RESUMO
AIMS: Nitric oxide synthases (NOSs) are key enzymes regulating vascular function. Previously, we reported that ß-adrenergic (ß-AR) overstimulation, a common feature of cardiovascular diseases, did not impair endothelium-dependent vasodilation, although it resulted in endothelial NOS (eNOS) uncoupling and reduced NO bioavailability. In addition to NO, neuronal NOS (nNOS) produces H2O2, which contributes to vasodilation. However, there is limited information regarding vascular ß-AR signaling and nNOS. In the present study, we assessed the possible role of nNOS-derived H2O2 and caveolins on endothelial vasodilation function following ß-AR overstimulation. MAIN METHODS: Male C57BL/6 wild-type and nNOS knockout mice (nNOS-/-) were treated with the ß-AR agonist isoproterenol (ISO, 15 mg·kg-1·day-1, s.c.) or vehicle (VHE) for seven days. Relaxation responses of aortic rings were evaluated using wire myograph and H2O2 by Amplex Red. KEY FINDINGS: Acetylcholine- or calcium ionophore A23187-induced endothelium-dependent relaxation was similar in aortic rings from VHE and ISO. However, this relaxation was significantly reduced in aortas from ISO compared to VHE when (1) caveolae were disrupted, (2) nNOS was pharmacologically inhibited or genetically suppressed and (3) H2O2 was scavenged. NOS-derived H2O2 production was higher in the aortas of ISO mice than in those of VHE mice. Aortas from ISO-treated mice showed increased expression of caveolin-1, nNOS and catalase, while caveolin-3 expression did not change. SIGNIFICANCE: The results suggest a role of caveolin-1 and the nNOS/H2O2 vasodilatory pathway in endothelium-dependent relaxation following ß-AR overstimulation and reinforce the protective role of nNOS in cardiovascular diseases associated with high adrenergic tone.
Assuntos
Caveolina 1/fisiologia , Óxido Nítrico Sintase Tipo I/fisiologia , Receptores Adrenérgicos alfa/metabolismo , Vasodilatação/fisiologia , Agonistas Adrenérgicos beta/farmacologia , Animais , Calcimicina/farmacologia , Ionóforos de Cálcio/farmacologia , Doenças Cardiovasculares/genética , Doenças Cardiovasculares/fisiopatologia , Caveolina 1/genética , Endotélio Vascular/efeitos dos fármacos , Endotélio Vascular/fisiologia , Peróxido de Hidrogênio/metabolismo , Isoproterenol/farmacologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Óxido Nítrico Sintase Tipo I/genética , Vasodilatação/efeitos dos fármacos , Vasodilatação/genéticaRESUMO
Caveolin-1 (CAV1), is a broadly expressed, membrane-associated scaffolding protein that acts both, as a tumor suppressor and a promoter of metastasis, depending on the type of cancer and stage. CAV1 is downregulated in human tumors, tumor cell lines and oncogene-transformed cells. The tumor suppressor activity of CAV1 is generally associated with its presence at the plasma membrane, where it participates, together with cavins, in the formation of caveolae and also has been suggested to interact with and inhibit a wide variety of proteins through interactions mediated by the scaffolding domain. However, a pool of CAV1 is also located at the endoplasmic reticulum (ER), modulating the secretory pathway in a manner dependent on serine-80 (S80) phosphorylation. In melanoma cells, CAV1 expression suppresses tumor formation, but the protein is largely absent from the plasma membrane and does not form caveolae. Perturbations to the function of the ER are emerging as a central driver of cancer, highlighting the activation of the unfolded protein response (UPR), a central pathway involved in stress mitigation. Here we provide evidence indicating that the expression of CAV1 represses the activation of the UPR in vitro and in solid tumors, reflected in the attenuation of PERK and IRE1α signaling. These effects correlated with increased susceptibility of cells to ER stress and hypoxia. Interestingly, the tumor suppressor activity of CAV1 was abrogated by site-directed mutagenesis of S80, correlating with a reduced ability to repress the UPR. We conclude that the tumor suppression by CAV1 involves the attenuation of the UPR, and identified S80 as essential in this context. This suggests that intracellular CAV1 regulates cancer through alternative signaling outputs.
