Exocyst Sec10 protects epithelial barrier integrity and enhances recovery following oxidative stress, by activation of the MAPK pathway.
Cell-cell contacts are essential for epithelial cell function, and disruption is associated with pathological conditions including ischemic kidney injury. We hypothesize that the exocyst, a highly-conserved eight-protein complex that targets secretory vesicles carrying membrane proteins, is involved in maintaining renal epithelial barrier integrity. Accordingly, increasing exocyst expression in renal tubule cells may protect barrier function from oxidative stress resulting from ischemia and reperfusion (I/R) injury. When cultured on plastic, Madin-Darby canine kidney (MDCK) cells overexpressing Sec10, a central exocyst component, formed domes showing increased resistance to hydrogen peroxide (H2O2). Transepithelial electric resistance (TER) of Sec10-overexpressing MDCK cells grown on Transwell filters was higher than in control MDCK cells, and the rate of TER decrease following H2O2 treatment was less in Sec10-overexpressing MDCK cells compared with control MDCK cells. After removal of H2O2, TER returned to normal more rapidly in Sec10-overexpressing compared with control MDCK cells. In collagen culture MDCK cells form cysts, and H2O2 treatment damaged Sec10-overexpressing MDCK cell cysts less than control MDCK cell cysts. The MAPK pathway has been shown to protect animals from I/R injury. Levels of active ERK, the final MAPK pathway step, were higher in Sec10-overexpressing compared with control MDCK cells. U0126 inhibited ERK activation, exacerbated the H2O2-induced decrease in TER and cyst disruption, and delayed recovery of TER following H2O2 removal. Finally, in mice with renal I/R injury, exocyst expression decreased early and returned to normal concomitant with functional recovery, suggesting that the exocyst may be involved in the recovery following I/R injury.
Park
Kwon Moo
KM
Department of Medicine, University of Pennsylvania, and the Veterans Administration Medical Center, Philadelphia, Pennsylvania, USA.
Fogelgren
Ben
B
Zuo
Xiaofeng
X
Kim
Jinu
J
Chung
Daniel C
DC
Lipschutz
Joshua H
JH
D000818:Animals; D002070:Butadienes / Q000494:pharmacology; D002352:Carrier Proteins / Q000378:metabolism; D002460:Cell Line; D003404:Creatinine / Q000097:blood; D004285:Dogs; D017097:Electric Impedance; D004789:Enzyme Activation; D004847:Epithelial Cells / Q000187:drug effects / Q000201:enzymology* / Q000473:pathology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D007668:Kidney / Q000187:drug effects / Q000201:enzymology* / Q000473:pathology / Q000503:physiopathology; D020935:MAP Kinase Signaling System / Q000187:drug effects; D008297:Male; D008565:Membrane Proteins; D051379:Mice; D008810:Mice, Inbred C57BL; D009570:Nitriles / Q000494:pharmacology; D016877:Oxidants / Q000494:pharmacology; D018384:Oxidative Stress / Q000187:drug effects; D010539:Permeability; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D015427:Reperfusion Injury / Q000201:enzymology* / Q000473:pathology / Q000503:physiopathology; D013997:Time Factors; D014162:Transfection; D033921:Vesicular Transport Proteins / Q000235:genetics / Q000378:metabolism*
D002070:Butadienes; D002352:Carrier Proteins; C419575:EXOC5 protein, human; D008565:Membrane Proteins; D009570:Nitriles; D016877:Oxidants; D047428:Protein Kinase Inhibitors; C489608:Sec8l1 protein, mouse; C113580:U 0126; D033921:Vesicular Transport Proteins; D003404:Creatinine; D006861:Hydrogen Peroxide; D048049:Extracellular Signal-Regulated MAP Kinases