Apical ezrin

Ciliary beating in the airway epithelium plays an important role in preventing infection by eliminating small particles and pathogens. Stimulation of β2 adrenergic receptor (β2 AR) increases [cAMP]i levels and strongly activates this ciliary beating. β2 AR is localized to the apical membrane of the airways by indirectly binding to ezrin, an actin-binding protein. Ezrin takes active phosphorylated and inactive dephosphorylated states at Thr-567. Previously we showed that procaterol-stimulated ciliary beating was impaired in the ezrin-knockdown mice...

The location of different actin-based structures is largely regulated by Rho GTPases through specific effectors. We use the apical aspect of epithelial cells as a model system to investigate how RhoA is locally regulated to contribute to two distinct adjacent actin-based structures. Assembly of the non-muscle myosin-2 filaments in the terminal web is dependent on RhoA activity, and assembly of the microvilli also requires active RhoA for phosphorylation and activation of ezrin. We show the RhoGAP, ARHGAP18, is localized by binding active microvillar ezrin, and this interaction enhances ARHGAP18's RhoGAP activity...

In 1985, I was accepted as postdoc by Professor Forte of UC Berkeley. He discovered H+ ,K+ -ATPase and established the membrane recycling theory as the activation mechanism for acid secretion using whole animals. H+ ,K+ -ATPase is an enzyme that exchanges H+ with K+ . In resting state, it locates on the tubulovesicles and the pump does not work because the membrane lacks K+ permeability. Upon stimulation, the tubulovesicles fuse to the apical membrane and acquire K+ permeability, turning the pump on. The main route was known to be protein kinase A (PKA), but its specific targets remained unknown...

Transporting epithelial cells of the gut and kidney interact with their luminal environment through a densely-packed collection of apical microvilli known as a brush border. Proper brush border assembly depends on the intermicrovillar adhesion complex (IMAC), a protocadherin-based adhesion complex found at the distal tips of microvilli that mediates adhesion between neighboring protrusions to promote their organized packing. Loss of the IMAC adhesion molecule Cadherin-related family member 5 (CDHR5) results in significant brush border defects, though the functional properties of this protocadherin have not been thoroughly explored...

Ezrin-binding phosphoprotein 50 (EBP50) is a scaffold protein that is required for epithelial polarity. Knockout (KO) of membranous EBP50 (Me-EBP50) in ovarian clear cell carcinoma (OCCC) cells induced an epithelial-mesenchymal transition (EMT)-like phenotype, along with decreased proliferation, accelerated migration capability, and induction of cancer stem cell (CSC)-like properties. Shotgun proteomics analysis of proteins that co-immunoprecipitated with EBP50 revealed that Me-EBP50 strongly interacts with myosin 9 (MYH9)...

BACKGROUND AND AIMS: Thiopurine-induced acute pancreatitis (TIP) is one of the most common adverse events among inflammatory bowel disease patients treated with azathioprine (AZA), representing a significant clinical burden. Previous studies focused on immune-mediated processes, however, the exact pathomechanism of TIP is essentially unclear. METHODS: To model TIP in vivo, we triggered cerulein-induced experimental pancreatitis in mice receiving a daily oral dose of 1...

Intestinal epithelial cells absorb nutrients through the brush border, composed of dense arrays of highly ordered microvilli at their apical membranes. A protocadherin-based intermicrovillar adhesion complex localized at microvilli tips mediates microvilli packing and organization. Here, we identified a second adhesion complex localized at the proximal base region of microvilli. This complex contained the immunoglobulin superfamily member TMIGD1, which directly interacted with the microvillar scaffolding proteins EBP50 and E3KARP...

Recent evidence has suggested that recurrent urinary tract infection (UTI) can cause not only infection stones but also metabolic stones (e.g., those containing calcium oxalate monohydrate or COM). However, precise mechanisms underlying UTI-induced metabolic stones remained unknown. In this study, Escherichia coli, the most common bacterium found in recurrent UTI was used to establish the in vitro model for persistent infection of renal epithelial cells. The promoting effects of persistent E. coli infection on kidney stone formation were validated by COM crystal-cell adhesion assay, followed by immunofluorescence study for changes in surface expression of the known COM crystal receptors...

BMP signaling is crucial for differentiation of secretory ameloblasts, the cells that secrete enamel matrix. However, whether BMP signaling is required for differentiation of maturation-stage ameloblasts (MA), which are instrumental for enamel maturation into hard tissue, is hitherto unknown. To address this, we used an in vivo genetic approach which revealed that combined deactivation of the Bmp2 and Bmp4 genes in the murine dental epithelium causes development of dysmorphic and dysfunctional MA. These fail to exhibit a ruffled apical plasma membrane and to reabsorb enamel matrix proteins, leading to enamel defects mimicking hypomaturation amelogenesis imperfecta...

Zonula occluden-1 (ZO-1) has been implicated as a major regulator of tight junction formation, functioning as a scaffolding protein and mediator between the junction and the actomyosin cytoskeleton. MDCK II cells that have ZO-1 knocked-down (ZO-1 KD) or knocked-out (ZO-1 KO) have observable phenotypic changes, including increased apical actin accumulation, increased cell height, and linearized junctions. The apical actin accumulation, resulting from the dysregulation of myosin II, is suspected to cause an increase in membrane tension seen in the ZO-1 KO, which may explain the phenotypic changes...

