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Abstract
Endocytosis can be separated into the categories of phagocytosis and pinocytosis. Phagocytosis can be distinguished from pinocytosis primarily by the size of particle ingested and by its dependence on actin polymerization as a key step in particle ingestion. Several specific forms of pinocytosis have been identified that can be distinguished based on their dependence on clathrin or caveolin. Both clathrin and caveolin-dependent pinocytosis appear to require the participation of dynamin to internalize the plasma membrane. Other, less well-characterized forms of pinocytosis have also been described. Although endocytosis has long been known to affect receptor density, recent studies have demonstrated that endocytosis through clathrin- and caveolin-dependent processes plays a key role in receptor-mediated signal transduction. In some cases, blockade of these processes attenuates, or even prevents, signal transduction from taking place. This information, coupled with a better understanding of endocytosis mechanisms, will help advance the field of cell biology as well as present new targets for drug development and disease treatment.
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Affiliation(s)
- Jiang Liu
- Department of Medicine, Room 12, Ruppert Center, 3120 Glendale Avenue, Toledo, OH 43614, USA.
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2
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Méndez-Giménez L, Rodríguez A, Balaguer I, Frühbeck G. Role of aquaglyceroporins and caveolins in energy and metabolic homeostasis. Mol Cell Endocrinol 2014; 397:78-92. [PMID: 25008241 DOI: 10.1016/j.mce.2014.06.017] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/30/2014] [Revised: 06/25/2014] [Accepted: 06/26/2014] [Indexed: 12/23/2022]
Abstract
Aquaglyceroporins and caveolins are submicroscopic integral membrane proteins that are particularly abundant in many mammalian cells. Aquaglyceroporins (AQP3, AQP7, AQP9 and AQP10) encompass a subfamily of aquaporins that allow the movement of water, but also of small solutes, such as glycerol, across cell membranes. Glycerol constitutes an important metabolite as a substrate for de novo synthesis of triacylglycerols and glucose as well as an energy substrate to produce ATP via the mitochondrial oxidative phosphorylation. In this sense, the control of glycerol influx/efflux in metabolic organs by aquaglyceroporins plays a crucial role with the dysregulation of these glycerol channels being associated with metabolic diseases, such as obesity, insulin resistance, non-alcoholic fatty liver disease and cardiac hypertrophy. On the other hand, caveolae have emerged as relevant plasma membrane sensors implicated in a wide range of cellular functions, including endocytosis, apoptosis, cholesterol homeostasis, proliferation and signal transduction. Caveolae-coating proteins, namely caveolins and cavins, can act as scaffolding proteins within caveolae by concentrating signaling molecules involved in free fatty acid and cholesterol uptake, proliferation, insulin signaling or vasorelaxation, among others. The importance of caveolae in whole-body homeostasis is highlighted by the link between homozygous mutations in genes encoding caveolins and cavins with metabolic diseases, such as lipodystrophy, dyslipidemia, muscular dystrophy and insulin resistance in rodents and humans. The present review focuses on the role of aquaglyceroporins and caveolins on lipid and glucose metabolism, insulin secretion and signaling, energy production and cardiovascular homeostasis, outlining their potential relevance in the development and treatment of metabolic diseases.
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Affiliation(s)
- Leire Méndez-Giménez
- Metabolic Research Laboratory, Clínica Universidad de Navarra, Pamplona, Spain; CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn), Instituto de Salud Carlos III, Pamplona, Spain
| | - Amaia Rodríguez
- Metabolic Research Laboratory, Clínica Universidad de Navarra, Pamplona, Spain; CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn), Instituto de Salud Carlos III, Pamplona, Spain.
| | - Inmaculada Balaguer
- Metabolic Research Laboratory, Clínica Universidad de Navarra, Pamplona, Spain
| | - Gema Frühbeck
- Metabolic Research Laboratory, Clínica Universidad de Navarra, Pamplona, Spain; CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn), Instituto de Salud Carlos III, Pamplona, Spain; Department of Endocrinology and Nutrition, Clínica Universidad de Navarra, Pamplona, Spain.
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3
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Abstract
Caveolin 1 expression is downregulated in various cancer cell lines. Interestingly, in several drug-resistant cancer cells, a strong induction of caveolin 1 expression has been reported suggesting a role for caveolin 1 in the acquisition and/or the maintenance of multidrug resistance phenotype. In addition, it was reported that p-glycoprotein localized to caveolin-rich membrane domains in these cells. In this study, we progressively exposed A549 lung adenocarcinoma cells to increasing doses of etoposide. Both R1 and R2 cell lines had greatly increased levels of p-glycoprotein expression while mrp expression levels were moderately increased but only R2 cells had raised caveolin levels compared to control A549 cells. Both caveolin-1 and p-glycoprotein colocalize in Triton-insoluble membrane domains in all our cell lines but only caveolins-1 was solubilized by the addition of octylglucoside at 4C suggesting that these two proteins are located in different membrane domains. Using an anti-caveolin-1 antibody, we did not succeed to immunoprecipitate p-glycoprotein. Interestingly, total cellular cholesterol (the major lipid component of caveolae and triton-insoluble domains) was greatly increased in both R1 and R2 cell lines compared to naive A549 cells.
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MESH Headings
- ATP Binding Cassette Transporter, Subfamily B, Member 1/genetics
- ATP Binding Cassette Transporter, Subfamily B, Member 1/metabolism
- Adenocarcinoma/drug therapy
- Adenocarcinoma/metabolism
- Adenocarcinoma/pathology
- Antineoplastic Agents, Phytogenic/pharmacology
- Antineoplastic Agents, Phytogenic/therapeutic use
- Caveolin 1
- Caveolins/physiology
- Cell Membrane/metabolism
- Cholesterol/metabolism
- Drug Resistance, Neoplasm
- Etoposide/therapeutic use
- Gene Expression Regulation, Neoplastic
- Humans
- Lung Neoplasms/drug therapy
- Lung Neoplasms/metabolism
- Lung Neoplasms/pathology
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Reverse Transcriptase Polymerase Chain Reaction
- Tumor Cells, Cultured
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Affiliation(s)
- Martin M Bélanger
- Unité de Recherche en Pneumologie, Institut Universitaire de Cardiologie et de Pneumologie, l'Université Laval, Centre de Recherche Hôpital Laval, Sainte-Foy, Québec, Canada
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4
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Shi D, Liu Y, Lian X, Zou W. [Cavins: new sights of caveolae-associated protein]. Sheng Wu Gong Cheng Xue Bao 2013; 29:1531-1537. [PMID: 24701818] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Caveolae are specialized lipid rafts that form flask-shaped invaginations of the plasma membrane. Many researches show that caveolae are involved in cell signaling and transport. Caveolin-1 is the major coat protein essential for the formation of caveolae. Recently, several reports indicated that the other caveolae-associated proteins, Cavins, are required for caveola formation and organization. It's worth noting that Cavin-1 could cooperate with Caveolin-1 to accommodate the structural integrity and function of caveolae. Here, we reviewed that the relationship between Cavins and Caveolins and explore the role of them in regulating caveolae.
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5
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Rath G, Dessy C, Feron O. Caveolae, caveolin and control of vascular tone: nitric oxide (NO) and endothelium derived hyperpolarizing factor (EDHF) regulation. J Physiol Pharmacol 2009; 60 Suppl 4:105-109. [PMID: 20083858] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Received: 08/05/2009] [Accepted: 09/10/2009] [Indexed: 05/28/2023]
Abstract
Endothelium plays a crucial role in the regulation of cardiovascular homeostasis through the release of vasoactive factors. Nitric oxide (NO) and endothelium-derived hyperpolarizing factors (EDHF) are the two major actors controlling the vasomotor tone. The endothelial nitric oxide synthase (eNOS) was reported in the mid 90ies to be under the control of caveolin, the structural protein of caveolae. Nowadays, a large body of evidence has confirmed that the caveolin/eNOS interaction was needed to prevent inadequate NO production under basal conditions but also to facilitate the integration of extracellular stimuli to intracellular NO signals. Compartmentation of key actors in the EDHF signaling pathway is now also proposed to take place into caveolae. Accordingly, caveolin-deficient animals revealed both an unopposed NO production promoting vessel dilation and a lack of EDHF-driven vasorelaxation. The transient receptor potential (TRP) channels are the link between caveolae and EDHF. Different TRP channels involved in the capacitative calcium entry were found to directly interact with caveolin-1 in endothelial cells. TRPC1 and TRPC4 form a complex with the endoplasmic reticulum IP3 receptor thereby optimizing calcium signaling. EDHF-driven vasodilation was documented to be altered in a TRPV4-deficient mouse model. The close vicinity between TRPV4 and SKCa channels in caveolae together with the gap-junctions subunits connexins support a role of these microdomains in the generation and propagation of EDHF to vascular smooth muscle cells. In conclusion, caveolae and caveolin are important control points in the control of blood pressure by the endothelium. This also highlights how any alteration in the caveolae integrity or caveolin abundance may lead to and/or exacerbate endothelial dysfunction and associated cardiovascular diseases.
