The E1784K mutation in SCN5A is associated with mixed clinical phenotype of type 3 long QT syndrome
J. Clin. Invest. Naomasa Makita, et al. 118:2219 doi:10.1172/JCI34057 [
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Figure 4Gating and trafficking properties of E1784K. (
A) The voltage dependence of steady-state fast inactivation and activation of E1784K, measured with standard pulse protocols shown in insets, were significantly shifted in the hyperpolarizing (–15.0 mV) and depolarizing (+12.5 mV) directions, respectively. (
B) Recovery from inactivation assessed by the double-pulse protocol was nearly identical between WT and E1784K. (
C) Slow inactivation, measured by the double-pulse protocol shown in inset, was significantly enhanced in E1784K (
P < 0.05) in the magnitude of slow inactivation at all prepulse durations from 10 ms to 2,000 ms. (
D) Cells expressing either FLAG-tagged WT or E1784K in the presence or absence of pCD8-IRES-β1 were immunostained with anti-FLAG antibody. Optical sections of Alexa Fluor 488 (green) were obtained using a confocal laser scanning microscope. Upper and lower panels show the
xy-stacked image and the
xy image sliced at
z axis on the
xz and the
yz images, respectively. The
xz and
yz images indicate horizontal and vertical sections at the
x axis and
y axis on the
xy image. Asterisks and scale bars in
xy-stacked images represent anti-CD8 Dynabeads and 5 μm, respectively. Note that both WT and E1784K predominantly localized to the plasma membrane regardless of β1 subunit coexpression. (
E) Membrane expression of Nav1.5 observed in
D was quantified as described in Methods. Fluorescence intensity of Nav1.5 staining at plasma membrane, expressed as percentage relative to that of entire cell area, was comparable between WT and E1784K regardless of β1 subunit coexpression.
