E-cadherin Mechanotransduction, Pluripotency and the Warburg Effect

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BACKGROUND. Embryonic stem cells (ESCs) are pluripotent meaning they have the ability to differentiate into any cell type in the body. We have observed that the pluripotency of murine (m)ESCs is promoted when mESC aggregates are stirred in bioreactors. Pluripotency is maintained even when the maintenance factor LIF is removed. Moreover, cellular reprogramming, the process of dedifferentiating cells to pluripotency, occurs 1000-fold more efficiently in the bioreactor. Our preliminary data indicates that the pluripotency transcription factor ß-catenin is translocated into the nucleus in response to fluid shear caused by stirring. Shear stress can modulate gene expression through mechano-transduction. In one pathway, fluid shear leads to the nuclear translocation of ß-catenin. Translocation is thought to occur when shear is sensed by E-cadherin, a protein responsible for cell-cell interaction and aggregate formation. In response to shear, ß-catenin may be displaced by vinculin, whose role is to strengthen cell architecture by tethering E-cadherin to the cytoskeleton. During cellular reprogramming, cellular metabolism shifts from oxidative phosphorylation (i.e. mitochondrial) to aerobic glycolysis (non-mitochondrial). Recently ß-catenin has also been shown to promote this so called Warburg effect in cancer cells by upregulating glycolytic genes. OBJECTIVES. Using the following objectives, we will test if fluid shear promotes mESC pluripotency and cellular reprograming in the bioreactor via mechanotransduction: 1. ß-catenin Mechanotransduction. Using flow chambers and molecular assays, in combination with pharmacological and genetic approaches, we will determine if ß-catenin is released from E-cadherin and translocates into the nucleus in reponse to shear. 2. E-cadherin Mechanoreception. Using magnetic twisting cytometry and molecular assays, in combination with pharmacological and genetic approaches, we will determine if shear applied to E-cadherin results in ß-catenin nuclear translocation. 3. Pluripotency and Warburg Effect. Using pharmacological and genetic approaches, we will determine if ß-catenin mechanotransduction promotes pluripotency and aerobic glycolysis during reprogramming and expansion in the bioreactor. IMPACT. Government investment in pluripotent stem cell (PSC) biobanking suggests bioreactors will become a future application standard. As leaders in the bioreactor expansion of PSCs, we are positioned to make a significant impact. Understanding the mechanism behind “mechano-pluripotency” will enable the development of more efficient and affordable bioprocesses for producing PSCs and their cell/tissue derivatives. We will continue to train students and postdocs in the research process, while simultaneously helping them to develop leadership and professional skills through experiential learning and knowledge translation.