Modulation of K(Ca)3.1 channels by eicosanoids, omega-3 fatty acids, and molecular determinants.
BACKGROUND
Cytochrome P450- and ω-hydrolase products (epoxyeicosatrienoic acids (EETs), hydroxyeicosatetraeonic acid (20-HETE)), natural omega-3 fatty acids (ω3), and pentacyclic triterpenes have been proposed to contribute to a wide range of vaso-protective and anti-fibrotic/anti-cancer signaling pathways including the modulation of membrane ion channels. Here we studied the modulation of intermediate-conductance Ca(2+)/calmodulin-regulated K(+) channels (K(Ca)3.1) by EETs, 20-HETE, ω3, and pentacyclic triterpenes and the structural requirements of these fatty acids to exert channel blockade.


RESULTS
We studied modulation of cloned human hK(Ca)3.1 and the mutant hK(Ca)3.1(V275A) in HEK-293 cells, of rK(Ca)3.1 in aortic endothelial cells, and of mK(Ca)3.1 in 3T3-fibroblasts by inside-out and whole-cell patch-clamp experiments, respectively. In inside-out patches, Ca(2+)-activated hK(Ca)3.1 were inhibited by the ω3, DHA and α-LA, and the ω6, AA, in the lower µmolar range and with similar potencies. 5,6-EET, 8,9-EET, 5,6-DiHETE, and saturated arachidic acid, had no appreciable effects. In contrast, 14,15-EET, its stable derivative, 14,15-EEZE, and 20-HETE produced channel inhibition. 11,12-EET displayed less inhibitory activity. The K(Ca)3.1(V275A) mutant channel was insensitive to any of the blocking EETs. Non-blocking 5,6-EET antagonized the inhibition caused by AA and augmented cloned hK(Ca)3.1 and rK(Ca)3.1 whole-cell currents. Pentacyclic triterpenes did not modulate K(Ca)3.1 currents.


CONCLUSIONS
Inhibition of K(Ca)3.1 by EETs (14,15-EET), 20-HETE, and ω3 critically depended on the presence of electron double bonds and hydrophobicity within the 10 carbons preceding the carboxyl-head of the molecules. From the physiological perspective, metabolism of AA to non-blocking 5,6,- and 8,9-EET may cause AA-de-blockade and contribute to cellular signal transduction processes influenced by these fatty acids.
Faculty of Medicine, Philipps-University Marburg & Medical Center I, Clemenshospital/University Hospital of University Münster, 48153 Münster, Germany.
Michael
M
Kacik
Aragon Institute of Health Sciences I+CS/IIS, 50009 Zaragoza, Spain.
Aida
A
Oliván-Viguera
Aragon Institute of Health Sciences I+CS/IIS, 50009 Zaragoza, Spain; Fundación Agencia Aragonesa para la Investigación y Desarrollo (ARAID), 50018 Zaragoza, Spain.
Ralf
R
Köhler
D016475:3T3 Cells; D000818:Animals; D020013:Calcium Signaling / Q000187:drug effects* / Q000502:physiology; D015777:Eicosanoids / Q000494:pharmacology*; D015525:Fatty Acids, Omega-3 / Q000494:pharmacology*; D057809:HEK293 Cells; D006801:Humans; D051660:Intermediate-Conductance Calcium-Activated Potassium Channels / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D051379:Mice
D015777:Eicosanoids; D015525:Fatty Acids, Omega-3; D051660:Intermediate-Conductance Calcium-Activated Potassium Channels; C496923:KCNN4 protein, human; C496925:Kcnn4 protein, mouse