Moesin Expression Research Articles

Tumor suppressive microRNA-133a regulates novel targets: Moesin contributes to cancer cell proliferation and invasion in head and neck squamous cell carcinoma

Recently, many studies suggest that microRNAs (miRNAs) contribute to the development, invasion and metastasis of various types of human cancers. Our recent study revealed that expression of microRNA-133a (miR-133a) was significantly reduced in head and neck squamous cell carcinoma (HNSCC) and that restoration of miR-133a inhibited cell proliferation, migration and invasion in HNSCC cell lines, suggesting that miR-133a function as a tumor suppressor. Genome-wide gene expression analysis of miR-133a transfectants and TargetScan database showed that moesin (MSN) was a promising candidate of miR-133a target gene. MSN is a member of the ERM (ezrin, radixin and moesin) protein family and ERM function as cross-linkers between plasma membrane and actin-based cytoskeleton. The functions of MSN in cancers are controversial in previous reports. In this study, we focused on MSN and investigated whether MSN was regulated by tumor suppressive miR-133a and contributed to HNSCC oncogenesis. Restoration of miR-133a in HNSCC cell lines (FaDu, HSC3, IMC-3 and SAS) suppressed the MSN expression both in mRNA and protein level. Silencing study of MSN in HNSCC cell lines demonstrated significant inhibitions of cell proliferation, migration and invasion activities in si-MSN transfectants. In clinical specimen with HNSCC, the expression level of MSN was significantly up-regulated in cancer tissues compared to adjacent non-cancerous tissues. These data suggest that MSN may function as oncogene and is regulated by tumor suppressive miR-133a. Our analysis data of novel tumor-suppressive miR-133a-mediated cancer pathways could provide new insights into the potential mechanisms of HNSCC oncogenesis.

Cytoplasmic Ezrin and Moesin Correlate with Poor Survival in Head and Neck Squamous Cell Carcinoma

Members of the 4.1 superfamily of proteins, including ezrin, moesin, merlin, and willin regulate many normal physiologic processes such as cellular shape, motility, and proliferation. In addition, they contribute both to tumor development and tumor progression. We reported previously that strong cytoplasmic ezrin expression was independently associated with poorer patient survival. One hundred and thirty-one histologically confirmed primary head and neck squamous cell carcinomas were examined prospectively for cancer progression and survival at a large health care center in the Bronx, NY, USA. Immunohistochemical analysis of ezrin, moesin, merlin, and willin expression in tissue microarray samples of primary head and neck squamous cell carcinoma revealed a significant association of increased cytoplasmic ezrin with poor cancer survival. Global RNA analyses suggest that cancers with high cytoplasmic ezrin have a more invasive phenotype. This study supports our previous findings associating cytoplasmic ezrin with more aggressive behavior and poorer outcome and indicates the need for a multi-institutional study to validate the use of cytoplasmic ezrin as a biomarker for treatment planning in head and neck squamous cell carcinoma.

Dynamic actin remodeling during epithelial–mesenchymal transition depends on increased moesin expression

Remodeling of actin filaments is necessary for epithelial-mesenchymal transition (EMT); however, understanding of how this is regulated in real time is limited. We used an actin filament reporter and high-resolution live-cell imaging to analyze the regulated dynamics of actin filaments during transforming growth factor-β-induced EMT of mammary epithelial cells. Progressive changes in cell morphology were accompanied by reorganization of actin filaments from thin cortical bundles in epithelial cells to thick, parallel, contractile bundles that disassembled more slowly but remained dynamic in transdifferentiated cells. We show that efficient actin filament remodeling during EMT depends on increased expression of the ezrin/radixin/moesin (ERM) protein moesin. Cells suppressed for moesin expression by short hairpin RNA had fewer, thinner, and less stable actin bundles, incomplete morphological transition, and decreased invasive capacity. These cells also had less α-smooth muscle actin and phosphorylated myosin light chain in cortical patches, decreased abundance of the adhesion receptor CD44 at membrane protrusions, and attenuated autophosphorylation of focal adhesion kinase. Our findings suggest that increased moesin expression promotes EMT by regulating adhesion and contractile elements for changes in actin filament organization. We propose that the transciptional program driving EMT controls progressive remodeling of actin filament architectures.

