title: Hypertonic stress promotes the upregulation and phosphorylation of zonula occludens 1.
abstract: Tight junction molecules form a barrier between adjacent cells and mediate the cells' ability to develop membranes that constitute boundaries of different compartments within the body. Membranes with selective ion and water passage are important for the electrolyte and water homeostasis in the kidney. Due to their role in the urinary concentration process, renal medullary cells are exposed to hyperosmotic stress. Therefore, we were interested in the question of how mouse inner medullary collecting duct cells (mIMCD3) manage to maintain their cell-cell contacts, despite hypertonicity-induced cell shrinkage. Employing mRNA expression analysis, we found that the zonula occludens type 1 (Zo-1), multi-PDZ domain protein 1 (MUPP1) and cortactin mRNA levels were upregulated in a tonicity-dependent manner. Using Western blot analysis, immunoprecipitation and immunofluorescence, we show that the Zo-1 protein is upregulated, phosphorylated and linked to the actin cytoskeleton in response to hypertonic stress. After cell exposure to hypertonicity, rearrangement of the actin cytoskeleton resulted in a stronger colocalization of actin fibres with Zo-1. Urea, which generates hyperosmolality, but no transcellular gradient, did not induce changes in Zo-1 protein expression or actin rearrangement. This data indicates that Zo-1 is a response protein to inner medullary tonicity and that extracellular stressors can promote Zo-1 protein expression, tyrosine phosphorylation and cytoskeleton association.
authors: Department of Internal Medicine II, University Medical Center, Regensburg, Germany.
authors: Cornelia
authors: C
authors: Then
authors: Tobias
authors: T
authors: Bergler
authors: Roland
authors: R
authors: Jeblick
authors: Bettina
authors: B
authors: Jung
authors: Bernhard
authors: B
authors: Banas
authors: Bernhard K
authors: BK
authors: Krämer
mesh_terms: D000199:Actins / Q000235:genetics / Q000378:metabolism; D000818:Animals; D015153:Blotting, Western; D002478:Cells, Cultured; D003599:Cytoskeleton / Q000187:drug effects / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005786:Gene Expression Regulation / Q000187:drug effects; D006982:Hypertonic Solutions / Q000494:pharmacology; D007679:Kidney Medulla / Q000166:cytology; D007685:Kidney Tubules, Collecting / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism*; D051379:Mice; D008856:Microscopy, Fluorescence; D010750:Phosphoproteins / Q000235:genetics* / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D011887:Raffinose / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012462:Saline Solution, Hypertonic / Q000494:pharmacology; D013312:Stress, Physiological / Q000502:physiology*; D013997:Time Factors; D015854:Up-Regulation / Q000187:drug effects; D014508:Urea / Q000494:pharmacology; D062826:Zonula Occludens-1 Protein
chemical_list: D000199:Actins; D006982:Hypertonic Solutions; D008565:Membrane Proteins; D010750:Phosphoproteins; D012462:Saline Solution, Hypertonic; C569043:Tjp1 protein, mouse; D062826:Zonula Occludens-1 Protein; D014508:Urea; D011887:Raffinose