Role Of Caveolin-1 Research Articles

The predictive role of caveolin 1 and CD34 coexpression in anticipating occult carcinoma in prostatic needle core biopsy

The predictive role of caveolin 1 and CD34 coexpression in anticipating occult carcinoma in prostatic needle core biopsy

Role of caveolin-1 in osteoclastogenesis

Searchable abstracts of presentations at key conferences on calcified tissues ISSN 2052-1219 (online)

Changes of Caveolin-1, IL-1β, VEGF in cerebrospinal fluid of children with viral encephalitis and their clinical significance

Objective To detect the disparity of three biological molecules Caveolin-1,IL-1β,VEGF in cerebrospinal fluid of children with viral encephalitis at the different stages; to explore the role of Caveolin-1,IL-1β,VEGF in the pathogenesis of viral encephalitis;and to evaluate their clinical significance in assessing the severity and prognosis of viral encephalitis.Methods We recruited 65 inpatients children with viral encephalitis in the Second Neurology Department of Hunan Children's Hospital from July 2011 to July 2012.Subjects were divided into 2 groups:54 cases of acute phase and 11 cases of recovery phase.According to the clinical manifestations,they were re-divided into 40 patients with mild viral encephalitis and 25 cases of severe viral encephalitis.Twenty healthy age matched controls (10 cases of epilepsy and 10 cases of congenital abnormality) were also taken for the study.Cerebrospinal fluid exam,EEG,head MRI and other tests were performed in all patients.Caveolin-1,IL-1β and VEGF levels in cerebrospinal fluid of 65 children with viral encephalitis and 20 age-matched controls were measured using ELISA.Results Cerebrospinal fluid Caveolin-1,IL-1β,VEGF levels in the acute phase of viral encephalitis were (49.209 ± 22.320) pg/ml,(16.923 ± 6.823) ng/ml,(44.342 ± 19.264) ng/ml respectively,and (33.253 ± 20.349)pg/ml,(11.724 ± 3.009)ng/ml,(30.312 ± 18.147) ng/ml in recovery phase,which were significantly higher than those of controls (P ＜0.01).The difference was statistically significant between acute phase and recovery phase (P ＜ 0.05).Acute viral encephalitis patients had higher Caveolin-l,IL-1β,VEGF levels than the epilepsy group,and the difference was statistically significant (P ＜ 0.05).In viral encephalitis group,children with cerebrospinal fluid protein content (0.5 ～ 1.0 g / L) had higher of Caveolin-1,IL-1β and VEGF levels as compared with those with cerebrospinal fluid protein content ≤ 0.5 g/L,and the difference was statistically significant (P ＜ 0.01).Cerebrospinal fluid Caveolin-1,IL-1 β and VEGF showed no significant difference among children with different severity of encephalitis,different levels of frequent seizures,different degrees EEG changes (P ＞ 0.05).But in the patients with severe head MRI changes,cerebrospinal fluid Caveolin-1,IL-1β,VEGF levels increased significantly (P ＜ 0.05).Conclusions Caveolin-1,IL-1β and VEGF may participate in the pathogenesis of viral encephalitis.Detection of these parameters may be helpful to the evaluation of the severity and prognosis of viral encephalitis. Key words: Viral encephalitis; Caveolin-1 ; Interleukin-1β; Vascular endothelial growth factor

Role of Caveolin-1 in Atrial Fibrillation as an Anti-Fibrotic Signaling Molecule in Human Atrial Fibroblasts

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia in the general population; yet, the precise mechanisms resulting in AF are not fully understood. Caveolin-1 (Cav-1), the principal structural component of caveolae organelles in cardiac fibroblasts, is involved in several cardiovascular conditions; however, the study on its function in atrium, in particular, in AF, is still lacking. This report examines the hypothesis that Cav-1 confers an anti-AF effect by mediating atrial structural remodeling through its anti-fibrotic action. We evaluated the expression of Cav-1, transforming growth factor-β1 (TGF-β1), and fibrosis in atrial specimens of 13 patients with AF and 10 subjects with sinus rhythm, and found that the expression of Cav-1 was significantly downregulated, whereas TGF-β1 level, collagens I/III contents and atrial fibrosis were markedly increased, in AF. Western blot analysis demonstrated that treatment of human atrial fibroblasts (HAFs) with TGF-β1 resulted in a concentration- and time-dependent repression of Cav-1. Downregulation of Cav-1 with siRNA increased the TGF-β1-induced activation of Smad signal pathway and collagens production in HAFs. Furthermore, incubation of HAFs with the peptides derived from Cav-1 to achieve Cav-1 gain-of-function abolished the TGF-β1-induced production of collagens I/III and decreases of MMP-2/-9 expression. Therefore it was concluded that Cav-1 is an important anti-AF signaling mediator by conferring its anti-fibrotic effects in atrium.

