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.
J Mol Cell Cardiol. 2011 Jul;51(1):4-15. doi: 10.1016/j.yjmcc.2011.03.001. Epub 2011 Apr 8.
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'.
RAS 激活与生理和病理心肌肥厚有关。 Ras 和钙调神经磷酸酶途径之间的串扰，后者也与心肌肥厚有关，被怀疑与病理性肥厚有关。我们最近的发现，编码下游 Ras 效应物的 RAF1 的种系突变导致 Noonan 和 LEOPARD 综合征，伴有高患病率的肥厚型心肌病，为阐述 RAF1 在心肌细胞生物学中的作用提供了机会。在这里，我们描述了 RAF1 信号在心肌细胞肥大中的作用，目的是确定潜在的治疗靶点。我们通过感染新生和成年大鼠心肌细胞（NRCM 和 ARCM），分别用编码野生型 RAF1 和三种 Noonan/LEOPARD 综合征相关 RAF1 突变体（S257L、D486N 或 L613V）的腺病毒来模拟肥厚型心肌病。除 D486N 外，这些 RAF1 蛋白可引起心肌细胞肥大。令人惊讶的是，这些效应分别在 NRCM 和 ARCM 中独立于和依赖于有丝分裂原激活的蛋白激酶。在 RAF1 过表达细胞中抑制 Mek1/2 可阻断 ARCM 中的肥大，但不能阻断 NRCM 中的肥大。此外，我们发现内源性和异源表达的 RAF1 与钙调神经磷酸酶复合物，以及在两种细胞类型中通过激活 T 细胞核因子（Nfat）信号的肥大 RAF1 突变体。钙调神经磷酸酶的参与也反映在 NRCM 中 Serca2a 的下调和钙信号的失调。此外，用钙调神经磷酸酶抑制剂环孢菌素治疗可阻断 RAF1 过表达的 NRCM 和 ARCM 的肥大。因此，我们已经确定钙调神经磷酸酶为 RAF1 的新相互作用伙伴，并建立了 RAF1 突变诱导的病理性心肌肥厚的机制联系和可能的治疗靶点。本文是特刊“可能的社论”的一部分。
