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Michael P. Lisanti - One of the best experts on this subject based on the ideXlab platform.
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inhibition of nuclear factor erythroid 2 related factor nrf2 by Caveolin 1 promotes stress induced premature senescence
Molecular Biology of the Cell, 2013Co-Authors: Daniela Volonte, Michael P. Lisanti, Zhongmin Liu, Paul M Musille, Elena Stoppani, Nobunao Wakabayashi, Thomas W Kensler, Ferruccio GalbiatiAbstract:Reactive oxygen species (ROS) can induce premature cellular senescence, which is believed to contribute to aging and age-related diseases. The nuclear erythroid 2 p45–related factor-2 (Nrf2) is a transcription factor that mediates cytoprotective responses against stress. We demonstrate that Caveolin-1 is a direct binding partner of Nrf2, as shown by the binding of the scaffolding domain of Caveolin-1 (amino acids 82–101) to the Caveolin-binding domain of Nrf2 (amino acids 281–289). Biochemical studies show that Nrf2 is concentrated into caveolar membranes in human and mouse fibroblasts, where it colocalizes with Caveolin-1, under resting conditions. After oxidative stress, Caveolin-1 limits the movement of Nrf2 from caveolar membranes to the nucleus. In contrast, Nrf2 is constitutively localized to the nucleus before and after oxidative stress in Caveolin-1–null mouse embryonic fibroblasts (MEFs), which do not express Caveolin-1. Functional studies demonstrate that Caveolin-1 acts as an endogenous inhibitor of Nrf2, as shown by the enhanced up-regulation of NQO1, an Nrf2 target gene, in Caveolin-1–null MEFs and the activation or inhibition of a luciferase construct carrying an antioxidant responsive element (ARE) after down-regulation of Caveolin-1 by small interfering RNA or overexpression of Caveolin-1, respectively. Expression of a mutant form of Nrf2 that cannot bind to Caveolin-1 (Φ→A-Nrf2) hyperactivates ARE and inhibits oxidative stress–induced activation of the p53/p21Waf1/Cip1 pathway and induction of premature senescence in fibroblasts. Finally, we show that overexpression of Caveolin-1 in colon cancer cells inhibits oxidant-induced activation of Nrf2-dependent signaling, promotes premature senescence, and inhibits their transformed phenotype. Thus, by inhibiting Nrf2-mediated signaling, Caveolin-1 links free radicals to the activation of the p53/senescence pathway.
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Role of Caveolin-1 in the regulation of lipoprotein metabolism.
American journal of physiology. Cell physiology, 2008Co-Authors: Philippe G. Frank, Stephanos Pavlides, Michelle W.-c. Cheung, Kristin M. Daumer, Michael P. LisantiAbstract:Lipoprotein metabolism plays an important role in the development of several human diseases, including coronary artery disease and the metabolic syndrome. A good comprehension of the factors that regulate the metabolism of the various lipoproteins is therefore key to better understanding the variables associated with the development of these diseases. Among the players identified are regulators such as Caveolins and caveolae. Caveolae are small plasma membrane invaginations that are observed in terminally differentiated cells. Their most important protein marker, Caveolin-1, has been shown to play a key role in the regulation of several cellular signaling pathways and in the regulation of plasma lipoprotein metabolism. In the present paper, we have examined the role of Caveolin-1 in lipoprotein metabolism using Caveolin-1-deficient (Cav-1(-/-)) mice. Our data show that, while Cav-1(-/-) mice show increased plasma triglyceride levels, they also display reduced hepatic very low-density lipoprotein (VLDL) secretion. Additionally, we also found that a Caveolin-1 deficiency is associated with an increase in high-density lipoprotein (HDL), and these HDL particles are enriched in cholesteryl ester in Cav-1(-/-) mice when compared with HDL obtained from wild-type mice. Finally, our data suggest that a Caveolin-1 deficiency prevents the transcytosis of LDL across endothelial cells, and therefore, that Caveolin-1 may be implicated in the regulation of plasma LDL levels. Taken together, our studies suggest that Caveolin-1 plays an important role in the regulation of lipoprotein metabolism by controlling their plasma levels as well as their lipid composition. Thus Caveolin-1 may also play an important role in the development of atherosclerosis.
