Wei Tang

Date of Award


Degree Type


Degree Name

Master of Science




Dr, Richard Rozmahel


Notch signaling, through its regulation of cell proliferation, differentiation and death, plays an important role in the development and progression of intestinal tumors. This pathway relies on presenilin (PS)-complex y-secretase mediated cleavage of the Notch receptor. Previous studies have shown that differential fatty acids (FAs) have profound effects on y-secretase activity towards its substrates. In particular, stearic acid (SA) can enhance y-secretase towards the amyloid precursor protein (APP) while oleic acid (OA) can reduce it. The aim of this study was to investigate the effects of OA (and SA) on y-secretase cleavage of Notch and activation of the Notch pathway in Cos7 cells. The in vitro results showed that OA enrichment significantly diminished y-secretase cleavage of Notch; while, in contrast, SA enrichment significantly elevated the y- secretase cleavage of Notch. Since both FAs did not significantly affect the PS-complex expression, the basis of the effects likely resides in the alteration of the composition of the cellular membrane. Gamma secretase (or OA) mediated-reduction of the overexpressed Notch intracellular domain (NICD) lead to an increase in cell growth, while SA induced- production of this fragment caused a decrease in cell growth accomplished by reduced cell viability. These observations demonstrated the effects of FAs on y-secretase cleavage of Notch and Notch signal activation. However, over-expression of an artificial Notch construct negated the y-secretase inhibitor (or SA) effect on the reduction (or induction) of the expression of a Notch downstream gene, Hesl. Therefore, a more physiological relevant in vitro model may be demanded in order to better understand the mechanisms responsible for regulating the Notch signaling pathway by FAs as well as the potential therapeutic values o f these FAs on colon cancer.



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