CD13 orients the apical-basal polarity axis necessary for lumen formation

AbstractPolarized epithelial cells can organize into complex structures with a characteristic central lumen. Lumen formation requires that cells coordinately orient their polarity axis so that the basolateral domain is on the outside and apical domain inside epithelial structures. Here we show that the transmembrane aminopeptidase, CD13, is a key determinant of epithelial polarity orientation. CD13 localizes to the apical membrane and associates with an apical complex with Par6. CD13-deficient cells display inverted polarity in which apical proteins are retained on the outer cell periphery and fail to accumulate at an intercellular apical initiation site. Here we show that CD13 is required to couple apical protein cargo to Rab11-endosomes and for capture of endosomes at the apical initiation site. This role in polarity utilizes the short intracellular domain but is independent of CD13 peptidase activity.

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Local phosphocycling mediated by LOK/SLK restricts ezrin function to the apical aspect of epithelial cells

The Journal of Cell Biology ◽

10.1083/jcb.201207047 ◽

2012 ◽

Vol 199 (6) ◽

pp. 969-984 ◽

Cited By ~ 57

Author(s):

Raghuvir Viswanatha ◽

Patrice Y. Ohouo ◽

Marcus B. Smolka ◽

Anthony Bretscher

Keyword(s):

Plasma Membrane ◽

Epithelial Cells ◽

Dynamic Process ◽

Ribonucleic Acid ◽

Kinase Activity ◽

Apical Membrane ◽

Drug Resistant ◽

Domain Specific ◽

Local Inhibition ◽

Apical Domain

In this paper, we describe how a dynamic regulatory process is necessary to restrict microvilli to the apical aspect of polarized epithelial cells. We found that local phosphocycling regulation of ezrin, a critical plasma membrane–cytoskeletal linker of microvilli, was required to restrict its function to the apical membrane. Proteomic approaches and ribonucleic acid interference knockdown identified lymphocyte-oriented kinase (LOK) and SLK as the relevant kinases. Using drug-resistant LOK and SLK variants showed that these kinases were sufficient to restrict ezrin function to the apical domain. Both kinases were enriched in microvilli and locally activated there. Unregulated kinase activity caused ezrin mislocalization toward the basolateral domain, whereas expression of the kinase regulatory regions of LOK or SLK resulted in local inhibition of ezrin phosphorylation by the endogenous kinases. Thus, the domain-specific presence of microvilli is a dynamic process requiring a localized kinase driving the phosphocycling of ezrin to continually bias its function to the apical membrane.

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Characterization of the composition and functioning of the Crumbs complex in C. elegans

10.1101/2021.08.10.455623 ◽

2021 ◽

Author(s):

Victoria G Castiglioni ◽

Joao J Ramalho ◽

Jason R Kroll ◽

Riccardo Stucchi ◽

Hanna van Beuzekom ◽

...

Keyword(s):

Epithelial Cells ◽

Apical Membrane ◽

Scaffolding Protein ◽

Animal Development ◽

C Elegans ◽

Apical Domain ◽

Junction Protein ◽

Crumbs Complex

The apical domain of epithelial cells can acquire a diverse array of morphologies and functions, which is critical for the function of epithelial tissues. The Crumbs proteins are evolutionary conserved transmembrane proteins with essential roles in promoting apical domain formation in epithelial cells. The short intracellular tail of Crumbs proteins interacts with a variety of proteins, including the scaffolding protein Pals1 (protein associated with LIN7, Stardust in Drosophila). Pals1 in turn binds to a second scaffolding protein termed PATJ (Pals1-associated tight junction protein), to form the core Crumbs/ Pals1/PATJ Crumbs complex. While essential roles in epithelial organization have been shown for Crumbs proteins in Drosophila and mammalian systems, the three Caenorhabditis elegans crumbs genes are dispensable for epithelial polarization and animal development. Moreover, the presence and functioning of orthologs of Pals1 and PATJ has not been investigated. Here, we identify MAGU-2 and MPZ-1 as the C. elegans orthologs of Pals1 and PATJ, respectively. We show that MAGU-2 interacts with all three Crumbs proteins as well as MPZ-1, and localizes to the apical membrane domain in a Crumbs-dependent fashion. Similar to crumbs mutants, a magu-2 null mutant shows no developmental or epithelial polarity defects. Finally, we show that overexpression of the Crumbs proteins EAT-20 or CRB-3 in the C. elegans intestine can lead to apical membrane expansion. Our results shed light into the composition of the C. elegans Crumbs complex and indicate that the role of Crumbs proteins in promoting apical domain identity is conserved.

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Interplay of MPP5a with Rab11 synergistically builds epithelial apical polarity and zonula adherens

Development ◽

10.1242/dev.184457 ◽

2020 ◽

Vol 147 (22) ◽

pp. dev184457

Author(s):

Yumei Hao ◽

Yao Zhou ◽

Yinhui Yu ◽

Mingjie Zheng ◽

Kechao Weng ◽

...

