Transcription of the caveolin-1 gene is differentially regulated in lung type I epithelial and endothelial cell lines. A role for ETS proteins in epithelial cell expression

Deletion of caveolin scaffolding domain alters cancer cell migration

Caveolin-1 (Cav-1) is an integral membrane protein that plays an important role in proliferative and terminally differentiated cells. As a structural component of Caveolae, Cav-1 interacts with signaling molecules via a caveolin scaffolding domain (CSD) regulating cell signaling. Recent reports have shown that Cav-1 is a negative regulator in tumor metastasis. Therefore, we hypothesize that Cav-1 inhibits cell migration through its CSD. HeLa cells were engineered to overexpress Cav-1 (Cav-1 OE), Cav-1 without a functional CSD (∆CSD), or enhanced green fluorescent protein (EGFP) as a control. HeLa cell migration was suppressed in Cav-1 OE cells while ∆CSD showed increased migration, which corresponded to a decrease in the tight junction protein, zonula occludens (ZO-1). The migration phenotype was confirmed in multiple cancer cell lines. Phosphorylated STAT-3 was decreased in Cav-1 OE cells compared to control and ∆CSD cells; reducing STAT-3 expression alone decreased cell migration. ∆CSD blunted HeLa proliferation by increasing the number of cells in the G2/M phase of the cell cycle. Overexpressing the CSD peptide alone suppressed HeLa cell migration and inhibited pSTAT3. These findings suggest that Cav-1 CSD may be critical in controlling the dynamic phenotype of cancer cells by facilitating the interaction of specific signal transduction pathways, regulating STAT3 and participating in a G2/M checkpoint. Modulating the CSD and targeting specific proteins may offer potential new therapies in the treatment of cancer metastasis.

Caveolin1 protects against diet induced hepatic lipid accumulation in mice

Background and aim

Caveolin1 (CAV1) is involved in lipid homeostasis and endocytosis, but little is known about the significance of CAV1 in the pathogenesis and development of nonalcoholic fatty liver disease (NAFLD). This study aimed to determine the role of CAV1 in NAFLD.

Methods

Expression of CAV1 in the in vitro and in vivo models of NAFLD was analyzed. The effects of CAV1 knockdown or overexpression on free fatty acid (FFA)-induced lipid accumulation in L02 cells and AML12 cells were determined. CAV1 knockout (CAV1-KO) mice and their wild-type (WT) littermates were subjected to a high fat diet (HFD) for 4 weeks, and the functional consequences of losing the CAV1 gene and its subsequent molecular mechanisms were also examined.

Results

Noticeably, CAV1 expression was markedly reduced in NAFLD. CAV1 knockdown led to the aggravation of steatosis that was induced by FFA in both L02 cells and AML12 cells, while CAV1 overexpression markedly attenuated lipid accumulation in the cells. Consistent with CAV1 repression in the livers of HFD-induced mice, the CAV1-KO mice exhibited more severe hepatic steatosis upon HFD intake. In addition, increased cholesterol levels and elevated transaminases were detected in the plasma of CAV1-KO mice. The protein expression of SREBP1, a key gene involved in lipogenesis, was augmented following CAV1 suppression in FFA-treated hepatocytes and in the livers of HFD-fed CAV1-KO mice.

Conclusions

CAV1 serves as an important protective factor in the development of NAFLD by modulating lipid metabolism gene expression.

Sickle Cell Hemoglobin in the Ferryl State Promotes βCys-93 Oxidation and Mitochondrial Dysfunction in Epithelial Lung Cells (E10)

Polymerization of intraerythrocytic deoxyhemoglobin S (HbS) is the primary molecular event that leads to hemolytic anemia in sickle cell disease (SCD). We reasoned that HbS may contribute to the complex pathophysiology of SCD in part due to its pseudoperoxidase activity. We compared oxidation reactions and the turnover of oxidation intermediates of purified human HbS and HbA. Hydrogen peroxide (H2O2) drives a catalytic cycle that includes the following three distinct steps: 1) initial oxidation of ferrous (oxy) to ferryl Hb; 2) autoreduction of the ferryl intermediate to ferric (metHb); and 3) reaction of metHb with an additional H2O2 molecule to regenerate the ferryl intermediate. Ferrous and ferric forms of both proteins underwent initial oxidation to the ferryl heme in the presence of H2O2 at equal rates. However, the rate of autoreduction of ferryl to the ferric form was slower in the HbS solutions. Using quantitative mass spectrometry and the spin trap, 5,5-dimethyl-1-pyrroline-N-oxide, we found more irreversibly oxidized βCys-93in HbS than in HbA. Incubation of the ferric or ferryl HbS with cultured lung epithelial cells (E10) induced a drop in mitochondrial oxygen consumption rate and impairment of cellular bioenergetics that was related to the redox state of the iron. Ferryl HbS induced a substantial drop in the mitochondrial transmembrane potential and increases in cytosolic heme oxygenase (HO-1) expression and mitochondrial colocalization in E10 cells. Thus, highly oxidizing ferryl Hb and heme, the product of oxidation, may be central to the evolution of vasculopathy in SCD and may suggest therapeutic modalities that interrupt heme-mediated inflammation.

