Antisense-mediated post-transcriptional silencing of SCN1B gene modulates sodium channel functional expression

Background information Voltage-dependent sodium channels are membrane proteins essential for cell excitability. They are composed by a pore-forming ?-subunit and one or more ? subunits. Nine ? subunit and five ? subunit isoforms have been identified in mammals: ?1, its splice variant ?1B, ?2, ?3 and ?4. Although they do not form the ion channel pore, ? subunits modulate both function as well as expression of sodium channels on cell membrane. Results To investigate the role of ?1 subunit on the modulation of sodium channel expression, we silenced this auxiliary subunit with specific antisense oligonucleotides (ASONs) in two rat cell lines, the GH3 and the H9C2, from neuro-ectoderm and cardiac myocyte origin, respectively. Treatment of cells with ASONs determined a reduction of about 50% of ?1 subunit mRNA and protein expression in both cell lines. We found that this level of ?1 subunit silencing resulted in an overall decrease of ? subunit mRNA, protein expression and a decrease of sodium current density, without altering significantly the voltage-dependent and kinetic properties of the currents. In GH3 cells, the ?1 subunit silencing reduced the expression of Nav1.1, Nav1.3 and Nav1.6 isoforms, whereas the Nav 1.2 isoform expression remained unaltered. The expression of the only ? subunit present in H9C2 cells, the Nav1.5, was also reduced by ?1 subunit silencing. Conclusions These results indicate that the ?1 subunit may exert an isoform-specific fine-tuned modulation of sodium channel expression