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Apical polarity

Masaki Murata, Makoto Osanai, Akira Takasawa, Kumi Takasawa, Tomoyuki Aoyama, Yuka Kawada, Akihiro Yamamoto, Yusuke Ono, Yutaro Hiratsuka, Takashi Kojima, Norimasa Sawada
Apical and basolateral cell membranes are separated by tight junctions (TJs). Microvilli are limited to the apical cell membrane. TJs and microvilli are the landmarks for epithelial cell polarity. However, the direct relationship between TJ proteins (TJPs) and the components of microvilli remains unclear. In this study, we investigated whether occludin, which is considered to be a functional TJP, is involved in microvillus formation. In occludin knockout mouse hepatic cells (OcKO cells), the microvillus density was less than that in wild-type (WT) cells and the length of microvilli was short...
March 16, 2018: Experimental Cell Research
Alec N Salt, Stefan K Plontke
Local drug delivery to the ear has gained wide clinical acceptance, with the choice of drug and application protocol in humans largely empirically-derived. Here, we review the pharmacokinetics underlying local therapy of the ear using the drugs commonly used in clinical practice as examples. Based on molecular properties and perilymph measurements interpreted through computer simulations we now better understand the principles underlying entry and distribution of these and other drugs in the ear. From our analysis, we have determined that dexamethasone-phosphate, a pro-drug widely-used clinically, has molecular and pharmacokinetic properties that make it ill-suited for use as a local therapy for hearing disorders...
March 11, 2018: Hearing Research
Saber Ben Mimoun, Alain Mauviel
The ubiquitous distribution of both Hippo and TGF-ß signaling cascade components and their critical implication in tissue homeostasis and disease has led to the discovery of a remarkable slew of interesting and unique features regarding their functional crosstalks. Upstream cellular cues regulating the Hippo pathway, including cell-cell contacts and apico-basal cell polarity have been well characterized. Herein, we provide an overview of the published models of compartmentalized signaling crosstalk mechanisms between Hippo signaling and the TGF-ß/SMAD pathway...
March 12, 2018: International Journal of Biochemistry & Cell Biology
Dhivya Kumar, Rebecca T Thomason, Maya Yankova, Jonathan D Gitlin, Richard E Mains, Betty A Eipper, Stephen M King
The assembly of membranous extensions such as microvilli and cilia in polarized cells is a tightly regulated, yet poorly understood, process. Peptidylglycine α-amidating monooxygenase (PAM), a membrane enzyme essential for the synthesis of amidated bioactive peptides, was recently identified in motile and non-motile (primary) cilia and has an essential role in ciliogenesis in Chlamydomonas, Schmidtea and mouse. In mammalian cells, changes in PAM levels alter secretion and organization of the actin cytoskeleton...
March 14, 2018: Scientific Reports
Dechao Xu, Jiayi Lv, Liangliang He, Lili Fu, Ruikun Hu, Ying Cao, Changlin Mei
Polarity complexes, including the PAR (Partitioning-defective), CRB (Crumbs) and SCRIB (Scribble) complexes, are required for the physiologic establishment, stabilization, and maintenance of a functional apical-basolateral polarity. Inactivation of some of the polarity complexes results in cystic kidneys, and apical-basolateral polarity defects are commonly observed in autosomal-dominant polycystic kidney disease (ADPKD); however, little is known about the role that polarity complexes play in ADPKD. Here, we demonstrate that Scribble, a core protein of the SCRIB complex, is down-regulated in ADPKD cell lines and the zebrafish model of this disease ( pkd2 morphants)...
March 12, 2018: FASEB Journal: Official Publication of the Federation of American Societies for Experimental Biology
Lars Kullmann, Michael P Krahn
Apical-basal polarity is an important characteristic of epithelia and Drosophila neural stem cells. The conserved Par complex, which consists of the atypical protein kinase C and the scaffold proteins Baz and Par6, is a key player in the establishment of apical-basal cell polarity. Membrane recruitment of Baz has been reported to be accomplished by several mechanisms, which might function in redundancy, to ensure the correct localization of the complex. However, none of the described interactions was sufficient to displace the protein from the apical junctions...
March 10, 2018: Cellular and Molecular Life Sciences: CMLS
Sofia Golenkina, Vishal Chaturvedi, Robert Saint, Michael J Murray
Netrin receptors of the DCC/NEO/UNC-40/Frazzled family have well established roles in cell migration and axon guidance but can also regulate epithelial features such as adhesion, polarity and adherens junction (AJ) stability. Previously, we have shown that overexpression of Drosophila Frazzled (Fra) in the peripodial epithelium (PE) inhibits wing disc eversion and also generates cellular protrusions typical of motile cells. Here, we tested whether the molecular pathways by which Fra inhibits eversion are distinct from those driving motility...
