Potential Role Of Caveolin-1 Research Articles

Potential Role of Caveolin-1 in Regulating the Function of Endothelial Progenitor Cells from Experimental MODS Model.

Multiple organ dysfunction syndrome (MODS) remains a great challenge in critical care because of its common occurrence, high cost of care, and high mortality. Vascular endothelial injury is the initiation step in the development of MODS, and EPCs are essential for the process of organ repair. It is unclear whether and how caveolin-1 (Cav-1) in EPCs contributes to the pathogenesis of MODS. The present study is aimed at investigating the potential role of Cav-1 in EPCs during MODS. We established a MODS model in pigs, isolated and characterized EPCs from the MODS model, and tracked Cav-1 expression and various in vitro behaviors of EPCs from the MODS model. Then, we knockdown Cav-1 expression with siRNA or induce Cav-1 expression with proinflammatory factors to evaluate potential effects on EPCs. Our results suggest that Cav-1 expression correlated with EPC functions during MODS and Cav-1 regulates the function of endothelial progenitor cells via PI3K/Akt/eNOS signaling during MODS. Thus, Cav-1 in EPCs could be an attractive target for the treatment of MODS.

The Impact of Simulated Weightlessness on Endothelium-Dependent Angiogenesis and the Role of Caveolae/Caveolin-1

Background/Aims: The potential role of caveolin-1 in modulating angiogenesis in microgravity environment is unexplored. Methods: Using simulated microgravity by clinostat, we measured the expressions and interactions of caveolin-1 and eNOS in human umbilical vein endothelial cells. Results: We found that decreased caveolin-1 expression is associated with increased expression and phosphorylation levels of eNOS in endothelial cells stimulated by microgravity, which causes a dissociation of eNOS from caveolin-1 complexes. As a result, microgravity induces cell migration and tube formation in endothelial cell in vitro that depends on the regulations of caveolin-1. Conclusion: Our study provides insight for the important endothelial functions in altered gravitational environments.

Caveolin-1: Oncogenic role in breast cancer? Clues from molecular profiling.

134 Background: Caveolin-1 (CAV1) is the structural component of caveolae, compartments within the plasma membrane that sequester signaling molecules, thus facilitating molecular “hot spots”. The role of CAV1 in breast cancer is an active area of investigation. We sought to understand the clinical and pathological characteristics of CAV1 positive tumors (CAV 1+) through a retrospective analysis of molecularly-profiled breast cancer patients. Methods: 2,728 breast cancer patients molecularly profiled with a commercial assay (Caris Life Sciences) were evaluated retrospectively for expression of various biomarkers by immunohistochemistry (IHC) and in situ hybridization. JMP statistical analysis tool was used to ascertain distributional differences. Results: Using a threshold of 2+ and 30%, 121/2728 (4%) of patients exhibited CAV1 over-expression by IHC. To observe clinicopathologic differences in the CAV1 + and CAV1- tumors, distribution by age, metastatic disease, and triple negative histology (TNBC) were analyzed. Average age for both groups was 55. 39% vs. 54% were metastatic and 74% vs. 26% were TNBC (p = 0.0001) among CAV1+ and CAV1- groups, respectively. To evaluate the potential oncogenic associations of CAV1, we evaluated the relationship between CAV1+ and various oncogenic pathways. Positive EGFR protein expression and presence of EGFR gene amplification, as well as cKIT over-expression associated with CAV1+ (all p-values < 0.001), whereas HER2 expression and amplification were associated with CAV1- (p = 0.001 for both). In addition, higher Ki67, p53 and TOP2A expression by IHC were observed in CAV1+ patients compared to the CAV1- subgroup (90% vs. 66%, 50% vs. 36%, 84% vs. 65% ; all p-values < 0.0001). Biomarker expression differences that did not meet statistical significance: ERCC1, MGMT, PDGFRA, RRM1, SPARC, TS and TOPO1. Conclusions: The majority of CAV1+ breast cancers are comprised of triple negative, higher proliferative tumors, with aberrant p53 expression as well as expression of other growth factor signaling proteins. This data supports the potential role of CAV1 in fostering molecular hubs for signaling and CAV-1 being a potential target for future therapeutic investigation in TNBC.

Potential role of caveolin-1 in regulation of immune cell activation.

Potential role of caveolin-1 in regulation of immune cell activation.

Abstract P6-06-03: Caveolin-1: A potential mediator of RhoC GTPase driven Inflammatory breast cancer cell invasion.