Assuntos
Caveolina 1/metabolismo , Resposta a Proteínas não Dobradas/fisiologia , Animais , Caveolina 1/fisiologia , Linhagem Celular Tumoral , Membrana Celular/metabolismo , Retículo Endoplasmático/metabolismo , Estresse do Retículo Endoplasmático/fisiologia , Endorribonucleases/metabolismo , Feminino , Humanos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Fosforilação , Proteínas Serina-Treonina Quinases/metabolismo , Transdução de Sinais/efeitos dos fármacos , eIF-2 Quinase/metabolismoRESUMO
In the mammalian sperm, the acrosome reaction (AR) is considered to be a regulated secretion that is an essential requirement for physiological fertilization. The AR is the all-or-nothing secretion system that allows for multiple membrane fusion events. It is a Ca(2)(+)-regulated exocytosis reaction that has also been shown to be regulated by several signaling pathways. CDC42 has a central role in the regulated exocytosis through the activation of SNARE proteins and actin polymerization. Furthermore, the lipid raft protein caveolin-1 (CAV1) functions as a scaffold and guanine nucleotide dissociation inhibitor protein for CDC42, which is inactivated when associated with CAV1. CDC42 and other RHO proteins have been shown to localize in the acrosome region of mammalian sperm; however, their relationship with the AR is unknown. Here, we present the first evidence that CDC42 and CAV1 could be involved in the regulation of capacitation and the AR. Our findings show that CDC42 is activated early during capacitation, reaching an activation maximum after 20 min of capacitation. Spontaneous and progesterone-induced ARs were inhibited when sperm were capacitated in presence of secramine A, a specific CDC42 inhibitor. CAV1 and CDC42 were co-immunoprecipitated from the membranes of noncapacitated sperm; this association was reduced in capacitated sperm, and our data suggest that the phosphorylation (Tyr14) of CAV1 by c-Src is involved in such reductions. We suggest that CDC42 activation is favored by the disruption of the CAV1-CDC42 interaction, allowing for its participation in the regulation of capacitation and the AR.
Assuntos
Reação Acrossômica/fisiologia , Caveolina 1/fisiologia , Capacitação Espermática/fisiologia , Proteína cdc42 de Ligação ao GTP/fisiologia , Acrossomo/química , Reação Acrossômica/efeitos dos fármacos , Animais , Benzazepinas/farmacologia , Caveolina 1/análise , Membrana Celular/química , Cobaias , Homeostase , Técnicas de Imunoadsorção , Masculino , Camundongos , Oximas/farmacologia , Fosforilação , Progesterona/farmacologia , Transdução de Sinais/fisiologia , Capacitação Espermática/efeitos dos fármacos , Espermatozoides/ultraestrutura , Proteína cdc42 de Ligação ao GTP/análise , Proteína cdc42 de Ligação ao GTP/antagonistas & inibidoresRESUMO
BACKGROUND: Caveolin is required to traffic the AT1 receptor through the exocytic pathway. The chaperone Hsp70 regulates a diverse set of signaling pathways via their interactions with proteins. METHOD: Here we examined the AT1 receptor antagonist Losartan effect on caveolin-1 and Hsp70 protein association in spontaneously hypertensive rat (SHR) proximal tubules. Hsp70 involvement in Losartan oxidative stress regulation was also studied. Five-week-old SHRs were randomized for receiving Losartan (40 mg/kg per day) (SHRLos) or no treatment (SHRH2O) during 6 weeks. Wistar-Kyoto rats (WKY) were normotensive controls. RESULTS: By western blotting, the relative abundance of caveolin-1 was two-fold higher in microdissected proximal tubule membrane fractions from treated SHRs vs. WKYH2O. Hsp70 membrane translocation was demonstrated in SHRLos through out the up-regulation of Hsp70 expression in microdissected proximal tubule membrane fractions when compared with WKYH2O (P < 0.001). Conversely, decreased Hsp70 protein levels were shown in microdissected proximal tubule cytosol fraction from SHRLos (P < 0.01). Interaction between caveolin-1 and Hsp70 was further determined by coimmunoprecipitation and by immunofluorescence co-localization in SHRLos proximal tubule membranes. After membrane translocation of Hsp70, the decreased NADPH oxidase activity (RFU/microprot per min incubation) near controls demonstrated on microdissected proximal tubule membranes from SHRLos vs. SHRH2O (P < 0.01) was reversed by the preincubation with anti-Hsp70 antibody. In addition, interaction between Hsp70 and Nox4 was determined by the coimmunoprecipitation strategy showing that membrane overexpression of Hsp70 was associated with decreased Nox4 after Losartan treatment in SHRs. CONCLUSION: After Losartan administration interaction of caveolin-1 and Hsp70 was shown in SHR proximal tubules. Translocation of Hsp70 to proximal tubule membranes in SHRLos might exert a cytoprotective effect by down-regulation of NADPH subunits Nox4.
