CAREER: Tyrosine Phosphorylation and Kinase Activity as a Regulator of Sodium-Glucose Transporters

The sodium-glucose-linked transporters (SGLTs) are proteins that are necessary for cellular uptake of glucose, which is an essential nutrient. Altered activity of these proteins can lead to poor glucose absorption and nutrient deficiency. Unfortunately, cellular events that regulate SGLT activity are poorly understood. This is particularly true for tyrosine phosphorylation, a form of modification that can change protein structure and function, that has not yet been studied in relation to SGLT activity. Therefore, the long-term goal of this NSF CAREER research project is to improve the understanding of how SGLT tyrosine phosphorylation, or tyrosine kinase proteins that activate this form of modification, regulate changes in glucose movement into cells. The project also includes several strategies for educational improvements that include highlighting the biological importance of SGLTs, as well as the training and recruitment of junior scientists who will lead future science, technology, engineering, and mathematic efforts. Collectively, this research project is expected to impact many scientific disciplines, including molecular, cellular, and systems biology, through educational insight and novel scientific discoveries involving glucose transporters. The research objective of this NSF CAREER project is to identify a novel post-translational event that regulates variability in SGLT activity and glucose absorption. Solute carrier transporters, including SGLTs, have been associated as passive pores that move substrates across cell membranes alone or with electrochemical gradients. However, the hypothesis to be tested as part of the current project is that SGLTs are tyrosine phosphorylated by specific kinases at the cell surface, and that these phosphorylation events are associated with transport function. To address this hypothesis, the project will 1) evaluate the phosphorylation status of SGLTs in different cellular compartments using cell fractionation and mass spectrometry; 2) identify the role of tyrosine phosphorylation sites in regulating SGLT activity using site-directed mutagenesis, kinase inhibitors, and SGLT activity assays; and 3) identify tyrosine kinases that mediate SGLT activity using phosphoproteomic analysis and kinase interaction assays. Additionally, the strategies and outcomes from the proposed research objectives will be used to improve basic scientific knowledge, generate a passion for research, and improve leadership capabilities in the field of biological sciences. This will be done by establishing an annual summer research position for high school students, working with middle school educators to increase recognition of reproducible and high-quality science, and developing online content that will increase familiarity with transporter proteins. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.