CAG STUDENT PRIZE. PHOSPHATIDYLINOSITOL-3-KINASE SIGNALLING PATHWAY CONTROLS HUMAN GASTRIC EPIT...

Search CDDW 2006 Abstracts

CAG STUDENT PRIZE. PHOSPHATIDYLINOSITOL-3-KINASE SIGNALLING PATHWAY CONTROLS HUMAN GASTRIC EPITHELIAL RESTITUTION

MP Tétreault, P Chailler, N Rivard, D Ménard
CIHR Group on Functional Development and Physiopathology of the Digestive Tract, Département d’Anatomie et de Biologie Cellulaire, Université de Sherbrooke, Sherbrooke, Québec

Human gastric mucosa is maintained through a constant renewal of the epithelium and its highly dynamic regenerative capacity upon wounding. Our previous studies established that growth factors (GFs: TGFa, HGF) differently regulate the regeneration of human gastric epithelial cells. However, the intracellular signalling pathways that transmit extracellular cues and that regulate basic and stimulated gastric epithelial cell migration are still unclear.
AIM: To investigate the involvement of PI3K signalling pathway in the regulation of gastric epithelial migration.
METHODS: Confluent HGE-17 cell monolayers were wounded with a razor blade and migration was quantified by counting the number of cells across the wound margin. The effects of a synthetic form of PtdIns(3,4,5)P₃ and of pharmacological inhibitors (LY294002, rapamycin, toxinB) were examined with and without growth factors. Wounded cultures were lysed at different time intervals and the activation profiles of Akt and p70S6K were analyzed. The biological consequences of wild-type Akt (wt-Akt) and myristylated Akt (myr-Akt) overexpression in HGE-17 cells were studied.
RESULTS: LY294002 (PI3K inhibitor) strongly decreased basal and GFs-induced cell migration (40% to 70%) and this inhibition was already significant after only 60 min exposure. In accordance, treatments with PtdIns(3,4,5)P₃ greatly accelerated cell migration by 230%. Putative targets such as Akt and p70S6K were all stimulated in a PI3K-depedent manner by wounding and GFs. Specific inhibitors of RhoGTPase and mTOR/p70S6K significantly decreased HGE-17 cell migration by 40% and 25% respectively. Even though wounding induced Akt activation as early as 5 min, overexpression of wt-Akt and myr-Akt did not accelerated migration.
CONCLUSION: Activation of PI3K is a central and early event involved in the control of basal and GFs stimulated gastric epithelial restitution but the intracellular targets responsible for the differential actions of GFs are probably downstream in the pathway.