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Affiliation(s)
- G Rath
- Unit of Pharmacology and Therapeutics, Universite Catholique de Louvain, UCL-FATH 5349, 52 Avenue E. Mounier, B-1200 Brussels, Belgium
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6
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Yuyama K, Sekino-Suzuki N, Kasahara K. [Lipid rafts and heterotrimeric G proteins]. Tanpakushitsu Kakusan Koso 2008; 53:1558-1563. [PMID: 21089366] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
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7
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Suetsugu S, Takano K. [Molecules that regulate morphology of the plasma membrane]. Tanpakushitsu Kakusan Koso 2008; 53:1326-1336. [PMID: 18788456] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
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8
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Coyne CB, Shen L, Turner JR, Bergelson JM. Coxsackievirus entry across epithelial tight junctions requires occludin and the small GTPases Rab34 and Rab5. Cell Host Microbe 2007; 2:181-92. [PMID: 18005733 DOI: 10.1016/j.chom.2007.07.003] [Citation(s) in RCA: 236] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2007] [Revised: 06/19/2007] [Accepted: 07/18/2007] [Indexed: 01/03/2023]
Abstract
The major group B coxsackievirus (CVB) receptor is a component of the epithelial tight junction (TJ), a protein complex that regulates the selective passage of ions and molecules across the epithelium. CVB enters polarized epithelial cells from the TJ, causing a transient disruption of TJ integrity. Here we show that CVB does not induce major reorganization of the TJ, but stimulates the specific internalization of occludin-a TJ integral membrane component-within macropinosomes. Although occludin does not interact directly with virus, depletion of occludin prevents CVB entry into the cytoplasm and inhibits infection. Both occludin internalization and CVB entry require caveolin but not dynamin; both are blocked by inhibitors of macropinocytosis and require the activity of Rab34, Ras, and Rab5, GTPases known to regulate macropinocytosis. Thus, CVB entry depends on occludin and occurs by a process that combines aspects of caveolar endocytosis with features characteristic of macropinocytosis.
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Affiliation(s)
- Carolyn B Coyne
- Division of Infectious Diseases, Children's Hospital of Philadelphia, Philadelphia, PA 19104, USA.
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9
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Del Pozo MA, Schwartz MA. Rac, membrane heterogeneity, caveolin and regulation of growth by integrins. Trends Cell Biol 2007; 17:246-50. [PMID: 17363257 DOI: 10.1016/j.tcb.2007.03.001] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2006] [Revised: 02/06/2007] [Accepted: 03/02/2007] [Indexed: 02/08/2023]
Abstract
Anchorage dependence of growth blocks cell proliferation in inappropriate environments, thereby inhibiting cancer cell invasion and metastasis. Inhibition of growth regulatory pathways, including Rac, Erk and PtdIns 3-kinase in non-adherent cells mediates this effect. Here, we review recent work showing that integrin-mediated adhesion controls Rac binding to membranes. Rac binding sites can be found within cholesterol-enriched membrane domains, which are internalized when cells are deprived of adhesion. Endocytosis of these domains is mediated by caveolae and regulated by caveolin-1 phosphorylated on Tyr 14. This mechanism can account for the control of multiple pathways by integrins, thus providing an important mechanism for anchorage dependence of growth.
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Affiliation(s)
- Miguel A Del Pozo
- Integrin Signalling Laboratory, Centro Nacional de Investigaciones Cardiovasculares, Melchor Fernández Almagro 3, Madrid, Spain
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10
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Pohl J, Ring A, Ehehalt R, Herrmann T, Stremmel W. New concepts of cellular fatty acid uptake: role of fatty acid transport proteins and of caveolae. Proc Nutr Soc 2007; 63:259-62. [PMID: 15294040 DOI: 10.1079/pns2004341] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Efficient uptake and channelling of long-chain fatty acids (LCFA) are critical cell functions. Evidence is emerging that proteins are important mediators of LCFA-trafficking into cells and various proteins have been suggested to be involved in this process. Amongst these proteins is a family of membrane-associated proteins termed fatty acid transport proteins (FATP). So far six members of this family, designated FATP 1–6, have been characterized. FATP 1, 2 and 6 show a highly-conserved AMP-binding region that participates in the activation of very-long-chain fatty acids (VLCFA) to form their acyl-CoA derivatives. The mechanisms by which FATP mediate LCFA uptake are not well understood, but several studies provide evidence that uptake of LCFA across cellular membranes is closely linked to acyl-CoA synthetase activity. It is proposed that FATP indirectly enhance LCFA uptake by activating VLCFA to their CoA esters, which are required to maintain the typical structure of lipid rafts in cellular membranes. Recent work has shown that the structural integrity of lipid rafts is essential for cellular LCFA uptake. This effect might be exerted by proteins, e.g. caveolin-1 and FAT/CD36, that use lipid rafts as platforms and bind or transport LCFA. The proposed molecular mechanisms await further experimental investigation.
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Affiliation(s)
- Jürgen Pohl
- Departments of Gastroenterology and Internal Medicine, University of Heidelberg, Bergheimer Str. 58, 69115 Heidelberg, Germany
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11
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Abstract
Caveolae (caveolin-containing lipid rafts) are plasma membrane domains that scaffold and organize a variety of important proteins in eukaryotic cells. Recent work shows that caveolins can act independently of caveolae, both in cells that lack caveolae (e.g. neurons and leukocytes) and in non-caveolar regions of cells that have caveolae (e.g. cardiac myocytes and fibroblasts). Phosphorylation of caveolins can influence the scaffolding of protein partners, and caveolins appear to participate in the protection and trafficking of proteins to and from the plasma membrane. Together, these results suggest that, despite their name, caveolins should now be thought of as proteins that scaffold signaling and other proteins in both caveolar and non-caveolar regions.
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Affiliation(s)
- Brian P Head
- Department of Pharmacology, University of California San Diego, La Jolla, CA 92093, USA
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12
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MESH Headings
- Animals
- Caveolins/metabolism
- Caveolins/physiology
- Humans
- Muscle, Smooth, Vascular/cytology
- Muscle, Smooth, Vascular/metabolism
- Muscle, Smooth, Vascular/physiology
- Reactive Oxygen Species/metabolism
- Receptor, Angiotensin, Type 1/metabolism
- Receptor, Angiotensin, Type 1/physiology
- Signal Transduction/physiology
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Affiliation(s)
- Masuko Ushio-Fukai
- Department of Medicine, Emory University School of Medicine, Atlanta, GA, USA.
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13
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Abstract
We show here that the GTPase RhoG is involved in caveolar trafficking. Wild-type RhoG moves sequentially to the plasma membrane, intracellular vesicles, and the Golgi apparatus along markers of this endocytic pathway. Such translocation is associated with changes in RhoG GDP/GTP levels and is highly dependent on lipid raft integrity and on the function of the GTPase dynamin2. In addition, the constitutively active RhoG(Q61L) mutant is preferentially located in endocytic vesicles that can be decorated with markers of the caveola-derived endocytic pathway. RhoG(Q61L), but not the analogous Rac1 mutant protein, affects caveola internalization and the subsequent delivery of endocytic vesicles to the Golgi apparatus. The expression of RhoG/Rac1 chimeric proteins and RhoG(Q61L) effector mutants in cells induces alterations in the internalization of caveolae and severe changes in vesicle structure, respectively. However, the knockdown of endogenous rhoG transcripts using small interfering RNAs does not affect significantly the trafficking of caveola-derived vesicles, suggesting that RhoG function is dispensable for this endocytic process or, alternatively, that its function is compensated by other molecules. Taken together, these observations assign a novel function to RhoG and suggest that caveolar trafficking, as previously shown for other endocytic routes, is modulated by GTPases of the Ras superfamily.
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Affiliation(s)
| | | | - XR Bustelo
- Correspondence: Dr XR Bustelo, Centro de Investigación del Cáncer, Instituto de Biología Molecular y Celular del Cáncer (IBMCC), and Red Temática Cooperativa de Centros de Cáncer, CSIC-University of Salamanca, Campus Unamuno, E-37007 Salamanca, Spain. E-mail:
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14
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Feron O, Balligand JL. Caveolins and the regulation of endothelial nitric oxide synthase in the heart. Cardiovasc Res 2006; 69:788-97. [PMID: 16483868 DOI: 10.1016/j.cardiores.2005.12.014] [Citation(s) in RCA: 115] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/07/2005] [Revised: 12/12/2005] [Accepted: 12/22/2005] [Indexed: 11/28/2022] Open
Abstract
Virtually all cell types within the myocardium express caveolae, where cell-specific isoforms of caveolin both maintain the structural organisation of these cholesterol-rich of the plasmalemma and serve as scaffolds for the dynamic constitution of "signalosomes", or hubs concentrating numerous transmembrane signaling proteins and their effectors. Analysis of the phenotype of mice with genetic deletion or overexpression of specific caveolin isoforms has provided key evidence for the importance of caveolins and caveolae in several aspects of the cardiovascular biology, including vascular contractility, lipid metabolism, angiogenesis, or the control of cardiac hypertrophy. Among specific protein-protein interactions involving caveolins in cardiac tissue, these genetic models unequivocally confirmed the functional importance of the dynamic association of the endothelial isoform of nitric oxide synthase (eNOS) for its post-translational regulation in endothelial cells and cardiac myocytes, which bears on the enzyme's capacity to modulate nitric oxide (NO)-dependent endothelial function, angiogenesis, and excitation-contraction coupling. We will review the current understanding of this regulation of eNOS (and potentially other NOS isoforms) through protein-protein interactions involving several G-protein-coupled receptors and other allosteric modulators in the context of emerging paradigms on the regulation of cardiac function by NO.
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Affiliation(s)
- Olivier Feron
- Unit of Pharmacology and Therapeutics, FATH 5349, Department of Medicine, Université catholique de Louvain, 53 avenue Mounier, 1200 Brussels, Belgium
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15
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Fleming I. Segregation and integration: roles played by caveolae and caveolins in the cardiovascular system. Cardiovasc Res 2006; 69:784-7. [PMID: 16464441 DOI: 10.1016/j.cardiores.2006.01.008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/06/2006] [Accepted: 01/10/2006] [Indexed: 11/18/2022] Open
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16
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Feron O. [Role of caveolin in angiogenesis and vasculogenesis processes: therapeutic implications in ischemic diseases and cancerology]. Bull Mem Acad R Med Belg 2006; 161:279-90; discussion 290-1. [PMID: 17283900] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Affiliation(s)
- O Feron
- Unit of Pharmacology and Therapeutics, UCL-FATH 5349
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17
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Abstract
Vascular endothelium is a continuous cell layer lining the cardiovascular system and serves as an interface between blood and the vascular wall tissue. Although the basic morphology of endothelial cells is similar in blood vessels of different organs and tissues, there is a great heterogeneity in endothelial cell types based on structural, metabolic, and developmental differences within each organ, particularly in the pulmonary vasculature. Current data about the usage of different markers for the immunohistochemical detection of endothelial cells in lung tissue are summarized, and functional aspects of caveolin expression after lung injury and in pulmonary hypertension are discussed.
