Abstract
Na v1.5 is the principal voltage-gated sodium channel expressed in heart, and is also expressed at lower abundance in embryonic dorsal root ganglia (DRG) with little or no expression reported postnatally. We report here the expression of Na v1.5 mRNA isoforms in adult mouse and rat DRG. The major isoform of mouse DRG is Na v1.5a, which encodes a protein with an IDII/III cytoplasmic loop reduced by 53 amino acids. Western blot analysis of adult mouse DRG membrane proteins confirmed the expression of Na v1.5 protein. The Na + current produced by the Na v1.5a isoform has a voltage-dependent inactivation significantly shifted to more negative potentials (by ∼ 5 mV) compared to the full-length Na v1.5 when expressed in the DRG neuroblastoma cell line ND7/23. These results imply that the alternatively spliced exon 18 of Na v1.5 plays a role in channel inactivation and that Na v1.5a is likely to make a significant contribution to adult DRG neuronal function.
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