Assuntos
Bloqueadores do Receptor Tipo 1 de Angiotensina II/farmacologia , Antioxidantes/farmacologia , Caveolina 1/fisiologia , Proteínas de Choque Térmico HSP70/fisiologia , Hipertensão/tratamento farmacológico , Túbulos Renais Proximais/efeitos dos fármacos , Losartan/farmacologia , Animais , Fracionamento Celular , Membrana Celular/efeitos dos fármacos , Membrana Celular/metabolismo , Modelos Animais de Doenças , Regulação para Baixo/efeitos dos fármacos , Hipertensão/metabolismo , Túbulos Renais Proximais/metabolismo , Microdissecção , NADPH Oxidase 4 , NADPH Oxidases/metabolismo , Estresse Oxidativo/efeitos dos fármacos , Ratos , Ratos Endogâmicos SHR , Espécies Reativas de Oxigênio/metabolismoRESUMO
Some receptors and signaling molecules, such as Rho-kinase (ROCK), localize in caveolae. We asked whether the function of histamine receptors (H(1)) and 5-hydroxytryptamine (serotonin) receptors (5-HT(2A)) in bovine tracheal smooth muscle are modified after caveolae disruption and if so, whether the altered ROCK activity plays a role in this modification. Methyl-beta-cyclodextrin (MbetaCD), used to deplete membrane cholesterol, was shown to disrupt caveolae and diminish sustained contractions to histamine (approximately 80%), 5-HT (100%), alpha-methyl-5-HT (100%), and KCl (approximately 30%). Cholesterol-loaded MbetaCD (CL-MbetaCD) restored the responses to KCl and partially restored the responses to agonists. ROCK inhibition by Y-27632 diminished contractions to histamine (approximately 85%) and 5-HT (approximately 59%). 5-HT or histamine stimulation augmented ROCK activity. These increases were reduced by MbetaCD and partially reestablished by CL-MbetaCD. The increase in intracellular Ca(2+) that was induced by both agonists was reduced by MbetaCD. The presence of caveolin-1 (Cav-1), H1, 5-HT(2A), and ROCK1 was corroborated by immunoblotting of membrane fractions from sucrose gradients and by confocal microscopy. H(1) receptors coimmunoprecipitated with Cav-1 in caveolar and noncaveolar membrane fractions, whereas 5-HT(2A) receptors appeared to be restricted to noncaveolar membrane fractions. We conclude that caveolar and cholesterol integrity are indispensable for the proper functionality of the H(1) and 5-HT(2A) receptors through their Rho/ROCK signaling.
Assuntos
Cavéolas/fisiologia , Colesterol/fisiologia , Lipídeos de Membrana/fisiologia , Músculo Liso/fisiologia , Receptor 5-HT2A de Serotonina/fisiologia , Receptores Histamínicos H1/fisiologia , Traqueia/fisiologia , Quinases Associadas a rho/fisiologia , Animais , Cálcio/metabolismo , Bovinos , Caveolina 1/fisiologia , Transdução de Sinais , beta-Ciclodextrinas/farmacologiaRESUMO
CONTEXT: Berardinelli-Seip congenital lipodystrophy (BSCL) is a rare recessive disease characterized by near absence of adipose tissue, resulting in severe dyslipidemia and insulin resistance. In most reported cases, BSCL is due to alterations in either seipin, of unknown function, or 1-acylglycerol-3-phosphate acyltransferase-beta (AGPAT2), which catalyzes the formation of phosphatidic acid. OBJECTIVE: We sought to determine the genetic origin of the unexplained cases of BSCL. We thus sequenced CAV1, encoding caveolin-1, as a candidate gene involved in insulin signaling and lipid homeostasis. CAV1 is a key structural component of plasma membrane caveolae, and Cav1-deficient mice display progressive loss of adipose tissue and insulin resistance. DESIGN: We undertook phenotyping studies and molecular screening of CAV1 in four patients with BSCL with no mutation in the genes encoding either seipin or AGPAT2. RESULTS: A homozygous nonsense mutation (p.Glu38X) was identified in CAV1 in a patient with BSCL born from a consanguineous union. This mutation affects both the alpha- and beta-CAV1 isoforms and ablates CAV1 expression in skin fibroblasts. Detailed magnetic resonance imaging of the proband confirmed near total absence of both sc and visceral adipose tissue, with only vestigial amounts in the dorsal sc regions. In keeping with the lack of adipose tissue, the proband was also severely insulin resistant and dyslipidemic. In addition, the proband had mild hypocalcemia likely due to vitamin D resistance. CONCLUSIONS: These findings identify CAV1 as a new BSCL-related gene and support a critical role for caveolins in human adipocyte function.