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Affiliation(s)
- Michael Kasper
- Institute of Anatomy, Medical Faculty Carl Gustav Carus, Technical University of Dresden, Dresden, Germany.
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18
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Schwartz E, Reaven E, Topper J, Tsao P. Transforming growth factor-beta receptors localize to caveolae and regulate endothelial nitric oxide synthase in normal human endothelial cells. Biochem J 2005; 390:199-206. [PMID: 15819614 PMCID: PMC1184575 DOI: 10.1042/bj20041182] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Caveolae (sphingolipid- and cholesterol-rich, 100 nm flask-shaped invaginations of the cell membrane) serve as a nexus of cell signalling. In the present study caveolin-rich lipid raft domains were extracted from HUVEC (human umbilical-vein endothelial cells) using both density gradient and immunoprecipitation techniques, and demonstrated localization of the TGF-beta (transforming growth factor-beta) receptors TbetaRI and TbetaRII to the Cav-1 (caveolin-1)-enriched raft fractions of these normal, human endothelial cells. Immunoprecipitation demonstrated an association between TbetaRI and TbetaRII, as well as an association of the TbetaRs receptors with Cav-1 and eNOS (endothelial nitric oxide synthase), suggesting a mutual co-localization to caveolae; after treatment of HUVEC with 5 ng/ml TGF-beta1 for 15 min, however, co-precipitation of eNOS with TbetaRI, TbetaRII and Cav-1 was diminished. The loss of immunoprecipitable eNOS from Cav-1-enriched fractions was accompanied by a decrease both in phosphorylation of eNOS and in enzymatic activity (conversion of arginine into citrulline). No change in the localization of eNOS to morphologically distinct caveolae could be detected by electron microscopy after treatment of HUVEC with TGF-beta1 for 20 min. The results of these investigations provide evidence that TbetaRI interacts with eNOS in the caveolae of normal, human endothelial cells and has a regulatory function on basal eNOS enzymatic activity.
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Affiliation(s)
- Eric A. Schwartz
- *Division of Cardiovascular Medicine, Stanford University School of Medicine, Falk Center, 300 Pasteur Dr., MC5406, Stanford, CA 94305-5406, U.S.A
- †Department of Endocrinology, Carl T. Hayden VA Medical Center, Phoenix, AZ 85012, U.S.A
| | - Eve Reaven
- ‡Electron Microscopy Laboratory, VA Palo Alto Health Care System, Palo Alto, CA 94304-1290, U.S.A
| | - James N. Topper
- *Division of Cardiovascular Medicine, Stanford University School of Medicine, Falk Center, 300 Pasteur Dr., MC5406, Stanford, CA 94305-5406, U.S.A
- §Frasier Healthcare Ventures, Palo Alto, CA 94301-1629, U.S.A
| | - Philip S. Tsao
- *Division of Cardiovascular Medicine, Stanford University School of Medicine, Falk Center, 300 Pasteur Dr., MC5406, Stanford, CA 94305-5406, U.S.A
- To whom correspondence should be addressed (email )
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19
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Song RXD, Zhang Z, Santen RJ. Estrogen rapid action via protein complex formation involving ERalpha and Src. Trends Endocrinol Metab 2005; 16:347-53. [PMID: 16126407 DOI: 10.1016/j.tem.2005.06.010] [Citation(s) in RCA: 113] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/23/2005] [Revised: 04/27/2005] [Accepted: 06/27/2005] [Indexed: 10/25/2022]
Abstract
This review provides insight into biomolecular knowledge regarding the non-genomic actions of estrogen in hormone-dependent breast cancer, particularly its role in the rapid stimulation of pathways that transmit signals to increase cell division or decrease programmed cell death. Until recently, attention to estrogenic effects focused primarily on events in the nucleus, where most estrogen receptors (ERalpha and beta) reside. However, a fraction of ERalpha associated with the cell membrane also participates in rapid estrogen-induced cell membrane-mediated events via formation of a protein complex with many signaling molecules, leading to activation of the mitogen-activated protein kinase and Akt signaling pathways. Understanding the mechanisms underlying these relationships, with the aim of abrogating specific steps, should lead to more targeted strategies to treat hormone-dependent breast cancer.
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Affiliation(s)
- Robert X-D Song
- Department of Internal Medicine, University of Virginia School of Medicine, Charlottesville, Virginia 22903, USA.
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20
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Abstract
Caveolae, discovered by electron microscope in the 1950s, are membrane invaginations that accommodate various molecules that are involved in cellular signaling. Caveolin, a major protein component of caveolae identified in 1990s, has been known to inhibit the function of multiple caveolar proteins, such as kinases, which are involved in cell growth and proliferation, and thus considered to be a general growth signal inhibitor. Recent studies using transgenic mouse models have suggested that insulin signal may be exempted from this inhibition, which rather requires the presence of caveolin for proper signaling. Caveolin may stabilize insulin receptor protein or directly stimulate insulin receptors. Other studies have demonstrated that caveolae provide the TC10 complex with cellular microdomains for glucose transportation through Glut4. These findings suggest that caveolin plays an important role in insulin signal to maintain glucose metabolism in intact animals. However, the role of caveolin in insulin signal may differ from that in other transmembrane receptor signals.
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Affiliation(s)
- Yoshihiro Ishikawa
- Department of Physiology, Yokohama City University School of Medicine, 3-9 Fukuura Kanazawa, Yokohama 236-0004, Japan
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21
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Abstract
BACKGROUND Multiple lines of evidence have implicated the CAV-1 gene in prostate cancer progression. CAV-1 is located within the prostate cancer aggressiveness locus at 7q31-33, and was identified as being overexpressed in prostate tumors. Mutation screening was performed as well as a case-control study to examine if polymorphisms in CAV-1 are associated with prostate cancer aggressiveness in a German population. METHODS We sequenced the CAV-1 promoter region and its open reading frame in prostate cancer families with linkage to chromosome 7q31-33. Additionally, 105 unrelated familial prostate cancer probands, 190 sporadic cases, and 191 controls were genotyped at four intronic single nucleotide polymorphisms. Resulting haplotypes were tested for association using age at diagnosis, tumor grade, TNM stage, and follow up information to stratify for aggressive disease. RESULTS No mutation was found in the CAV-1 coding region or in the promoter. One of the 11 observed haplotypes showed an increased frequency in cases with high tumor stage (P = 0.03). CONCLUSIONS This is the first report providing evidence for CAV-1 being involved in predisposition to aggressive prostate cancer. The association of a potential risk haplotype agrees well with a role of CAV-1 in tumor progression but needs further confirmation.
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Abstract
Early results suggested that the amphotropic murine leukemia virus (A-MLV) does not enter cells via endocytosis through clathrin-coated pits and this gammaretrovirus has therefore been anticipated to fuse directly with the plasma membrane. However, here we present data implicating a caveola-mediated endocytic entry route for A-MLV via its receptor Pit2. Caveolae belong to the cholesterol-rich microdomains characterized by resistance to nonionic detergents such as Triton X-100. Extraction of murine fibroblastic NIH 3T3 cells in cold Triton X-100 showed the presence of the A-MLV receptor Pit2 in detergent-insoluble microdomains. Using coimmunoprecipitation of cell extracts, we were able to demonstrate direct association of Pit2 with caveolin-1, the structural protein of caveolae. Other investigations revealed that A-MLV infection in contrast to vesicular stomatitis virus infection is a slow process (t(1/2) approximately 5 h), which is dependent on plasma membrane cholesterol but independent of NH4Cl treatment of cells; NH4Cl impairs entry via clathrin-coated pits. Furthermore, expression of dominant-negative caveolin-1 decreased the susceptibility to infection via Pit2 by approximately 70%. These results show that A-MLV can enter cells via a caveola-dependent entry route. Moreover, increase in A-MLV infection by treatment with okadaic acid as well as entry of fusion-defective fluorescent A-MLV virions in NIH 3T3 cells further confirmed our findings and show that A-MLV can enter mouse fibroblasts via an endocytic entry route involving caveolae. Finally, we also found colocalization of fusion-defective fluorescent A-MLV virions with caveolin-1 in NIH 3T3 cells. This is the first time substantial evidence has been presented implicating the existence of a caveola-dependent endocytic entry pathway for a retrovirus.
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Affiliation(s)
- Christiane Beer
- Department of Molecular Biology, Aarhus University, C. F. Møllers Allé, Bldg. 130, DK-8000 Aarhus C, Denmark
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23
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Abstract
In mammalian cells a complex interplay regulates the distribution of cholesterol between intracellular membrane compartments. One important aspect of cholesterol regulation is intracellular cholesterol storage in neutral lipid storage organelles called lipid droplets or lipid bodies (LBs). Recent work has thrust the LB into the limelight as a complex and dynamic cellular organelle. LBs play a crucial role in maintaining the cellular levels of cholesterol by regulating the interplay between lipid storage, hydrolysis and trafficking. Studies of caveolins, caveolar membrane proteins linked to lipid regulation, are providing new insights into the role of LBs in regulating cholesterol balance.