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Caveolin-1 and liver regeneration: role in proliferation and lipogenesis.
Cell Cycle, 2007Co-Authors: Philippe G. Frank, Michael P. LisantiAbstract:Caveolin-1 is an essential component of caveolae, which form 50-100 nm cell surface plasma membrane invaginations. Caveolin-1 has been previously implicated in the regulation of cellular proliferation and lipogenesis. Current data now suggest that Caveolin-1 plays an essential role in the regulation of liver regeneration and that it is implicated in the regulation of triglyceride accumulation, which is an essential process that plays a critical role in the regulation of liver regeneration. These findings are consistent with the importance of a lipogenesis program in the regulation of liver regeneration.
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Overexpression of Caveolin-1 inhibits endothelial cell proliferation by arresting the cell cycle at G0/G1 phase.
Cell Cycle, 2007Co-Authors: Kai Fang, Andrew R. Beardsley, Wei Fu, Michael P. LisantiAbstract:Angiogenesis, the development of new blood vessels from pre-existing capillary, is required for tumor growth and metastasis. The process is not fully understood yet, but involves endothelial cell proliferation, migration and differentiation. Recently, we have shown that over-expression of Caveolin-1, a putative transformation suppressor gene, inhibits VEGFR-2 and MEK-1-mediated mitogenic signal to the nucleus. Conversely, angiogenic activators suppress Caveolin-1 expression in endothelial cells. However, whether Caveolin-1 expression affects endothelial cell proliferation is not clear. In the present study, we infect human endothelial cells with adenovirus expressing Caveolin-1 and show that transient over-expression of Caveolin-1 dramatically inhibits the proliferation of human endothelial cells. Consistent with Caveolin-1 functioning as an inhibitor for protein kinases, over-expression of Caveolin-1 inhibits the activity of VEGFR-2 (KDR) and down-stream p42/44 MAP kinase. Furthermore, over-expression of...
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Caveolin-1 Expression Is Essential for Proper Nonshivering Thermogenesis in Brown Adipose Tissue
Diabetes, 2005Co-Authors: Alex W. Cohen, William Schubert, Dawn L. Brasaemle, Philipp E. Scherer, Michael P. LisantiAbstract: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°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.
Ferruccio Galbiati - One of the best experts on this subject based on the ideXlab platform.
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Caveolin-1, a master regulator of cellular senescence
Cancer and Metastasis Reviews, 2020Co-Authors: Daniela Volonte, Ferruccio GalbiatiAbstract:Cellular senescence is a feature of most somatic cells. It is characterized by an irreversible cell cycle arrest and by the ability to secrete a plethora of mediators of inflammation and growth factors, which can alter the senescent cell’s microenvironment. Senescent cells accumulate in tissues over time and contribute to both aging and the development of age-associated diseases. Senescent cells have antagonistic pleiotropic roles in cancer. Given the inability of senescent cells to proliferate, cellular senescence is a powerful tumor suppressor mechanism in young individuals. However, accumulation of senescent stromal cells during aging can fuel cancer cell growth in virtue of their capacity to release factors that stimulate cell proliferation. Caveolin-1 is a structural protein component of caveolae, invaginations of the plasma membrane involved in a variety of cellular processes, including signal transduction. Mounting evidence over the last 10–15 years has demonstrated a central role of Caveolin-1 in the development of a senescent phenotype and the regulation of both the anti-tumorigenic and pro-tumorigenic properties of cellular senescence. In this review, we discuss the cellular mechanisms and functions of Caveolin-1 in the context of cellular senescence and their relevance to the biology of cancer.