Keyword(s):

Epithelial Cells ◽

Driving Force ◽

Adherens Junction ◽

Small Gtpase ◽

Epithelial Polarity ◽

Apical Domain ◽

Neuroepithelial Cells ◽

Apical Polarity ◽

Crumbs Complex ◽

Remodeling Pattern

ABSTRACTAdherens junction remodeling regulated by apical polarity proteins constitutes a major driving force for tissue morphogenesis, although the precise mechanism remains inconclusive. Here, we report that, in zebrafish, the Crumbs complex component MPP5a interacts with small GTPase Rab11 in Golgi to transport cadherin and Crumbs components synergistically to the apical domain, thus establishing apical epithelial polarity and adherens junctions. In contrast, Par complex recruited by MPP5a is incapable of interacting with Rab11 but might assemble cytoskeleton to facilitate cadherin exocytosis. In accordance, dysfunction of MPP5a induces an invasive migration of epithelial cells. This adherens junction remodeling pattern is frequently observed in zebrafish lens epithelial cells and neuroepithelial cells. The data identify an unrecognized MPP5a-Rab11 complex and describe its essential role in guiding apical polarization and zonula adherens formation in epithelial cells.

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De novo apical domain formation inside the Drosophila adult midgut epithelium

10.1101/2021.12.10.472136 ◽

2021 ◽

Author(s):

Jia Chen ◽

Daniel St Johnston

Keyword(s):

De Novo ◽

Initiation Site ◽

Septate Junction ◽

Intestinal Stem Cells ◽

Apical Surface ◽

Domain Formation ◽

Septate Junctions ◽

Lumen Formation ◽

Apical Domain ◽

Apical Compartment

AbstractIn the adult Drosophila midgut, basal intestinal stem cells give rise to enteroblasts that integrate into the epithelium as they differentiate into enterocytes. Integrating enteroblasts must generate a new apical domain and break through the septate junctions between neighboring enterocytes, while maintaining barrier function. We observe that enteroblasts form an apical membrane initiation site when they reach the septate junction between the enterocytes. Cadherin clears from the apical surface and an apical space appears above the enteroblast. New septate junctions then form laterally with the enterocytes and the AMIS develops into pre-apical compartment before it has a free apical surface in contact with the gut lumen. Finally, the enterocyte septate junction dissolves and the pre-enterocyte reaches the gut lumen with a fully-formed brush border. The process of enteroblast integration resembles lumen formation in mammalian epithelial cysts, highlighting the similarities between the fly midgut and mammalian epithelia.

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Faculty Opinions recommendation of Distinct cytoskeletal tracks direct individual vesicle populations to the apical membrane of epithelial cells.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.1013083.188960 ◽

2003 ◽

Author(s):

William Bement

Keyword(s):

Epithelial Cells ◽

Apical Membrane ◽

Individual Vesicle

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Faculty Opinions recommendation of Regulated and polarized PtdIns(3,4,5)P3 accumulation is essential for apical membrane morphogenesis in photoreceptor epithelial cells.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.1031003.363465 ◽

2006 ◽

Author(s):

Andreas Wodarz

Keyword(s):

Epithelial Cells ◽

Apical Membrane ◽

Membrane Morphogenesis

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Faculty Opinions recommendation of Phase coexistence and connectivity in the apical membrane of polarized epithelial cells.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.1030333.357550 ◽

2006 ◽

Author(s):

Akihiro Kusumi

Keyword(s):

Epithelial Cells ◽

Apical Membrane ◽

Phase Coexistence ◽

Polarized Epithelial Cells

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c-erbB-3

The Journal of Cell Biology ◽

10.1083/jcb.200109033 ◽

2002 ◽

Vol 157 (6) ◽

pp. 929-940 ◽

Cited By ~ 145

Author(s):

Martin Offterdinger ◽

Christian Schöfer ◽

Klara Weipoltshammer ◽

Thomas W. Grunt

Keyword(s):

Epithelial Cells ◽

Nuclear Localization ◽

Nuclear Export ◽

Mammary Epithelial Cells ◽

Mammary Epithelial ◽

Site Directed Mutagenesis ◽

Receptor Protein ◽

Erbb Receptors ◽

Cell Fractionation ◽

Epithelial Polarity

c-erbB receptors are usually located in cell membranes and are activated by extracellular binding of EGF-like growth factors. Unexpectedly, using immunofluorescence we found high levels of c-erbB-3 within the nuclei of MTSV1-7 immortalized nonmalignant human mammary epithelial cells. Nuclear localization was mediated by the COOH terminus of c-erbB-3, and a nuclear localization signal was identified by site-directed mutagenesis and by transfer of the signal to chicken pyruvate kinase. A nuclear export inhibitor caused accumulation of c-erbB-3 in the nuclei of other mammary epithelial cell lines as demonstrated by immunofluorescence and biochemical cell fractionation, suggesting that c-erbB-3 shuttles between nuclear and nonnuclear compartments in these cells. Growth of MTSV1-7 on permeable filters induced epithelial polarity and concentration of c-erbB-3 within the nucleoli. However, the c-erbB-3 ligand heregulin β1 shifted c-erbB-3 from the nucleolus into the nucleoplasm and then into the cytoplasm. The subcellular localization of c-erbB-3 obviously depends on exogenous stimuli and on the stage of epithelial polarity and challenges the specific function of c-erbB-3 as a transmembrane receptor protein arguing for additional, as yet unidentified, roles of c-erbB-3 within the nucle(ol)us of mammary epithelial cells.

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