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Affiliation(s)
- Sally Martin
- Institute for Molecular Bioscience and Centre for Microscopy and Microanalysis, University of Queensland, Brisbane, Qld 4072, Australia
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24
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Tyagi MG, Namboodri KV. Evaluation of vasopressin mediated effects on hemostatic mechanisms: relationship with aquaporins and caveolin proteins. Indian J Exp Biol 2005; 43:710-4. [PMID: 16121712] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
With a view to evaluate the role of AQP-1 and caveolin proteins in the hemostatic actions of vasopressin, hemostasis was evaluated by bleeding and clotting time respectively. Groups of mice and guinea pigs were treated with arginine vasopressin (AVP) and 1-deamino-8D-AVP (DDAVP) to evaluate their effects on the hemostasis. DDAVP and AVP were able to appreciably reduce the bleeding and clotting time after sodium thiopentone, but not effectively after TEA treatment. Animal groups were pretreated with aquaporin-1 (AQP-1) blockers or water deprived to enhance the expression of AQP-1 water channels. Another group of animals were treated with caveolin protein modulators, cholera toxin (CTX) and the effect of vasopressin analogues evaluated. The results suggest that AQP-1 water channels and caveolin proteins contribute to modulate the hemostatic mechanisms of vasopressin.
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Affiliation(s)
- Manoj G Tyagi
- Department of Pharmacology, Christian Medical College, Vellore 632 002, India.
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25
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Gamboa S, Ramalho-Santos J. SNARE proteins and caveolin-1 in stallion spermatozoa: possible implications for fertility. Theriogenology 2005; 64:275-91. [PMID: 15955353 DOI: 10.1016/j.theriogenology.2004.11.021] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2004] [Revised: 11/25/2004] [Accepted: 11/30/2004] [Indexed: 10/25/2022]
Abstract
Proteins implicated in the "SNARE hypothesis" for membrane fusion have been characterized in the acrosome of several mammalian species, and a functional role for these proteins during the acrosome reaction has been proposed. We have investigated the presence of SNAREs in equine sperm, using semen samples obtained from stallions with varying fertility. Immunocytochemical analysis revealed that members of different SNARE families can be detected on the acrosome of equine sperm, notably in the acrosomal cap and equatorial segment. These proteins include the t-SNARE syntaxin, the v-SNARE synaptobrevin/VAMP, the calcium sensor synaptotagmin, and the ATPase NSF. Also present is caveolin-1, a component of lipid rafts. Stallions with fertility problems presented the worst quality of sperm and acrosomal membrane, and had less sperm cells stained positively for SNAREs and caveolin-1, than sperm from fertile donors (p < 0.001). Ubiquitin surface staining was also performed and it seemed to inversely correlate with stallion fertility, supporting data obtained with the negative staining technique. A male-related problem was confirmed when mares that had failed to impregnate with samples from an infertile stallion were successfully inseminated with sperm from a fertile donor. Furthermore NSF, synaptotagmin and caveolin-1 staining seemed to be useful in predicting stallion fertility, i.e. significantly more sperm cells stained positively for these proteins in samples from fertile males. Although these results need to be expanded on a larger scale, they suggest that acrosomal and surface staining of equine sperm with novel probes may constitute useful tools in predicting stallion fertility.
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Affiliation(s)
- Sandra Gamboa
- Department of Zootechnic Sciences, Agricultural School, Polytechnic Institute of Coimbra, Bencanta, 3040-316 Coimbra, Portugal
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26
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Abstract
In this issue of Molecular Pharmacology, Oliveras-Reyes et al. (p. 356) describe the agonist-stimulated formation of a caveolin-dependent signalplex that includes both the angiotensin AT(1) receptor and the epidermal growth factor receptor, and probably also a number of other signal transduction intermediates. The signalplex is thought to facilitate the action of protein kinases that mediate angiotensin II-induced transactivation of the epidermal growth factor receptor and activation of extracellular signal-regulated kinase, and epidermal growth factor-induced inositol phosphate accumulation and phosphorylation/desensitization of the AT(1) receptor. This work contributes to an emerging view of the complexity and nonlinearity of signaling via G protein-coupled receptors and receptor tyrosine kinases, and of the importance of membrane compartmentalization to signal transduction.
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Affiliation(s)
- Kim A Neve
- VA Medical Center (R&D-30), 3710 SW US Veterans Hospital Rd, Portland, OR 97239-2999, USA.
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27
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Abstract
Caveolin-1 (CAV1) is the structural protein of the filamentous coat that decorates the cytoplasmic surface of each caveola. Cell culture studies have implicated CAV1 in playing an important role in intracellular cholesterol trafficking. In addition, it has been reported that CAV1 forms a detergent-resistant protein complex with Annexin-2 in enterocytes that can be disrupted by the cholesterol absorption inhibitor ezetimibe, suggesting a possible role for CAV1 in cholesterol absorption. In this report, we have evaluated cholesterol homeostasis in Cav1 knock-out mice. Deletion of CAV1 does not result in either a compensatory increase of CAV2 or CAV3 in intestine. In addition, Cav1 knock-out mice display normal mRNA and protein levels of Annexin-2 or the putative cholesterol transport protein Niemann-Pick C1-like 1 (NPC1L1) in proximal intestinal mucosa. Fractional cholesterol absorption and fecal neutral sterol excretion are statistically similar in Cav1 knock-out mice and their wild-type littermates. Moreover, oral administration of ezetimibe is equally effective in decreasing cholesterol absorption in Cav1 null mice and wild-type controls. The mRNA expression levels of genes sensitive to intracellular cholesterol concentration (ATP-binding cassette transporters ABCA1 and ABCG5, hydroxymethylglutaryl-CoA synthase and the LDL receptor) are similarly altered in the proximal intestinal mucosa of Cav1 null and wild-type mice following ezetimibe treatment. These results demonstrate that CAV1 is not required for cholesterol absorption or ezetimibe sensitivity in the mouse.
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Affiliation(s)
- Mark A Valasek
- Department of Physiology, The University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390, USA
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28
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Abstract
The regulatory function of caveolin-2 in cell cycle regulation by insulin was investigated in human insulin receptor-overexpressed rat 1 fibroblast (Hirc-B) cells. Insulin increased induction of the caveolin-2 gene in a time-dependent manner. Direct interaction between ERK and caveolin-2 was confirmed by immunoprecipitation and phosphorylated ERK increased the specific interaction in response to insulin. That insulin induced their nuclear co-localization over time was demonstrated by immunofluorescence microscopy. Insulin increased the S phase in the cell cycle by 6-fold. When recombinant caveolin-1 was transiently expressed, a decrease in the S phase was detected by flow-cytometry. The results indicate that the up-regulation of caveolin-2 in response to insulin activates the downstream signal cascades in the cell cycle, chiefly the increased phosphorylation of ERK, the nuclear translocation of phosphorylated ERK, and the subsequent activation of G0/G1 to S phase transition of the cell cycle. The results also suggest that DNA synthesis and the activation of the cell cycle by insulin are achieved concomitantly with an increase in the interaction between caveolin-2 and phosphorylated ERK, and the nuclear translocation of that complex. Taken together, we conclude that caveolin-2 positively regulates the insulin-induced cell cycle through activation of and direct interaction with ERK in Hirc-B cells.
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Affiliation(s)
- Sangmin Kim
- Department of Biochemistry, Division of Life Science, College of Natural Sciences, Graduate School of Applied Life Science, Gyeongsang National University, Jinju 660-701, Republic of Korea
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29
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Perez-Rosello T, Figueroa A, Salgado H, Vilchis C, Tecuapetla F, Guzman JN, Galarraga E, Bargas J. Cholinergic Control of Firing Pattern and Neurotransmission in Rat Neostriatal Projection Neurons: Role of CaV2.1 and CaV2.2 Ca2+ Channels. J Neurophysiol 2005; 93:2507-19. [PMID: 15615835 DOI: 10.1152/jn.00853.2004] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Besides a reduction of L-type Ca2+-currents (CaV1), muscarine and the peptidic M1-selective agonist, MT-1, reduced currents through CaV2.1 (P/Q) and CaV2.2 (N) Ca2+ channel types. This modulation was strongly blocked by the peptide MT-7, a specific muscarinic M1-type receptor antagonist but not significantly reduced by the peptide MT-3, a specific muscarinic M4-type receptor antagonist. Accordingly, MT-7, but not MT-3, blocked a muscarinic reduction of the afterhyperpolarizing potential (AHP) and decreased the GABAergic inhibitory postsynaptic currents (IPSCs) produced by axon collaterals that interconnect spiny neurons. Both these functions are known to be dependent on P/Q and N types Ca2+ channels. The action on the AHP had an important effect in increasing firing frequency. The action on the IPSCs was shown to be caused presynaptically as it coursed with an increase in the paired-pulse ratio. These results show: first, that muscarinic M1-type receptor activation is the main cholinergic mechanism that modulates Ca2+ entry through voltage-dependent Ca2+ channels in spiny neurons. Second, this muscarinic modulation produces a postsynaptic facilitation of discharge together with a presynaptic inhibition of the GABAergic control mediated by axon collaterals. Together, both effects would tend to recruit more spiny neurons for the same task.
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Affiliation(s)
- Tamara Perez-Rosello
- Departamento de Biofísica, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City DF, Mexico
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30
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Abstract
Ischaemia-reperfusion and toxic injury are leading causes of acute renal failure (ARF). Both of these injury initiators use secondary mediators of damage in oxygen-derived free radicals. Several recent publications about ischaemia-reperfusion and toxin-induced ARF have indicated that plasma membrane structures called caveolae, and their proteins, the caveolins, are potential participants in protecting or repairing renal tissues. Caveolae and caveolins have previously been ascribed many functions, a number of which may mediate cell death or survival of injured renal cells. This review proposes possible pathophysiological mechanisms by which altered caveolin-1 expression and localization may affect renal cell survival following oxidative stress.