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Caveolin 1 promotes the tumor suppressor properties of oncogene induced cellular senescence
Journal of Biological Chemistry, 2017Co-Authors: Daniela Volonte, Avani R Vyas, Chen Chen, Sanja Dacic, Laura P Stabile, Brenda F Kurland, Shira Abberbock, Timothy F Burns, James G Herman, Ferruccio GalbiatiAbstract:Oncogene-induced senescence (OIS) is considered a powerful tumor suppressor mechanism. Caveolin-1 acts as a scaffolding protein to functionally regulate signaling molecules. We demonstrate that a lack of Caveolin-1 expression inhibits oncogenic K-Ras (K-RasG12V)-induced premature senescence in mouse embryonic fibroblasts and normal human bronchial epithelial cells. Oncogenic K-Ras induces senescence by limiting the detoxification function of MTH1. We found that K-RasG12V promotes the interaction of Caveolin-1 with MTH1, which results in inhibition of MTH1 activity. Lung cancer cells expressing oncogenic K-Ras have bypassed the senescence barrier. Interestingly, overexpression of Caveolin-1 restores cellular senescence in both A549 and H460 lung cancer cells and inhibits their transformed phenotype. In support of these findings, our in vivo data demonstrate that overexpression of oncogenic K-Ras (K-RasG12D) induces cellular senescence in the lung of wildtype but not Caveolin-1-null mice. A lack of K-RasG12D-induced premature senescence in Caveolin-1-null mice results in the formation of more abundant lung tumors. Consistent with these data, Caveolin-1-null mice overexpressing K-RasG12D display accelerated mortality. Finally, our animal data were supported by human sample analysis in which we show that Caveolin-1 expression is dramatically down-regulated in lung adenocarcinomas from lung cancer patients, both at the mRNA and protein levels, and that low Caveolin-1 expression is associated with poor survival. Together, our data suggest that lung cancer cells escape oncogene-induced premature senescence through down-regulation of Caveolin-1 expression to progress from premalignant lesions to cancer.
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Caveolin-1 controls mitochondrial function through regulation of m -AAA mitochondrial protease
Aging, 2016Co-Authors: Daniela Volonte, Zhongmin Liu, Sruti Shiva, Ferruccio GalbiatiAbstract:Mitochondrial proteases ensure mitochondrial integrity and function after oxidative stress by providing mitochondrial protein quality control. However, the molecular mechanisms that regulate this basic biological function in eukaryotic cells remain largely unknown. Caveolin-1 is a scaffolding protein involved in signal transduction. We find that AFG3L2, a m-AAA type of mitochondrial protease, is a novel Caveolin-1-interacting protein in vitro. We show that oxidative stress promotes the translocation of both Caveolin-1 and AFG3L2 to mitochondria, enhances the interaction of Caveolin-1 with AFG3L2 in mitochondria and stimulates mitochondrial protease activity in wild-type fibroblasts. Localization of AFG3L2 to mitochondria after oxidative stress is inhibited in fibroblasts lacking Caveolin-1, which results in impaired mitochondrial protein quality control, an oxidative phosphorylation to aerobic glycolysis switch and reduced ATP production. Mechanistically, we demonstrate that a lack of Caveolin-1 does not alter either mitochondrial number or morphology but leads to the cytoplasmic and proteasome-dependent degradation of complexes I, III, IV and V upon oxidant stimulation. Restoration of mitochondrial respiratory chain complexes in Caveolin-1 null fibroblasts reverts the enhanced glycolysis observed in these cells. Expression of a mutant form of AFG3L2, which has reduced affinity for Caveolin-1, fails to localize to mitochondria and promotes degradation of complex IV after oxidative stress. Thus, Caveolin-1 maintains mitochondrial integrity and function when cells are challenged with free radicals by promoting the mitochondrial localization of m-AAA protease and its quality control functions.
