Journal
AMERICAN JOURNAL OF PHYSIOLOGY-CELL PHYSIOLOGY
Volume 311, Issue 2, Pages C255-C268Publisher
AMER PHYSIOLOGICAL SOC
DOI: 10.1152/ajpcell.00277.2015
Keywords
potassium channels; PUFAs; inactivation
Categories
Funding
- Heart and Stroke Foundation of British Columbia and Yukon [G-15-0009086]
- Natural Sciences and Engineering Research Council of Canada [RGPIN-04759 NSERC]
- NSERC Canada Graduate Scholarship
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Polyunsaturated fatty acids (PUFAs) modulate voltage-gated K+ channel inactivation by an unknown site and mechanism. The effects of omega-6 and omega-3 PUFAs were investigated on the heterologously expressed K(v)1.4 channel. PUFAs inhibited wild-type K(v)1.4 during repetitive pulsing as a result of slowing of recovery from inactivation. In a mutant K(v)1.4 channel lacking N-type inactivation, PUFAs reversibly enhanced C-type inactivation (Kd, 15-43 mu M). C-type inactivation was affected by extracellular H+ and K+ as well as PUFAs and there was an interaction among the three: the effect of PUFAs was reversed during acidosis and abolished on raising K+. Replacement of two positively charged residues in the extracellular pore (H508 and K532) abolished the effects of the PUFAs (and extracellular H+ and K+) on C-type inactivation but had no effect on the lipoelectric modulation of voltage sensor activation, suggesting two separable interaction sites/mechanisms of action of PUFAs. Charge calculations suggest that the acidic head group of the PUFAs raises the pK(a) of H508 and this reduces the K+ occupancy of the selectivity filter, stabilizing the C-type inactivated state.
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