title: Endothelial SK3 channel-associated Ca2+ microdomains modulate blood pressure.
abstract: Activation of vascular endothelial small- (KCa2.3, SK3) or intermediate- (KCa3.1, IK1) conductance Ca(2+)-activated potassium channels induces vasorelaxation via an endothelium-derived hyperpolarization (EDH) pathway. Although the activation of SK3 and IK1 channels converges on EDH, their subcellular effects on signal transduction are different and not completely clear. In this study, a novel endothelium-specific SK3 knockout (SK3(-/-)) mouse model was utilized to specifically examine the contribution of SK3 channels to mesenteric artery vasorelaxation, endothelial Ca(2+) dynamics, and blood pressure. The absence of SK3 expression was confirmed using real-time quantitative PCR and Western blot analysis. Functional studies showed impaired EDH-mediated vasorelaxation in SK3(-/-) small mesenteric arteries. Immunostaining results from SK3(-/-) vessels confirmed the absence of SK3 and further showed altered distribution of transient receptor potential channels, type 4 (TRPV4). Electrophysiological recordings showed a lack of SK3 channel activity, while TRPV4-IK1 channel coupling remained intact in SK3(-/-) endothelial cells. Moreover, Ca(2+) imaging studies in SK3(-/-) endothelium showed increased Ca(2+) transients with reduced amplitude and duration under basal conditions. Importantly, SK3(-/-) endothelium lacked a distinct type of Ca(2+) dynamic that is sensitive to TRPV4 activation. Blood pressure measurements showed that the SK3(-/-) mice were hypertensive, and the blood pressure increase was further enhanced during the 12-h dark cycle when animals are most active. Taken together, our results reveal a previously unappreciated SK3 signaling microdomain that modulates endothelial Ca(2+) dynamics, vascular tone, and blood pressure.
authors.affiliation: Department of Physiology and Cell Biology, University of South Alabama, Mobile, Alabama;
authors.forename: Fui C
authors.initials: FC
authors.lastname: Yap
authors.affiliation: Department of Physiology and Cell Biology, University of South Alabama, Mobile, Alabama;
authors.forename: David S
authors.initials: DS
authors.lastname: Weber
authors.affiliation: Department of Physiology and Cell Biology, University of South Alabama, Mobile, Alabama;
authors.forename: Mark S
authors.initials: MS
authors.lastname: Taylor
authors.affiliation: Department of Physiology and Cell Biology, University of South Alabama, Mobile, Alabama;
authors.forename: Mary I
authors.initials: MI
authors.lastname: Townsley
authors.affiliation: Department of Cellular and Integrative Physiology, Indiana University, Indianapolis, Indiana;
authors.forename: Brian S
authors.initials: BS
authors.lastname: Comer
authors.affiliation: Department of Obstetrics and Gynecology, Oregon Health & Science University, Portland, Oregon; and.
authors.forename: James
authors.initials: J
authors.lastname: Maylie
authors.affiliation: Vollum Institute, Oregon Health & Science University, Portland, Oregon.
authors.forename: John P
authors.initials: JP
authors.lastname: Adelman
authors.affiliation: Department of Physiology and Cell Biology, University of South Alabama, Mobile, Alabama; mlin@southalabama.edu.
authors.forename: Mike T
authors.initials: MT
authors.lastname: Lin
mesh_terms: D000204:Activity Cycles; D000818:Animals; D001794:Blood Pressure; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling; D042783:Endothelial Cells / Q000378:metabolism*; D020022:Genetic Predisposition to Disease; D006973:Hypertension / Q000235:genetics / Q000378:metabolism* / Q000503:physiopathology; D051660:Intermediate-Conductance Calcium-Activated Potassium Channels / Q000378:metabolism; D021962:Membrane Microdomains / Q000378:metabolism*; D008564:Membrane Potentials; D008638:Mesenteric Arteries / Q000378:metabolism*; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010641:Phenotype; D051640:Small-Conductance Calcium-Activated Potassium Channels / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D050916:TRPV Cation Channels / Q000378:metabolism; D013997:Time Factors; D014664:Vasodilation
chemical_list: D051660:Intermediate-Conductance Calcium-Activated Potassium Channels; C496900:Kcnn3 protein, mouse; D051640:Small-Conductance Calcium-Activated Potassium Channels; D050916:TRPV Cation Channels; C486576:Trpv4 protein, mouse; D002118:Calcium
keywords: calcium microdomain; endothelium; intermediate-conductance Ca2+-activated potassium channel; small conductance Ca2+-activated potassium channel; transient receptor potential vanilloid 4