investigator's application): Ion channels compromise a specialized class of membrane proteins that underlie electrical signalling in nerve, muscle and other cells. Modulation of ion channels properties, particularly by protein phosphorylation, is of fundamental importance for the functioning of many cell types. Although serine/threonine phosphorylation of ion channels has been studied thoroughly, modulation of ion channels by tyrosine phosphorylation is largely unexplored. The investigator proposes to examine modulatory interactions between protein tyrosine kinases and voltage-gated potassium (Kv) channels. The investigators will focus on two representative members of the Kv channel family: Dv1.3, which is prominent in T lymphocytes and some brain neurons, and Kv1.5, which is expressed highly in heart and brain. This proposal will test two hypotheses, each of which is based on extensive preliminary data. The first is that some Kv channels can associate tightly with tyrosine kinases in a regulatory complex, and the second is that there is reciprocal regulation of Kv channels and tyrosine kinases - that is, channels and kinases can regulate each other's activities. The investigator's specific aims are: 1) To investigate the molecular mechanisms and functional consequences of direct association of Kv channels and tyrosine kinases; 2) to investigate the molecular mechanisms by which tyrosine phosphorylation modulates Kv channels current; and 3) to investigate the reciprocal regulation of Kv channels and tyrosine kinsases. The properties of cloned Kv1.3 and Kv1.5 will be examined following their heterologous expression in a human embryonic kidney (HEK 293 cell line, and native Kv channel current will be investigated in cultured olfactory bulb neurons. For each of these specific aims, the investigators will use a combination of biochemical, physiological and molecular approaches to dissect the molecular details and functional consequences of modulatory interactions between Kv channels and tyrosine kinases.
