Mechanism of arachidonic acid modulation of the T-type Ca2+ channel α1G

被引:47
作者
Talavera, K [1 ]
Staes, M [1 ]
Janssens, A [1 ]
Droogmans, G [1 ]
Nilius, B [1 ]
机构
[1] Catholic Univ Louvain, Fysiol Lab, B-3000 Louvain, Belgium
关键词
low voltage-activated calcium channel; fatty acid; kinetic model; inactivation; mutant;
D O I
10.1085/jgp.200409050
中图分类号
Q4 [生理学];
学科分类号
071003 ;
摘要
Arachidonic acid (AA) modulates T-type Ca2+ channels and is therefore a potential regulator of diverse cell functions, including neuronal and cardiac excitability. The underlying mechanism of modulation is unknown. Here we analyze the effects of AA on the T-type Ca2+ channel alpha(1G) heterologously expressed in HEK-293 cells. AA inhibited alpha(1G) Currents within a few minutes, regardless of preceding exposure to inhibitors of AA metabolism (ETYA and 17-ODYA). Current inhibition was also observed in cell-free inside-out patches, indicating a membrane-delimited interaction of AA with the channel. AA action was consistent with a decrease of the open probability without changes in the size of unitary currents. AA shifted the inactivation curve to more negative potentials, increased the speed of macroscopic inactivation, and decreased the extent of recovery from inactivation at -80 mV but not at -110 mV. AA induced a slight increase of activation near the threshold and did not significantly change the deactivation kinetics or the rectification pattern. We observed a tonic Current inhibition, regardless of whether the channels were held in resting or inactivated states during AA perfusion, suggesting a state-independent interaction with the channel. Model simulations indicate that AA inhibits T-type currents by switching the channels into a nonavailable conformation and by affecting transitions between inactivated states, which results in the negative Shift Of the inactivation curve. Slow-inactivating alpha(1G) mutants showed an increased affinity for AA with respect to the wild type. indicating that the structural determinants of fast inactivation are involved in the AA-channel interaction.
引用
收藏
页码:225 / 238
页数:14
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