Role of caveolin-1 in the biology of the blood-brain barrier

Caveolin-1 is the principal marker of caveolae in endothelial cells. It plays an important role in physiological and pathological conditions of the blood-brain barrier and serves as a mediator in drug delivery through the blood-brain barrier. Caveolin-1 is related to the diminished expression of tight junction-associated proteins and metabolic pinocytosis vesicles when the blood-brain barrier is destroyed by outside invaders or malignant stimulus. The permeability of the blood-brain barrier, regulated by types of drugs or physical irradiation, is connected with drug transportation with the participation of caveolin-1. Caveolin-1, which serves as a platform or medium for signal transduction, cooperates with several signal molecules by forming a complex. Silencing of caveolin-1 and disruption of caveolae can attenuate or remove pathological damage and even engender the opposite effects in the blood-brain barrier. This review considers the role of caveolin-1 in the blood-brain barrier that may have profound implications for central nervous system disease and drug delivery through the blood-brain barrier.

Ca2+-dependent regulatory activity of recoverin in photoreceptor raft structures: The role of caveolin-1

Recoverin is a Ca2+-binding protein implicated in the Ca2+-dependent regulation of desensitization of visual receptor rhodopsin in vertebrate retinal rods. Here we report that Ca2+ sensitivity of recoverin regulating rhodopsin phosphorylation increases in the presence of the photoreceptor membranes enriched in raft structures. The observed effect is mediated by a key protein component of raft structures caveolin-1. The presence of recombinant fragment Phe81-Arg101 of the caveolin-1 cytoplasmic domain enhances Ca2+ affinity of recoverin, therefore affecting its Ca2+-dependent regulatory activity.

Abstract 18096: Novel Role of Caveolin-1 in Endothelial Function by Regulating Extracellular SOD Activity and Cu Transporter ATP7A Function

Caveolin (Cav)-enriched lipid raft (C/LR) microdomains play an important role for regulating insulin signaling and endothelial function; however underlying mechanisms is incompletely understood. Vascular extracellular superoxide dismutase (ecSOD), a secretory copper (Cu) enzyme synthesized from vascular smooth muscle cells (VSMCs), preserves nitric oxide (NO)-mediated endothelial function by reducing extracellular superoxide anion (O2•-) levels. We previously demonstrated that Cu transporter ATP7A is required for full activity of ecSOD and that both ecSOD and ATP7A are found in C/LR. However, the functional significance of ATP7A-ecSOD pathway in insulin signaling and C/LR remains unknown. Here we show that in organoid culture of mouse aorta, insulin stimulation increases ecSOD specific activity (47%) and ATP7A expression. In cultured VSMCs, insulin stimulation promotes ATP7A translocation to the C/LR (1.7 fold) where ecSOD is activated by ATP7A through their binding. Furthermore, insulin stimulation promotes ATP7A association with Cav1 as shown by immunofluorescence and co-immunoprecipitation assay. Specific activity of ecSOD, but not Cu/Zn SOD, is significantly decreased (60%) in aorta of Cav1 knockout (KO) mice, indicating that Cav1 or C/LR is required for full ecSOD activity. Of note, ATP7A expression is decreased in aorta from Cav1 KO mice or Cav1-depleted VSMCs with siRNA, which is due to enhanced ATP7A ubiquitination. These results suggest that Cav1 binding to ATP7A at C/LR protects ATP7A from proteosomal degradation, thereby increasing ecSOD activity. Functionally, NO-dependent vasorelaxation induced by acetylcholine, but not NO-independent relaxation induced by sodium nitroprusside, is impaired in mesenteric arteries of Cav1 KO mice vs. wild type mice (P<0.05), which is associated with overproduction of O2•- in the vessels and rescued by gene transfer of ecSOD. In summary, Cav1 plays an essential role for insulin-induced full ecSOD activation by regulating ATP7A translocation and expression. Our studies will provide novel insights into the Cav1-ATP7A-ecSOD axis as a potential therapeutic target for promoting endothelial function against oxidative stress-dependent cardiovascular and metabolic diseases.

