Glycosylation affects the protein stability and cell surface expression of Kv1.4 but not Kv1.1 potassium channels - A pore region determinant dictates the effect of glycosylation on trafficking

Kv1.1 and Kv1.4 potassium channels are plasma membrane glycoproteins involved in action potential repolarization. We have shown previously that glycosylation affects the gating function of Kv1.1 (Watanabe, I., Wang, H. G., Sutachan, J. J., Zhu, J., Recio-Pinto, E. & Thornhill, W. B. (2003) J. Physiol. (Lond.) 550, 51-66) and that a pore region determinant of Kv1.1 and Kv1.4 affects their cell surface trafficking negatively or positively, respectively (Zhu, J., Watanabe, I., Gomez, B. & Thornhill, W. B. (2001) J. Biol. Chem. 276, 39419-39427). Here we investigated the role of N-glycosylation of Kv1.1 and Kv1.4 on their protein stability, cellular localization pattern, and trafficking to the cell surface. We found that preventing N-glycosylation of Kv1.4 decreased its protein stability, induced its high partial intracellular retention, and decreased its cell surface protein levels, whereas it had little or no effect on these parameters for Kv1.1. Exchanging a trafficking pore region determinant between Kv1.1 and Kv1.4 reversed these effects of glycosylation on these chimeric channels. Thus it appeared that the Kv1.4 pore region determinant and the sugar tree attached to the S1-S2 linker showed some type of dependence in promoting proper trafficking of the protein to the cell surface, and this dependence can be transferred to chimeric Kv1.1 proteins that contain the Kv1.4 pore. Understanding the different trafficking programs of Kv1 channels, and whether they are altered by glycosylation, will highlight the different posttranslational mechanisms available to cells to modify their cell surface ion channel levels and possibly their signaling characteristics.