Expression of CAVEOLIN 1 in uterine mesenchymal tumors: No relationship between malignancy and CAVEOLIN 1 expression

Although most smooth muscle neoplasms detected in the human uterus are benign, uterine leiomyosarcoma (Ut-LMS) is extremely malignant with high rates of recurrence and metastasis. CAVEOLIN 1 (CAV1) levels in the epithelial cells of some carcinomas have been reported to increase during tumor progression. We herein evaluated the relationship between CAV1 expression and the pathological features of patients diagnosed with uterine mesenchymal tumors at several clinical facilities. No clinical link was observed between CAV1 expression and the malignancy of human uterine mesenchymal tumors. CAV1 expression was decreased in the normal myometrium, whereas it was strongly expressed in uterine mesenchymal tumors. However, the expression of CAV1 was not a potential biomarker to distinguish Ut-LMS from other types of uterine mesenchymal tumors. The perivascular expression of CAV1 was clearly observed in all types of uterine mesenchymal tumors and myometria. Therefore, the results of the present study suggest that CAV1 may not act as a potential biomarker of uterine malignant mesenchymal tumors.

Aberrant miR199a-5p/caveolin1/PPARα axis in hepatic steatosis

The prevalence of non-alcoholic fatty liver disease (NAFLD), a condition characterized by an excessive accumulation of triglycerides (TGs) in hepatocytes, has dramatically increased globally during recent decades. MicroRNAs (miRs) have been suggested to play crucial roles in many complex diseases and lipid metabolism. Our results indicated that miR199a-5p was remarkably upregulated in free fatty acid (FA)-treated hepatocytes. To investigate the role of miR199a-5p in the pathogenesis of fatty liver and the potential mechanism by which miR199a-5p regulates NAFLD, we first transfected two hepatocyte cell lines, HepG2 and AML12 cells, with agomiR199a-5p or antagomiR199a-5p. Our results indicated that miR199a-5p overexpression exacerbated deposition of FA and inhibited ATP levels and mitochondrial DNA (mtDNA) contents. Consistently, suppression of miR199a-5p partially alleviated deposition of FA and increased ATP levels and mtDNA contents. Moreover, miR199a-5p suppressed the expression of mitochondrial FA β-oxidation-related genes through inhibition of caveolin1 (CAV1) and the related peroxisome proliferator-activated receptor alpha (PPARα) pathway. Furthermore, suppression of CAV1 gene expression by CAV1 siRNA inhibited the PPARα signalling pathway. Finally, we examined the expression of miR199a-5p in liver samples derived from mice fed a high-fat diet, db/db mice, ob/ob mice and NAFLD patients, and found that miR199a-5p was upregulated while CAV1 and PPARA were downregulated in these systems, which was strongly indicative of the essential role of miR199a-5p in NAFLD. In summary, miR199a-5p plays a vital role in lipid metabolism, mitochondrial activity and mitochondrial β-oxidation in liver. Upregulated miR199a-5p in hepatocytes may contribute to impaired FA β-oxidation in mitochondria and aberrant lipid deposits, probably via CAV1 and the PPARα pathway.

Impaired expression of caveolin-1 contributes to hepatic ischemia and reperfusion injury

Caveolae are membrane structures enriched in glycosphingolipids and cholesterol, and caveolin-1 (Cav-1) has been recognized to be pivotal in ischemic tolerance. Sphingosine-1-phosphate (S1P), one of the sphingolipid metabolites, is well known for its anti-apoptotic properties, counteracting ischemia and reperfusion (IR) injury. Here, we investigated the cytoprotective mechanism of Cav-1 against IR injury. Male C57BL/6 mice underwent 70% hepatic ischemia for 60 min, followed by reperfusion. Mice were pretreated with methyl-beta-cyclodextrin (MβCD, 10, 25 and 50mg/kg, i.p.), a caveolae disruptor, or saline 48 and 24h before ischemia. Serum and liver tissues were collected at the end of ischemia, at 0, 1, 4 and 24h of reperfusion. Decreases in the expression of Cav-1 protein and in the number of caveolae of the liver ultrastructure were observed during IR, which were augmented by pretreatment with MβCD. MβCD also augmented the IR-induced increases in serum alanine aminotransferase and tumor necrosis factor-α levels. IR decreased the levels of sphingosine kinase 2 (SK2) and S1P receptor 2 (S1P2) mRNA expressions, while MβCD also augmented these decreases. Moreover, IR resulted in increases of mitochondrial cytochrome c release, caspase 3, 8 activities and Bax/Bcl-xL ratio, and MβCD augmented all of these apoptotic parameters. MβCD also increased p38 MAPK and JNK phosphorylation, but did not affect ERK and PI3K/Akt. Our findings demonstrate that downregulation of Cav-1 mediates IR-induced liver damage by inhibiting SK2/S1P2 signaling and enhancing the apoptotic pathway.

