title: Arachidonic acid activation of BKCa (Slo1) channels associated to the β1-subunit in human vascular smooth muscle cells.
abstract: Arachidonic acid (AA) is a polyunsaturated fatty acid involved in a complex network of cell signaling. It is well known that this fatty acid can directly modulate several cellular target structures, among them, ion channels. We explored the effects of AA on high conductance Ca(2+)- and voltage-dependent K(+) channel (BKCa) in vascular smooth muscle cells (VSMCs) where the presence of β1-subunit was functionally demonstrated by lithocholic acid activation. Using patch-clamp technique, we show at the single channel level that 10 μM AA increases the open probability (Po) of BKCa channels tenfold, mainly by a reduction of closed dwell times. AA also induces a left-shift in Po versus voltage curves without modifying their steepness. Furthermore, AA accelerates the kinetics of the voltage channel activation by a fourfold reduction in latencies to first channel opening. When AA was tested on BKCa channel expressed in HEK cells with or without the β1-subunit, activation only occurs in presence of the modulatory subunit. These results contribute to highlight the molecular mechanism of AA-dependent BKCa activation. We conclude that AA itself selectively activates the β1-associated BKCa channel, destabilizing its closed state probably by interacting with the β1-subunit, without modifying the channel voltage sensitivity. Since BKCa channels physiologically contribute to regulation of VSMCs contractility and blood pressure, we used the whole-cell configuration to show that AA is able to activate these channels, inducing significant cell hyperpolarization that can lead to VSMCs relaxation.
authors.affiliation: GINFIV-CONICET-Grupo de Investigación en Fisiología Vascular, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, Calles 47 y 115, La Plata, 1900, Argentina.
authors.forename: Pedro
authors.initials: P
authors.lastname: Martín
authors.forename: Melisa
authors.initials: M
authors.lastname: Moncada
authors.forename: Nicolás
authors.initials: N
authors.lastname: Enrique
authors.forename: Agustín
authors.initials: A
authors.lastname: Asuaje
authors.forename: Juan Manuel
authors.initials: JM
authors.lastname: Valdez Capuccino
authors.forename: Carlos
authors.initials: C
authors.lastname: Gonzalez
authors.forename: Verónica
authors.initials: V
authors.lastname: Milesi
mesh_terms: D016718:Arachidonic Acid / Q000378:metabolism* / Q000494:pharmacology; D057809:HEK293 Cells; D006801:Humans; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits / Q000378:metabolism*; D009126:Muscle Relaxation / Q000187:drug effects / Q000502:physiology; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism*; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D021122:Protein Subunits / Q000378:metabolism; D014162:Transfection
chemical_list: C494841:KCNMA1 protein, human; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; D021122:Protein Subunits; D016718:Arachidonic Acid