title: Cyclosporine attenuates cardiomyocyte hypertrophy induced by RAF1 mutants in Noonan and LEOPARD syndromes.
abstract: RAS activation is implicated in physiologic and pathologic cardiac hypertrophy. Cross-talk between the Ras and calcineurin pathways, the latter also having been implicated in cardiac hypertrophy, has been suspected for pathologic hypertrophy. Our recent discovery that germ-line mutations in RAF1, which encodes a downstream RAS effector, cause Noonan and LEOPARD syndromes with a high prevalence of hypertrophic cardiomyopathy provided an opportunity to elaborate the role of RAF1 in cardiomyocyte biology. Here, we characterize the role of RAF1 signaling in cardiomyocyte hypertrophy with an aim of identifying potential therapeutic targets. We modeled hypertrophic cardiomyopathy by infecting neonatal and adult rat cardiomyocytes (NRCMs and ARCMs, respectively) with adenoviruses encoding wild-type RAF1 and three Noonan/LEOPARD syndrome-associated RAF1 mutants (S257L, D486N or L613V). These RAF1 proteins, except D486N, engendered cardiomyocyte hypertrophy. Surprisingly, these effects were independent and dependent of mitogen activated protein kinases in NRCMs and ARCMs, respectively. Inhibiting Mek1/2 in RAF1 overexpressing cells blocked hypertrophy in ARCMs but not in NRCMs. Further, we found that endogenous and heterologously expressed RAF1 complexed with calcineurin, and RAF1 mutants causing hypertrophy signaled via nuclear factor of activated T cells (Nfat) in both cell types. The involvement of calcineurin was also reflected by down regulation of Serca2a and dysregulation of calcium signaling in NRCMs. Furthermore, treatment with the calcineurin inhibitor cyclosporine blocked hypertrophy in NRCMs and ARCMs overexpressing RAF1. Thus, we have identified calcineurin as a novel interaction partner for RAF1 and established a mechanistic link and possible therapeutic target for pathological cardiomyocyte hypertrophy induced by mutant RAF1. This article is part of a Special Issue entitled 'Possible Editorial'.
authors: Departments of Pediatrics and Genetics and Genomic Sciences and the Child Health and Development Institute, Mount Sinai School of Medicine, One Gustave L. Levy Place, New York, NY 10029, USA.
authors: Perundurai S
authors: PS
authors: Dhandapany
authors: Frank
authors: F
authors: Fabris
authors: Rahul
authors: R
authors: Tonk
authors: Ardo
authors: A
authors: Illaste
authors: Ioannis
authors: I
authors: Karakikes
authors: Mehran
authors: M
authors: Sorourian
authors: Jipo
authors: J
authors: Sheng
authors: Roger J
authors: RJ
authors: Hajjar
authors: Marco
authors: M
authors: Tartaglia
authors: Eric A
authors: EA
authors: Sobie
authors: Djamel
authors: D
authors: Lebeche
authors: Bruce D
authors: BD
authors: Gelb
mesh_terms: D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D000831:Animals, Newborn; D019703:Calcineurin / Q000378:metabolism; D020013:Calcium Signaling; D006332:Cardiomegaly / Q000517:prevention & control*; D002312:Cardiomyopathy, Hypertrophic / Q000235:genetics / Q000517:prevention & control*; D016572:Cyclosporine / Q000494:pharmacology*; D004195:Disease Models, Animal; D044542:LEOPARD Syndrome / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D009154:Mutation; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D009634:Noonan Syndrome / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D019908:Proto-Oncogene Proteins c-raf / Q000235:genetics* / Q000378:metabolism*; D051381:Rats; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000096:biosynthesis / Q000235:genetics; D015398:Signal Transduction / Q000187:drug effects; D013601:T-Lymphocytes / Q000378:metabolism; D018631:ras Proteins / Q000378:metabolism
chemical_list: C506948:Atp2a2 protein, rat; D016572:Cyclosporine; D019908:Proto-Oncogene Proteins c-raf; D019703:Calcineurin; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D018631:ras Proteins