Figure 4.

Magi-1 knockdown decreases Na_V1.8 plasma membrane expression. A) Representative whole-cell voltage clamp current traces of total I_Na and TTX-resistant I_Na in cultured DRG neurons 3 d after transfection with Magi-1–targeting siRNA or nontargeting scrambled siRNA. B) Current density analysis of I_Na with different conditions. Sodium currents in neurons were recorded in either the presence or absence of 250 nM TTX. The total and TTX-resistant I_Na was significantly reduced after siRNA-mediated Magi-1 knockdown in cultured DRG neurons. A total of 9–12 cells per experimental group were analyzed, and values are expressed as means ± sem. C) Quantification of peak I_Na and TTX-resistant peak I_Na (at voltage step −20 mV) after Magi-1 knockdown. A total of 9–12 cells per experimental group were analyzed, and values are expressed as means ± sem [ANOVA, F_(3,26) = 66.24]. *P < 0.0106, ***P < 0.001 vs. respective controls (scrambled siRNA with or without TTX). D) Representative immunoblots from surface biotinylation experiments of DRG neurons depicting reduced Na_V1.8 surface expression after Magi-1 knockdown (left). Quantification of Na_V1.8 surface expression is shown on the right. For quantification, 4 independent DRG cultures per experimental condition were analyzed, and values are expressed as ± sem [ANOVA, F_(2,6) = 7.319]. *P < 0.05 vs. respective controls.