beta-HDL, has a reactivity much lower than that of native lipoprotein FC acceptors.
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Affiliation(s)
- C J Fielding
- Cardiovascular Research Institute and Departments of Physiology and Medicine, Box 0130, University of California Medical Center, San Francisco, CA 94143-0130, USA.
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