Hypoxia-inducible factor/MAZ-dependent induction of caveolin-1 regulates colon permeability through suppression of occludin, leading to hypoxia-induced inflammation

Caveolae are specialized microdomains on membranes that are critical for signal transduction, cholesterol transport, and endocytosis. Caveolin-1 (CAV1) is a multifunctional protein and a major component of caveolae. Cav1 is directly activated by hypoxia-inducible factor (HIF). HIFs are heterodimers of an oxygen-sensitive α subunit, HIF1α or HIF2α, and a constitutively expressed β subunit, aryl hydrocarbon receptor nuclear translocator (ARNT). Whole-genome expression analysis demonstrated that Cav1 is highly induced in mouse models of constitutively activated HIF signaling in the intestine. Interestingly, Cav1 was increased only in the colon and not in the small intestine. Currently, the mechanism and role of HIF induction of CAV1 in the colon are unclear. In mouse models, mice that overexpressed HIF1α or HIF2α specifically in intestinal epithelial cells demonstrated an increase in Cav1 gene expression in the colon but not in the duodenum, jejunum, or ileum. HIF2α activated the Cav1 promoter in a HIF response element-independent manner. myc-associated zinc finger (MAZ) protein was essential for HIF2α activation of the Cav1 promoter. Hypoxic induction of CAV1 in the colon was essential for intestinal barrier integrity by regulating occludin expression. This may provide an additional mechanism by which chronic hypoxia can activate intestinal inflammation.

Simultaneous expression of flotillin-1, flotillin-2, stomatin and caveolin-1 in non-small cell lung cancer and soft tissue sarcomas

BACKGROUND

At the present time, there is a lack of data about the involvement of flotillins and stomatin in the development of non-small cell lung cancer (NSCLC) and soft tissue sarcomas (STS). Moreover, changes in expression of members of different families of the microdomain-forming proteins (caveolins and SPFH-domain containing family) are usually investigated independently of each other. In this study we performed a combined analysis of flotillins, stomatin, and caveolin-1 expression in these pathologies and evaluated correlations between generated data and clinicopathological characteristics of the specimens.

METHODS

The protein and mRNA expression was analyzed by Western blotting and real-time PCR, respectively, in tissue specimens of patients undergoing surgery for non-small cell lung cancer and soft tissue sarcomas. Association between expression of studied proteins and patient clinicopathological characteristics or outcome was evaluated.

RESULTS

Stomatin protein expression was down-regulated in 80% of NSCLC samples and this decrease significantly associated with presence of lymph node metastases. Flotillin-2 protein expression was up-regulated in the majority of NSCLC samples whereas caveolin-1α expression was decreased. We revealed a strong correlation between STOM and FLOT-1 mRNA expression in both pathologies, although the gene expression changes were diverse.

CONCLUSIONS

Our data demonstrate for the first time that expression of stomatin, a poorly studied microdomain-forming protein, significantly changes in human tumors, thus pointing to its importance in the progression of NSCLC. We also suggest the existence of some relationship between the expression of these proteins.

Caveolin and β1-integrin coordinate angiotensinogen expression in cardiac myocytes

BACKGROUND

The cardiac renin-angiotensin system (RAS) has been implicated in mediating myocyte hypertrophy and remodeling, although the biochemical mechanisms responsible for regulating the local RAS are poorly understood. Caveolin-1 (Cav-1)/Cav-3 double-knockout mice display cardiac hypertrophy, and in vitro disruption of lipid rafts/caveolae using methyl-β-cyclodextrin (MβCD) abolishes cardiac protection.

METHODS

In this study, neonatal rat ventricular myocytes (NRVM) were used to determine whether lipid rafts/caveolae may be involved in the regulation of angiotensinogen (Ao) gene expression, a substrate of the RAS system.

