The long-term goal of this research is to elucidate the mechanisms of quality control that ensure that only properly folded and assembled potassium channels are expressed on the cell surface. Potassium channels adopt their native structures in the ER. Channel proteins that fail to fold or assemble properly are recognized by a stringent quality control system and retained in the ER. This system prevents transport of misfolded or incompletely assembled proteins to locations where aberrant functional properties could disrupt cellular physiology. The proposed research focuses on two aspects of potassium channel quality control. First, how are structurally immature, misfolded, or unassembled potassium channel proteins retained in the ER? Second, what pathways dispose of ER-retained potassium channel proteins? What are the roles of proteasomal degradation and aggresome formation, which have been implicated in the disposal of other ER-retained proteins? The proposed research is relevant to the etiology of channelopathies, such as Long QT Syndrome Type 2, in which channel proteins are retained in the ER and may be subjected to ER-associated degradation. We will accomplish the following specific aims: (1) to determine the role of cytoplasmic domains in ER retention and release during biogenesis of Shaker and Kv1.3 potassium channels; (2) to identify mechanisms used by mammalian cells to dispose of ER-retained potassium channel proteins; and (3) to compare the quality control of HERG channel biogenesis in a mammalian cell line and in cardiac ventricular myocytes. Channel proteins will be expressed in HEK293T cells or cultured ventricular myocytes for studies of protein maturation, stability, protease inhibitors. Experimental approaches will include expression and biochemical analysis of wild type and mutant channel proteins, confocal microscopy, cell surface labeling, and electrophysiology. The proposed research will advance our knowledge of basic aspects of ion channel cell biology and improve our understanding of the etiology of channelopathies.
| Waters, Michael F; Minassian, Natali A; Stevanin, Giovanni et al. (2006) Mutations in voltage-gated potassium channel KCNC3 cause degenerative and developmental central nervous system phenotypes. Nat Genet 38:447-51 |
| Khanna, Rajesh; Lee, Eun Jeon; Papazian, Diane M (2004) Transient calnexin interaction confers long-term stability on folded K+ channel protein in the ER. J Cell Sci 117:2897-908 |
| Myers, Michael P; Khanna, Rajesh; Lee, Eun Jeon et al. (2004) Voltage sensor mutations differentially target misfolded K+ channel subunits to proteasomal and non-proteasomal disposal pathways. FEBS Lett 568:110-6 |
