Molecular cloning, distribution and functional analysis of the NA V1.6. Voltage-gated sodium channel from human brain

Abstract

We have cloned and expressed the full-length human Na V1.6 sodium channel cDNA. Northern analysis showed that the hNa V1.6 gene, like its rodent orthologues, is abundantly expressed in adult brain but not other tissues including heart and skeletal muscle. Within the adult brain, hNa V1.6 mRNA is widely expressed with particularly high levels in the cerebellum, occipital pole and frontal lobe. When stably expressed in human embryonic kidney cells (HEK293), the hNa V1.6 channel was found to be very similar in its biophysical properties to human Na V1.2 and Na V1.3 channels [Eur. J. Neurosci. 12 (2000) 4281–4289; Pflügers Arch. 441 (2001) 425–433]. Only relatively subtle differences were observed, for example, in the voltage dependence of gating. Like hNa V1.3 channels, hNa V1.6 produced sodium currents with a prominent persistent component when expressed in HEK293 cells. These persistent currents were similar to those reported for the rat Na V1.2 channel [Neuron 19 (1997) 443–452], although they were not dependent on over-expression of G protein βγ subunits. These data are consistent with the proposal that Na V1.6 channels may generate the persistent currents observed in cerebellar Purkinje neurons [J. Neurosci. 17 (1997) 4157–4536]. However, in our hNa V1.6 cell line we have been unable to detect the resurgent currents that have also been described in Purkinje cells. Although Na V1.6 channels have been implicated in producing these resurgent currents [Neuron 19 (1997) 881–891], our data suggest that this may require modification of the Na V1.6 α subunit by additional factors found in Purkinje neurons but not in HEK293 cells.