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inhibition of nuclear factor erythroid 2 related factor nrf2 by Caveolin 1 promotes stress induced premature senescence
Molecular Biology of the Cell, 2013Co-Authors: Daniela Volonte, Michael P. Lisanti, Zhongmin Liu, Paul M Musille, Elena Stoppani, Nobunao Wakabayashi, Thomas W Kensler, Ferruccio GalbiatiAbstract:Reactive oxygen species (ROS) can induce premature cellular senescence, which is believed to contribute to aging and age-related diseases. The nuclear erythroid 2 p45–related factor-2 (Nrf2) is a transcription factor that mediates cytoprotective responses against stress. We demonstrate that Caveolin-1 is a direct binding partner of Nrf2, as shown by the binding of the scaffolding domain of Caveolin-1 (amino acids 82–101) to the Caveolin-binding domain of Nrf2 (amino acids 281–289). Biochemical studies show that Nrf2 is concentrated into caveolar membranes in human and mouse fibroblasts, where it colocalizes with Caveolin-1, under resting conditions. After oxidative stress, Caveolin-1 limits the movement of Nrf2 from caveolar membranes to the nucleus. In contrast, Nrf2 is constitutively localized to the nucleus before and after oxidative stress in Caveolin-1–null mouse embryonic fibroblasts (MEFs), which do not express Caveolin-1. Functional studies demonstrate that Caveolin-1 acts as an endogenous inhibitor of Nrf2, as shown by the enhanced up-regulation of NQO1, an Nrf2 target gene, in Caveolin-1–null MEFs and the activation or inhibition of a luciferase construct carrying an antioxidant responsive element (ARE) after down-regulation of Caveolin-1 by small interfering RNA or overexpression of Caveolin-1, respectively. Expression of a mutant form of Nrf2 that cannot bind to Caveolin-1 (Φ→A-Nrf2) hyperactivates ARE and inhibits oxidative stress–induced activation of the p53/p21Waf1/Cip1 pathway and induction of premature senescence in fibroblasts. Finally, we show that overexpression of Caveolin-1 in colon cancer cells inhibits oxidant-induced activation of Nrf2-dependent signaling, promotes premature senescence, and inhibits their transformed phenotype. Thus, by inhibiting Nrf2-mediated signaling, Caveolin-1 links free radicals to the activation of the p53/senescence pathway.
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The cyclin D1 gene is transcriptionally repressed by Caveolin-1.
The Journal of biological chemistry, 2000Co-Authors: James Hulit, Chris Albanese, Ferruccio Galbiati, Tal Bash, Daniel R. Sage, Amnon Schlegel, Jacob Zhurinsky, Michael Shtutman, Avri Ben-ze'evAbstract:Abstract The cyclin D1 gene encodes the regulatory subunit of the holoenzyme that phosphorylates and inactivates the retinoblastoma pRB protein. Cyclin D1 protein levels are elevated by mitogenic and oncogenic signaling pathways, and antisense mRNA to cyclin D1 inhibits transformation by the ras,neu, and src oncogenes, thus linking cyclin D1 regulation to cellular transformation. Caveolins are the principal protein components of caveolae, vesicular plasma membrane invaginations that also function in signal transduction. We show here that Caveolin-1 expression levels inversely correlate with cyclin D1 abundance levels in transformed cells. Expression of antisense Caveolin-1 increased cyclin D1 levels, whereas Caveolin-1 overexpression inhibited expression of the cyclin D1 gene. Cyclin D1 promoter activity was selectively repressed by Caveolin-1, but not by Caveolin-3, and this repression required the Caveolin-1 N terminus. Maximal inhibition of the cyclin D1 gene promoter by Caveolin-1 was dependent on the cyclin D1 promoter T-cell factor/lymphoid enhancer factor-1-binding site between −81 to −73. The T-cell factor/lymphoid enhancer factor sequence was sufficient for repression by Caveolin-1. We suggest that transcriptional repression of the cyclin D1 gene may contribute to the inhibition of transformation by Caveolin-1.
Richard Béliveau - One of the best experts on this subject based on the ideXlab platform.
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Regulation of brain endothelial cells migration and angiogenesis by P-glycoprotein/Caveolin-1 interaction.
Biochemical and Biophysical Research Communications, 2008Co-Authors: Shimaa Barakat, Mp Lachambre, Michel Demeule, Stephane Turcotte, Ahmed Regina, Lg Baggetto, Richard BéliveauAbstract:We have investigated the involvement of P-glycoprotein (P-gp)/Caveolin-1 interaction in the regulation of brain endothelial cells (EC) migration and tubulogenesis. P-gp overexpression in MDCK-MDR cells was correlated with enhanced cell migration whereas treatment with P-gp inhibitors CsA or PSC833 reduced it. Transfection of RBE4 rat brain endothelial cells with mutated versions of MDR1, in the Caveolin-1 interaction motif, decreased the interaction between P-gp and Caveolin-1, enhanced P-gp transport activity and cell migration. Moreover, down-regulation of Caveolin-1 in RBE4 cells by siRNA against Caveolin-1 stimulated cell migration. Interestingly, the inhibition of P-gp/Caveolin-1 interaction increased also EC tubulogenesis. Furthermore, decrease of P-gp expression by siRNA inhibited EC tubulogenesis. These data indicate that the level of P-gp/Caveolin-1 interaction can modulate brain endothelial angiogenesis and P-gp dependent cell migration.We have investigated the involvement of P-glycoprotein (P-gp)/Caveolin-1 interaction in the regulation of brain endothelial cells (EC) migration and tubulogenesis. P-gp overexpression in MDCK-MDR cells was correlated with enhanced cell migration whereas treatment with P-gp inhibitors CsA or PSC833 reduced it. Transfection of RBE4 rat brain endothelial cells with mutated versions of MDR1, in the Caveolin-1 interaction motif, decreased the interaction between P-gp and Caveolin-1, enhanced P-gp transport activity and cell migration. Moreover, down-regulation of Caveolin-1 in RBE4 cells by siRNA against Caveolin-1 stimulated cell migration. Interestingly, the inhibition of P-gp/Caveolin-1 interaction increased also EC tubulogenesis. Furthermore, decrease of P-gp expression by siRNA inhibited EC tubulogenesis. These data indicate that the level of P-gp/Caveolin-1 interaction can modulate brain endothelial angiogenesis and P-gp dependent cell migration.
