Coexpression with beta(1)-subunit modifies the kinetics and fatty acid block of hH1(alpha) Na(+) channels.
Voltage-gated cardiac Na(+) channels are composed of alpha- and beta(1)-subunits. In this study beta(1)-subunit was cotransfected with the alpha-subunit of the human cardiac Na(+) channel (hH1(alpha)) in human embryonic kidney (HEK293t) cells. The effects of this coexpression on the kinetics and fatty acid-induced suppression of Na(+) currents were assessed. Current density was significantly greater in HEK293t cells coexpressing alpha- and beta(1)-subunits (I(Na,alpha beta)) than in HEK293t cells expressing alpha-subunit alone (I(Na,alpha)). Compared with I(Na,alpha), the voltage-dependent inactivation and activation of I(Na,alpha beta) were significantly shifted in the depolarizing direction. In addition, coexpression with beta(1)-subunit prolonged the duration of recovery from inactivation. Eicosapentaenoic acid [EPA, C20:5(n-3)] significantly reduced I(Na,alpha beta) in a concentration-dependent manner and at 5 microM shifted the midpoint voltage of the steady-state inactivation by -22 +/- 1 mV. EPA also significantly accelerated channel transition from the resting state to the inactivated state and prolonged the recovery time from inactivation. Docosahexaenoic acid [C22:6(n-3)], alpha-linolenic acid [C18:3(n-3)], and conjugated linoleic acid [C18:2(n-6)] at 5 microM significantly inhibited both I(Na,alpha beta) and I(Na,alpha.) In contrast, saturated and monounsaturated fatty acids had no effects on I(Na,alpha beta). This finding differs from the results for I(Na,alpha), which was significantly inhibited by both saturated and unsaturated fatty acids. Our data demonstrate that functional association of beta(1)-subunit with hH1(alpha) modifies the kinetics and fatty acid block of the Na(+) channel.
Xiao
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YF
Charles A. Dana Research Institute and Harvard-Thorndike Laboratory, Cardiovascular Division, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts 02215, USA. yxaio@caregroup.harvard.edu
Wright
S N
SN
Wang
G K
GK
Morgan
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JP
Leaf
A
A
D002460:Cell Line; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology; D004281:Docosahexaenoic Acids / Q000494:pharmacology; D015118:Eicosapentaenoic Acid / Q000494:pharmacology; D004558:Electric Stimulation; D005230:Fatty Acids, Nonesterified / Q000494:pharmacology*; D005231:Fatty Acids, Unsaturated / Q000494:pharmacology*; D006801:Humans; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology; D007668:Kidney; D007700:Kinetics; D046911:Macromolecular Substances; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009206:Myocardium / Q000378:metabolism; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D026941:Sodium Channel Blockers; D015222:Sodium Channels / Q000235:genetics / Q000502:physiology*; D014162:Transfection; D014212:Tretinoin / Q000494:pharmacology*
D005230:Fatty Acids, Nonesterified; D005231:Fatty Acids, Unsaturated; D046911:Macromolecular Substances; D011994:Recombinant Proteins; D026941:Sodium Channel Blockers; D015222:Sodium Channels; D004281:Docosahexaenoic Acids; D014212:Tretinoin; D015118:Eicosapentaenoic Acid