The augmentation of BK channel activity by nitric oxide signaling in rat cerebral arteries involves co-localized regulatory elements.
Large conductance, Ca2+-activated K+(BK) channels control cerebrovascular tone; however, the regulatory processes influencing these channels remain poorly understood. Here, we investigate the cellular mechanisms underlying the enhancement of BK current in rat cerebral arteries by nitric oxide (NO) signaling. In isolated cerebral myocytes, BK current magnitude was reversibly increased by sodium nitroprusside (SNP, 100 μM) and sensitive to the BK channel inhibitor, penitrem-A (100 nM). Fostriecin (30 nM), a protein phosphatase type 2A (PP2A) inhibitor, significantly prolonged the SNP-induced augmentation of BK current and a similar effect was produced by sildenafil (30 nM), a phosphodiesterase 5 (PDE5) inhibitor. Using proximity ligation assay (PLA)-based co-immunostaining, BK channels were observed to co-localize with PP2A, PDE5, and cGMP-dependent protein kinase (cGKI) (spatial restriction < 40 nm); cGKI co-localization increased following SNP exposure. SNP (10 μM) reversibly inhibited myogenic tone in cannulated cerebral arteries, which was augmented by either fostriecin or sildenafil and inhibited by penitrem-A. Collectively, these data suggest that (1) cGKI, PDE5, and PP2A are compartmentalized with cerebrovascular BK channels and determine the extent of BK current augmentation by NO/cGMP signaling, and (2) the dynamic regulation of BK activity by co-localized signaling enzymes modulates NO-evoked dilation of cerebral resistance arteries.
Department of Physiology and Pharmacology and Libin Cardiovascular Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.
Barry D
BD
Kyle
Department of Physiology and Pharmacology and Libin Cardiovascular Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.
Ramesh C
RC
Mishra
Department of Physiology and Pharmacology and Libin Cardiovascular Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.
Andrew P
AP
Braun
D000818:Animals; D002478:Cells, Cultured; D002536:Cerebral Arteries / Q000502:physiology*; D006152:Cyclic GMP / Q000378:metabolism; D054706:Cyclic Nucleotide Phosphodiesterases, Type 5 / Q000032:analysis / Q000378:metabolism; D051036:Large-Conductance Calcium-Activated Potassium Channels / Q000032:analysis / Q000378:metabolism*; D008297:Male; D009569:Nitric Oxide / Q000378:metabolism*; D054648:Protein Phosphatase 2 / Q000032:analysis / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction; D014664:Vasodilation
D051036:Large-Conductance Calcium-Activated Potassium Channels; D009569:Nitric Oxide; D054648:Protein Phosphatase 2; D054706:Cyclic Nucleotide Phosphodiesterases, Type 5; D006152:Cyclic GMP
BK channel; nitric oxide; protein kinase; protein phosphatase; vasodilation