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Down-regulation of Caveolin-1 in glioma vasculature: modulation by radiotherapy
Journal of Neuroscience Research, 2004Co-Authors: Anthony Régina, Michel Demeule, Julie Jodoin, Paul Khoueir, Yannève Rolland, France Berthelet, Robert Moumdjian, Laurence Fenart, Roméo Cecchelli, Richard BéliveauAbstract:Primary brain tumors, particularly glioblastomas (GB), remain a challenge for oncology. An element of the malignant brain tumors' aggressive behavior is the fact that GB are among the most densely vascularized tumors. To determine some of the molecular regulations occuring at the brain tumor endothelium level during tumoral progression would be an asset in understanding brain tumor biology. Caveolin-1 is an essential structural constituent of caveolae that has been implicated in mitogenic signaling, oncogenesis, and angiogenesis. In this work we investigated regulation of Caveolin-1 expression in brain endothelial cells (ECs) under angiogenic conditions. In vitro, brain EC Caveolin-1 is down-regulated by angiogenic factors treament and by hypoxia. Coculture of brain ECs with tumoral cells induced a similar downregulation. In addition, activation of the p42/44 MAP kinase is demonstrated. By using an in vivo brain tumor model, we purified ECs from gliomas as well as from normal brain to investigate possible regulation of Caveolin-1 expression in tumoral brain vasculature. We show that Caveolin-1 expression is strikingly down-regulated in glioma ECs, whereas an increase of phosphorylated Caveolin-1 is observed. Whole-brain radiation treatment, a classical way in which GB is currently being treated, resulted in increased Caveolin-1 expression in tumor isolated ECs. The level of tumor cells spreading around newly formed blood vessels was also elevated. The regulation of Caveolin-1 expression in tumoral ECs may reflect the tumoral vasculature state and correlates with angiogenesis kinetics.
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regulation of vascular endothelial growth factor receptor 2 activity by Caveolin 1 and plasma membrane cholesterol
Molecular Biology of the Cell, 2003Co-Authors: Lyne Labrecque, Isabelle Royal, David S Surprenant, Cam W Patterson, Denis Gingras, Richard BéliveauAbstract:The stimulation of vascular endothelial growth factor receptor-2 (VEGFR-2) by tumor-derived VEGF represents a key event in the initiation of angiogenesis. In this work, we report that VEGFR-2 is localized in endothelial caveolae, associated with Caveolin-1, and that this complex is rapidly dissociated upon stimulation with VEGF. The kinetics of Caveolin-1 dissociation correlated with those of VEGF-dependent VEGFR-2 tyrosine phosphorylation, suggesting that Caveolin-1 acts as a negative regulator of VEGF R-2 activity. Interestingly, we observed that in an overexpression system in which VEGFR-2 is constitutively active, Caveolin-1 overexpression inhibits VEGFR-2 activity but allows VEGFR-2 to undergo VEGF-dependent activation, suggesting that Caveolin-1 can confer ligand dependency to a receptor system. Removal of Caveolin and VEGFR-2 from caveolae by cholesterol depletion resulted in an increase in both basal and VEGF-induced phosphorylation of VEGFR-2, but led to the inhibition of VEGF-induced ERK activation and endothelial cell migration, suggesting that localization of VEGFR-2 to these domains is crucial for VEGF-mediated signaling. Dissociation of the VEGFR-2/Caveolin-1 complex by VEGF or cyclodextrin led to a PP2-sensitive phosphorylation of Caveolin-1 on tyrosine 14, suggesting the participation of Src family kinases in this process. Overall, these results suggest that Caveolin-1 plays multiple roles in the VEGF-induced signaling cascade.
