Identification of amino acids in the pore region of Kv1.2 potassium channel that regulate its glycosylation and cell surface expression.

The Kv1.4 potassium channel is reported to exhibit higher cell surface expression than the Kv1.1 potassium channel when expressed as a homomer in cell lines. Kv1.4 also shows highly efficient trans-Golgi glycosylation whereas Kv1.1 is not glycosylated. The surface expression and glycosylation of Kv1.2 is intermediate between those of Kv1.1 and Kv1.4. Amino acid determinants controlling the surface expression of Kv1 channels were localized to the highly conserved pore region and both positive and negative determinants of Kv1.1 and Kv1.4 trafficking have been reported. In this study, we analyzed the effect of substituting amino acids in the pore region of Kv1.2 with the corresponding amino acid present in Kv1.1 or Kv1.4 on glycosylation and trafficking of Kv1.2. Mutations in the outer pore region of Kv1.2 of Arg(354) to Pro (corresponding to Kv1.4) and to Ala (corresponding to Kv1.1) enhanced and reduced, respectively, cell surface expression of Kv1.2. Mutations in a different outer pore region of Val(381) to Lys (Kv1.4) and Tyr (Kv1.1) both reduced the cell surface expression. In contrast, mutation in the deep pore region of Ser(371) to Thr (Kv1.4) markedly enhanced cell surface expression. These results suggest that the cell surface expression of Kv1.2 is regulated by specific amino acids in the pore region in a similar manner to Kv1.1 and Kv1.4, and that the cell surface expression of Kv1.2, a channel intermediate between Kv1.1 and Kv1.4, can be attributed to these specific residues.