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Affiliation(s)
- Christine Percy
- Department of Molecular and Cellular Pathology, University of Queensland School of Medicine, Herston, Brisbane, Queensland, Australia
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31
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Abstract
Tissue factor pathway inhibitor (TFPI) blocks tissue factor-factor VIIa (TF-FVIIa) activation of factors X and IX through the formation of the TF-FVIIa-FXa-TFPI complex. Most TFPI in vivo associates with caveolae in endothelial cells (EC). The mechanism of this association and the anticoagulant role of caveolar TFPI are not yet known. Here we show that expression of caveolin-1 (Cav-1) in 293 cells keeps TFPI exposed on the plasmalemma surface, decreases the membrane lateral mobility of TFPI, and increases the TFPI-dependent inhibition of TF-FVIIa. Caveolae-associated TFPI supports the co-localization of the quaternary complex with caveolae. To investigate the significance of these observations for EC we used RNA interference to deplete the cells of Cav-1. Functional assays and fluorescence microscopy revealed that the inhibitory properties of TFPI were diminished in EC lacking Cav-1, apparently through deficient assembly of the quaternary complex. These findings demonstrate that caveolae regulate the inhibition by cell-bound TFPI of the active protease production by the extrinsic pathway of coagulation.
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Affiliation(s)
- Cristina Lupu
- Cardiovascular Biology Research Program, Oklahoma Medical Research Foundation, 825 NE 13th Street, Oklahoma City, OK 73104, USA.
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32
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Abstract
Caveolae and lipid rafts are discrete regions within the plasma membrane that coordinate and regulate a variety of signaling processes. The exact relationship between caveolae and lipid rafts is unclear. However, caveolae contain a protein called caveolin that serves as a biochemical marker for caveolae. In addition, caveolin plays a role in maintaining the lipid composition of caveolae, the morphology of caveolae, and the signals that emanate from caveolae. The physiologic importance of caveolae is evidenced by recent studies using caveolin knockout mice that show dramatic abnormalities in the cardiovascular system, such as pulmonary hypertension and cardiac hypertrophy. In this review, we will focus on the role of caveolae in the cardiovascular system.
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Affiliation(s)
- Xiang-An Li
- University of Kentucky Medical School, Department of Pediatrics, Lexington, 40536-0230, USA
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33
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Williams TM, Hassan GS, Li J, Cohen AW, Medina F, Frank PG, Pestell RG, Di Vizio D, Loda M, Lisanti MP. Caveolin-1 promotes tumor progression in an autochthonous mouse model of prostate cancer: genetic ablation of Cav-1 delays advanced prostate tumor development in tramp mice. J Biol Chem 2005; 280:25134-45. [PMID: 15802273 DOI: 10.1074/jbc.m501186200] [Citation(s) in RCA: 131] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Caveolin-1 (Cav-1) is the primary structural component of caveolae and is implicated in the processes of vesicular transport, cholesterol balance, transformation, and tumorigenesis. Despite an abundance of data suggesting that Cav-1 has transformation suppressor properties both in vitro and in vivo, Cav-1 is expressed at increased levels in human prostate cancer. To investigate the role of Cav-1 in prostate cancer onset and progression, we interbred Cav-1(-/-) null mice with a TRAMP (transgenic adenocarcinoma of mouse prostate) model that spontaneously develops advanced prostate cancer and metastatic disease. We found that, although the loss of Cav-1 did not affect the appearance of minimally invasive prostate cancer, its absence significantly impeded progression to highly invasive and metastatic disease. Inactivation of one (+/-) or both (-/-) alleles of Cav-1 resulted in significant reductions in prostate tumor burden, as well as decreases in regional lymph node metastases. Moreover, further examination revealed decreased metastasis to distant organs, such as the lungs, in TRAMP/Cav-1(-/-) mice. Utilizing prostate carcinoma cell lines (C1, C2, and C3) derived from TRAMP tumors, we also showed a positive correlation between Cav-1 expression and the ability of these cells to form tumors in vivo. Furthermore, down-regulation of Cav-1 expression in these cells, using a small interfering RNA approach, significantly reduced their tumorigenic and metastatic potential. Mechanistically, we showed that loss or down-regulation of Cav-1 expression results in increased apoptosis, with increased prostate apoptosis response factor-4 and PTEN levels in Cav-1(-/-) null prostate tumors. Our current findings provide the first in vivo molecular genetic evidence that Cav-1 does indeed function as a tumor promoter during prostate carcinogenesis, rather than as a tumor suppressor.
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Affiliation(s)
- Terence M Williams
- Department of Molecular Pharmacology and The Albert Einstein Cancer Center, Department of Urology, Albert Einstein College of Medicine, Bronx, New York 10461, USA
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34
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Ravid D, Maor S, Werner H, Liscovitch M. Caveolin-1 inhibits cell detachment-induced p53 activation and anoikis by upregulation of insulin-like growth factor-I receptors and signaling. Oncogene 2005; 24:1338-47. [PMID: 15592498 DOI: 10.1038/sj.onc.1208337] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Caveolin-1 is an essential structural constituent of caveolae that has been implicated in mitogenic signaling and oncogenesis. Utilizing MCF-7 human breast cancer cells, stably transfected with caveolin-1 (MCF-7/Cav1), we previously demonstrated that caveolin-1 expression decreases MCF-7 cell proliferation and colony formation in soft agar. However, the loss of anchorage-independent growth is associated with inhibition of anoikis, as MCF-7/Cav1 cells exhibit increased survival after detachment. Herein we show that this phenotype is associated with suppression of detachment-induced activation of p53 and of the consequent induction of cyclin-dependent kinase inhibitor p21(WAF1/Cip1). In contrast, activation of p53 and p21(WAF1/Cip1) induced by doxorubicin in MCF-7/Cav1 cells remains largely unaffected. The phenotypic changes observed in MCF-7/Cav1 cells are not accompanied by changes in caspase-6, -7, -8 and -9 and cannot be explained by changes in Bid and Bcl-2 expression. However, MCF-7/Cav1 cells exhibit a constitutively phosphorylated Akt kinase and at least one phosphorylated high molecular weight putative Akt substrate which we designated pp340. In addition, MCF-7/Cav1 cells exhibit elevated expression of insulin-like growth factor-I (IGF-I) receptor expression and increased IGF-I signaling to Erk1/2 and to Akt, as well as IGF-I-induced stimulation of pp340 phosphorylation. The addition of IGF-I to the medium rescues the parental MCF-7 cells from anoikis, indicating that IGF-1 can act as a survival factor for suspended MCF-7 cells. Finally, the levels of caveolin-1 are dramatically elevated in a time-dependent manner upon detachment of anoikis-resistant MCF-7/Cav1 cells and HT-29-MDR human multidrug resistant colon cancer cells. We conclude that expression of caveolin-1 in human breast cancer cells enhances matrix-independent cell survival that is mediated by upregulation of IGF-I receptor expression and signaling.
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Affiliation(s)
- Dana Ravid
- Department of Biological Regulation, Weizmann Institute of Science, Candiotty 138, PO Box 26, Rehovot 76100, Israel
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35
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Linder AE, McCluskey LP, Cole KR, Lanning KM, Webb RC. Dynamic association of nitric oxide downstream signaling molecules with endothelial caveolin-1 in rat aorta. J Pharmacol Exp Ther 2005; 314:9-15. [PMID: 15778264 DOI: 10.1124/jpet.105.083634] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Classically, nitric oxide (NO) formed by endothelial NO synthase (eNOS) freely diffuses from its generation site to smooth muscle cells where it activates soluble guanylyl cyclase (sGC), producing cGMP. Subsequently, cGMP activates both cGMP- and cAMP-dependent protein kinases [cGMP-dependent protein kinase (PKG) and cAMP-dependent protein kinase (PKA), respectively], leading to smooth muscle relaxation. In endothelial cells, eNOS has been localized to caveolae, small invaginations of the plasma membrane rich in cholesterol. Membrane cholesterol depletion impairs acetylcholine (ACh)-induced relaxation due to alteration in caveolar structure. Given the nature of NO to be more soluble in a hydrophobic environment than in water, and assuming that colocalization of components in a signal transduction cascade seems to be a critical determinant of signaling efficiency by eNOS activation, we hypothesize that sGC, PKA, and PKG activation may occur at the plasma membrane caveolae. In endothelium-intact rat aortic rings, the relaxation induced by ACh, by the sGC activator 3-(5'-hydroxymethyl-2'furyl)-1-benzyl indazole (YC-1), and by 8-bromo-cGMP was impaired in the presence of methyl-beta-cyclodextrin, a drug that disassembles caveolae by sequestering cholesterol from the membrane. sGC, PKG, and PKA were colocalized with caveolin-1 in aortic endothelium, and this colocalization was abolished by methyl-beta-cyclodextrin. Methyl-beta-cyclodextrin efficiently disassembled caveolae in endothelium. In summary, our results provide evidence of compartmentalization of sGC, PKG, and PKA in endothelial caveolae contributing to NO signaling cascade, giving new insights by which the endothelium mediates vascular smooth muscle relaxation.
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Affiliation(s)
- A Elizabeth Linder
- Medical College of Georgia, Department of Physiology (CA-3101), 1120 Fifteenth St., Augusta, GA 30912-3000, USA.
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36
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Abstract
Recently, we have shown that loss of caveolin-1 leads to marked alterations in insulin signaling and lipolysis in white adipose tissue. However, little is known about the role of caveolin-1 in brown adipose tissue (BAT), a tissue responsible for nonshivering thermogenesis. Here, we show that caveolin-1 null mice have a mildly, yet significantly, decreased resting core body temperature. To investigate this in detail, we next subjected the mice to fasting (for 24 h) or cold treatment (4 degrees C for 24 h), individually or in combination. Interestingly, caveolin-1 null mice showed markedly decreased body temperatures in response to fasting or fasting/cold treatment; however, cold treatment alone had no effect. In addition, under these conditions caveolin-1 null mice failed to show the normal increase in serum nonesterified fatty acids induced by fasting or fasting/cold treatment, suggesting that these mice are unable to liberate triglyceride stores for heat production. In accordance with these results, the triglyceride content of BAT was reduced nearly 10-fold in wild-type mice after fasting/cold treatment, but it was reduced only 3-fold in caveolin-1 null mice. Finally, electron microscopy of adipose tissue revealed dramatic perturbations in the mitochondria of caveolin-1 null interscapular brown adipocytes. Taken together, our data provide the first molecular genetic evidence that caveolin-1 plays a critical functional and structural role in the modulation of thermogenesis via an effect on lipid mobilization.