Babak Razani - One of the best experts on this subject based on the ideXlab platform.
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role of Caveolin 1 in the modulation of lipolysis and lipid droplet formation
Diabetes, 2004Co-Authors: Alex W. Cohen, William Schubert, Dawn L. Brasaemle, Philipp E. Scherer, Babak Razani, Terence M Williams, Xiao Bo Wang, Puneeth Iyengar, Michael P. LisantiAbstract:Recently, it was shown that Caveolin-1 can be redirected from the cell surface to intracellular lipid droplets in a variety of cell types. Here, we directly address the role of Caveolin-1 in lipid droplet formation and breakdown, showing that Caveolin-1 null mice exhibit markedly attenuated lipolytic activity. Mechanistically, although the activity of protein kinase A (PKA) was greatly increased in Caveolin-1 null adipocytes, the phosphorylation of perilipin was dramatically reduced, indicating that Caveolin-1 may facilitate the PKA-mediated phosphorylation of perilipin. In support of this hypothesis, coimmunoprecipitation experiments revealed that treatment with a β 3 -adrenergic receptor agonist resulted in ligand-induced complex formation between perilipin, Caveolin-1, and the catalytic subunit of PKA in wild-type but not in Caveolin-1 null fat pads. We also show that Caveolin-1 expression is important for efficient lipid droplet formation because Caveolin-1 null embryonic fibroblasts stably transfected with perilipin accumulated ∼4.5-fold less lipid than perilipin-transfected wild-type cells. Finally, high-pressure freeze-substitution electron microscopy of adipose tissue revealed dramatic perturbations in the architecture of the “lipid droplet cortex” (the interface between the lipid droplet surface and the cytoplasm) in Caveolin-1 null perigonadal 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 both lipid droplet biogenesis and metabolism in vivo.
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role of Caveolin 1 in the modulation of lipolysis and lipid droplet formation
Diabetes, 2004Co-Authors: Alex W. Cohen, William Schubert, Dawn L. Brasaemle, Philipp E. Scherer, Babak Razani, Terence M Williams, Xiao Bo Wang, Puneeth Iyengar, Michael P. LisantiAbstract:Recently, it was shown that Caveolin-1 can be redirected from the cell surface to intracellular lipid droplets in a variety of cell types. Here, we directly address the role of Caveolin-1 in lipid droplet formation and breakdown, showing that Caveolin-1 null mice exhibit markedly attenuated lipolytic activity. Mechanistically, although the activity of protein kinase A (PKA) was greatly increased in Caveolin-1 null adipocytes, the phosphorylation of perilipin was dramatically reduced, indicating that Caveolin-1 may facilitate the PKA-mediated phosphorylation of perilipin. In support of this hypothesis, coimmunoprecipitation experiments revealed that treatment with a beta(3)-adrenergic receptor agonist resulted in ligand-induced complex formation between perilipin, Caveolin-1, and the catalytic subunit of PKA in wild-type but not in Caveolin-1 null fat pads. We also show that Caveolin-1 expression is important for efficient lipid droplet formation because Caveolin-1 null embryonic fibroblasts stably transfected with perilipin accumulated approximately 4.5-fold less lipid than perilipin-transfected wild-type cells. Finally, high-pressure freeze-substitution electron microscopy of adipose tissue revealed dramatic perturbations in the architecture of the "lipid droplet cortex" (the interface between the lipid droplet surface and the cytoplasm) in Caveolin-1 null perigonadal 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 both lipid droplet biogenesis and metabolism in vivo.