Functional role of caveolin-1 in airway smooth muscle cells proliferation and regulatory effect of roxithromycin

To explore the functional role of caveolin-1 in airway smooth muscle cells (ASMCs) proliferation and examine the regulatory effect of roxithromycin. The rat model of bronchial asthma was established. Electron microscope was employed to observe the status of caveolae and light microscope for the histological changes in pulmonary tissues. The primarily cultured ASMCs were divided into 5 groups: control (group A), asthmatic ASMCs (group B), PD98059 (group C), roxithromycin (group D) and methyl-β-cyclodextrin (group E). Cell proliferation was detected by Cell Counting Kit-8 (CCK-8). And the expressions of caveolin-1, extracellular regulated protein kinases (ERK) and monocyte chemotactic protein (MCP)-1 were detected by Western blot and reverse transcription polymerase chain reaction (RT-PCR). The cell proliferation of asthmatic ASMCs (0.68 ± 0.15, 0.63 ± 0.13) in groups C and D were significantly less than those in group B (0.96 ± 0.14) (both P < 0.05) while group E was more than group B (1.26 ± 0.11 vs 0.96 ± 0.14, P < 0.05). The content of caveolin-1 (0.392 ± 0.064, 0.332 ± 0.057) in groups C and D were higher than those in group B (0.237 ± 0.032) (both P < 0.05) while ERK1/2 protein level in groups C and D (0.241 ± 0.017, 0.268 ± 0.007) were less than those in group B (0.346 ± 0.009) (both P < 0.01). And MCP-1 protein level in groups C and D (0.198 ± 0.015, 0.286 ± 0.019) were less than those in group B (0.482 ± 0.026) (both P < 0.01). The ERK mRNA level in groups C and D (0.277 ± 0.043, 0.338 ± 0.026) were less than those in group B (0.591 ± 0.022) (both P < 0.01). And also MCP-1 mRNA in groups C and D (0.212 ± 0.042, 0.249 ± 0.032) were less than those in group B (0.676 ± 0.053) (all P < 0.01) CONCLUSIONS: Caveolin-1 preventing the proliferation of asthmatic ASMCs is most likely mediated by ERK1/2 signal pathway and a down-regulation of MCP-1 expression. And roxithromycin reduces the proliferation of asthmatic ASMCs through up-regulating the expression of caveolin-1 and inhibiting the expression of MCP-1.

Caveolae, lipid droplets, and adipose tissue biology: pathophysiological aspects.

Adipocytes are specialized cells that function to store energy in the form of lipids, predominantly triglycerides (TGs), and as a regulatory system contributing to metabolic homoeostasis through the production and secretion of hormones and cytokines. The regulation of lipid homeostasis by adipose tissue is an important aspect of whole-body metabolism. Owing to the central nature of adipose tissue in lipid metabolism, dysregulation has wide-ranging effects, contributing to disorders as diverse as diabetes, cardiovascular disease, cancer, and neurodegeneration. Excess lipids are stored in specialized organelles called lipid droplets (LDs). The surface of the lipid droplet can be considered a highly regulated membrane domain that both protects the contents of the LD from unregulated lipolysis and the cell from the cytotoxic effects of elevated free fatty acids. The surface of the LD is coated with a variety of regulatory proteins, either resident or transiently associated, including enzymes involved in the breakdown of TG, lipid transport proteins, and cofactors. Recent studies have begun to unravel the range of LD-associated proteins and to define their functional significance. Importantly, the involvement of LD proteins in pathophysiological disorders is beginning to be understood. This review will outline recent advances in defining the diversity of LD-associated proteins and their links to metabolic disorders including the integral membrane protein, caveolin-1 (CAV1). Analysis of the role of CAV1 in adipose tissue has highlighted the interconnectedness between the regulation of lipid storage and the function of the adipocyte plasma membrane.