RESULTS

Treatment with MβCD caused a time-dependent upregulation of Ao gene expression, which was associated with differential regulation of mitogen-activated protein (MAP) kinases ERK1/2, p38 and JNK phosphorylation. JNK was highly phosphorylated shortly after MβCD treatment (2-30 min), whereas marked activation of ERK1/2 and p38 occurred much later (2-4h). β1D-Integrin was required for MβCD-induced activation of the MAP kinases. Pharmacologic inhibition of ERK1/2 and JNK enhanced MβCD-induced Ao gene expression, whereas p38 blockade inhibited this response. Adenovirus-mediated expression of wild-type p38α enhanced MβCD-induced Ao gene expression; conversely expression of dominant negative p38α blocked the stimulatory effects of MβCD. Expression of Cav-3 siRNA stimulated Ao gene expression, whereas overexpression of Cav-3 was inhibitory. Cav-1 and Cav-3 expression levels were found to be positively regulated by p38, but unaffected by ERK1/2 and JNK.

CONCLUSION

Collectively, these studies indicate that lipid rafts/caveolae couple to Ao gene expression through a mechanism that involves β1-integrin and the differential actions of MAP kinase family members.

Volatile anesthetics protect cancer cells against tumor necrosis factor-related apoptosis-inducing ligand-induced apoptosis via caveolins

BACKGROUND

Volatile anesthetics have a dual effect on cell survival dependent on caveolin expression. The effect of volatile anesthetics on cancer cell survival and death after anesthetic exposure has not been well investigated. The authors examined the effects of isoflurane exposure on apoptosis and its regulation by caveolin-1 (Cav-1).

METHODS

The authors exposed human colon cancer cell lines to isoflurane and proapoptotic stimuli and assessed what role Cav-1 plays in cell protection. They evaluated apoptosis using assays for nucleosomal fragmentation, cleaved caspase 3 expression, and caspase activity assays. To test the mechanism, they used pharmacologic inhibitors (i.e., pertussis toxin) and assessed changes in glycolysis.

RESULTS

Apoptosis as measured by nucleosomal fragmentation was enhanced by isoflurane (1.2% in air) in HT29 (by 64% relative to control, P < 0.001) and decreased in HCT116 (by 23% relative to control, P < 0.001) cells. Knockdown of Cav-1 in HCT116 cells increased the sensitivity to apoptotic stimuli but not with scrambled small interfering RNA (siRNA) treatment (19.7 ± 0.4 vs. 20.0 ± 0.6, P = 0.7786 and 19.7 ± 0.5 vs. 16.3 ± 0.4, P = 0.0012, isoflurane vs. control in Cav-1 small interfering RNA vs. scrambled small interfering RNA treated cells, respectively). The protective effect of isoflurane with various exposure times on apoptosis was enhanced in HT29 cells overexpressing Cav-1 (P < 0.001 by two-way ANOVA). Pertussis toxin effectively blocked the antiapoptotic effect of isoflurane exhibited by Cav-1 in all cell lines. Cav-1 cells had increased glycolysis with isoflurane exposure; however, in the presence of tumor necrosis factor-related apoptosis-inducing ligand, this increase in glycolysis was maintained in HT29-Cav-1 but not control cells.

CONCLUSION

Brief isoflurane exposure leads to resistance against apoptosis via a Cav-1-dependent mechanism.

Transcriptional repression of Caveolin-1 (CAV1) gene expression by GATA-6 in bladder smooth muscle hypertrophy in mice and human beings

Hypertrophy occurs in urinary bladder wall smooth muscle (BSM) in men with partial bladder outlet obstruction (PBOO) caused by benign prostatic hyperplasia (BPH) and in animal models of PBOO. Hypertrophied BSM from the rabbit model exhibits down-regulation of caveolin-1, a structural and functional protein of caveolae that function as signaling platforms to mediate interaction between receptor proteins and adaptor and effector molecules to regulate signal generation, amplification, and diversification. Caveolin-1 expression is diminished in PBOO-induced BSM hypertrophy in mice and in men with BPH. The proximal promoter of the human and mouse caveolin-1 (CAV1) gene was characterized, and it was observed that the transcription factor GATA-6 binds this promoter, causing reduced expression of caveolin-1. Furthermore, caveolin-1 expression levels inversely correlate with the abundance of GATA-6 in BSM hypertrophy in mice and human beings. Silencing of GATA6 gene expression up-regulates caveolin-1 expression, whereas overexpression of GATA-6 protein sustains the transcriptional repression of caveolin-1 in bladder smooth muscle cells. Together, these data suggest that GATA-6 acts as a transcriptional repressor of CAV1 gene expression in PBOO-induced BSM hypertrophy in men and mice. GATA-6-induced transcriptional repression represents a new regulatory mechanism of CAV1 gene expression in pathologic BSM, and may serve as a target for new therapy for BPH-induced bladder dysfunction in aging men.

