The mammalian Kv7 (KCNQ) potassium channels play a major role in regulating cellular excitability due to their low threshold of activation, slow kinetics, and lack of inactivation. Four out of five of the known Kv7 subunits have been implicated in cardiac or neurological disease. These channels are modulated by a number of diverse intracellular messengers and receptor-mediated pathways. Our laboratory recently cloned and described the only known Drosophila Kv7 ortholog, dKCNQ. Like mammalian Kv7 channels, dKCNQ utilizes calmodulin as an accessory subunit, can be inhibited by muscarinic receptor activation, and is blocked by linopirdine. We recently performed a yeast-two-hybrid assay using the C-terminus of dKCNQ as bait and recovered a number of unexpected proteins. Our preliminary data show that two of these proteins, DnaJ-1 and bicaudal D, can co-immunoprecipitate with dKCNQ when expressed in heterologous cells. We also found that DnaJ-1 alters the functional properties of dKCNQ. The main goal of the work proposed herein is to describe in detail the functional impact of these proteins on dKCNQ function and explore their possible role in receptor-mediated dKCNQ modulation. In addition, using mutagenesis and coimmunoprecipitation, I will characterize the molecular details of dKCNQ-BicD and DnaJ-1 binding. Based on the role these channels play in human disease, the identification of novel modulatory mechanisms could provide the scientific community with new targets for drug design and other therapeutic approaches. ? ? ?
