title: Differential regulation of junctional complex assembly in renal epithelial cell lines.
abstract: Several signaling pathways that regulate tight junction and adherens junction assembly are being characterized. Calpeptin activates stress fiber assembly in fibroblasts by inhibiting SH2-containing phosphatase-2 (SHP-2), thereby activating Rho-GTPase signaling. Here, we have examined the effects of calpeptin on stress fiber and junctional complex assembly in Madin-Darby canine kidney (MDCK) and LLC-PK epithelial cells. Calpeptin induced disassembly of stress fibers and inhibition of Rho GTPase activity in MDCK cells. Interestingly, calpeptin augmented stress fiber formation in LLC-PK epithelial cells. Calpeptin treatment of MDCK cells resulted in a displacement of zonula occludens-1 (ZO-1) and occludin from cell-cell junctions and a loss of phosphotyrosine on ZO-1 and ZO-2, without any detectable effect on tight junction permeability. Surprisingly, calpeptin increased paracellular permeability in LLC-PK cells even though it did not affect tight junction assembly. Calpeptin also modulated adherens junction assembly in MDCK cells but not in LLC-PK cells. Calpeptin treatment of MDCK cells induced redistribution of E-cadherin and beta-catenin from intercellular junctions and reduced the association of p120ctn with the E-cadherin/catenin complex. Together, our studies demonstrate that calpeptin differentially regulates stress fiber and junctional complex assembly in MDCK and LLC-PK epithelial cells, indicating that these pathways may be regulated in a cell line-specific manner.
authors.affiliation: Department of Medicine, Indiana University Medical Center, Indianapolis, IN 46202-5181, USA.
authors.forename: Shobha
authors.initials: S
authors.lastname: Gopalakrishnan
authors.forename: Mark A
authors.initials: MA
authors.lastname: Hallett
authors.forename: Simon J
authors.initials: SJ
authors.lastname: Atkinson
authors.forename: James A
authors.initials: JA
authors.lastname: Marrs
mesh_terms: D016475:3T3 Cells; D022005:Adherens Junctions / Q000502:physiology*; D000818:Animals; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004151:Dipeptides / Q000494:pharmacology; D015536:Down-Regulation / Q000187:drug effects; D004847:Epithelial Cells / Q000502:physiology*; D007668:Kidney / Q000166:cytology*; D018374:LLC-PK1 Cells; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D062793:Occludin; D010750:Phosphoproteins / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D022502:Stress Fibers / Q000187:drug effects / Q000201:enzymology; D013552:Swine; D019108:Tight Junctions / Q000502:physiology*; D062826:Zonula Occludens-1 Protein; D020741:rho GTP-Binding Proteins / Q000378:metabolism
chemical_list: D015853:Cysteine Proteinase Inhibitors; D004151:Dipeptides; D008565:Membrane Proteins; D062793:Occludin; C568986:Ocln protein, mouse; D010750:Phosphoproteins; C569043:Tjp1 protein, mouse; D062826:Zonula Occludens-1 Protein; C071482:calpeptin; D020741:rho GTP-Binding Proteins