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Affiliation(s)
- Alex W Cohen
- Department of Molecular Pharmacology, The Albert Einstein Cancer Center, 1300 Morris Park Ave., Bronx, NY 10461, USA
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37
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Wang XL, Ye D, Peterson TE, Cao S, Shah VH, Katusic ZS, Sieck GC, Lee HC. Caveolae Targeting and Regulation of Large Conductance Ca2+-activated K+ Channels in Vascular Endothelial Cells. J Biol Chem 2005; 280:11656-64. [PMID: 15665381 DOI: 10.1074/jbc.m410987200] [Citation(s) in RCA: 112] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The vascular endothelium is richly endowed with caveolae, which are specialized membrane microdomains that facilitate the integration of specific cellular signal transduction processes. We found that the large conductance Ca(2+)-activated K+ (BK) channels are associated with caveolin-1 in bovine aortic endothelial cells (BAECs). OptiPrep gradient cell fractionation demonstrated that BK channels were concentrated in the caveolae-rich fraction in BAECs. Immunofluorescence imaging showed co-localization of caveolin-1 and BK channels in the BAEC membrane. Immunoprecipitation and glutathione S-transferase pull-down assay results indicated that caveolin-1 and BK channels are physically associated. However, whole cell patch clamp recordings could not detect BK (iberiotoxin-sensitive) currents in cultured BAECs under baseline conditions, even though the presence of BK mRNA and protein expression was confirmed by reverse transcription-PCR and Western blots. Cholesterol depletion redistributed the BK channels to non-caveolar fractions of BAECs, resulting in BK channel activation (7.3 +/- 1.6 pA/picofarad (pF), n = 5). BK currents were also activated by isoproterenol (ISO, 1 microM, 6.9 +/- 2.4 pA/pF, n = 6). Inclusion of a caveolin-1 scaffolding domain peptide (10 microM) in the pipette solution completely abrogated the effects of ISO on BK channel activation, whereas inclusion of the scrambled control peptide (10 microM) did not inhibit the ISO effects. We have also found that caveolin-1 knockdown by small interference RNA activated BK currents (5.3 +/- 1.4 pA/pF, n = 6). We conclude that: 1) BK channels are targeted to caveolae microdomains in vascular endothelial cells; 2) caveolin-1 interacts with BK channels and exerts a negative regulatory effect on channel functions; and 3) BK channels are inactive under control conditions but can be activated by cholesterol depletion, knockdown of caveolin-1 expression, or ISO stimulation. These novel findings may have important implications for the role of BK channels in the regulation of endothelial function.
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Affiliation(s)
- Xiao-Li Wang
- Department of Medicine, Mayo Clinic, Rochester, Minnesota 55905, USA
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38
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Sedding DG, Hermsen J, Seay U, Eickelberg O, Kummer W, Schwencke C, Strasser RH, Tillmanns H, Braun-Dullaeus RC. Caveolin-1 facilitates mechanosensitive protein kinase B (Akt) signaling in vitro and in vivo. Circ Res 2005; 96:635-42. [PMID: 15731459 DOI: 10.1161/01.res.0000160610.61306.0f] [Citation(s) in RCA: 128] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Mechanotransduction represents an integral part of vascular homeostasis and contributes to vascular lesion formation. Previously, we demonstrated a mechanosensitive activation of phosphoinositide 3-kinase (PI3-K)/protein kinase B (Akt) resulting in p27Kip1 transcriptional downregulation and cell cycle entry of vascular smooth muscle cells (VSMC). In this study, we further elucidated the signaling from outside-in toward PI3-K/Akt in vitro and in an in vivo model of elevated tensile force. When VSMC were subjected to cyclic stretch (0.5 Hz at 125% resting length), PI3-K, Akt, and Src kinases were found activated. Disrupting caveolar structures with beta-cyclodextrin or transfection of VSMC with caveolin-1 antisense oligonucleotides (ODN) prevented PI3-K and Akt activation and cell cycle entry. Furthermore, PI3-K and Akt were resistant to activation when Src kinases were inhibited pharmacologically or by overexpression of a kinase-dead c-Src mutant. alpha(V)beta3 integrins were identified to colocalize with PI3-K/caveolin-1 complexes, and blockade of alpha(V)beta3 integrins prevented Akt activation. The central role of caveolin-1 in mechanotransduction was further examined in an in vivo model of elevated tensile force. Interposition of wild-type (WT) jugular veins into WT carotid arteries resulted in a rapid Akt activation within the veins that was almost abolished when veins of caveolin-1 knockout (KO) mice were used. Furthermore, late neointima formation within the KO veins was significantly reduced. Our study provides evidence that PI3-K/Akt is critically involved in mechanotransduction of VSMC in vitro and within the vasculature in vivo. Furthermore, caveolin-1 is essential for the integrin-mediated activation of PI3-K/Akt.
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MESH Headings
- Anastomosis, Surgical
- Androstadienes/pharmacology
- Animals
- Aorta/cytology
- Carotid Artery, Common/surgery
- Caveolae/drug effects
- Caveolae/physiology
- Caveolae/ultrastructure
- Caveolin 1
- Caveolins/deficiency
- Caveolins/genetics
- Caveolins/physiology
- Cells, Cultured/enzymology
- Cells, Cultured/physiology
- Cholesterol/metabolism
- Chromones/pharmacology
- Enzyme Activation
- Extracellular Signal-Regulated MAP Kinases/physiology
- Focal Adhesions/metabolism
- Integrin alphaVbeta3/physiology
- Jugular Veins/transplantation
- Male
- Membrane Lipids/metabolism
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Morpholines/pharmacology
- Muscle, Smooth, Vascular/cytology
- Myocytes, Smooth Muscle/enzymology
- Myocytes, Smooth Muscle/physiology
- Phosphatidylinositol 3-Kinases/physiology
- Phosphoinositide-3 Kinase Inhibitors
- Protein Serine-Threonine Kinases/physiology
- Proto-Oncogene Proteins/physiology
- Proto-Oncogene Proteins c-akt
- Proto-Oncogene Proteins pp60(c-src)/physiology
- Pyrazoles/pharmacology
- Pyrimidines/pharmacology
- Rats
- Rats, Sprague-Dawley
- Signal Transduction/physiology
- Stress, Mechanical
- Tunica Intima/pathology
- Wortmannin
- beta-Cyclodextrins/pharmacology
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Affiliation(s)
- Daniel G Sedding
- Department of Internal Medicine I/Cardiology, Giessen University, Giessen, Germany
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39
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López-Rivera E, Lizarbe TR, Martínez-Moreno M, López-Novoa JM, Rodríguez-Barbero A, Rodrigo J, Fernández AP, Alvarez-Barrientos A, Lamas S, Zaragoza C. Matrix metalloproteinase 13 mediates nitric oxide activation of endothelial cell migration. Proc Natl Acad Sci U S A 2005; 102:3685-90. [PMID: 15728377 PMCID: PMC553299 DOI: 10.1073/pnas.0408217102] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
To explore the mechanisms by which NO elicits endothelial cell (EC) migration we used murine and bovine aortic ECs in an in vitro wound-healing model. We found that exogenous or endogenous NO stimulated EC migration. Moreover, migration was significantly delayed in ECs derived from endothelial NO synthase-deficient mice compared with WT murine aortic EC. To assess the contribution of matrix metalloproteinase (MMP)-13 to NO-mediated EC migration, we used RNA interference to silence MMP-13 expression in ECs. Migration was delayed in cells in which MMP-13 was silenced. In untreated cells MMP-13 was localized to caveolae, forming a complex with caveolin-1. Stimulation with NO disrupted this complex and significantly increased extracellular MMP-13 abundance, leading to collagen breakdown. Our findings show that MMP-13 is an important effector of NO-activated endothelial migration.
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Affiliation(s)
- Esther López-Rivera
- Fundación Centro Nacional de Investigaciones Cardiovasculares, Ronda de Poniente 5 Tres Cantos, 28760 Madrid, Spain
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40
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Takenouchi T, Miyashita N, Ozutsumi K, Rose MT, Aso H. Role of caveolin-1 and cytoskeletal proteins, actin and vimentin, in adipogenesis of bovine intramuscular preadipocyte cells. Cell Biol Int 2005; 28:615-23. [PMID: 15350596 DOI: 10.1016/j.cellbi.2004.05.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2003] [Revised: 04/27/2004] [Accepted: 05/25/2004] [Indexed: 10/26/2022]
Abstract
We investigated the involvement of caveolin-1 and the cytoskeletal proteins, actin and vimentin, in the adipogenesis of bovine intramuscular preadipocyte (BIP) cells. Immunoblot analysis demonstrated that levels of caveolin-1 and actin gradually increased during adipose conversion in BIP cells, whereas a slight decrease was observed for vimentin. We found that part of the vimentin was clearly distributed to caveolin-1-enriched membrane fractions in BIP cells, but actin was not. During adipogenesis of BIP cells, treatment with the tubulin depolymerizer, nocodazole, significantly increased intracellular triglyceride accumulation compared to non-treated cells. Immunocytochemical analysis showed that actin microfilaments were significantly disrupted in nocodazole-treated cells. Also, a decrease in the localization of vimentin in caveolin-1-enriched fractions and a failure of vimentin to co-immunoisolate with caveolin-1 were observed in nocodazole-treated cells. These results suggest that a rearrangement of cytoskeletal proteins has a role in the intracellular accumulation of lipid droplets during adipogenesis of BIP cells.