Caveolin-1 and migration of bone-marrow derived cells in the mouse eye

Bone marrow derived cells (BMDCs) can be found in almost every tissue showing a distinct turnover and density. Since caveolin-1 regulates junction-associated proteins in endothelial and epithelial cells, its role for BMDC was investigated in the eyes of caveolin-1 knock-out mice transplanted with GFP-marked BMDC. Distribution and turnover of BMDC in connective tissues (cornea, iris, ciliary body and choroid) was not altered. The absence of caveolin-1, however, caused a significant decrease of BMDC turnover in cornea epithelium, ciliary epithelium, and in the retina. This finding emphasizes an important, hitherto unknown role of caveolin-1 in neuronal and epithelial tissues.

AMP-dependent Kinase Inhibits Oxidative Stress-induced Caveolin-1 Phosphorylation and Endocytosis by Suppressing the Dissociation between c-Abl and Prdx1 Proteins in Endothelial Cells

Caveolin-1 is the primary structural component of endothelial caveolae that is essential for transcellular trafficking of albumin and is also a critical scaffolding protein that regulates the activity of signaling molecules in caveolae. Phosphorylation of caveolin-1 plays a fundamental role in the mechanism of oxidant-induced vascular hyper permeability. However, the regulatory mechanism of caveolin-1 phosphorylation remains unclear. Here we identify a previously unexpected role for AMPK in inhibition of caveolin-1 phosphorylation under oxidative stress. A pharmacological activator of AMPK, 5-amino-4-imidazole carboxamide riboside (AICAR), inhibited oxidative stress-induced phosphorylation of both caveolin-1 and c-Abl, which is the major kinase of caveolin-1, and endocytosis of albumin in human umbilical vein endothelial cell. These effects were abolished by treatment with two specific inhibitors of AICAR, dipyridamole, and 5-iodotubericidin. Consistently, knockdown of the catalytic AMPKα subunit by siRNA abolished the inhibitory effect of AICAR on oxidant-induced phosphorylation of both caveolin-1 and c-Abl. Pretreatment with specific c-Abl inhibitor, imatinib mesylate, and knock down of c-Abl significantly decreased the caveolin-1 phosphorylation after H2O2 exposure and abolished the inhibitory effect of AICAR on the caveolin-1 phosphorylation. Interestingly, knockdown of Prdx-1, an antioxidant enzyme associated with c-Abl, increased phosphorylation of both caveolin-1 and c-Abl and abolished the inhibitory effect of AICAR on the caveolin-1 phosphorylation. Furthermore, co-immunoprecipitation experiment showed that AICAR suppressed the oxidant-induced dissociation between c-Abl and Prdx1. Overall, our results suggest that activation of AMPK inhibits oxidative stress-induced caveolin-1 phosphorylation and endocytosis, and this effect is mediated in part by stabilizing the interaction between c-Abl and Prdx-1.

Abstract 279: Role of Caveolin-1 in Abdominal Aortic Aneurysm induced by Angiotensin II

Abdominal aortic aneurysm (AAA) is a significant cause of mortality for adults aged &gt;60 years. Accumulating evidence suggests that activation of the AT1 receptor by angiotensin II (AngII) in AAA formation. While several downstream signals and target proteins have been identified in this pathway, there is a huge void in our knowledge regarding the AngII-sensitive proximal events primarily responsible for AAA formation. We recently reported that caveolae membrane microdomains in vascular smooth muscle cells (VSMC) mediate a metalloprotease ADAM17-dependent EGF receptor (EGFR) transactivation which linked to vascular remodeling induced by AngII. Given that ADAM17 expression is one of the key features in AAA, we have tested our hypothesis that caveolin-1 (Cav1), a major structural protein of caveolae, in the vasculature plays a critical role for development of AAA via its regulation on ADAM17. 8 week old male Cav1-/- mice and the control C57Bl/6 wild-type (WT) mice were co-infused with AngII and BAPN, a lysyl oxidase inhibitor, to induce AAA. We found that Cav1-/- mice did not develop AAA compared to C57Bl/6 mice in spite of hypertension assessed by telemetry in both groups. This finding suggests that the AngII signaling essential for vascular contraction remains in place in Cav1-/- mice. We found an increased expression of ADAM17 and auto-phosphorylation of EGFR in WT abdominal aortae with aneurysms that were markedly attenuated in Cav1-/- mice infused with AngII+BAPN. Furthermore, Cav1-/- mice with the infusion showed less oxidative stress and ER stress than their WT counterparts as assessed by nitrotyrosine staining and KDEL/p-eIF2a staining, respectively. In conclusion, Cav1 and presumably vascular caveolae micro-domain appear to play a critical role in the formation of AAA in mice via regulation of the ADAM17/EGFR signaling axis and subsequent induction of ER/oxidative stress.