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Caveolin 1 null mice are viable but show evidence of hyperproliferative and vascular abnormalities
Journal of Biological Chemistry, 2001Co-Authors: Babak Razani, William Schubert, Richard G Pestell, Xiao Bo Wang, Xiao Lan Zhang, Jeffery A Engelman, Carolyn B Marks, Frank P Macaluso, Robert G Russell, Dolores Di VizioAbstract:Abstract Caveolin-1 is the principal structural protein of caveolae membranes in fibroblasts and endothelia. Recently, we have shown that the human CAV-1 gene is localized to a suspected tumor suppressor locus, and mutations in Cav-1 have been implicated in human cancer. Here, we created a Caveolin-1 null (CAV-1 −/−) mouse model, using standard homologous recombination techniques, to assess the role of Caveolin-1 in caveolae biogenesis, endocytosis, cell proliferation, and endothelial nitric-oxide synthase (eNOS) signaling. Surprisingly, Cav-1 null mice are viable. We show that these mice lack Caveolin-1 protein expression and plasmalemmal caveolae. In addition, analysis of cultured fibroblasts from Cav-1 null embryos reveals the following: (i) a loss of Caveolin-2 protein expression; (ii) defects in the endocytosis of a known caveolar ligand, i.e.fluorescein isothiocyanate-albumin; and (iii) a hyperproliferative phenotype. Importantly, these phenotypic changes are reversed by recombinant expression of the Caveolin-1 cDNA. Furthermore, examination of the lung parenchyma (an endothelial-rich tissue) shows hypercellularity with thickened alveolar septa and an increase in the number of vascular endothelial growth factor receptor (Flk-1)-positive endothelial cells. As predicted, endothelial cells from Cav-1 null mice lack caveolae membranes. Finally, we examined eNOS signaling by measuring the physiological response of aortic rings to various stimuli. Our results indicate that eNOS activity is up-regulated in Cav-1 null animals, and this activity can be blunted by using a specific NOS inhibitor, nitro-l-arginine methyl ester. These findings are in accordance with previous in vitro studies showing that Caveolin-1 is an endogenous inhibitor of eNOS. Thus, Caveolin-1 expression is required to stabilize the Caveolin-2 protein product, to mediate the caveolar endocytosis of specific ligands, to negatively regulate the proliferation of certain cell types, and to provide tonic inhibition of eNOS activity in endothelial cells.
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p42 44 map kinase dependent and independent signaling pathways regulate Caveolin 1 gene expression activation of ras map kinase and protein kinase a signaling cascades transcriptionally down regulates Caveolin 1 promoter activity
Journal of Biological Chemistry, 1999Co-Authors: Jeffrey A Engelman, Richard G Pestell, Babak Razani, Xiao Lan Zhang, Michael P. LisantiAbstract:Caveolin-1 is a principal component of caveolae membranes in vivo. Caveolin-1 mRNA and protein expression are down-regulated in NIH 3T3 cells in response to transformation by activated oncogenes, such as H-Ras(G12V) and v-Abl. The mechanisms governing this down-regulation event remain unknown. Here, we show that Caveolin-1 gene expression is directly regulated by activation of the Ras-p42/44 MAP kinase cascade. Down regulation of Caveolin-1 protein expression by Ras is independent of (i) the type of activating mutation (G12V versus Q61L) and (ii) the form of activated Ras transfected (H-Ras versus K-Ras versus N-Ras). Treatment of Ras or Raf-transformed NIH 3T3 cells with a well characterized MEK inhibitor (PD 98059) restores Caveolin-1 protein expression. In contrast, treatment of v-Src and v-Abl transformed NIH 3T3 cells with PD 98059 does not restore Caveolin-1 expression. Thus, there must be at least two pathways for down-regulating Caveolin-1 expression: one that is p42/44 MAP kinase-dependent and another that is p42/44 MAP kinase-independent. We focused our efforts on the p42/44 MAP kinase-dependent pathway. The activity of a panel of Caveolin-1 promoter constructs was evaluated using transient expression in H-Ras(G12V) transformed NIH 3T3 cells. We show that Caveolin-1 promoter activity is up-regulated approximately 5-fold by inhibition of the p42/44 MAP kinase cascade. Using electrophoretic mobility shift assays we provide evidence that the Caveolin-1 promoter (from -156 to -561) is differentially bound by transcription factors in normal and H-Ras(G12V)-transformed cells. We also show that activation of protein kinase A (PKA) signaling is sufficient to down-regulate Caveolin-1 protein expression and promoter activity. Thus, we have identified two signaling pathways (Ras-p42/44 MAP kinase and PKA) that transcriptionally down-regulate Caveolin-1 gene expression.