Macroautophagy/autophagy, an evolutionarily conserved degradation system, serves to clear intracellular components through the lysosomal pathway. Mounting evidence has revealed cytoprotective roles of autophagy; however, the intracellular causes of overactivated autophagy, which has cytotoxic effects, remain elusive. Here we show that sustained proteotoxic stress induced by loss of the <u>RI</u>NG and <u>Ke</u>lch repeat-containing protein C53A5.6/RIKE-1 induces sequestration of LET-363/MTOR complex and overactivation of autophagy, and consequently impairs epithelial integrity in C...

Microvilli are conserved actin-based surface protrusions that have been repurposed throughout evolution to fulfill diverse cell functions. In the case of transporting epithelia, microvilli are supported by a core of actin filaments bundled in parallel by villin, fimbrin, and espin. Remarkably, microvilli biogenesis persists in mice lacking all three of these factors, suggesting the existence of unknown bundlers. We identified Mitotic Spindle Positioning (MISP) as an actin-binding factor that localizes specifically to the rootlet end of the microvillus...

Several tissues contain cells with multiple motile cilia that generate a fluid or particle flow to support development and organ functions; defective motility causes human disease. Developmental cues orient motile cilia, but how cilia are locked into their final position to maintain a directional flow is not understood. Here we find that the actin cytoskeleton is highly dynamic during early development of multiciliated cells (MCCs). While apical actin bundles become increasingly more static, subapical actin filaments are nucleated from the distal tip of ciliary rootlets...

The mucociliary clearance, which is conducted by the beating cilia cooperating with the surface mucous layer, is a major host defense mechanism of the airway epithelium. Ezrin, a crosslinker between membrane proteins and actin cytoskeleton, is located in microvilli and around the basal bodies in airway ciliary cells. It is also likely that ezrin may play the important role of apical localization of β2-adrenergic receptor (β2AR) in airway ciliary cells. Here we studied the physiological roles of ezrin by using the trachea and airway epithelial cells prepared from the ezrin-knockdown (Vil2kd/kd) mice...

Aquaporin-5 (AQP5) is selectively expressed in the apical membrane of exocrine glands, such as salivary, sweat, and submucosal airway glands, and plays important roles in maintaining their secretory functions. Because AQP5 is not regulated by gating, localization on the plasma membrane is important for its water-permeable function. Ezrin is an ezrin-radixin-moesin family protein that serves as a crosslinker between the plasma membrane and actin cytoskeleton network. It plays important roles in translocation of various membrane proteins to mediate vesicle trafficking to the plasma membrane...

Neisseria gonorrhoeae (GC) establishes infection in women from the cervix, lined with heterogeneous epithelial cells from non-polarized stratified at the ectocervix to polarized columnar at the endocervix. We have previously shown that GC differentially colonize and transmigrate across the ecto and endocervical epithelia. However, whether and how GC invade into heterogeneous cervical epithelial cells is unknown. This study examined GC entry of epithelial cells with various properties, using human cervical tissue explant and non-polarized/polarized epithelial cell line models...

Here we report on the related TBC/RabGAPs EPI64A and EPI64B and show that they function to organize the apical aspect of epithelial cells. EPI64A binds the scaffolding protein EBP50/NHERF1, which itself binds active ezrin in epithelial cell microvilli. Epithelial cells additionally express EPI64B that also localizes to microvilli. However, EPI64B does not bind EBP50 and both proteins are shown to have a microvillar localization domain that spans the RabGAP domains. CRISPR/Cas9 was used to inactivate expression of each protein individually or both in Jeg-3 and Caco2 cells...

BACKGROUND: The cell adhesion molecule transmembrane and immunoglobulin (Ig) domain containing1 (TMIGD1) is a novel tumor suppressor that plays important roles in regulating cell-cell adhesion, cell proliferation and cell cycle. However, the mechanisms of TMIGD1 signaling are not yet fully elucidated. RESULTS: TMIGD1 binds to the ERM family proteins moesin and ezrin, and an evolutionarily conserved RRKK motif on the carboxyl terminus of TMIGD1 mediates the interaction of TMIGD1 with the N-terminal ERM domains of moesin and ezrin...

Sjögren's syndrome (SS) is an exocrinopathy characterized by the hypofunction of salivary glands (SGs). Aquaporin-5 (AQP5); a water channel involved in saliva formation; is aberrantly distributed in SS SG acini and contributes to glandular dysfunction. We aimed to investigate the role of ezrin in AQP5 mislocalization in SS SGs. The AQP5-ezrin interaction was assessed by immunoprecipitation and proteome analysis and by proximity ligation assay in immortalized human SG cells. We demonstrated, for the first time, an interaction between ezrin and AQP5...

The Neurofibromatosis type 2 gene encodes the Nf2/merlin tumor suppressor protein that is responsible for the regulation of cell proliferation. Once activated, Nf2/merlin modulates adhesive signaling pathways and thereby inhibits cell growth. Nf2/merlin controls oncogenic gene expression by modulating the Hippo pathway. By responding to several physical and biochemical stimuli, Hippo signaling determines contact inhibition of proliferation as well as organ size. The large tumor suppressor (LATS) serine/threonine-protein kinase is the key enzyme in the highly conserved kinase cascade that negatively regulates the activity and localization of the transcriptional coactivators Yes-associated protein (YAP) and its paralogue transcriptional coactivator with PDZ-binding motif (TAZ)...