The zebrafish β1 subunit modulates the biophysical properties of the zebrafish sodium channel α subunit zNa
1.5 in CHO cells. A) Typical whole-cell sodium current trace of zNav1.5 following expression of the pBK-CMV-zscn5a expression vector in CHO cells (n = 8). B) Typical whole-cell sodium current trace of zNav1.5 + zβ1 (variant D) following co-expression of pBK-CMV-zscn5a and pGFP-IRES-zβ1D. zβ1 significantly increased the peak amplitude of sodium current by 68% (p = 0.005) at a -30 millivolt (mV) depolarizing pulse (n = 5). C) Current-voltage relationship demonstrating an increase in sodium current at every test potential between -50 and +50 mV. Filled circles = zNav1.5 alone; open circles = zNav1.5 + zβ1. D) Voltage dependence of activation (zNav1.5 alone, n = 8; zNav1.5 + zβ1, n = 5). E) Voltage-dependence of inactivation. (zNav1.5 alone, n = 5; zNav1.5 + zβ1, n = 6). F) Recovery from inactivation (zNav1.5 alone, n = 4; zNav1.5 + zβ1, n = 6). Pulse protocol in inset. Summary data is reported in table 6.