Transactivation of EGFR mediates insulin-stimulated ERK1/2 activation and enhanced cell migration in human corneal epithelial cells.
OBJECTIVE
Insulin activates phosphatidylinositol 3-kinase (PI3K) and extracellular signal-regulated kinase (ERK)-1/2 in human corneal epithelial cells. These events have been shown to be involved in wound healing. However, the mechanism of insulin-induced ERK pathway is not clear during corneal wound healing. In this study, the effect of insulin associated with epidermal growth factor receptor (EGFR) on wound healing in transformed human corneal epithelial cells was investigated to determine the signaling mechanism involved.


METHODS
SV40-immortalized human corneal epithelial (THCE) cells were cultured on a diluted Matrigel matrix that resembled the basement membrane of the corneal epithelium. A wound was introduced with a micropipette tip, and closure of the scratch wound was photographed 12 h after exposure to insulin. Activation of EGFR was analyzed by immunoprecipitation, and cytoskeletal rearrangements were visualized with rhodamine-conjugated phalloidin.


RESULTS
Exposure of corneal epithelial cells to insulin induced phosphorylation of EGFR. Inhibition of EGFR activation by AG1478 or the MMP inhibitor, GM6001, reduced phosphorylation of insulin-induced ERK in the presence of insulin and delayed wound closure. In addition, cells exposed to insulin contained stress fibers and their submembranous cortical actin was depleted. These effects were inhibited by AG1478.


CONCLUSIONS
Inhibition of EGFR activity decreases cell migration involved in insulin-induced wound repair, an effect that mimics inhibition of MMP activation. Inhibition of MMP activity leads to decreased EGFR phosphorylation. Our data show that insulin stimulates wound healing in the corneal epithelium by activating EGFR, and point to a novel insulin signaling pathway that acts during corneal wound healing.
Lyu
Jungmook
J
Department of Ophthalmology and Visual Science, College of Medicine, The Catholic University of Korea, Seoul, Korea.
Lee
Kyung-Suk
KS
Joo
Choun-Ki
CK
D002461:Cell Line, Transformed; D002465:Cell Movement / Q000187:drug effects; D003599:Cytoskeleton / Q000648:ultrastructure; D004151:Dipeptides / Q000494:pharmacology; D004789:Enzyme Activation; D019573:Epithelium, Corneal / Q000187:drug effects / Q000293:injuries* / Q000473:pathology / Q000503:physiopathology*; D066246:ErbB Receptors / Q000037:antagonists & inhibitors / Q000235:genetics*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D006801:Humans; D007328:Insulin / Q000494:pharmacology*; D007527:Isoenzymes / Q000378:metabolism; D008666:Metalloendopeptidases / Q000037:antagonists & inhibitors; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011480:Protease Inhibitors / Q000494:pharmacology; D011799:Quinazolines; D015533:Transcriptional Activation; D020032:Tyrphostins / Q000494:pharmacology; D014945:Wound Healing
D004151:Dipeptides; D007328:Insulin; D007527:Isoenzymes; C078131:N-(2(R)-2-(hydroxamidocarbonylmethyl)-4-methylpentanoyl)-L-tryptophan methylamide; D011480:Protease Inhibitors; D011799:Quinazolines; D020032:Tyrphostins; C101044:RTKI cpd; D019869:Phosphatidylinositol 3-Kinases; D066246:ErbB Receptors; D048049:Extracellular Signal-Regulated MAP Kinases; D008666:Metalloendopeptidases