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Chronic Hypoxia Downregulates Colocalization of PKG with its Target BK Channel Proteins in Ovine Cerebral Arteries
Author(s) -
Thorpe Richard Burdette,
Williams James M,
Pearce William J
Publication year - 2016
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.30.1_supplement.985.2
Subject(s) - colocalization , hypoxia (environmental) , cerebral arteries , medicine , endocrinology , chemistry , biology , microbiology and biotechnology , organic chemistry , oxygen
BACKGROUND Previous studies have shown that chronic hypoxia ablates the endothelium‐dependent NO‐mediated vasorelaxation pathway of which protein kinase G (PKG) is a key effector. Direct activation of PKG likewise demonstrates attenuated PKG influence on 5HT‐induced vascular tone in chronic hypoxic cerebral arteries compared with normoxic arteries. Furthermore, these effects have been shown to correlate with reduced BK channel activity (potassium currents). Taken together, this suggests that the direct influence of PKG on BK channel function is diminished in conditions of chronic hypoxia. OBJECTIVE Given that PKG phosphorylates multiple known targets, this present study explores the hypothesis that the proximal association of PKG with its target BK‐channel proteins is altered by chronic hypoxia, and that this diminished colocalization accounts for a significant loss of function with regards to cerebral vasorelaxation.METHODS Pregnant and Non‐Pregnant ewes were held at sea level (normoxic) or at 3820m (hypoxic) for the final 110 days of gestation. Middle cerebral arteries from non‐pregnant adults and term fetal sheep were prepared for organ culture with ±8‐pCPT‐cGMP. Colocalization of PKG with the alpha and beta isoforms of the BK channel proteins, as well as colocalization of BK‐alpha and ‐beta proteins with each other, was determined by confocal microscopy. RESULTS Chronic hypoxia reduced the ability of PKG to localize with its target BK channel proteins. Chronic hypoxia also reduced the colocalization of BK‐alpha with BK‐beta channel proteins. Activation of PKG with 8‐p‐CPT‐cGMP in organ culture did not overcome these effects of chronic hypoxia on PKG colocalization. CONCLUSIONS PKG‐mediated activation of BK channels accounts for a significant portion of PKG‐induced vasorelaxation in ovine middle cerebral arteries. Chronic hypoxia attenuates the ability of PKG to associate with BK channel proteins, and thereby attenuates the influence of PKG on BK channel activity. This loss of association explains in part how chronic hypoxia ablates the ability of PKG to relax 5HT‐induced vascular tone. Support or Funding Information The work reported here was supported by USPHS Grants HL54120, HD31266, HL64867 and the Loma Linda University School of Medicine