Assuntos
Caveolina 1/genética , Códon sem Sentido , Lipodistrofia Generalizada Congênita/genética , Adipócitos/fisiologia , Tecido Adiposo/metabolismo , Adulto , Caveolina 1/fisiologia , Feminino , HumanosRESUMO
Progestin regulation of gene expression was assessed in the progestin-dependent murine tumor line C4HD which requires MPA, a synthetic progestin, for in vivo growth and expresses high levels of progesterone receptor (PR). By using suppressive subtractive hybridization, caveolin-1 was identified as a gene whose expression was increased with in vivo MPA treatment. By Northern and Western blot analysis, we further confirmed that caveolin-1 mRNA and protein expression increased in MPA-treated tumors as compared with untreated tumors. When primary cultures of C4HD cells were treated in vitro with MPA, caveolin-1 levels also increased, effect that was abolished by pre-treatment with progestin antagonist RU486. In addition, MPA promoted strong caveolin-1 promoter transcriptional activation both in mouse and human breast cancer cells. We also showed that MPA regulation of caveolin-1 expression involved in activation of two signaling pathways: MAPK and PI-3K. Short-term MPA treatment of C4HD cells led to tyrosine phosphorylation of caveolin-1 protein, where Src was the kinase involved. Additionally, we showed that MPA-induced association of caveolin-1 and PR, which was detected by coimmunoprecipitation and by confocal microscopy. Finally, we proved that MPA-induced proliferation of C4HD cells was inhibited by suppression of caveolin-1 expression with antisense oligodeoxynucleotides to caveolin-1 mRNA. Furthermore, we observed that inhibition of caveolin-1 expression abrogated PR capacity to induced luciferase activity from a progesterone response element-driven reporter plasmid. Comprehensively, our results demonstrated for the first time that caveolin-1 expression is upregulated by progestin in breast cancer. We also demonstrated that caveolin-1 is a downstream effector of MPA that is partially responsible for the stimulation of growth of breast cancer cells.
Assuntos
Caveolina 1/fisiologia , Regulação Neoplásica da Expressão Gênica/efeitos dos fármacos , Neoplasias Mamárias Experimentais/patologia , Acetato de Medroxiprogesterona/farmacologia , Sequência de Aminoácidos , Animais , Sequência de Bases , Caveolina 1/genética , Feminino , Sistema de Sinalização das MAP Quinases , Camundongos , Camundongos Endogâmicos BALB C , Dados de Sequência Molecular , Fosfatidilinositol 3-Quinases/fisiologia , Fosforilação , Regiões Promotoras Genéticas , Receptores de Progesterona/efeitos dos fármacos , Receptores de Progesterona/fisiologia , Quinases da Família src/fisiologiaRESUMO
Endothelial nitric oxide synthase (eNOS) is the primary physiological source of nitric oxide (NO) that regulates cardiovascular homeostasis. Historically eNOS has been thought to be a constitutively expressed enzyme regulated by calcium and calmodulin. However, in the last five years it is clear that eNOS activity and NO release can be regulated by post-translational control mechanisms (fatty acid modification and phosphorylation) and protein-protein interactions (with caveolin-1 and heat shock protein 90) that direct impinge upon the duration and magnitude of NO release. This review will summarize this information and apply the post-translational control mechanisms to disease states.
Assuntos
Arteriosclerose/metabolismo , Diabetes Mellitus/metabolismo , Endotélio Vascular/metabolismo , Cirrose Hepática/metabolismo , Óxido Nítrico Sintase Tipo III/metabolismo , Óxido Nítrico/metabolismo , Animais , Caveolina 1/fisiologia , Ativação Enzimática , Proteínas de Choque Térmico HSP90/fisiologia , HumanosRESUMO
Endothelial nitric oxide synthase (eNOS) is the primary physiological source of nitric oxide (NO) that regulates cardiovascular homeostasis. Historically eNOS has been thought to be a constitutively expressed enzyme regulated by calcium and calmodulin. However, in the last five years it is clear that eNOS activity and NO release can be regulated by post-translational control mechanisms (fatty acid modification and phosphorylation) and protein-protein interactions (with caveolin-1 and heat shock protein 90) that direct impinge upon the duration and magnitude of NO release. This review will summarize this information and apply the post-translational control mechanisms to disease states.