Karlett Parra, Ph.D., University of New Mexico

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Project Description:

V-ATPases are highly conserved proton pumps important for pH homeostasis. In malignant tumors, V-ATPases sustain an altered pH gradient between the cytoplasm and the lumen of intracellular vesicles; and generate the acid extracellular microenvironment necessary for cancer progression and metastasis. Lack of V-ATPase function blocks cancer progression but the mechanism involved is not known. Our long term goal is to understand how cancer cells regulate V-ATPase pumps and how V-ATPases assist in cancer progression to metastasis.  Glucose metabolism regulates V-ATPases in normal cells. When glucose is limiting or glycolysis is interrupted  the two domains comprising V-ATPases (V1 and Vo) disassemble. Disassembly inactivates the pump and is reversed by glucose readdition.  We postulate that glucose also controls V-ATPase assembly and activity in malignant tumors where anaerobic glycolysis dominates metabolism (Warburg effect). To test this novel hypothesis we will use a cell model of human prostate cancer progression; and human primary cell cultures of normal prostate and prostate cancer tissue. V-ATPases are abundant in the prostate and the energy metabolism of the prostate is highly specialized for fine tuning glycolytic activity which makes the prostate an attractive system for these studies. We will establish parallels between glucose utilization and V-ATPase assembly by measuring reversible disassembly, V-ATPase activity, and cytosolic and lysosomal pH in cells exposed to glucose, glycolytic inhibitors, and starvation (Aim 1). V-ATPase deficient cells, as a result of siRNA-mediated  knockdown and treatment with V-ATPase inhibitors, will be used to further discern connections between V-ATPase activity, pH homeostasis, and resistance to oxidative stress (Aim 2). These studies will lend new insight into how V-ATPases aid prostate cancer cells in controlling luminal, cytosolic, and extracellular pH. They may lead to the development of more effective therapeutic strategies to control the V-ATPase-generated abnormal pH gradients, which are essential for tumorigenesis, cancer progression, metastasis, and drug resistance.