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angiogenesis activators and inhibitors differentially regulate Caveolin 1 expression and caveolae formation in vascular endothelial cells angiogenesis inhibitors block vascular endothelial growth factor induced down regulation of Caveolin 1
Journal of Biological Chemistry, 1999Co-Authors: Jun Liu, Babak Razani, Shaoqing Tang, Bruce I Terman, Anthony J Ware, Michael P. LisantiAbstract:Angiogenesis is the process by which new blood vessels are formed via proliferation of vascular endothelial cells. A variety of angiogenesis inhibitors that antagonize the effects of vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) have recently been identified. However, the mechanism by which these diverse angiogenesis inhibitors exert their common effects remains largely unknown. Caveolin-1 and -2 are known to be highly expressed in vascular endothelial cells both in vitro andin vivo. Here, we examine the potential role of Caveolins in the angiogenic response. For this purpose, we used the well established human umbilical vein endothelial cell line, ECV 304. Treatment of ECV 304 cells with known angiogenic growth factors (VEGF, bFGF, or hepatocyte growth factor/scatter factor), resulted in a dramatic reduction in the expression of Caveolin-1. This down-regulation event was selective for Caveolin-1, as Caveolin-2 levels remained constant under these conditions of growth factor stimulation. VEGF-induced down-regulation of Caveolin-1 expression also resulted in the morphological loss of cell surface caveolae organelles as seen by transmission electron microscopy. A variety of well characterized angiogenesis inhibitors (including angiostatin, fumagillin, 2-methoxy estradiol, transforming growth factor-β, and thalidomide) effectively blocked VEGF-induced down-regulation of Caveolin-1 as seen by immunoblotting and immunofluorescence microscopy. However, treatment with angiogenesis inhibitors alone did not significantly affect the expression of Caveolin-1. PD98059, a specific inhibitor of mitogen-activated protein kinase and a known angiogenesis inhibitor, also blocked the observed VEGF-induced down-regulation of Caveolin-1. Furthermore, we show that Caveolin-1 can function as a negative regulator of VEGF-R (KDR) signal transduction in vivo. Thus, down-regulation of Caveolin-1 may be an important step along the pathway toward endothelial cell proliferation.
Taekyun Shin - One of the best experts on this subject based on the ideXlab platform.
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Increased phosphorylation of Caveolin-1 in the sciatic nerves of Lewis rats with experimental autoimmune neuritis
Brain Research, 2006Co-Authors: Changjong Moon, Yoh Matsumoto, Taekyun ShinAbstract:Abstract The levels of phosphorylated Caveolin-1 (p-Caveolin-1) were analyzed in the sciatic nerves of Lewis rats with experimental autoimmune neuritis (EAN). Western blot analysis showed that the phosphorylation of Caveolin-1 increased significantly in the sciatic nerves of EAN-affected rats at the paralytic stage of EAN on day 14 post-immunization (PI) (P
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Immunohistochemical study of Caveolin-1 in the sciatic nerves of Lewis rats with experimental autoimmune neuritis
Brain Research, 2006Co-Authors: Changjong Moon, Yoh Matsumoto, Taekyun ShinAbstract:Abstract The expression of Caveolin-1 and the related molecule endothelial nitric oxide synthase (eNOS) was analyzed in the sciatic nerves of Lewis rats with experimental autoimmune neuritis (EAN). Western blot analysis showed that Caveolin-1 significantly increased in the sciatic nerves with EAN upon initiation of cell infiltration during the early and peak stages (days 10 and 14 post-immunization, p.i.) and declined thereafter. The pattern of eNOS expression over the course of EAN largely matched that of Caveolin-1. Immunohistochemistry showed that in EAN lesions, intense Caveolin-1 immunostaining occurred in ED1-positive macrophages as well as in vessels, while the Caveolin-1 immunoreaction was reduced in Schwann cells in the inflammatory lesions. Consequently, we postulated that Caveolin-1 expression increased in the sciatic nerves with EAN; this possibly mediated either molecular trafficking or nitric oxide generation partly through the activation of eNOS in vascular endothelial cells, as well as in inflammatory macrophages in EAN and/or cellular apoptosis of inflammatory cells.