8.A.17.2.1
Sodium channel β2 or β1B subunit of 215 aas and 1 or 2 TMSs, a large very hydrophobic TMS at the C-terminus, and possibly a much more hydrophilic TMS at the N-terminus.  Distinctive biophysical properties of INa in atrial and ventricular myocytes can be attributed to inhomogeneous expression of NaVβ2 and NaVβ4 subunits, and atrial INa is more sensitive to inhibition by dronedarone (Chen et al. 2016). It is crucial for the assembly, expression, and functional modulation of the heterotrimeric complex of the sodium channel. The subunit beta-2 causes an increase in the plasma membrane surface area and in its folding into microvilli. It interacts with TNR and may play a crucial role in clustering and regulation of activity of sodium channels at nodes of Ranvier (Chen et al. 2016).  The voltage-gated sodium (Na_V) channel is critical for cardiomyocyte function since it is responsible for action potential initiation and its propagation throughout the cell. It consists of a protein complex made of a pore forming α subunit and associated β subunits, which regulate α subunit function and subcellular localization (Cortada et al. 2024).