Knockdown of ERM Family Member Moesin in Host Cells Increases HIV Type 1 Replication

Moesin is a member of the ERM (ezrin, radixin, moesin) family of cytoskeleton/membrane structure organizing and signal transduction proteins. Previously, we found an increased expression of moesin during HIV-1 infection. Moesin was also reported to be incorporated into HIV-1 virions. To analyze whether moesin is a host factor affecting the replication cycle of human immunodeficiency virus type 1 (HIV-1), we used small interfering RNAs (siRNAs) to evaluate the effect of moesin knockdown on HIV-1 replication in P4-CCR5 cells. Moesin's knockdown did not affect the cell viability or cell phenotype. Interestingly, we observed a marked increase in viral replication, as demonstrated by enhanced HIV-1 RNA, p24 antigen, and ß-galactosidase reporter expression. Moesin-dependent enhancement of HIV-1 replication was confirmed in lymphocytic host cells (Jurkat). These results suggest an overall rather restrictive role of moesin for HIV-1 replication in host cells in vitro.

PDZD8 is a novel moesin-interacting cytoskeletal regulatory protein that suppresses infection by herpes simplex virus type 1

The host cytoskeleton plays a central role in the life cycle of many viruses yet our knowledge of cytoskeletal regulators and their role in viral infection remains limited. Recently, moesin and ezrin, two members of the ERM (Ezrin/Radixin/Moesin) family of proteins that regulate actin and plasma membrane cross-linking and microtubule (MT) stability, have been shown to inhibit retroviral infection. To further understand how ERM proteins function and whether they also influence infection by other viruses, we identified PDZD8 as a novel moesin-interacting protein. PDZD8 is a poorly understood protein whose function is unknown. Exogenous expression of either moesin or PDZD8 reduced the levels of stable MTs, suggesting that these proteins functioned as part of a cytoskeletal regulatory complex. Additionally, exogenous expression or siRNA-mediated knockdown of either factor affected Herpes Simplex Virus type 1 (HSV-1) infection, identifying a cellular function for PDZD8 and novel antiviral properties for these two cytoskeletal regulatory proteins.

Dynamic cortical actin remodeling by ERM proteins controls BCR microcluster organization and integrity

Signaling microclusters are a common feature of lymphocyte activation. However, the mechanisms controlling the size and organization of these discrete structures are poorly understood. The Ezrin-Radixin-Moesin (ERM) proteins, which link plasma membrane proteins with the actin cytoskeleton and regulate the steady-state diffusion dynamics of the B cell receptor (BCR), are transiently dephosphorylated upon antigen receptor stimulation. In this study, we show that the ERM proteins ezrin and moesin influence the organization and integrity of BCR microclusters. BCR-driven inactivation of ERM proteins is accompanied by a temporary increase in BCR diffusion, followed by BCR immobilization. Disruption of ERM protein function using dominant-negative or constitutively active ezrin constructs or knockdown of ezrin and moesin expression quantitatively and qualitatively alters BCR microcluster formation, antigen aggregation, and downstream BCR signal transduction. Chemical inhibition of actin polymerization also altered the structure and integrity of BCR microclusters. Together, these findings highlight a crucial role for the cortical actin cytoskeleton during B cell spreading and microcluster formation and function.

Advanced glycation end products induce moesin phosphorylation in murine retinal endothelium

Increase in vascular permeability is the most important pathological event during the development of diabetic retinopathy. Deposition of advanced glycation end products (AGEs) plays a crucial role in the process of diabetes. This study was to investigate the role of moesin and its underlying signal transduction in retinal vascular hyper-permeability induced by AGE-modified mouse serum albumin (AGE-MSA). Female C57BL/6 mice were used to produce an AGE-treated model by intraperitoneal administration of AGE-MSA for seven consecutive days. The inner blood-retinal barrier was quantified by Evans blue leakage assay. Endothelial F-actin cytoskeleton in retinal vasculature was visualized by fluorescence probe staining. The expression and phosphorylation of moesin in retinal vessels were detected by RT-PCR and western blotting. Further studies were performed to explore the effects of Rho kinase (ROCK) and p38 MAPK pathway on the involvement of moesin in AGE-induced retinal vascular hyper-permeability response. Treatment with AGE-MSA significantly increased the permeability of the retinal microvessels and induced the disorganization of F-actin in retinal vascular endothelial cells. The threonine (T558) phosphorylation of moesin in retinal vessels was enhanced remarkably after AGE administration. The phosphorylation of moesin was attenuated by inhibitions of ROCK and p38 MAPK, while this treatment also prevented the dysfunction of inner blood-retinal barrier and the reorganization of F-actin in retinal vascular endothelial cells. These results demonstrate that moesin is involved in AGE-induced retinal vascular endothelial dysfunction and the phosphorylation of moesin is triggered via ROCK and p38 MAPK activation.