E‐cadherin determines Caveolin‐1 tumor suppression or metastasis enhancing function in melanoma cells

The role of caveolin-1 (CAV1) in cancer is highly controversial. CAV1 suppresses genes that favor tumor development, yet also promotes focal adhesion turnover and migration of metastatic cells. How these contrasting observations relate to CAV1 function in vivo is unclear. Our previous studies implicate E-cadherin in CAV1-dependent tumor suppression. Here, we use murine melanoma B16F10 cells, with low levels of endogenous CAV1 and E-cadherin, to unravel how CAV1 affects tumor growth and metastasis and to assess how co-expression of E-cadherin modulates CAV1 function in vivo in C57BL/6 mice. We find that overexpression of CAV1 in B16F10 (cav-1) cells reduces subcutaneous tumor formation, but enhances metastasis relative to control cells. Furthermore, E-cadherin expression in B16F10 (E-cad) cells reduces subcutaneous tumor formation and lung metastasis when intravenously injected. Importantly, co-expression of CAV1 and E-cadherin in B16F10 (cav-1/E-cad) cells abolishes tumor formation, lung metastasis, increased Rac-1 activity, and cell migration observed with B16F10 (cav-1) cells. Finally, consistent with the notion that CAV1 participates in switching human melanomas to a more malignant phenotype, elevated levels of CAV1 expression correlated with enhanced migration and Rac-1 activation in these cells.

Role of caveolin-1 in fibrotic diseases

Fibrosis underlies the pathogenesis of numerous diseases and leads to severe damage of vital body organs and, frequently, to death. Better understanding of the mechanisms resulting in fibrosis is essential for developing appropriate treatment solutions and is therefore of upmost importance. Recent evidence suggests a significant antifibrotic potential of an integral membrane protein, caveolin-1. While caveolin-1 has been widely studied for its role in the regulation of cell signaling and endocytosis, its possible implication in fibrosis remains largely unclear. In this review we survey involvement of caveolin-1 in various cellular processes and highlight different aspects of its antifibrotic activity. We hypothesize that caveolin-1 conveys a homeostatic function in the process of fibrosis by (a) regulating TGF-β1 and its downstream signaling; (b) regulating critical cellular processes involved in tissue repair, such as migration, adhesion and cellular response to mechanical stress; and (c) antagonizing profibrotic processes, such as proliferation. Finally, we consider this homeostatic function of caveolin-1 as a possible novel approach in treatment of fibroproliferative diseases.

The effects of TNF‐alpha and Ceramide on Insulin Receptor signaling and its localization to Caveolae in C2C12 Myocytes

TNF‐α and ceramide are associated with the etiology of insulin resistance. There is evidence for the involvement of caveolae membrane rafts in the modulation of insulin signaling and glucose uptake. Thus, we propose to elucidate the signaling mechanisms by which TNF‐α and ceramide induce insulin resistance in C2C12 myocytes and the role of caveolins in the organization of this pathway within the membrane. We hypothesized that exposure of C2C12 myocytes to TNF‐α and ceramide will result in altered insulin signaling, decreased glucose uptake, and translocation of the insulin signaling cascade away from caveolae. C2C12 myocytes were treated with TNF‐α, ceramide, and insulin, individually and in combination. The treated cells were subjected to Western blot analysis for insulin receptor‐β (IR‐β), phosphorylated IR (p‐IR), Protein Kinase B (PKB or Akt), phosphorylated Akt (p‐Akt), Cav‐3, Glut‐4, and actin (as loading control). The total protein expression of IR, Cav‐3, and Glut‐4 was unaltered with treatment. However, there was a significant increase in the total expression of Akt in cells treated with TNF‐α. In addition, there was a significantly higher activation of Akt and IR in cells treated with TNF‐α after 48 hours exposure. This data suggests that the effect of TNF‐α on insulin signaling in a result of a cross‐talk mechanism. This data will further the identification of novel signaling mechanisms leading to insulin resistance as a prerequisite to improved diagnosis and therapeutic treatments for diabetes.

