Neuronal nitric oxide synthase localizes to utrophin expressing intercalated discs and stabilizes their structural integrity.
The neuronal nitric-oxide synthase (nNOS) splice variant nNOSµ is essential for skeletal muscle function. Its localization is dependent on dystrophin, which stabilizes the dystrophin glycoprotein complex (DGC) at the sarcolemma of skeletal muscle fibers. In Duchenne muscular dystrophy (DMD) dystrophin is absent and sarcolemmal nNOS is lost. This leads to functional ischemia due to a decrease in contraction-induced vasodilation. In cardiomyocytes, nNOSµ is believed to be the predominant NOS isoform. However, the association of nNOS with the DGC in the heart is unclear. Here, we report nNOS localization at the intercalated discs (IDs) of cardiomyocytes, where utrophin is highly expressed. In mdx, mdx:utr, nNOSµ knock-out (KO), and mdx:nNOSµ KO mice, we observed a gradual reduction of nNOS at IDs and disrupted ID morphology, compared to wild-type. In mdx:nNOSµ KO mice, but not in mdx or nNOSµ KO mice, we also observed an early development of cardiac fibrosis. These findings suggest that nNOS localization in the heart may not depend exclusively on the presence of dystrophin. Additionally, the β1 subunit of soluble guanylyl cyclase (sGC), responsible for the production of cGMP through nitric oxide (NO) signaling, was also detected at the IDs. Together, our results suggest a new role of nNOS at the IDs for the cGMP-dependent NO pathway and the maintenance of ID morphology.
Department of Cell Biology and Molecular Medicine, Rutgers Biomedical and Health Sciences, New Jersey Medical School, Newark, NJ, 07103, USA.
J Patrick
JP
Gonzalez
Department of Pharmacology, Physiology and Neuroscience, Rutgers Biomedical and Health Sciences, New Jersey Medical School, Newark, NJ, 07103, USA.
Pierre-Antoine
PA
Crassous
Department of Cell Biology and Molecular Medicine, Rutgers Biomedical and Health Sciences, New Jersey Medical School, Newark, NJ, 07103, USA.
Joel S
JS
Schneider
Department of Pharmacology, Physiology and Neuroscience, Rutgers Biomedical and Health Sciences, New Jersey Medical School, Newark, NJ, 07103, USA.
Annie
A
Beuve
Department of Cell Biology and Molecular Medicine, Rutgers Biomedical and Health Sciences, New Jersey Medical School, Newark, NJ, 07103, USA. Electronic address: fraidedi@rutgers.edu.
Diego
D
Fraidenraich
D000818:Animals; D006162:Guanylate Cyclase / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018101:Mice, Inbred mdx; D018345:Mice, Knockout; D032383:Myocytes, Cardiac / Q000201:enzymology* / Q000473:pathology*; D052248:Nitric Oxide Synthase Type I / Q000235:genetics / Q000378:metabolism*; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D012508:Sarcolemma / Q000201:enzymology; D000071756:Soluble Guanylyl Cyclase; D049411:Utrophin / Q000235:genetics / Q000378:metabolism*
D018160:Receptors, Cytoplasmic and Nuclear; D049411:Utrophin; D052248:Nitric Oxide Synthase Type I; D006162:Guanylate Cyclase; D000071756:Soluble Guanylyl Cyclase
Cardiomyopathy; Duchenne muscular dystrophy; Intercalated discs; Nitric oxide; Nitric oxide synthase; Utrophin