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Negative charges in the DIII–DIV linker of human skeletal muscle Na + channels regulate deactivation gating
Author(s) -
Groome James R.,
Fujimoto Esther,
Ruben Peter C.
Publication year - 2003
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.2003.00085.x
Subject(s) - chemistry , gating , anatomy , pacemaker potential , peristalsis , electrophysiology , biophysics , ion channel , skeletal muscle , medicine , neuroscience , biology , receptor , biochemistry
Charge reversing, neutralizing and substituting mutations at D1309 and EE1314,15 in the DIII–DIV linker of the human skeletal muscle sodium channel hNa v 1.4 were constructed and expressed in Xenopus oocytes. The effects of these mutations on conductance, inactivation and deactivation were determined using on‐cell macropatches. D1309R caused a depolarizing shift of the conductance–voltage ( g ( V )) curve and increased the apparent valency of activation. D1309R and EE1314,15RR increased time to peak activation. D1309R caused a depolarizing shift of the steady‐state fast inactivation curve, whereas EE1314,15RR produced a hyperpolarizing shift and decreased the apparent valency. Charge reversal at either D1309 or EE1314,15 slowed open‐state fast inactivation and accelerated closed‐state fast inactivation. D1309R accelerated recovery from fast inactivation, whereas EE1314,15RR and EE1314,15QQ slowed recovery. Deactivation from the inactivated state was determined by the delay in the onset to recovery from fast inactivation. Recovery delay was abbreviated for D1309R but was prolonged for EE1314,15RR and EE1314,15QQ. Open‐state deactivation was determined from the time constant of the decay (τ D ) of tail currents. τ D was slowed by D1309R, D1309E, EE1314,15RR and EE1314,15QQ. Our findings suggest an important role in deactivation gating in hNa v 1.4 for the negative cluster of charge at EE1314,15. These and previous findings suggest that clusters of negatively and positively charged residues in the hNa v 1.4 DIII–DIV linker differentially regulate the kinetics of fast inactivation.