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Role of the Occluding Septate Junction Protein Mesh in Epithelial Integrity and Ion Transport in the Drosophila Renal Tubules
Author(s) -
Jonusaite Sima,
Rodan Aylin
Publication year - 2018
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.2018.32.1_supplement.624.30
Subject(s) - septate junctions , microbiology and biotechnology , tight junction , paracellular transport , gene knockdown , midgut , tubule , scaffold protein , biology , epithelium , chemistry , anatomy , kidney , gap junction , biochemistry , signal transduction , gene , intracellular , endocrinology , botany , genetics , membrane , larva , permeability (electromagnetism)
Background/objective Epithelial occluding junctions are specialized cell‐cell junctions that establish and maintain cell polarity and control paracellular ion, solute and water transport. Tight junctions are the occluding junctions in the epithelia of vertebrates, whereas the epithelia of invertebrates possess septate junctions (SJs). Molecular and genetic analysis of Drosophila SJs have identified a number of transmembrane as well as cytoplasmic scaffolding proteins expressed in a tissue‐specific manner. However, many questions about the role of these proteins in SJ assembly, maintenance and function remain open. Recently, an integral protein, Mesh, has been identified within the SJs of Drosophila midgut and renal tubule epithelia, and shown to be required for the barrier function of the midgut. Here, we report, for the first time, examination of the role of Mesh in adult fly renal tubules, whose function in the maintenance of internal homeostasis relies on regulated transepithelial ion and water secretion/absorption. Methods mesh knockdown in the fly tubules was achieved using the GAL4‐UAS system. Expression and localization of Mesh and a scaffolding SJ protein, Discs large (Dlg), in control and mutant tubules were determined using confocal microscopy and available antibodies. Transepithelial fluid and K + transport in the main segment of the control and mesh knockdown tubules were measured using the Ramsay assay and a K + ‐specific electrode. Results Adult fly renal tubules consist of four major morphologically and functionally distinct segments and have two cell types, the larger principal cells and smaller intercalated stellate cells. We found that developmental mesh knockdown in the tubule principal cells was associated with enlarged initial and main segments of the adult fly tubule and reduced septate junctional localization of a scaffolding protein, Dlg, especially in the enlarged initial segment. In addition, the main segment transepithelial fluid and K + transport in isotonic condition was abolished in mesh knockdown tubules compared to the control groups. Conclusions and significance These data suggest that the SJ protein Mesh is required for SJ assembly, epithelial integrity and ion transport in the fly renal tubule epithelium. Since the Mesh mammalian homolog, Susd2, is also highly expressed in the mouse renal epithelium with unknown function, these studies pave the way for further characterization of the Mesh/Susd2 family of proteins in both invertebrates and vertebrates. Support or Funding Information This project was supported by NIH/NIDDK to ARR This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .

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