The role of caveolin-1 for carbon black nanoparticles uptake in vitro

To investigate the protein expression of caveolin-1 in type II alveolar epithelial cells (A549) exposed to carbon black nanoparticles (CB NPs) and the role of caveolin in the endocytosis of CB NPs. A549 cells were exposed to 0, 25, 50, 100, 200, and 400 µg/ml CB NPs for 24 h; then, trypan blue assay was applied to determine the cell viability. A549 cells were also exposed to 0, 25, 50, and 100 µg/ml CB NPs for 24 h, then, transmission electron microscopy (TEM) and flow cytometry were applied to observe the morphological change of cells and cellular side scatter (SSC), and Western blot was used to analyze the effect of CB NPs on the protein expression of caveolin-1. A549 cells were co-exposed to1 µg/ml filipin and 100 µg/ml CB NPs for 24 h, then, the cellular SSC was observed. Compared with controls, the A549 cells exposed to 200 and 400 µg/ml CB NPs had the cell viability decreased by 38.2% and 46.6%, respectively (P < 0.05), while those exposed to 25, 50, and 100 µg/ml CB NPs showed no significant decrease in cell vitality (P > 0.05). The protein expression of caveolin-1 was significantly higher in the cells exposed to 50 and 100 µg/ml CB NPs than in controls (P < 0.05). The TEM showed that plasmalemmal vesicles containing black particles were found in the cytoplasm of the cells exposed to 50 and 100 µg/ml CB NPs. The flow cytometry showed that the cellular SSC ratio increased from 1.007 to 1.331 as the dose of CB NPs rose within 0 ∼ 100 µg/ml and fell to 1.25 after the cells were co-exposed to1 µg/ml filipin and 100 µg/ml CB NPs. Carbon black nanoparticles can be transferred into A549 cells by endocytosis, but caveolin-mediated endocytic pathway plays a minor role in this process.

Caveolin and caveolae in age associated cardiovascular disease.

It is estimated that the elderly (> 65 years of age) will increase from 13%−14% to 25% by 2035. If this trend continues, > 50% of the United States population and more than two billion people worldwide will be “aged” in the next 50 years. Aged individuals face formidable challenges to their health, as aging is associated with a myriad of diseases. Cardiovascular disease is the leading cause of morbidity and mortality in the United States with > 50% of mortality attributed to coronary artery disease and > 80% of these deaths occurring in those age 65 and older. Therefore, age is an important predictor of cardiovascular disease. The efficiency of youth is built upon cellular signaling scaffolds that provide tight and coordinated signaling. Lipid rafts are one such scaffold of which caveolae are a subset. In this review, we consider the importance of caveolae in common cardiovascular diseases of the aged and as potential therapeutic targets. We specifically address the role of caveolin in heart failure, myocardial ischemia, and pulmonary hypertension.

Caveolin-1 Regulates Endothelial Adhesion of Lung Cancer Cells via Reactive Oxygen Species-Dependent Mechanism

The knowledge regarding the role of caveolin-1 (Cav-1) protein on endothelium adhesion of cancer cells is unclear. The present study revealed that Cav-1 plays a negative regulatory role on cancer-endothelium interaction. Endogenous Cav-1 was shown to down-regulate during cell detachment and the level of such a protein was conversely associated with tumor-endothelial adhesion. Furthermore, the ectopic overexpression of Cav-1 attenuated the ability of the cancer cells to adhere to endothelium while shRNA-mediated Cav-1 knock-down exhibited the opposite effect. We found that cell detachment increased cellular hydrogen peroxide and hydroxyl radical generation and such reactive oxygen species (ROS) were responsible for the increasing interaction between cancer cells and endothelial cells through vascular endothelial cell adhesion molecule-1 (VCAM-1). Importantly, Cav-1 was shown to suppress hydrogen peroxide and hydroxyl radical formation by sustaining the level of activated Akt which was critical for the role of Cav-1 in attenuating the cell adhesion. Together, the present study revealed the novel role of Cav-1 and underlying mechanism on tumor adhesion which explain and highlight an important role of Cav-1 on lung cancer cell metastasis.

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.