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Affiliation(s)
- Takato Takenouchi
- Laboratory of Animal Cell Biology, National Institute of Agrobiological Sciences, Kannondai 3-1-5, Tsukuba, Ibaraki 305-8602, Japan.
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41
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Capozza F, Combs TP, Cohen AW, Cho YR, Park SY, Schubert W, Williams TM, Brasaemle DL, Jelicks LA, Scherer PE, Kim JK, Lisanti MP. Caveolin-3 knockout mice show increased adiposity and whole body insulin resistance, with ligand-induced insulin receptor instability in skeletal muscle. Am J Physiol Cell Physiol 2005; 288:C1317-31. [PMID: 15689413 DOI: 10.1152/ajpcell.00489.2004] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Caveolin-3 (Cav-3) is expressed predominantly in skeletal muscle fibers, where it drives caveolae formation at the muscle cell's plasma membrane. In vitro studies have suggested that Cav-3 may play a positive role in insulin signaling and energy metabolism. We directly address the in vivo metabolic consequences of genetic ablation of Cav-3 in mice as it relates to insulin action, glucose metabolism, and lipid homeostasis. At age 2 mo, Cav-3 null mice are significantly larger than wild-type mice, and display significant postprandial hyperinsulinemia, whole body insulin resistance, and whole body glucose intolerance. Studies using hyperinsulinemic-euglycemic clamps revealed that Cav-3 null mice exhibited 20% and 40% decreases in insulin-stimulated whole body glucose uptake and whole body glycogen synthesis, respectively. Whole body insulin resistance was mostly attributed to 20% and 40% decreases in insulin-stimulated glucose uptake and glucose metabolic flux in the skeletal muscle of Cav-3 null mice. In addition, insulin-mediated suppression of hepatic glucose production was significantly reduced in Cav-3 null mice, indicating hepatic insulin resistance. Insulin-stimulated glucose uptake in white adipose tissue, which does not express Cav-3, was decreased by approximately 70% in Cav-3 null mice, suggestive of an insulin-resistant state for this tissue. During fasting, Cav-3 null mice possess normal insulin receptor protein levels in their skeletal muscle. However, after 15 min of acute insulin stimulation, Cav-3 null mice show dramatically reduced levels of the insulin receptor protein, compared with wild-type mice treated identically. These results suggest that Cav-3 normally functions to increase the stability of the insulin receptor at the plasma membrane, preventing its rapid degradation, i.e., by blocking or slowing ligand-induced receptor downregulation. Thus our results demonstrate the importance of Cav-3 in regulating whole body glucose homeostasis in vivo and its possible role in the development of insulin resistance. These findings may have clinical implications for the early diagnosis and treatment of caveolinopathies.
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Affiliation(s)
- Franco Capozza
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, 1300 Morris Park Ave., Bronx, NY 10461, USA
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42
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Abstract
Remodeling and plasticity in the adult brain require cholesterol redistribution and synthesis for the formation of new membrane components. Caveolin-1 is a cholesterol-binding membrane protein involved in cellular cholesterol transport and homeostasis. Evidence presented here demonstrates an up-regulation of caveolin-1 in the hippocampus, which was temporally correlated with an increase in synaptophysin during the reinnervation phase in a mouse model of hippocampal deafferentation. Using an in vitro model of neuronal reactive plasticity, we examined the effect of virally mediated overexpression of caveolin-1 on injured differentiated PC12 cells undergoing terminal remodeling. Three days post lesion, caveolin-1-overexpressing cells revealed increases in synaptophysin and GAP-43, two markers of neurite sprouting and synaptogenesis. Morphologically, caveolin-1-overexpressing cells showed a decrease in primary neurite outgrowth and branching as well as an increase in neurite density. Caveolin-1-overexpressing cells also revealed the presence of terminal swelling and beading along processes, consistent with a possible alteration of microtubules stability. Moreover, a focal enrichment of caveolin-1 immunofluorescence was observed at the bases of axonal and dendritic terminals of mouse primary hippocampal neurons. Altogether, these results indicate that caveolin-1 plays an active role in the regulation of injury-induced synaptic and terminal remodeling in the adult CNS.
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Affiliation(s)
- Sophie B Gaudreault
- Douglas Hospital Research Center, Neurological Sciences Department, McGill University, Montreal, Canada
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43
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Damm EM, Pelkmans L, Kartenbeck J, Mezzacasa A, Kurzchalia T, Helenius A. Clathrin- and caveolin-1-independent endocytosis: entry of simian virus 40 into cells devoid of caveolae. ACTA ACUST UNITED AC 2005; 168:477-88. [PMID: 15668298 PMCID: PMC2171728 DOI: 10.1083/jcb.200407113] [Citation(s) in RCA: 370] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Simian Virus 40 (SV40) has been shown to enter host cells by caveolar endocytosis followed by transport via caveosomes to the endoplasmic reticulum (ER). Using a caveolin-1 (cav-1)-deficient cell line (human hepatoma 7) and embryonic fibroblasts from a cav-1 knockout mouse, we found that in the absence of caveolae, but also in wild-type embryonic fibroblasts, the virus exploits an alternative, cav-1-independent pathway. Internalization was rapid (t1/2 = 20 min) and cholesterol and tyrosine kinase dependent but independent of clathrin, dynamin II, and ARF6. The viruses were internalized in small, tight-fitting vesicles and transported to membrane-bounded, pH-neutral organelles similar to caveosomes but devoid of cav-1 and -2. The viruses were next transferred by microtubule-dependent vesicular transport to the ER, a step that was required for infectivity. Our results revealed the existence of a virus-activated endocytic pathway from the plasma membrane to the ER that involves neither clathrin nor caveolae and that can be activated also in the presence of cav-1.
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MESH Headings
- ADP-Ribosylation Factor 6
- ADP-Ribosylation Factors/genetics
- ADP-Ribosylation Factors/physiology
- Actin Cytoskeleton/drug effects
- Actin Cytoskeleton/physiology
- Adaptor Proteins, Signal Transducing
- Animals
- Antigens, Viral, Tumor/metabolism
- Brefeldin A/pharmacology
- Bridged Bicyclo Compounds, Heterocyclic/pharmacology
- Calcium-Binding Proteins/genetics
- Caveolae/physiology
- Caveolin 1
- Caveolin 2
- Caveolins/analysis
- Caveolins/genetics
- Caveolins/physiology
- Cell Line
- Cell Line, Tumor
- Cholesterol/deficiency
- Cholesterol/physiology
- Clathrin/physiology
- Detergents/chemistry
- Dynamin II/genetics
- Dynamin II/physiology
- Embryo, Mammalian/cytology
- Endocytosis/drug effects
- Endocytosis/physiology
- Endoplasmic Reticulum, Smooth/chemistry
- Endoplasmic Reticulum, Smooth/physiology
- Fibroblasts/drug effects
- Fibroblasts/ultrastructure
- Fibroblasts/virology
- Gene Expression
- Genistein/pharmacology
- Humans
- Intracellular Signaling Peptides and Proteins
- Membrane Microdomains/chemistry
- Membrane Microdomains/physiology
- Membrane Proteins/metabolism
- Mice
- Mice, Knockout
- Microscopy, Electron, Transmission
- Microscopy, Fluorescence
- Microtubules/drug effects
- Microtubules/physiology
- Nocodazole/pharmacology
- Phosphoproteins/genetics
- Semliki forest virus/physiology
- Simian virus 40/metabolism
- Thiazoles/pharmacology
- Thiazolidines
- Transferrin/metabolism
- Transport Vesicles/physiology
- Transport Vesicles/ultrastructure
- Tubulin/genetics
- Vesicular Transport Proteins
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Affiliation(s)
- Eva-Maria Damm
- Institute of Biochemistry, Swiss Federal Institute of Technology Zürich (ETHZ), CH-8093 Zürich, Switzerland
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44
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Kirkham M, Fujita A, Chadda R, Nixon SJ, Kurzchalia TV, Sharma DK, Pagano RE, Hancock JF, Mayor S, Parton RG. Ultrastructural identification of uncoated caveolin-independent early endocytic vehicles. ACTA ACUST UNITED AC 2005; 168:465-76. [PMID: 15668297 PMCID: PMC2171740 DOI: 10.1083/jcb.200407078] [Citation(s) in RCA: 330] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Using quantitative light microscopy and a modified immunoelectron microscopic technique, we have characterized the entry pathway of the cholera toxin binding subunit (CTB) in primary embryonic fibroblasts. CTB trafficking to the Golgi complex was identical in caveolin-1null (Cav1−/−) mouse embryonic fibroblasts (MEFs) and wild-type (WT) MEFs. CTB entry in the Cav1−/− MEFs was predominantly clathrin and dynamin independent but relatively cholesterol dependent. Immunoelectron microscopy was used to quantify budded and surface-connected caveolae and to identify noncaveolar endocytic vehicles. In WT MEFs, a small fraction of the total Cav1-positive structures were shown to bud from the plasma membrane (2% per minute), and budding increased upon okadaic acid or lactosyl ceramide treatment. However, the major carriers involved in initial entry of CTB were identified as uncoated tubular or ring-shaped structures. These carriers contained GPI-anchored proteins and fluid phase markers and represented the major vehicles mediating CTB uptake in both WT and caveolae-null cells.
