[Show abstract][Hide abstract] ABSTRACT: 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.
Journal of Neurochemistry 12/2009; 112(4):913-23. · 4.24 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: An infecting strain VLA2/18 of Campylobacter jejuni was obtained from an individual with campylobacteriosis and used to prepare chicken sera by experimental infection to investigate the role of serum anti-ganglioside antibodies in Guillain-Barré syndrome. Both sera of the patient and chicken contained anti-ganglioside antibodies and anti-Lipid A (anti-Kdo2-Lipid A) antibodies directed against the lipid A portion of the bacterial lipooligosaccharide. The anti-Kdo2-Lipid A activities inhibited voltage-gated Na (Nav) channel of NSC-34 cells in culture. We hypothesized that anti-Kdo2-Lipid A antibody acts on the functional inhibition of Nav1.4. To test this possibility, a rabbit peptide antibody (anti-Nav1.4 pAb) against a 19-mer peptide (KELKDNHILNHVGLTDGPR) on the alpha subunit of Nav1.4 was produced. Anti-Nav1.4 pAb was cross-reactive to Kdo2-Lipid A. Anti-Kdo2-lipid A antibody activity in the chicken serum was tested for the Na(+) current inhibition in NSC-34 cells in combination with mu-Conotoxin and tetrodotoxin. Contrary to our expectations, the anti-Kdo2-Lipid A antibody activity was extended to Nav channels other than Nav1.4. By overlapping structural analysis, it was found that there might be multiple peptide epitopes containing certain dipeptides showing a structural similarity with v-Lipid A. Thus, our study suggests the possibility that there are multiple epitopic peptides on the extracellular domains of Nav1.1 to 1.9, and some of them may represent target sites for anti-Kdo2-Lipid A antibody, to induce neurophysiological changes in GBS by disrupting the normal function of the Nav channels.
Journal of Neuroscience Research 08/2008; 86(15):3359-74. · 2.73 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We investigated the expression and localization of Kv1 channels in dorsal spinal roots (DRs) and ventral spinal roots (VRs) in rats. Among Kv1.1-1.6 tested by RT-PCR, mRNAs of Kv1.1, 1.2, and 1.5 were moderately expressed, those of Kv1.3 and Kv1.6 were weakly expressed, and that of Kv1.4 was hardly expressed at all in both DRs and VRs, whereas all six mRNAs were detected in spinal cord. Western blotting revealed that the major immunoreactive proteins were Kv1.1 and Kv1.2 in both DRs and VRs. Quantitative analysis indicated that levels of Kv1.1 and Kv1.2 protein were significantly higher in DRs than VRs. Immunohistochemical examination showed that Kv1.1 and Kv1.2 were colocalized in juxtaparanodal regions of axons in both DRs and VRs. Finally, immunoprecipitation experiments revealed that Kv1.1 and Kv1.2 were coassembled. These findings indicate that Kv1 subtypes in DRs and VRs are somewhat different from those in spinal cord, and that the numbers of Kv1.1 and Kv1.2 channels are higher in DRs than VRs.