The C-terminal region as a modulator of rNav1.7 and rNav1.8 expression levels

Mammalian cells poorly express rNav1.8 channels. In contrast, rNav1.7 dorsal root ganglion channels have 90-fold higher peak Na+ current densities. We investigated the role of rNav1.7 and rNav1.8 carboxy-termini in modulating the expression of rNav1.7 and rNav1.8 channels in tsA201 cells. Mutations in the ubiquitination site of the C-terminus did not improve rNav1.8 current levels. However, rNav1.8 chimeras containing the entire or the proximal portion of the rNav1.7 C-terminus expressed 3.2-fold and 4.8-fold higher peak current densities, respectively, than parent rNav1.8 channels. We conclude that the two Na+ channels may have different endoplasmic reticulum processing signals.