Advanced glycation end products induce moesin phosphorylation in murine brain endothelium

Advanced glycation end products (AGEs) have been found to play an important role in the development of diabetes, and AGE levels are correlated with the severity of diabetic complications. We have demonstrated that moesin, a protein linker between actin filaments and the plasma membrane, undergoes phosphorylation of its threonine 558 residue by AGE stimulation in human dermal microvascular endothelial cells through activation of p38 and Rho kinase (ROCK) pathways. In this study, we observed in situ whether AGEs caused phosphorylation of vascular endothelial cells in the brains of AGE-stimulated mice. The animals were injected with AGE-modified mouse serum albumin (AGE-MSA) for 7 consecutive days. Immunohistochemistry was conducted to assess the phosphorylation of moesin in brain vessels. The level of moesin protein phosphorylation was also assessed in cerebral microvessels by western blotting. The effects of p38 and ROCK activation were determined by application of a p38 inhibitor (SB203580) and a ROCK inhibitor (Y27632) at 30min before each AGE administration. The results showed specific expression of moesin in murine brain vascular endothelial cells. AGE treatment induced a significant increase of threonine 558 phosphorylation in moesin, while inhibition of p38 and ROCK remarkably attenuated the phosphorylation of moesin. The level of moesin protein phosphorylation was also increased in cerebral microvessels, along with an increased permeability of the blood–brain barrier, while inhibition of the p38 and ROCK attenuated these responses. These results demonstrate that AGEs cause the phosphorylation of moesin in murine brain microvascular endothelial cells, with p38 and ROCK being involved in this process.

Ezrin Is Highly Expressed in Early Thymocytes, but Dispensable for T Cell Development in Mice

BackgroundEzrin/radixin/moesin (ERM) proteins are highly homologous proteins that function to link cargo molecules to the actin cytoskeleton. Ezrin and moesin are both expressed in mature lymphocytes, where they play overlapping roles in cell signaling and polarity, but their role in lymphoid development has not been explored.Methodology/Principal FindingsWe characterized ERM protein expression in lymphoid tissues and analyzed the requirement for ezrin expression in lymphoid development. In wildtype mice, we found that most cells in the spleen and thymus express both ezrin and moesin, but little radixin. ERM protein expression in the thymus was differentially regulated, such that ezrin expression was highest in immature thymocytes and diminished during T cell development. In contrast, moesin expression was low in early thymocytes and upregulated during T cell development. Mice bearing a germline deletion of ezrin exhibited profound defects in the size and cellularity of the spleen and thymus, abnormal thymic architecture, diminished hematopoiesis, and increased proportions of granulocytic precursors. Further analysis using fetal liver chimeras and thymic transplants showed that ezrin expression is dispensable in hematopoietic and stromal lineages, and that most of the defects in lymphoid development in ezrin−/− mice likely arise as a consequence of nutritional stress.Conclusions/SignificanceWe conclude that despite high expression in lymphoid precursor cells, ezrin is dispensable for lymphoid development, most likely due to redundancy with moesin.