2018: PloS One
Yunxia O'Malley, Pavana G Rotti, Ian M Thornell, Oriana G Vanegas Calderón, Christopher Febres-Aldana, Katelin Durham, Jianrong Yao, Xiaopeng Li, Zheng Zhu, Andrew W Norris, Joseph Zabner, John F Engelhardt, Aliye Uc
Pancreatic ductular epithelial cells comprise the majority of duct cells in pancreas, control cystic fibrosis transmembrane conductance regulator (CFTR)-dependent bicarbonate [HCO3 - ] secretion, but are difficult to grow as a polarized monolayer. Using NIH-3T3-J2 fibroblast feeder cells and a Rho-associated kinase inhibitor, we produced well-differentiated and polarized porcine pancreatic ductular epithelial cells. Cells grown on semipermeable filters at air-liquid interface (ALI) developed typical epithelial cell morphology and stable transepithelial resistance (TER), expressed epithelial cell markers (zona occludens-1 and beta catenin), duct cell markers (SOX-9 and CFTR), but no acinar (amylase) or islet cell (chromogranin) markers...
March 8, 2018: Journal of Applied Physiology
Sun K Kim, Siwei Zhang, Michael E Werner, Eva J Brotslaw, Jennifer W Mitchell, Mohamed M Altabbaa, Brian J Mitchell
Most epithelial cells polarize along the axis of the tissue, a feature known as planar cell polarity (PCP). The initiation of PCP requires cell-cell signaling via the noncanonical Wnt/PCP pathway. Additionally, changes in the cytoskeleton both facilitate and reflect this polarity. We have identified CLAMP/Spef1 as a novel regulator of PCP signaling. In addition to decorating microtubules (MTs) and the ciliary rootlet, a pool of CLAMP localizes at the apical cell cortex. Depletion of CLAMP leads to the loss of PCP protein asymmetry, defects in cilia polarity, and defects in the angle of cell division...
March 7, 2018: Journal of Cell Biology
Bhargavi Manda, Hina Mir, Ruchika Gangwar, Avtar S Meena, Shrunali Amin, Pradeep K Shukla, Kesha Dalal, Takuya Suzuki, Radha Krishna Rao
The apical junctional complex (AJC), which includes tight junction (TJ) and adherens junction (AJ) determine the epithelial polarity, cell-cell adhesion and permeability barrier. An intriguing characteristic of TJ is the dynamic nature of its multiprotein complex. Occludin is the most mobile TJ protein, but its significance in TJ dynamics is poorly understood. On the basis of phosphorylation sites we distinguished a sequence in the C-terminal domain of occludin as a regulatory motif (ORM). Deletion of ORM and expression of deletion mutant occludin in renal and intestinal epithelia reduced the mobility of occludin at the TJ...
March 5, 2018: Journal of Cell Science
Autumn N Harris, P Richard Grimm, Hyun-Wook Lee, Eric Delpire, Lijuan Fang, Jill W Verlander, Paul A Welling, I David Weiner
Background Hyperkalemia in association with metabolic acidosis that are out of proportion to changes in glomerular filtration rate defines type 4 renal tubular acidosis (RTA), the most common RTA observed, but the molecular mechanisms underlying the associated metabolic acidosis are incompletely understood. We sought to determine whether hyperkalemia directly causes metabolic acidosis and, if so, the mechanisms through which this occurs. Methods We studied a genetic model of hyperkalemia that results from early distal convoluted tubule (DCT)-specific overexpression of constitutively active Ste20/SPS1-related proline-alanine-rich kinase (DCT-CA-SPAK)...
February 26, 2018: Journal of the American Society of Nephrology: JASN
Deepak Saini, Yojiro Yamanaka
During the first few days in the mouse preimplantation embryo, two types of cells, polar and apolar cells are generated from spherical totipotent blastomeres. Sequential morphogenetic events, polarization, compaction, and asymmetric division, are essential for the generation of the first distinct cell populations, polar and apolar cells, which establish the outer/inner configuration within the embryo. This leads to position-dependent activation of the Hippo signaling pathway and lineage-specific gene expression to form the trophectoderm and inner cell mass in a blastocyst...
2018: Current Topics in Developmental Biology
Eun-Hye Hong, Ji-Ye Kim, Jeong-Hoon Kim, Dae-Sik Lim, Minkyu Kim, Jeong-Yoon Kim
Proper dendrite development is essential for establishing neural circuitry, and Rho GTPases play key regulatory roles in this process. From mouse brain lysates, we identified Brefeldin A-inhibited guanine exchange factor 2 (BIG2) as a novel Rho GTPase regulatory protein involved in dendrite growth and maintenance. BIG2 was highly expressed during early development, and knockdown of the ARFGEF2 gene encoding BIG2 significantly reduced total dendrite length and the number of branches. Expression of the constitutively active ADP-ribosylation factor 1 ARF1 Q71L rescued the defective dendrite morphogenesis of ARFGEF2-null neurons, indicating that BIG2 controls dendrite growth and maintenance by activating ARF1...