Endothelial differentiation: molecular mechanisms of specification and heterogeneity

A complex and diverse vascular system is requisite for the survival of higher organisms. The process of vascular development is highly regulated, involving the de novo formation of vessels (vasculogenesis), followed by expansion and remodeling of the primitive vasculature (angiogenesis), culminating in differentiation of endothelial phenotypes, as found in the mature vascular system. Over the last decade, significant advances have been made in understanding the molecular regulation of endothelial cell development and differentiation. Endothelial development, in particular the mechanisms in play during vasculogenesis and angiogenesis, is discussed in a sister review to this article. This review highlights the key pathways governing in endothelial differentiation, with a focus on the major molecular mechanisms of endothelial specification and heterogeneity.

Nanocarriers for pulmonary administration of peptides and therapeutic proteins

Peptides and therapeutic proteins have been the target of intense research and development in recent years by the pharmaceutical and biotechnology industry. Preferably, they are administered through the parenteral route, which is associated with reduced patient compliance. Formulations for noninvasive administration of peptides and therapeutic proteins are currently being developed. Among them, inhalation appears as a promising alternative for the administration of such products. Several formulations for pulmonary delivery are in various stages of development. Despite positive results, conventional formulations have some limitations such as reduced bioavailability and side effects. Nanocarriers may be an alternative way to overcome the problems of conventional formulations. Some nanocarrier-based formulations of peptides and therapeutic proteins are currently under development. The results obtained are promising, revealing the usefulness of these systems in the delivery of such drugs.

Human lung innate immune cytokine response to adenovirus type 7

Adenovirus (Ad) type 7 can cause severe infection, including pneumonia, in military recruits and children. The initial inflammation is a neutrophilic interstitial infiltration with neutrophilic alveolitis. Subsequently, monocytes become evident and, finally, there is a predominantly lymphocytic infiltrate. We have established that Ad7 infection of epithelial cells stimulates release of the neutrophil chemotaxin interleukin (IL)-8, and have extended these studies to a human lung tissue model. Here, we studied cytokine responses to Ad7 in human alveolar macrophages (HAM) and our human lung tissue model. Both ELISA and RNase-protection assay (RPA) data demonstrated that, upon Ad7 infection, IP-10 and MIP-1alpha/beta are released from HAM. IP-10 and MIP-1alpha/beta protein levels were induced 2- and 3-fold, respectively, in HAM 24 h after Ad7 infection. We then investigated induction of specific cytokines in human lung tissue by RPA and ELISA. The results showed that IL-8 and IL-6 were induced 8 h after infection and, by 24 h, levels of IL-8, IL-6, MIP-1alpha/beta and MCP-1 were all increased. IP-10, a monocyte and lymphocyte chemokine, was also induced 30-fold, but only 24 h after infection. Immunohistochemistry staining confirmed that IL-8 was only released from the epithelial cells of lung slices and not from macrophages. IP-10 was secreted from both macrophages and epithelial cells. Moreover, full induction of IP-10 is likely to require participation and cooperation of both epithelial cells and macrophages in intact lung. Understanding the cytokine and chemokine induction during Ad7 infection may lead to novel ways to modulate the response to this pathogen.

Epigenetic mechanisms modulate thyroid transcription factor 1-mediated transcription of the surfactant protein B gene

Epigenetic regulation of transcription plays an important role in cell-specific gene expression by altering chromatin structure and access of transcriptional regulators to DNA binding sites. Surfactant protein B (Sftpb) is a developmentally regulated lung epithelial gene critical for lung function. Thyroid transcription factor 1 (Nkx2-1) regulates Sftpb gene expression in various species. We show that Nkx2-1 binds to the mouse Sftpb (mSftpb) promoter in the lung. In a mouse lung epithelial cell line (MLE-15), Nkx2-1 knockdown reduces Sftpb expression, and mutation of Nkx2-1 cis-elements significantly reduces mSftpb promoter activity. Whether chromatin structure modulates Nkx2-1 regulation of Sftpb transcription is unknown. We found that DNA methylation of the mSftpb promoter inversely correlates with known patterns of Sftpb expression in vivo. The mSftpb promoter activity can be manipulated by altering its cytosine methylation status in vitro. Nkx2-1 activation of the mSftpb promoter is impaired by DNA methylation. The unmethylated Sftpb promoter shows an active chromatin structure enriched in the histone modification H3K4me3 (histone 3-lysine 4 trimethylated). The ATP-dependent chromatin remodeling protein Brg1 is recruited to the Sftpb promoter in Sftpb-expressing, but not in non-expressing tissues and cell lines. Brg1 knockdown in MLE-15 cells greatly decreases H3K4me3 levels at the Sftpb promoter region and expression of the Sftpb gene. Brg1 can be co-immunoprecipitated with Nkx2-1 protein. Last, Nkx2-1 and Brg1 with intact ATPase activity are required for mSftpb promoter activation in vitro. Our findings suggest that DNA methylation and chromatin modifications cooperate with Nkx2-1 to regulate Sftpb gene cell specific expression.