Moesin-induced signaling in response to lipopolysaccharide in macrophages

Many physiological and pathophysiological conditions are attributable in part to cytoskeletal regulation of cellular responses to signals. Moesin (membrane-organizing extension spike protein), an ERM (ezrin, radixin and moesin) family member, is involved in lipopolysaccharide (LPS)-mediated events in mononuclear phagocytes; however, its role in signaling is not fully understood. The aim of this study was to investigate the LPS-induced moesin signaling pathways in macrophages. Macrophages were stimulated with 500 ng/mL LPS in macrophage serum-free medium. For blocking experiments, cells were pre-incubated with anti-moesin antibody. Moesin total protein and phosphorylation were studied with western blotting. Moesin mRNA was assessed using quantitative real-time PCR. To explore binding of moesin to LPS, native polyacrylamide gel electrophoresis (PAGE) gel shift assay was performed. Moesin immunoprecipitation with CD14, MD-2 and Toll-like receptor 4 (TLR4) and co-immunoprecipitation of MyD88-interleukin-1 receptor-associated kinase (IRAK) and IRAK-tumor necrosis factor receptor-activated factor 6 (TRAF6) were analyzed. Phosphorylation of IRAK and activities of MAPK, nuclear factor kappaB (NF-kappaB) and IkappaBalpha were studied. Tumor necrosis factor alpha, interleukin-1beta and interferon beta were measured by ELISA. Moesin was identified as part of a protein cluster that facilitates LPS recognition and results in the expression of proinflammatory cytokines. Lipopolysaccharide stimulates moesin expression and phosphorylation by binding directly to the moesin carboxyl-terminus. Moesin is temporally associated with TLR4 and MD-2 after LPS stimulation, while CD14 is continuously bound to moesin. Lipopolysaccharide-induced signaling is transferred downstream to p38, p44/42 MAPK and NF-kappaB activation. Blockage of moesin function interrupts the LPS response through an inhibition of MyD88, IRAK and TRAF6, negatively affecting subsequent activation of the MAP kinases (p38 and ERK), NF-kappaB activation and translocation to the nucleus. These results suggest an important role for moesin in the innate immune response and TLR4-mediated pattern recognition in periodontal disease.

661 SKP2 oncogene is a MYC target gene in human leukemia cells

The host cytoskeleton plays a central role in the life cycle of many viruses yet our knowledge of cytoskeletal regulators and their role in viral infection remains limited. Recently, moesin and ezrin, two members of the ERM (Ezrin/Radixin/Moesin) family of proteins that regulate actin and plasma membrane cross-linking and microtubule (MT) stability, have been shown to inhibit retroviral infection. To further understand how ERM proteins function and whether they also influence infection by other viruses, we identified PDZD8 as a novel moesin-interacting protein. PDZD8 is a poorly understood protein whose function is unknown. Exogenous expression of either moesin or PDZD8 reduced the levels of stable MTs, suggesting that these proteins functioned as part of a cytoskeletal regulatory complex. Additionally, exogenous expression or siRNA-mediated knockdown of either factor affected Herpes Simplex Virus type 1 (HSV-1) infection, identifying a cellular function for PDZD8 and novel antiviral properties for these two cytoskeletal regulatory proteins.

Vascular endothelial growth factor C promotes cervical cancer metastasis via up-regulation and activation of RhoA/ROCK-2/moesin cascade

BackgroundThe elevated expression of vascular endothelial growth factor C (VEGF-C) is correlated with clinical cervical cancer metastasis and patient survival, which is interpreted by VEGF-C functions to stimulate angiogenesis and lymphatic genesis. However, the direct impact of VEGF-C on cervical cancer cell motility remains largely unknown.MethodsIn this study, we investigated the effects of VEGF-C on actin cytoskeleton remodeling and on cervical cancer cell migration and invasion and how the actin-regulatory protein, moesin regulated these effects through RhoA/ROCK-2 signaling pathway.ResultsOn cervical carcinoma cell line SiHa cells, exposure of VEGF-C triggered remodeling of the actin cytoskeleton and the formation of membrane ruffles, which was required for cell movement. VEGF-C significantly enhanced SiHa cells horizontal migration and three-dimensional invasion into matrices. These actions were dependent on increased expression and phosphorylation of the actin-regulatory protein moesin and specific moesin siRNA severely impaired VEGF-C stimulated-cell migration. The extracellular small GTPase RhoA/ROCK-2 cascade mediated the increased moesin expression and phosphorylation, which was discovered by the use of Y-27632, a specific inhibitor of Rho kinase and by transfected constitutively active, dominant-negative RhoA as well as ROCK-2 SiRNA. Furthermore, in the surgical cervical specimen from the patients with FIGO stage at cervical intra-epithelial neoplasia and I-II cervical squamous cell carcinoma, the expression levels of moesin were found to be significantly correlated with tumor malignancy and metastasis.ConclusionsThese results implied that VEGF-C promoted cervical cancer metastasis by upregulation and activation of moesin protein through RhoA/ROCK-2 pathway. Our findings offer new insight into the role of VEGF-C on cervical cancer progression and may provide potential targets for cervical cancer therapy.