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Affiliation(s)
- Matthew Kirkham
- Institute for Molecular Bioscience, University of Queensland, Queensland 4072, Australia
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45
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Woodman SE, Sotgia F, Galbiati F, Minetti C, Lisanti MP. Caveolinopathies: mutations in caveolin-3 cause four distinct autosomal dominant muscle diseases. Neurology 2005; 62:538-43. [PMID: 14981167 DOI: 10.1212/wnl.62.4.538] [Citation(s) in RCA: 125] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The caveolin-3 protein is expressed exclusively in muscle cells. Caveolin-3 expression is sufficient to form caveolae-sarcolemmal invaginations that are 50 to 100 nm in diameter. Monomers of caveolin-3 oligomerize to form high molecular mass scaffolding on the cytoplasmic surface of the sarcolemmal membrane. A mutation in one caveolin-3 allele produces an aberrant protein product capable of sequestering the normal caveolin-3 protein in the Golgi apparatus of skeletal muscle cells. Improper caveolin-3 oligomerization and membrane localization result in skeletal muscle T-tubule system derangement, sarcolemmal membrane alterations, and large subsarcolemmal vesicle formation. To date, there have been eight autosomal dominant caveolin-3 mutations identified in the human population. Caveolin-3 mutations can result in four distinct, sometimes overlapping, muscle disease phenotypes: limb girdle muscular dystrophy, rippling muscle disease, distal myopathy, and hyperCKemia. Thus, the caveolin-3 mutant genotype-to-phenotype relation represents a clear example of how genetic background can influence phenotypic outcome. This review examines in detail the reported cases of patients with caveolin-3 mutations and their corresponding muscle disease phenotypes.
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Affiliation(s)
- S E Woodman
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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46
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Bernatchez PN, Bauer PM, Yu J, Prendergast JS, He P, Sessa WC. Dissecting the molecular control of endothelial NO synthase by caveolin-1 using cell-permeable peptides. Proc Natl Acad Sci U S A 2005; 102:761-6. [PMID: 15637154 PMCID: PMC545535 DOI: 10.1073/pnas.0407224102] [Citation(s) in RCA: 157] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
In endothelia, NO is synthesized by endothelial NO synthase (eNOS), which is negatively regulated by caveolin-1 (Cav-1), the primary coat protein of caveolae. We show that delivery of Cav-1 amino acids 82-101 (Cav) fused to an internalization sequence from Antennapedia (AP) blocks NO release in vitro and inflammation and tumor angiogenesis in vivo. To characterize the molecular mechanism by which the AP-Cav peptide and Cav-1 mediate eNOS inhibition, we subdivided the Cav portion of AP-Cav into three domains (Cav-A, -B, and -C), synthesized five overlapping peptides (AP-Cav-A, -AB, -B, -BC, and -C), and tested their effects on eNOS-dependent activities. Peptides containing the Cav-B domain (amino acids 89-95) induced time- and dose-dependent inhibition of eNOS-dependent NO release in cultured endothelial cells, NO-dependent inflammation in the ear, and hydraulic conductivity in isolated venules. Alanine scanning of AP-Cav-B revealed that Thr-90 and -91 (T90,91) and Phe-92 (F92) are crucial for AP-Cav-B- and AP-Cav-mediated inhibition of eNOS. Mutation of F92 to A92 in the Cav-1 cDNA caused the loss of eNOS inhibitory activity compared with wild-type Cav-1. These data highlight the importance of amino acids 89-95 and particularly F92 in mediating eNOS inhibition by AP-Cav and Cav-1.
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Affiliation(s)
- Pascal N Bernatchez
- Department of Pharmacology and Program in Vascular Cell Signaling and Therapeutics, Boyer Center for Molecular Medicine, Yale University School of Medicine, New Haven, CT 06536, USA
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47
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Abstract
The heme oxygenase (HO) and nitric oxide synthase (NOS) enzymes generate the gaseous signaling molecules carbon monoxide (CO) and nitric oxide, respectively. Constitutive NOSs localize to caveolae, and their activities are modulated by caveolin-1. Nothing is known of the localization of the inducible heme oxygenase-1 (HO-1) in plasma membrane caveolae. Thus, we examined the distribution and subcellular localization of HO-1, biliverdin reductase (BVR), and NADPH:cytochrome P450 reductase (NPR) in pulmonary artery endothelial cells. Each of these proteins localized in part to plasma membrane caveolae in endothelial cells. Inducers of HO-1 or overexpression of HO-1 increased the content of this protein in a detergent-resistant fraction containing caveolin-1. Inducible HO activity appeared in plasma membrane, cytosol, and isolated caveolae. In addition, caveolae contained endogenous BVR activity, supporting the same compartmentalization of both enzymes. Caveolin-1 physically interacted with HO-1, as shown by coimmunoprecipitation studies. HO activity dramatically increased in cells expressing caveolin-1 antisense transcripts, suggesting a negative regulatory role for caveolin-1. Conversely, caveolin-1 expression attenuated LPS-inducible HO activity. Since their initial characterization in 1969, HO enzymes have been described as endoplasmic reticulum-associated proteins. We demonstrate for the first time the localization of heme degradation enzymes to plasma membrane caveolae, and present novel evidence that caveolin-1 interacts with and modulates HO activity.
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Affiliation(s)
- Hong Pyo Kim
- Division of Pulmonary, Allergy, and Critical Care Medicine, Dept. of Medicine, MUH 628NW, 3459 Fifth Ave., Pittsburgh, PA, 15213, USA.
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48
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Abstract
Caveolae are specialized plasma membrane subdomains capable of transport and sophisticated compartmentalization of cell signaling. Numerous cell functions, including cell type-specific functions, involve caveolae and require caveolin-1, the major protein component of these organelles. Caveolae are particularly abundant in endothelial cells and participate in endothelial transcytosis, vascular permeability, vasomotor tone control, and vascular reactivity. Caveolin-1 drives the formation of plasma membrane caveolae and anchors them to the actin cytoskeleton, modulates cell interaction with the extracellular matrix, pulls together and regulates signaling molecules, and transports cholesterol. Via these functions, caveolin-1 might play an important role in cell movement through control of cell membrane composition and membrane surface expansion, polarization of signaling molecules and matrix proteolysis, and/or cytoskeleton remodeling. Caveolae and caveolin-1 are polarized in migrating endothelial cells, indicating they may play a role in cell motility. Several studies have shown that manipulation of caveolin-1 expression affects cell migration in a complex way. We are reviewing the current data and hypotheses in favor of an essential role for caveolae in cell migration.
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Affiliation(s)
- Angels Navarro
- Department of Anesthesiology Research, Cleveland Clinic Foundation, Cleveland, Ohio 44122, USA
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49
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Lai HH, Boone TB, Yang G, Smith CP, Kiss S, Thompson TC, Somogyi GT. Loss of caveolin-1 expression is associated with disruption of muscarinic cholinergic activities in the urinary bladder. Neurochem Int 2004; 45:1185-93. [PMID: 15380628 DOI: 10.1016/j.neuint.2004.06.016] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2004] [Accepted: 06/14/2004] [Indexed: 10/26/2022]
Abstract
Caveolin-1 (Cav1), a structural protein of caveolae, plays cell- and context-dependent roles in signal transduction pathway regulation. We have generated a knockout mouse homozygous for a null mutation of the Cav1 gene. Cav1 knockout mice exhibited impaired urinary bladder contractions in vivo during cystometry. Contractions of male bladder strips were evoked with electric and pharmacologic stimulation (5-40 Hz, 1-10 microM carbachol, 10 mM alpha,beta-methylene ATP, 100 mM KCl). Acetylcholine (ACh) and norepinephrine (NE) release from bladder strips were measured with a radiochemical method by incubating the strips with 14C-choline and 3H-NE prior to electric stimulation, whereas ATP release was measured using the luciferin-luciferase assay with a luminometer. A 60-75% decline in contractility was observed when Cav1 knockout muscle strips were stimulated with electric current or carbachol, compared to wildtype muscle strips. No difference in contractility was noted when contractions were evoked either by the purinergic agonist alpha,beta-methylene ATP, or by extracellular potassium. To investigate the relative contribution of non-cholinergic activity to bladder contractility, the amplitude of the electric stimulation-evoked contractions was compared in the presence of the muscarinic antagonist atropine (1 microM). While the non-muscarinic (purinergic) response was unaltered, muscarinic cholinergic response was principally disrupted in Cav1 knockout mice. The loss of Cav1 gene expression was also associated with a 70% reduction in ACh release. NE and ATP release was not altered. It is concluded that the loss of caveolin-1 is associated with disruption of M3 muscarinic cholinergic activity in the bladder. Both pre-junctional (acetylcholine neurotransmitter release from neuromuscular junctions) and post-junctional (M3 receptor-mediated signal transduction in bladder smooth muscles) mechanisms are disrupted, resulting in impaired bladder contraction.
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Affiliation(s)
- H Henry Lai
- Neurourology Laboratory, Scott Department of Urology, Baylor College of Medicine, Houston, TX 77030, USA
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50
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Abstract
Caveolin-1 was identified in a screen for genes involved in breast cancer progression. Caveolin-1 is the major protein component of caveolae, flask-shaped invaginations found in a number of different cell types. Using an orthotopic model of spontaneous breast cancer metastasis, caveolin-1 was found to be expressed in low and non-metastatic primary tumors, but at much lower levels in highly metastatic 4T1.2 and 4T1.13 tumors. Exogenous expression of caveolin-1 at moderate levels in 4T1.2 cells was sufficient to suppress primary tumor growth after inoculation of cells into the mammary gland. Expression of high levels of caveolin-1 also inhibited subsequent metastasis to distant organs. Cells expressing high levels of caveolin-1 showed reduced capacity to invade Matrigel, diminished response to laminin-1 stimulation and decreased metastasis to lung and bone. This study provides the first functional evidence that caveolin-1 regulates primary breast tumor growth and spontaneous metastasis of breast cancer.
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Affiliation(s)
- Erica K Sloan
- Peter MacCallum Cancer Centre, Locked Bag #1, A'Beckett Street, Melbourne, Victoria 8006, Australia
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