Transforming growth factor-β1 downregulates caveolin-1 expression and enhances sphingosine 1-phosphate signaling in cultured vascular endothelial cells

In vascular endothelial cells, specialized microdomains of plasma membrane termed caveolae modulate various receptor signal transduction pathways regulated by caveolin-1, a resident protein of caveolae. We examined whether transforming growth factor-β1 (TGF-β1), a multifunctional cytokine, alters expression levels of caveolin-1 and influences heterologous receptor signaling. Treatment of cultured bovine aortic endothelial cells (BAEC) with TGF-β1 induces marked decreases in caveolin-1 expression in a time- and dose-dependent fashion at both levels of protein and mRNA. A pharmacological inhibitor of activin receptor-like kinase 5 (ALK-5) counteracts caveolin-1 downregulation by TGF-β1, indicating the involvement of ALK-5 receptor subtype for TGF-β1. Sphingosine 1-phosphate (S1P) is a serum-borne angiogenic lipid growth factor that exerts a wide variety of biological actions. S1P modulates G protein-coupled S1P receptors, activating downstream molecules kinases AMP-activated protein kinase (AMPK), and Akt as well as a small G protein Rac1, ultimately to promote migration. Because S1P receptor signaling is associated with caveolae/caveolin-1, we examined whether pretreatment with TGF-β1 enhances effects of S1P on BAEC. Whereas S1P alone evokes robust BAEC responses to S1P, pretreatment with TGF-β1 leads to even higher magnitudes of S1P-elicited signaling responses and cell migration. Conversely, genetic knockdown of caveolin-1 using small interfering RNA mimics TGF-β1-induced promotion of BAEC responses to S1P. Collectively, these data demonstrate that TGF-β1 downregulates caveolin-1 of cultured endothelial cells, involving ALK-5 receptor subtype. Because downregulation of caveolin-1 by TGF-β1 promotes subsequent heterologous receptor signaling by S1P, these results may also identify novel point of cross-talk between cytokines and sphingolipids within endothelial signal transduction machineries.

Increased PEA3/E1AF and decreased Net/Elk-3, both ETS proteins, characterize human NSCLC progression and regulate caveolin-1 transcription in Calu-1 and NCI-H23 NSCLC cell lines

Caveolin-1 protein has been called a 'conditional tumor suppressor' because it can either suppress or enhance tumor progression depending on cellular context. Caveolin-1 levels are dynamic in non-small-cell lung cancer, with increased levels in metastatic tumor cells. We have shown previously that transactivation of an erythroblastosis virus-transforming sequence (ETS) cis-element enhances caveolin-1 expression in a murine lung epithelial cell line. Based on high sequence homology between the murine and human caveolin-1 promoters, we proposed that ETS proteins might regulate caveolin-1 expression in human lung tumorigenesis. We confirm that caveolin-1 is not detected in well-differentiated primary lung tumors. Polyoma virus enhancer activator 3 (PEA3), a pro-metastatic ETS protein in breast cancer, is expressed at low levels in well-differentiated tumors and high levels in poorly differentiated tumors. Conversely, Net, a known ETS repressor, is expressed at high levels in the nucleus of well-differentiated primary tumor cells. In tumor cells in metastatic lymph node sites, caveolin-1 and PEA3 are highly expressed, whereas Net is now expressed in the cytoplasm. We studied transcriptional regulation of caveolin-1 in two human lung cancer cell lines, Calu-1 (high caveolin-1 expressing) and NCI-H23 (low caveolin-1 expressing). Chromatin immunoprecipitation-binding assays and small interfering RNA experiments show that PEA3 is a transcriptional activator in Calu-1 cells and that Net is a transcriptional repressor in NCI-H23 cells. These results suggest that Net may suppress caveolin-1 transcription in primary lung tumors and that PEA3 may activate caveolin-1 transcription in metastatic lymph nodes.

Caveolin-1: an ambiguous partner in cell signalling and cancer

Caveolae are small plasma membrane invaginations that have been implicated in a variety of functions including transcytosis, potocytosis and cholesterol transport and signal transduction. The major protein component of this compartment is a family of proteins called caveolins. Experimental data obtained in knockout mice have provided unequivocal evidence for a requirement of caveolins to generate morphologically detectable caveolae structures. However, expression of caveolins is not sufficient per seto assure the presence of these structures. With respect to other roles attributed to caveolins in the regulation of cellular function, insights are even less clear. Here we will consider, more specifically, the data concerning the ambiguous roles ascribed to caveolin-1 in signal transduction and cancer. In particular, evidence indicating that caveolin-1 function is cell context dependent will be discussed.