Knockdown of Moesin Expression Accelerates Cellular Senescence of Human Dermal Microvascular Endothelial Cells

PurposeEndothelial cells maintain the homeostasis of blood, which consists of plasma and cellular components, and regulate the interaction between blood and the surrounding tissues. They also have essential roles in vascular permeability, the circulation, coagulation, inflammation, wound healing, and tissue growth. The senescence of endothelial cells is closely related to the aging of the adjacent tissues and to age-related vascular disease. Recently, the expression of moesin was found to be decreased in elderly human dermal microvascular endothelial cells (HDMECs), and an association between moesin and senescence has been suggested. This study examined the functional role of moesin in cellular senescence.Materials and MethodsTo study the effects of decreased moesin expression on cellular senescence and metabolism, HDMECs were transfected with short hairpin-RNA (shRNA) lentivirus to silence moesin gene expression. In addition, specimens from young and old human skin were stained with anti-moesin and anti-p16 antibodies as an in vivo study.ResultsUsing shRNAl-entivirus, moesin knock-down HDMECs developed characteristics associated with aging and expressed senescence associated-beta-galactosidase during early passages. They also showed increased p16 expression, decreased metabolic activity, and cell growth retardation. Human skin tissue from elderly persons showed decreased moesin expression and increased p16 expression.ConclusionThese findings suggest that there is a functional association between moesin expression and cellular senescence. Further study of the functional mechanism of moesin in the cytoskeleton and cellular senescence is needed. In addition, this study provides a useful model for developing anti-aging treatments.

MOESIN DEPENDENT CYTOSKELETON REMODELING IS ASSOCIATED WITH AN ANAPLASTIC PHENOTYPE OF PANCREATIC CANCER

Cell motility is controlled by the dynamic cytoskeleton and its related proteins, such as members of the ezrin/radixin/moesin (ERM) family, which act as signalling molecules inducing cytoskeleton remodelling. Although ERM proteins have been identified as important factors in various malignancies, functional redundancy between these proteins has hindered the dissection of their individual contribution. The aim of the present study was to analyse the functional role of moesin in pancreatic malignancies. Cancer cells of different malignant lesions of human and transgenic mice pancreata were evaluated by immunohistochemistry. For functional analysis, cell growth, adhesion and invasion assays were carried out after transient and stable knock-down of moesin expression in pancreatic cancer cells. In vivo tumourigenicity was determined using orthotopic and metastatic mouse tumour models. We now show that moesin knock-down increases migration, invasion and metastasis and influences extracellular matrix organization of pancreatic cancer. Moesin-regulated migratory activities of pancreatic cancer cells were in part promoted through cellular translocation of β-catenin, and re-distribution and organization of the cytoskeleton. Analysis of human and different transgenic mouse pancreatic cancers demonstrated that moesin is a phenotypic marker for anaplastic carcinoma, suggesting that this ERM protein plays a specific role in pancreatic carcinogenesis.

Phospholipase C–mediated hydrolysis of PIP2 releases ERM proteins from lymphocyte membrane

Mechanisms controlling the disassembly of ezrin/radixin/moesin (ERM) proteins, which link the cytoskeleton to the plasma membrane, are incompletely understood. In lymphocytes, chemokine (e.g., SDF-1) stimulation inactivates ERM proteins, causing their release from the plasma membrane and dephosphorylation. SDF-1–mediated inactivation of ERM proteins is blocked by phospholipase C (PLC) inhibitors. Conversely, reduction of phosphatidylinositol 4,5-bisphosphate (PIP2) levels by activation of PLC, expression of active PLC mutants, or acute targeting of phosphoinositide 5-phosphatase to the plasma membrane promotes release and dephosphorylation of moesin and ezrin. Although expression of phosphomimetic moesin (T558D) or ezrin (T567D) mutants enhances membrane association, activation of PLC still relocalizes them to the cytosol. Similarly, in vitro binding of ERM proteins to the cytoplasmic tail of CD44 is also dependent on PIP2. These results demonstrate a new role of PLCs in rapid cytoskeletal remodeling and an additional key role of PIP2 in ERM protein biology, namely hydrolysis-mediated ERM inactivation.

