Alterations to Protein Level and Cellular Location of the BKCa α‐Subunit in the Coronary Vasculature are Dependent on Sex Hormones, Metabolic Status, and Species: A Retrospective Study in Multiple Swine Models of Pressure Overload‐Induced Heart Failure

Abstract

We have previously reported coronary vascular dysfunction mediated by the large conductance Ca2+‐activated K+ channel (BKCa) in swine models of pressure overload‐induced heart failure (HF). The purpose of this study was to determine whether the observed dysfunction is due to a change in the protein level or cellular location of the pore‐forming α‐subunit of the BKCa channel (α‐BKCa) in female swine with HF accompanied by a number of different experimental conditions including ovariectomy, and obesity/metabolic syndrome. We hypothesized that there would be a decrease in total α‐BKCa, as well as a decrease in membrane bound α‐BKCa in all HF animals. We retrospectively analyzed two cohorts of female swine. The first was composed of Yucatan mini‐swine, fed standard chow and assigned into four groups: control intact (Y‐CON, n=5), aortic‐banded intact (AB, n=7), control ovariectomized (OVX, n=6), and aortic‐banded ovariectomized (AB‐OVX, n=7). The second was composed of Ossabaw swine, all intact and assigned into two groups: standard chow fed control (O‐CON, n=5) and Western‐diet fed aortic‐banded (WD‐AB, n=3). Total vascular α‐BKCa protein was measured in coronary arterioles. Biotinylation of membrane bound α‐BKCa was performed to determine the proportion of membrane versus cytosolic expression of α‐BKCa and measured in the right coronary artery. Protein levels were then quantified via Western blot. Results showed no change in total α‐BKCa in the Yucatan cohort; however, there was a significant decrease in total α‐BKCa in the WD‐AB Ossabaws compared to O‐CON (P<0.05). Quantification of the distribution of α‐BKCa between plasma membrane and cytosolic fractions in the Yucatan HF model revealed an increase in membrane bound α‐BKCa in the OVX animals (P<0.05 vs CON) and AB‐OVX animals (P=0.067 vs CON) and a subsequent decrease in cytosolic α‐BKCa in the same groups. We found no significant changes in α‐BKCa membrane versus cytosol distribution in the Ossabaw pigs. A species‐related difference was found when comparing Yucatan versus Ossabaw pigs, evident as an increase in membrane bound α‐BKCa (P<0.05) and subsequent decrease in cytosolic α‐BKCa (P<0.05), as well as an increase in the ratio of membrane to cytosolic α‐BKCa (P<0.05) in O‐CON compared to Y‐CON animals. In conclusion, BKCa‐mediated coronary vascular dysfunction in a setting of pressure overload‐induced HF may be due to changes in the protein level and cellular location of the pore‐forming α‐subunit, and dependent on female sex hormones, associated comorbidities, and pig species.Support or Funding InformationNIH R01 HL112998, PI: Craig A. Emter; AHA 16POST2776005, PI: T. Dylan Olver; University of Missouri Research Board, PI's: Craig A. Emter and R. Scott Rector; NIH K01 HL125503, PI: Jaume PadillaThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.