Down-regulation of caveolin-1, an inhibitor of transforming growth factor-beta signaling, in acute allergen-induced airway remodeling

Asthma can progress to subepithelial airway fibrosis, mediated in large part by transforming growth factor-beta (TGF-beta). The scaffolding protein caveolin-1 (cav1) can inhibit the activity of TGF-beta, perhaps by forming membrane invaginations that enfold TGF-beta receptors. The study goals were 1) to evaluate how allergen challenge affects lung expression of cav1 and the density of caveolae in vivo 2) to determine whether reduced cav1 expression is mediated by interleukin (IL)-4 and 3) to measure the effects of decreased expression of cav1 on TGF-beta signaling. C57BL/6J, IL-4-deficient mice, and cav1-deficient mice, sensitized by intraperitoneal injections of phosphate-buffered saline or ovalbumin (OVA) at days 0 and 12, received intranasal phosphate-buffered saline or OVA challenges at days 24, 26, and 28. Additionally, another group of C57BL/6J mice received IL-4 by intratracheal instillation for 7 days. We confirmed that the OVA-allergen challenge increased eosinophilia and T-helper type 2-related cytokine levels (IL-4, IL-5, and IL-13) in bronchoalveolar lavage. Allergen challenge reduced lung cav1 mRNA abundance by 40%, cav1 protein by 30%, and the number of lung fibroblast caveolae by 50%. Administration of IL-4 in vivo also substantially decreased cav1 expression. In contrast, the allergen challenge did not decrease cav1 expression in IL-4-deficient mice. The reduced expression of cav1 was associated with activation of TGF-beta signaling that was further enhanced in OVA-sensitized and challenged cav1-deficient mice. This study demonstrates a previously unknown modulation of TGF-beta signaling by IL-4, via cav1, suggesting novel therapeutic targets for controlling the effects of TGF-beta and thereby ameliorating pathological airway remodeling.

ERM is expressed by alveolar epithelial cells in adult mouse lung and regulates caveolin-1 transcription in mouse lung epithelial cell lines

We previously identified an Ets cis-element in the mouse caveolin-1 promoter that is selectively activated in lung epithelial (E10), but not lung endothelial murine lung endothelial cell line (MFLM-4), cell lines and therefore appears important for differential, cell-specific caveolin-1 transcription. In the present study, we demonstrate that immunostaining of adult mouse lung detects the ETS protein Ets-related molecule (ERM PEA3) in distal lung epithelium in alveolar type I and II cells, but not in bronchial epithelium or lung endothelial cells. We tested ERM and polyomavirus enhancer activator 3 (PEA3) for their ability to increase endogenous caveolin-1 transcripts and to activate caveolin-1 promoter fragments containing the -865 Ets cis-element. Chromatin immunoprecipitation (ChIP) assays show that both ERM and PEA3 bind to the caveolin-1 promoter in murine E10, but not MFLM-4, cells. Normalized luciferase activities show that only ERM activates the caveolin-1 promoter in E10 cells, but neither protein enhances promoter activity in MFLM-4 cells. Mutation of the Ets site blocks ERM-mediated promoter activation in E10 cells. Furthermore, overexpression of ERM increases the cellular content of caveolin-1 mRNA and protein, in E10, but not MFLM-4, cells. The effects of PEA3 on the cellular content of endogenous caveolin-1 expression are variable. These results demonstrate that ERM is involved in caveolin-1 regulation in a murine lung epithelial, but not lung endothelial cell line. We conclude that transcriptional regulation of caveolin-1 differs markedly between lung epithelial and endothelial cell lines, perhaps explaining why the onset of caveolin-1 expression differs in epithelial and endothelial cells during lung development.

Transcriptional control of lung morphogenesis

The vertebrate lung consists of multiple cell types that are derived primarily from endodermal and mesodermal compartments of the early embryo. The process of pulmonary organogenesis requires the generation of precise signaling centers that are linked to transcriptional programs that, in turn, regulate cell numbers, differentiation, and behavior, as branching morphogenesis and alveolarization proceed. This review summarizes knowledge regarding the expression and proposed roles of transcription factors influencing lung formation and function with particular focus on knowledge derived from the study of the mouse. A group of transcription factors active in the endodermally derived cells of the developing lung tubules, including thyroid transcription factor-1 (TTF-1), beta-catenin, Forkhead orthologs (FOX), GATA, SOX, and ETS family members are required for normal lung morphogenesis and function. In contrast, a group of distinct proteins, including FOXF1, POD1, GLI, and HOX family members, play important roles in the developing lung mesenchyme, from which pulmonary vessels and bronchial smooth muscle develop. Lung formation is dependent on reciprocal signaling among cells of both endodermal and mesenchymal compartments that instruct transcriptional processes mediating lung formation and adaptation to breathing after birth.