February 17, 2018: Molecular Neurobiology
Pranitha Jenardhanan, Manivel Panneerselvam, Premendu P Mathur
The Sertoli cell, the somatic component of seminiferous tubule, provides nutritional support and immunological protection and supports overall growth and division of germ cells. Cytoskeletons, junction proteins, and kinases in Sertoli cells are prime targets for reproductive toxicants and other environmental contaminants. Among the varied targets, the kinases that are crucial for regulating varied activities in spermatogenesis such as assembly/disassembly of blood-testis barrier and apical ES and those that are involved in conferring polarity are highly targeted...
2018: Methods in Molecular Biology
Marrah E Lachowicz-Scroggins, Erin D Gordon, Agata Wesolowska-Andersen, Nathan D Jackson, Hannah J MacLeod, Louis Z Sharp, Matthew Sun, Max A Seibold, John V Fahy
Polarization of the airway epithelial cells (AECs) in the airway lumen is critical to the proper function of the mucociliary escalator and maintenance of lung health, but the cellular requirements for polarization of AECs are poorly understood. Using human AECs and cell lines, we demonstrate that cadherin-26 (CDH26) is abundantly expressed in differentiated AECs, localizes to the cell apices near ciliary membranes, and has functional cadherin domains with homotypic binding. We find a unique and non-redundant role for CDH26, previously uncharacterized in AECs, in regulation of cell-cell contact and cell integrity through maintaining cytoskeletal structures...
2018: Cell Discovery
Mario Aguilar-Aragon, Ahmed Elbediwy, Valentina Foglizzo, Georgina C Fletcher, Vivian S W Li, Barry J Thompson
Epithelial cells are polarized along their apical-basal axis by the action of the small GTPase Cdc42, which is known to activate the aPKC kinase at the apical domain. However, loss of aPKC kinase activity was reported to have only mild effects on epithelial cell polarity. Here, we show that Cdc42 also activates a second kinase, Pak1, to specify apical domain identity in Drosophila and mammalian epithelia. aPKC and Pak1 phosphorylate an overlapping set of polarity substrates in kinase assays. Inactivating both aPKC kinase activity and the Pak1 kinase leads to a complete loss of epithelial polarity and morphology, with cells losing markers of apical polarization such as Crumbs, Par3/Bazooka, or ZO-1...
February 13, 2018: Cell Reports
Magdalena Kasendra, Alessio Tovaglieri, Alexandra Sontheimer-Phelps, Sasan Jalili-Firoozinezhad, Amir Bein, Angeliki Chalkiadaki, William Scholl, Cheng Zhang, Hannah Rickner, Camilla A Richmond, Hu Li, David T Breault, Donald E Ingber
Here we describe a method for fabricating a primary human Small Intestine-on-a-Chip (Intestine Chip) containing epithelial cells isolated from healthy regions of intestinal biopsies. The primary epithelial cells are expanded as 3D organoids, dissociated, and cultured on a porous membrane within a microfluidic device with human intestinal microvascular endothelium cultured in a parallel microchannel under flow and cyclic deformation. In the Intestine Chip, the epithelium forms villi-like projections lined by polarized epithelial cells that undergo multi-lineage differentiation similar to that of intestinal organoids, however, these cells expose their apical surfaces to an open lumen and interface with endothelium...
February 13, 2018: Scientific Reports
Shotaro Sakakibara, Tomohiko Maruo, Muneaki Miyata, Kiyohito Mizutani, Yoshimi Takai
The apical junctional complex consists of adherens junctions (AJs) and tight junctions (TJs) in polarized epithelial cells, which are attached to each other to form a sheet. Actin filaments (F-actin) are associated with AJs and TJs and required for the formation and maintenance of this complex. l-Afadin is an F-actin-binding protein, which is localized at AJs through binding to the cell adhesion molecule nectin, and regulates the formation of AJs and TJs. However, the role of the F-actin-binding activity of l-afadin for the formation of the apical junctional complex remains unknown...
February 12, 2018: Genes to Cells: Devoted to Molecular & Cellular Mechanisms
Hervé Alégot, Pierre Pouchin, Olivier Bardot, Vincent Mirouse
Tissue elongation and its control by spatiotemporal signals is a major developmental question. Currently, it is thought that Drosophila ovarian follicular epithelium elongation requires the planar polarization of the basal domain cytoskeleton and of the extra-cellular matrix, associated with a dynamic process of rotation around the anteroposterior axis. Here we show, by careful kinetic analysis of fat2 mutants, that neither basal planar polarization nor rotation is required during a first phase of follicle elongation...
February 8, 2018: ELife
Lorenzo Alibardi
Appendage regeneration occurs by a sequence of events resembling those that take place during development in the embryo. This requires embryonic conditions such as hydration and hyaluronate content where Wnt and other signaling pathways, together with non- coding RNAs, can be re-expressed. These conditions among vertebrates are fully met only in amputated limbs of amphibians, likely because they are neotenic and maintain larval characteristics, including immaturity of their immune system and permanence of numerous stem cells...
February 3, 2018: Annals of Anatomy, Anatomischer Anzeiger: Official Organ of the Anatomische Gesellschaft
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