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Adducins regulate remodeling of apical junctions in human epithelial cells
Nayden G Naydenov1, Andrei I Ivanov
1Department of Medicine, University of Rochester, Rochester, NY 14642, USA.
Molecular Biology of the Cell
|September 3, 2010
Summary
Adducins stabilize epithelial junctions by linking the plasma membrane to the actin cytoskeleton. Down-regulating adducins disrupts adherens junctions (AJs) and tight junctions (TJs), impacting cell layer integrity.
Area of Science:
- Cell biology
- Epithelial biology
- Cytoskeletal dynamics
Background:
- Epithelial adherens junctions (AJs) and tight junctions (TJs) are crucial for tissue integrity and are regulated by dynamic membrane-cytoskeleton interactions.
- Spectrin-adducin-ankyrin complexes are key mediators of membrane-actin cytoskeleton linkage, with adducins facilitating spectrin-actin interactions.
- The precise roles of adducins in epithelial junction remodeling remain largely unelucidated.
Purpose of the Study:
- To investigate the function of adducins in the remodeling of epithelial adherens junctions (AJs) and tight junctions (TJs).
- To determine the molecular mechanisms by which adducins influence epithelial junction assembly and disassembly.
Main Methods:
- Utilized human colonic (SK-CO15) and pancreatic (HPAF-II) epithelial cell monolayers.
- Employed small interfering RNA (siRNA) to down-regulate α- and γ-adducin expression.
- Assessed effects on AJ and TJ assembly/disassembly, βII-spectrin expression, F-actin content, and perijunctional actin bundle formation.
Main Results:
- Both α- and γ-adducin isoforms were expressed, positively regulated each other's levels, and localized to AJs with E-cadherin and β-catenin.
- Adducin depletion via siRNA significantly impaired calcium-dependent AJ and TJ assembly and accelerated disassembly triggered by protein kinase C.
- Impaired junction assembly in adducin-depleted cells was attributed to reduced βII-spectrin expression/recruitment and decreased F-actin content with disrupted perijunctional actin bundles.
Conclusions:
- Adducins play a critical role in the stabilization and dynamic remodeling of epithelial adherens junctions and tight junctions.
- Adducins regulate junctional integrity through mechanisms involving βII-spectrin and the F-actin cytoskeleton.
- These findings reveal novel functions for adducins in maintaining epithelial barrier function.
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