Differential regulation of junctional complex assembly in renal epithelial cell lines.
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.
Gopalakrishnan
Shobha
S
Department of Medicine, Indiana University Medical Center, Indianapolis, IN 46202-5181, USA.
Hallett
Mark A
MA
Atkinson
Simon J
SJ
Marrs
James A
JA
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
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