Anti-Moesin Antibodies in the Serum of Patients with Aplastic Anemia Stimulate Peripheral Blood Mononuclear Cells to Secrete TNF-α and IFN-γ

Moesin is an intracellular protein that links the cell membrane and cytoskeleton, while also mediating the formation of microtubules and cell adhesion sites as well as ruffling of the cell membrane. To determine the roles of anti-moesin Abs derived from the serum of patients with aplastic anemia (AA) in the pathophysiology of bone marrow failure, we studied the expression of moesin on various blood cells and the effects of anti-moesin Abs on the moesin-expressing cells. The proteins recognized by anti-moesin mAbs were detectable on the surface of T cells, NK cells, and monocytes from healthy individuals as well as on THP-1 cells. The peptide mass fingerprinting of the THP-1 cell surface protein and the knock-down experiments using short hairpin RNA proved that the protein is moesin itself. Both the anti-moesin mAbs and the anti-moesin polyclonal Abs purified from the AA patients' sera stimulated THP-1 cells and the PBMCs of healthy individuals and AA patients to secrete 60-80% as much TNF-alpha as did LPS 100 ng/ml. Although the polyclonal Abs induced IFN-gamma secretion from the PBMCs of healthy individuals only when the PBMCs were prestimulated by anti-CD3 mAbs, the anti-moesin Abs were capable of inducing IFN-gamma secretion from the PBMCs of AA patients by themselves. Anti-moesin Abs may therefore indirectly contribute to the suppression of hematopoiesis in AA patients by inducing myelosuppressive cytokines from immunocompetent cells.

Novel insights of the gastric gland organization revealed by chief cell specific expression of moesin

ERM (ezrin, radixin, and moesin) proteins play critical roles in epithelial and endothelial cell polarity, among other functions. In gastric glands, ezrin is mainly expressed in acid-secreting parietal cells, but not in mucous neck cells or zymogenic chief cells. In looking for other ERM proteins, moesin was found lining the lumen of much of the gastric gland, but it was not expressed in parietal cells. No significant radixin expression was detected in the gastric glands. Moesin showed an increased gradient of expression from the neck to the base of the glands. In addition, the staining pattern of moesin revealed a branched morphology for the gastric lumen. This pattern of short branches extending from the glandular lumen was confirmed by using antibody against zonula occludens-1 (ZO-1) to stain tight junctions. With a mucous neck cell probe (lectin GSII, from Griffonia simplicifolia) and a chief cell marker (pepsinogen C), immunohistochemistry revealed that the mucous neck cells at the top of the glands do not express moesin, but, progressing toward the base, mucous cells showing decreased GSII staining had low or moderate level of moesin expression. The level of moesin expression continued to increase toward the base of the glands and reached a plateau in the base where chief cells and parietal cells abound. The level of pepsinogen expression also increased toward the base. Pepsinogen C was located on cytoplasmic granules and/or more generally distributed in chief cells, whereas moesin was exclusively expressed on the apical membrane. This is a clear demonstration of distinctive cellular expression of two ERM family members in the same tissue. The results provide the first evidence that moesin is involved in the cell biology of chief cells. Novel insights on gastric gland morphology revealed by the moesin and ZO-1 staining provide the basis for a model of cell maturation and migration within the gland.

Moesin is required for HIV-1-induced CD4-CXCR4 interaction, F-actin redistribution, membrane fusion and viral infection in lymphocytes

