Elucidating the role of Wnt/beta-catenin in mitochondrial metabolism and cell behavior

About This Grant

PROJECT SUMMARY/ABSTRACT Metabolism is one of the most tightly regulated cellular processes and is important for the maintenance of homeostasis; its deregulation is a hallmark for many diseases, including diabetes, cancer, and neurodegenerative diseases. The mitochondrial pyruvate carrier (MPC - comprised of the MPC1 and MPC2 proteins) is a transmembrane protein that resides in the inner mitochondria membrane and facilitates the entry of pyruvate, which is necessary in several metabolic reactions such as TCA cycle. Our lab has previously shown that low MPC expression promotes cell proliferation, and that MPC expression is negatively correlated with Wnt/β-catenin target gene expression. However, the molecular mechanism behind this correlation is not known. To test the hypothesis that Wnt/β-catenin regulates MPC expression, we performed a screen based on technology developed in the Rutter lab (TRoUT-FISH) and found that β-catenin suppresses the expression of the MPC genes. I validated this finding by showing that treatment with GSK3 inhibitors, which activate the Wnt/β- catenin pathway, caused reduced MPC1 and MPC2 mRNA and protein expression. Moreover, I examined the effects of silencing or overexpressing c-Myc (a downstream target of the Wnt/β-catenin pathway) on MPC mRNA expression using human dermal fibroblasts. I found that overexpression of c-Myc resulted in decreased MPC1 expression, whereas knockdown of c-Myc resulted in increased MPC1 expression. I hypothesize that β-catenin, through its target gene c-Myc, acts as a repressor of the MPC as part of its pro-proliferation transcriptional program. Building on my preliminary results, the objective of my K99/R00 proposal is to define the mechanisms by which β-catenin and c-Myc regulate MPC1 and MPC2 expression, and the significance of this regulation in cell metabolism and cell behavior. To test this hypothesis, I propose the following specific aims: (Aim 1) Determine the molecular mechanisms by which activation of Wnt/β-catenin represses MPC1 and MPC2 expression [K99 phase]; (Aim 2) Elucidate the role of Wnt/β-catenin in cell metabolism and cell fate [K99 phase]; and (Aim 3) Unravel the distinct roles of mitochondrial metabolism in stem cells and differentiated cells [R00 phase]. My long-term goal is to become an independent scientist at an R1 institution working at the intersection of mitochondrial metabolism and cell biology. To achieve this, I have worked with Dr. Rutter to assemble my mentoring committee which includes experts with a strong publication record in mitochondrial metabolism, cell biology/cell signaling, metabolomics/proteomics and metabolic tracing. Overall, the tools and skills learned during the mentored phase will be essential for my development as an independent scientist and for me to successfully establish a strong and differentiated research program studying the distinct roles of mitochondrial metabolism in stem cells and differentiated cells and its implication in health and disease.