Characterization of trafficking and processing determinants in the outer pore -forming region of Kv1 potassium channels
The Kv1 subfamily of voltage-gated potassium channels (Kv1.1-Kv1.6) is involved in repolarizing the membrane potential after an action potential, shaping the action potential, and neurotransmitter release. The ability to carry out these functions requires proper trafficking and localization to the cell surface. Kv1 subfamily members have very different trafficking and TGG patterns despite having very similar amino acid sequences. Both positive and negative amino acid trafficking determinants of these processes have been mapped to the outer pore-forming region, which differ in these channels. The two important amino acid determinants responsible for those differences have been identified by lab personnel. Using a site-directed mutagenesis approach to make targeted substitutions, I have defined the physical and chemical properties at those two key positions that affect the Kv1.4 potassium channel's localization pattern and TGG. The mutations were characterized by their effect on levels of surface and total protein, protein stability, and on cellular localization. It is hypothesized that the trafficking determinant on the channel's outer pore-forming region exerts its effect by binding a trafficking factor that causes either high partial intracellular retention or trafficking through the secretory pathway. Members of the Kv1 subfamily have very similar amino acid sequences. Kv1.1 and Kv1.4, for instance have 74.0% similarity over their core region. However, Kv1.1 and Kv1.4 homomers display different cell surface expression levels and TGG efficiencies when assembled as homomers in transfected cultured cell lines. Alterations in either parameter are predicted to affect cell signaling. When cotransfected into the same cell lines, Kv1.1 and Kv1.4 assemble into heteromers in which Kv1.1 acts in a dominant negative manner to reduce cell surface expression of the heteromers compared with Kv1.4 homomers. Both Kv1.1/Kv1.4 heteromers and Kv1.4 homomers have been observed in brain, suggesting that neurons may also combine subunits with differing trafficking programs into heteromers to regulate surface levels of channels.
Gomez, Barbara, "Characterization of trafficking and processing determinants in the outer pore -forming region of Kv1 potassium channels" (2006). ETD Collection for Fordham University. AAI3255043.