The human immunodeficiency virus 1 (HIV-1) envelope regulates the initial attachment of viral particles to target cells through its association with CD4 and either CXCR4 or CCR5. Although F-actin is required for CD4 and CXCR4 redistribution, little is known about the molecular mechanisms underlying this fundamental process in HIV infection. Using CD4(+) CXCR4(+) permissive human leukemic CEM T cells and primary lymphocytes, we have investigated whether HIV-1 Env might promote viral entry and infection by activating ERM (ezrin-radixin-moesin) proteins to regulate F-actin reorganization and CD4/CXCR4 co-clustering. The interaction of the X4-tropic protein HIV-1 gp120 with CD4 augments ezrin and moesin phosphorylation in human permissive T cells, thereby regulating ezrin-moesin activation. Moreover, the association and clustering of CD4-CXCR4 induced by HIV-1 gp120 requires moesin-mediated anchoring of actin in the plasma membrane. Suppression of moesin expression with dominant-negative N-moesin or specific moesin silencing impedes reorganization of F-actin and HIV-1 entry and infection mediated by the HIV-1 envelope protein complex. Therefore, we propose that activated moesin promotes F-actin redistribution and CD4-CXCR4 clustering and is also required for efficient X4-tropic HIV-1 infection in permissive lymphocytes.

Rho-ROCK-Dependent Ezrin-Radixin-Moesin Phosphorylation Regulates Fas-Mediated Apoptosis in Jurkat Cells

Upon engagement by its ligand, the Fas receptor (CD95/APO-1) is oligomerized in a manner dependent on F-actin. It has been shown that ezrin, a member of the ERM (ezrin-radixin-moesin) protein family can link Fas to the actin cytoskeleton. We show herein that in Jurkat cells, not only ezrin but also moesin can associate with Fas. The same observation was made in activated human peripheral blood T cells. Fas/ezrin or moesin (E/M) association increases in Jurkat cells following Fas triggering and occurs concomitantly with the formation of SDS- and 2-ME-stable high molecular mass Fas aggregates. Ezrin and moesin have to be present together for the formation of Fas aggregates since down-regulation of either ezrin or moesin expression with small interfering RNAs completely inhibits Fas aggregate formation. Although FADD (Fas-associated death domain protein) and caspase-8 associate with Fas in the absence of E/M, subsequent events such as caspase-8 activation and sensitivity to apoptosis are decreased. During the course of Fas stimulation, ezrin and moesin become phosphorylated, respectively, on T567 and on T558. This phosphorylation is mediated by the kinase ROCK (Rho-associated coiled coil-containing protein kinase) I subsequently to Rho activation. Indeed, inhibition of either Rho or ROCK prevents ezrin and moesin phosphorylation, abrogates the formation of Fas aggregates, and interferes with caspase-8 activation. Thus, phosphorylation of E/M by ROCK is involved in the early steps of apoptotic signaling following Fas triggering and regulates apoptosis induction.

Extra-Nuclear Signalling of Estrogen Receptor to Breast Cancer Cytoskeletal Remodelling, Migration and Invasion

BackgroundEstrogen is an established enhancer of breast cancer development, but less is known on its effect on local progression or metastasis. We studied the effect of estrogen receptor recruitment on actin cytoskeleton remodeling and breast cancer cell movement and invasion. Moreover, we characterized the signaling steps through which these actions are enacted.Methodology/Principal FindingsIn estrogen receptor (ER) positive T47-D breast cancer cells ER activation with 17β-estradiol induces rapid and dynamic actin cytoskeleton remodeling with the formation of specialized cell membrane structures like ruffles and pseudopodia. These effects depend on the rapid recruitment of the actin-binding protein moesin. Moesin activation by estradiol depends on the interaction of ERα with the G protein Gα13, which results in the recruitment of the small GTPase RhoA and in the subsequent activation of its downstream effector Rho-associated kinase-2 (ROCK-2). ROCK-2 is responsible for moesin phosphorylation. The Gα13/RhoA/ROCK/moesin cascade is necessary for the cytoskeletal remodeling and for the enhancement of breast cancer cell horizontal migration and invasion of three-dimensional matrices induced by estrogen. In addition, human samples of normal breast tissue, fibroadenomas and invasive ductal carcinomas show that the expression of wild-type moesin as well as of its active form is deranged in cancers, with increased protein amounts and a loss of association with the cell membrane.Conclusions/SignificanceThese results provide an original mechanism through which estrogen can facilitate breast cancer local and distant progression, identifying the extra-nuclear Gα13/RhoA/ROCK/moesin signaling cascade as a target of ERα in breast cancer cells. This information helps to understand the effects of estrogen on breast cancer metastasis and may provide new targets for therapeutic interventions.