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The Structural Basis For the Dual Effects of Fatty Acids on Kv4 Channel Function
Author(s) -
Timoney Gabriela Garcia,
Spicer Lori M,
Boland Linda M
Publication year - 2009
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.23.1_supplement.703.16
Subject(s) - gating , potassium channel , inhibitory postsynaptic potential , biophysics , chemistry , mutagenesis , arachidonic acid , polyunsaturated fatty acid , microbiology and biotechnology , patch clamp , biochemistry , serine , electrophysiology , mutant , alanine , amino acid , biology , neuroscience , fatty acid , phosphorylation , receptor , enzyme , gene
Polyunsaturated fatty acids (PUFAs), including arachidonic acid (AA) and docosahexanoic acid (DHA), modulate fast‐inactivating Kv4/KChIP potassium channels, speeding inactivation by inhibiting the outward potassium current. These channels are localized to post‐synaptic regions of neurons and are linked to synaptic plasticity in the brain. This research is designed to identify structural determinants and a molecular mechanism PUFA inhibition of Kv4/KChIP channel. Recombinant channel subunits are expressed in frog oocytes and studied by two electrode voltage clamp electrophysiology. Using site‐directed mutagenesis, we substituted serine or alanine for a highly conserved threonine in the pore region. The T370S mutation largely prevented PUFA inhibition of outward potassium current, greatly reduced the kinetic effect of PUFAs on channels co‐expressed with KChIPs, and induced an unexpected leftward shift in the activation curve of the macroscopic current. To test the impact of this change in activation gating, a mutation in a conserved arginine of the S4 voltage sensor region of Kv4 channels was tested, inducing a similar leftward shift in activation gating, but failing to prevent inhibitory effects of PUFAs on outward current, when co‐expressed with KChIPs. This suggests that the ability of the T370S pore mutant to prevent PUFA inhibition of the current is not a result of the change in activation gating.