Abstract
The molecular mechanism of endoplasmic reticulum (ER) stress in vascular pathophysiology remains inadequately understood. We studied the role of ER stress in homocysteine-induced impairment of coronary dilator function, with uncovering the molecular basis of the effect of ER stress on smooth muscle large-conductance Ca2+-activated K+ (BKCa) channels. The vasodilatory function of BKCa channels was studied in a myograph using endothelium-denuded porcine small coronary arteries. Primary cultured porcine coronary artery smooth muscle cells were used for mRNA and protein measurements and current recording of BKCa channels. Homocysteine inhibited vasorelaxant response to the BKCachannel opener NS1619, lowered BKCa β1 subunit protein level and suppressed BKCa current. Inhibition of ER stress restored BKCa β1 protein level and NS1619-evoked vasorelaxation. Selective blockade of the PKR-like ER kinase (PERK) yielded similarly efficient restoration of BKCa β1, preserving BKCa current and BKCa-mediated vasorelaxation. The restoration of BKCa β1 by PERK inhibition was associated with reduced atrogin-1 expression and decreased nuclear localization of forkhead box O transcription factor 3a (FoxO3a). Silencing of atrogin-1 prevented homocysteine-induced BKCa β1 loss and silencing of FoxO3a prevented atrogin-1 upregulation induced by homocysteine, accompanied by preservation of BKCa β1 protein level and BKCa current. ER stress mediates homocysteine-induced BKCa channel inhibition in coronary arteries. Activation of FoxO3a by PERK branch underlies the ER stress-mediated BKCa inhibition through a mechanism involving ubiquitin ligase-enhanced degradation of the channel β1 subunit.
Highlights
Calcium-activated potassium (KCa) channels contribute to the control of vascular tone
Exposure to homocysteine for 24 h did not alter the resting force of coronary arteries and there were no significant differences among groups with regard to U46619-induced pre-contraction, whereas the NS1619induced vasorelaxation was attenuated (Rmax: 61.9±2.3% vs. 80.6±3.6% in control, p
These results suggest that activation of PKR-like ER kinase (PERK) pathway of ER stress is responsible for homocysteine-induced atrogin-1 expression in porcine coronary artery smooth muscle cells (PCASMCs)
Summary
Calcium-activated potassium (KCa) channels contribute to the control of vascular tone. Being abundantly expressed in vascular smooth muscle cells, functional large-conductance KCa (BKCa) channel is a tetrameric assembly of pore-forming α-subunits in complex with auxiliary β-subunits by which the channel activity is tightly regulated [1]. Activation of BKCachannels opposes vasoconstriction via hyperpolarizing cell membrane limiting extracellular Ca2+ entry through voltagedependent Ca2+ channels in smooth muscle cells [2]. Disturbed function of BKCa channel has been found to be associated with various cardiovascular disorders such as hypertension [7] and diabetes [8]. Previous studies reported the inhibitory effect of homocysteine on smooth muscle BKCa channels. The BKCa current was observed to be significantly suppressed in animal and human vascular smooth muscle cells subjected to homocysteine exposure [16, 17]. The mechanisms by which homocysteine inhibits BKCa channels remain poorly studied
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