Phenotypic Heterogeneity of the Endothelium

Endothelial cells, which form the inner cellular lining of blood vessels and lymphatics, display remarkable heterogeneity in structure and function. This is the first of a 2-part review focused on phenotypic heterogeneity of blood vessel endothelium. This review provides an historical perspective of our understanding of endothelial heterogeneity, discusses the scope of phenotypic diversity across the vascular tree, and addresses proximate and evolutionary mechanisms of endothelial cell heterogeneity. The overall goal is to underscore the importance of phenotypic heterogeneity as a core property of the endothelium.

Caveolin-1 (CAV1) is a target of EWS/FLI-1 and a key determinant of the oncogenic phenotype and tumorigenicity of Ewing's sarcoma cells

Tumors of the Ewing's sarcoma family (ESFT), such as Ewing's sarcoma (EWS) and primitive neuroectodermal tumors (PNET), are highly aggressive malignancies predominantly affecting children and young adults. ESFT express chimeric transcription factors encoded by hybrid genes fusing the EWS gene with several ETS genes, most commonly FLI-1. EWS/FLI-1 proteins are responsible for the malignant phenotype of ESFT, but only few of their transcriptional targets are known. Using antisense and short hairpin RNA-mediated gene expression knockdown, array analyses, chromatin immunoprecipitation methods, and reexpression studies, we show that caveolin-1 (CAV1) is a new direct target of EWS/FLI-1 that is overexpressed in ESFT cell lines and tumor specimens and is necessary for ESFT tumorigenesis. CAV1 knockdown led to up-regulation of Snail and the concomitant loss of E-cadherin expression. Consistently, loss of CAV1 expression inhibited the anchorage-independent growth of EWS cells and markedly reduced the growth of EWS cell-derived tumors in nude mice xenografts, indicating that CAV1 promotes the malignant phenotype in EWS carcinogenesis. Reexpression of CAV1 or E-cadherin in CAV1 knockdown EWS cells rescued the oncogenic phenotype of the original EWS cells, showing that the CAV1/Snail/E-cadherin pathway plays a central role in the expression of the oncogenic transformation functions of EWS/FLI-1. Overall, these data identify CAV1 as a key determinant of the tumorigenicity of ESFT and imply that targeting CAV1 may allow the development of new molecular therapeutic strategies for ESFT patients.

Computational prediction of novel components of lung transcriptional networks

MOTIVATION

Little is known regarding the transcriptional mechanisms involved in forming and maintaining epithelial cell lineages of the mammalian respiratory tract.

RESULTS

Herein, a motif discovery approach was used to identify novel transcriptional regulators in the lung using genes previously found to be regulated by Foxa2 or Wnt signaling pathways. A human-mouse comparison of both novel and known motifs was also performed. Some of the factors and families identified here were previously shown to be involved epithelial cell differentiation (ETS family, HES-1 and MEIS-1), and ciliogenesis (RFX family), but have never been characterized in lung epithelia. Other unidentified over-represented motifs suggest the existence of novel mammalian lung transcription factors. Of the fraction of motifs examined we describe 25 transcription factor family predictions for lung. Fifteen novel factors were shown here to be expressed in mouse lung, and/or human bronchial or distal lung epithelial tissues or lung epithelial cell lineages.

AVAILABILITY

DME: http://rulai.cshl.edu/dme. MATCOMPARE: http://rulai.cshl.edu/MatCompare. MOTIFCLASS is available from the authors.

Phenotypic Characterization of Pulmonary Arteries in Normal and Diseased Lung

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.

KLF11-mediated repression antagonizes Sp1/sterol-responsive element-binding protein-induced transcriptional activation of caveolin-1 in response to cholesterol signaling

Cholesterol is a potent regulator of gene expression via a canonical pathway co-regulated by SREBP and Sp1. Here we establish the caveolin-1 gene promoter as a cell type-specific model for SREBP/Sp1 regulation whereby lipoprotein cholesterol depletion activates caveolin-1 transcription in endothelial type cells, but not in fibroblasts, both in vitro and in vivo. By extending this model, we describe a novel pathway distinct from the prototypical SREBP/Sp1 regulatory loop involving the Sp1-like protein, KLF11. Through a combination of RNA interference, chromatin immunoprecipitation assays, electrophoretic mobility shift assays, and reporter assays, we demonstrate that in the presence of cholesterol, KLF11 acts as a dominant repressor of the caveolin-1 gene. Mechanistically, cholesterol depletion results in displacement of KLF11 from an Sp1 site flanking an SRE, indicating that activation by SREBP/Sp1 requires antagonism of KLF11 repression. The displacement of KLF11 results from both a down-regulation of its expression and competition by Sp1 for DNA binding. Therefore, these studies identify a novel pathway whereby KLF11 repression is coordinated with Sp1/SREBP activation of cholesterol-dependent gene expression in a cell type-specific manner and outline the mechanisms by which these functions are achieved.