Regulation of ubiquitin ligase Nedd4-2 and cardiac sodium and potassium ion channels

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BACKGROUND: Ion channels are membrane proteins which generate electrical signals essential for cell communication. They control many vital physiological processes such as brain function and muscle contractions. The number of channels in the plasma membrane is a key determinant for the amplitude of electrical signals. The channel numbers are tightly regulated by the creation and destruction. Recent work by us and others have shown that a molecule called Nedd4-2 (neural precursor cell expressed, developmentally down-regulated 4-2) mediates the degradation of several ion channels. Presently, it is not known how the activity of Nedd4-2 is regulated. Given its pivotal role, it is therefore critical to understand the regulation of Nedd4-2 function, which further determines the number of ion channels in the cell membrane.HYPOTHESIS: Activity of Nedd4-2 is regulated by intracellular Ca2+ levels, GTPase Rab4, and glucocorticoid-inducible kinase (SGK), which in turn regulates sodium and potassium channel expressions.OBJECTIVE: Using electrophysiology, cell biology and cell imaging techniques in cell line systems and rat cardiomyocytes, we will determine (1) the effect of intracellular Ca2+ on the function of Nedd4-2; (2) the effects of the small GTPase Rab4 on the Nedd4-2 activity; (3) the effects of SGK activation on the Nedd4-2 activity. We will further investigate the effects of altered Nedd4-2 on the function and expression of cardiac ion channels (e.g. Nav1.5, KCNQ1 and hERG) and the electrical properties of cardiac myocytes.SIGNIFICANCE: Information obtained from the present project focusing on ion channels will not only extend our understanding of human biology but also is essential for developing biotech products such as artificial pacemakers, and muscle prostheses. HQP involved will attain critical thinking skills and expertise in molecular biology and electrophysiology. They will become invaluable resources for education, biotech companies, and research laboratories. Such training will enhance Canada's Workforce Skills and will benefit Canadian economy.