Abstract 14952: Disruption of a Newly Identified Complex Between soluble Guanylyl Cyclase and Connexin 43 is Potentially Linked to Cardiac Contractile Dysfunction
Background: The role of nitric oxide (NO) in regulation of excitation-contraction (EC) coupling remains controversial. NO activates soluble Guanylyl Cyclase (sGC), a heme-containing heterodimer (α/ß subunits), to increase cGMP production and regulate downstream targets such as Protein Kinase G (PKG) and phosphodiesterases (PDE). Intercalated discs (ID) are essential for electro-mechanical coupling between cardiomyocytes. Connexin 43 (Cx43) via formation of gap junctions at the ID mediate the electrical coupling. Cx43 targeting and assembly at the ID involved phosphorylation by many protein kinases, including cAMP-activated PKA. In various cardiomyopathies such as arrhythmia, Cx43 is relocated from ID to the lateral membrane of cardiomyocytes. Recently, we discovered that sGCβ is localized at the ID with Cx43 and PDE3A, using immunofluorescence (IF) and Triton/Urea heart fractionation. Importantly, we showed by co-immunoprecipitation (co-IP) that sGC physically interacts with Cx43 in the heart.
Hypothesis: Cx43 assembly and function at the ID through PKA-dependent Cx43 phosphorylation depends on NO-sGC-cGMP microdomain inducing inhibition of PDE3A.
Methods and Results: To assess the role and relevance of the sGC-Cx43 complex, we used Angiotensin II (AngII) to induce cardiac hypertrophy and arrhythmia in wild-type (WT) mice and sGCα-KO mice, which are depleted for sGC activity. Co-IP indicates that sGC-Cx43 complex is decreased in AngII-treated WT (n=5), independently of decreased Cx43 expression and IF showed Cx43 lateralization. NO-dependent cGMP in membrane fraction of AngII-hearts was decreased by 50%. Conversely, in sGCα-KO mice Cx43-sGC complex was reduced and even more so with AngII treatment. In addition to a significant increased cardiac hypertrophy in sGCα-KO mice (heart to body weight ratio KO: 5.16±0.19 vs WT: 4.45±0.04, n=4-8, P<0.05), preliminary EKG (n=4) indicates that sGCα-KO mice suffer from cardiac arrhythmia with, intriguingly, alteration in P waves.
Conclusion: Altogether, our data suggest that sGC via modulation of Cx43 location at ID is potentially involved in EC regulation. We currently explore the mechanism underlying these observations with in vivo, biochemical approaches and imaging.
Author Disclosures: P. Crassous: None. C. Huang: None. P. Shu: None. P. Brouckaert: None. L. Xie: None. A. Beuve: None.
- © 2015 by American Heart Association, Inc.