Abstract The proposed study focuses on Inflammatory Breast Cancer (IBC), which is one of the most aggressive forms of locally advanced breast cancer. IBC is an understudied disease in terms of identifying various molecular entities that could potentially be responsible for the aggressiveness of this disease. Recent advancements reveal that IBC has a unique molecular profile when compared with non-IBC. Caveolin-1 is found to have opposite expression pattern in IBC versus non-IBC. Our lab has shown that Caveolin-1 is found to be over-expressed in IBC whereas in non-IBC its expression is much reduced compared to normal mammary epithelial cells. Caveolin-1 is known to be associated with specialized lipid rafts in the plasma membrane called ‘caveolae’. ‘Caveolin scaffolding domain (CSD)’ from amino acids 82–101 concentrates variety of signaling molecules such as growth factor receptors, protein kinases, heterotrimeric G proteins and Rho GTPases. Thus it is known as a potential regulator of many signaling pathways. Rho GTPases are members of the Ras superfamily of small GTP binding proteins involved in cytoskeletal rearrangements during cell motility and invasion. Our lab has previously shown that RhoC GTPase is over expressed in IBC and that exogenous expression of RhoC GTPase produces motile and invasive phenotype in human mammary epithelial cells (HMECs) similar to SUM149 IBC cells. Thus the overall objective of this study is to determine if caveolin-1 over expression mediates the RhoC GTPase driven invasive phenotype of IBC via its scaffolding action. The first objective of this study is to elucidate the effect of caveolin-1 over expression on SUM149 IBC cell invasion. This was done by down regulating caveolin-1 to a level that is comparable to human mammary epithelial cells (HMECs) by using si caveolin-1. With the same si caveolin-1 or exogenous CSD synthetic peptide, we performed Matrigel invasion assays followed by cell viability and proliferation assay. Si caveolin-1 did not produce significant changes in cell viability over the period of four days as well as in Ki-67 staining which was used as a proliferation marker. Caveolin-1 down regulation reduced cell invasion by 90% compared to untreated cells. Similarly, exogenous CSD synthetic peptide treatment reduced SUM149 cell invasion significantly. In order to understand caveolin-1 localization in SUM149 cells, we performed immuno gold labeling of caveolin-1 by transmission electron microscopy as well as sucrose gradient centrifugation. Both these methods showed distinct pool of cytoplasmic caveolin-1 in addition to plasma membrane associated caveolin-1. Co-localization of caveolin-1 and RhoC GTPase was studied by co-transfecting cells with GFP-caveolin-1 and RFP-RhoC GTPase. Thus, this data suggests potential role of caveolin-1 over expression in regulating IBC cell invasion. Due to its ability to concentrate variety of signaling molecules, caveolin-1 could act as a principle regulator of several downstream events that make cells motile and invasive through RhoC GTPase activation. Thus studying caveolin-1 localization and effect of its regulation on the signaling pathways could help understand the important molecular mechanisms in IBC. Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P6-06-03.

Potential role of caveolin-1 in acetaminophen-induced hepatotoxicity

Caveolin-1 (Cav-1) is a membrane scaffolding protein, which functions to regulate intracellular compartmentalization of various signaling molecules. In the present studies, transgenic mice with a targeted disruption of the Cav-1 gene (Cav-1 −/−) were used to assess the role of Cav-1 in acetaminophen-induced hepatotoxicity. Treatment of wild-type mice with acetaminophen (300 mg/kg) resulted in centrilobular hepatic necrosis and increases in serum transaminases. This was correlated with decreased expression of Cav-1 in the liver. Acetaminophen-induced hepatotoxicity was significantly attenuated in Cav-1 −/− mice, an effect that was independent of acetaminophen metabolism. Acetaminophen administration resulted in increased hepatic expression of the oxidative stress marker, lipocalin 24p3, as well as hemeoxygenase-1, but decreased glutathione and superoxide dismutase-1; no differences were noted between the genotypes suggesting that reduced toxicity in Cav-1 −/− mice is not due to alterations in antioxidant defense. In wild-type mice, acetaminophen increased mRNA expression of the pro-inflammatory cytokines, interleukin-1β, and monocyte chemoattractant protein-1 (MCP-1), as well as cyclooxygenase-2, while 15-lipoxygenase (15-LOX), which generates anti-inflammatory lipoxins, decreased. Acetaminophen-induced changes in MCP-1 and 15-LOX expression were greater in Cav-1 −/− mice. Although expression of tumor necrosis factor-α, a potent hepatocyte mitogen, was up-regulated in the liver of Cav-1 −/− mice after acetaminophen, expression of proliferating cell nuclear antigen and survivin, markers of cellular proliferation, were delayed, which may reflect the reduced need for tissue repair. Taken together, these data demonstrate that Cav-1 plays a role in promoting inflammation and toxicity during the pathogenesis of acetaminophen-induced injury.

Caveolin-1 expression sensitizes fibroblastic and epithelial cells to apoptotic stimulation.

The potential role of caveolin-1 in apoptosis remains controversial. Here, we investigate whether caveolin-1 expression is proapoptotic or antiapoptotic using a well-defined antisense approach. We show that NIH/3T3 cells harboring antisense caveolin-1 are resistant to staurosporine-induced apoptosis, as assessed using cell morphology, DNA content, caspase 3 activation, and focal adhesion kinase cleavage. Importantly, sensitivity to apoptosis is recovered when caveolin-1 levels are restored. Conversely, recombinant stable expression of caveolin-1 in T24 bladder carcinoma cells sensitizes these cells to caspase 3 activation. Consistent with the observations using NIH/3T3 cells, downregulation of caveolin-1 in T24 cells substantially diminishes caspase 3-like activity. Loss of sensitivity to apoptotic stimulation is recovered by inhibition of the phosphatidylinositol 3-kinase pathway using LY-294002, suggesting a possible mechanism for the sensitizing effect of caveolin-1. Thus our results suggest that caveolin-1 may act as a coupling or sensitizing factor in signaling apoptotic cell death in both fibroblastic (NIH/3T3) and epithelial (T24) cells.