Targeting Cbl for Cardiac Repair Post-Myocardial Infarction

心力衰竭（HF）是全球发病率和死亡率的主要原因。在缺乏有意义的 再生，成年哺乳动物心脏在心肌梗死（MI）后经历病理性重塑， 这有助于HF的发展。相比之下，新生儿的心脏可以在损伤后再生， MI，主要是因为新生心肌细胞（CM）对增殖信号作出反应。出生后， 大多数CM退出细胞周期并失去损伤后完全再生心肌的能力。 最近的证据表明，成年哺乳动物CM具有可测量的，但有限的增殖潜力。的 CM增殖和再生新生心脏的能力表明了一种独特的分子和细胞特征 这在很大程度上是随着CM过渡到成年而丢失的。了解CM细胞周期调控机制 在成人心脏中观察到的发育阶段和无法分裂代表了一个挑战，但可能允许 成人心脏再生策略的发展。最近，我们发现了一个新的作用，为原- 癌基因Casitas b系淋巴瘤（Cbl）在CM生存和死亡中的作用。Cbl功能丧失与 减少CM死亡，增加血管生成和改善心脏收缩功能，证明了其作用 Cbl的心脏保护作用。初步数据显示，Cbl缺乏与CM增加有关。 在MI后的成年小鼠中的增殖，表明Cbl在心脏再生中的未被认识的作用。分析 新生小鼠心脏中CM增殖进一步支持了这一假设，并显示了CM增殖的显著增加。 与野生型（WT）小鼠相比，Cbl敲除小鼠中CM的循环速率。Cbl功能依赖于激活 其E3泛素连接酶活性，其负调节受体酪氨酸激酶（RTK）信号传导，和/或 它的衔接子功能是介导Cbl与包括磷酸肌醇-3激酶在内的几种分子的相互作用 （PI3K）。我们对Cbl激活的分析表明Cbl结构域在调节CM增殖或增殖中的不同作用。 死亡是对外界刺激的反应。基于这些初步数据，我们假设异常激活 Cbl E3泛素连接酶活性的负调节受体酪氨酸激酶（RTK）信号传导和CM 增殖，而增加的Cbl与PI 3 K的相互作用介导CM存活和增殖，并改善CM的存活和增殖。 心脏再生和功能。在目标1中，我们将确定Cbl函数的增益和损失对CM的影响 出生后心脏发育过程中的增殖。在目标2中，我们将研究Cbll表达对细胞的影响。 新生和成年小鼠MI后CM增殖。最后，目标3将定义分子机制 Cbl通过其影响新生儿和成人心脏中的CM增殖和心脏再生。拟议 实验将为Cbl调节CM增殖的机制提供新的见解， 心肌梗死后新生儿和成人心脏的分化，并使用我们对Cbl功能的新理解来揭示新的 增强MI后心脏修复/再生的方法。

Heart failure (HF) is a leading cause of morbidity and mortality worldwide. In the absence of meaningful regeneration, the adult mammalian heart undergoes pathological remodeling after myocardial infarction (MI), which contributes to the development of HF. In contrast, the neonatal heart can regenerate after injury such as MI, primarily because neonatal cardiomyocytes (CMs) respond to proliferative signaling. After birth, the vast majority of CMs withdraw from the cell cycle and lose the ability to fully regenerate the myocardium after injury. Recent evidence shows that adult mammalian CMs harbor measurable, but limited, proliferative potential. The ability of CMs to proliferate and regenerate the neonatal heart suggests a distinct molecular and cellular signature that is largely lost as CMs transition to adulthood. Understanding the mechanisms regulating CM cell cycle during developmental stages and inability to divide as observed in the adult heart represents a challenge, but may allow development of strategies for adult heart regeneration. Recently, we have identified a novel role for proto- oncogene Casitas b-lineage lymphoma (Cbl) in CM survival and death. Loss-of-Cbl function was associated with decreased CM death, increased angiogenesis and improved cardiac contractile function, demonstrating a role of Cbl in cardioprotection. Preliminary data shows that Cbl deficiency is associated with increased CM proliferation in adult mice after MI, suggesting an unrecognized role of Cbl in cardiac regeneration. Analysis of CM proliferation in neonatal mouse heart further supports this hypothesis and shows a marked increase in the rate of cycling CMs in Cbl knockout compared to wild-type (WT) mice. Cbl function is dependent on the activation of its E3 ubiquitin ligase activity, which negatively regulates receptor tyrosine kinase (RTK) signaling, and/or on its adaptor functions that mediate Cbl interaction with several molecules including phosphoinositide-3 kinase (PI3K). Our analysis of Cbl activation suggests a differential role of Cbl domains in regulating CM proliferation or death in response to external stimuli. Based on these preliminary data, we hypothesize that aberrant activation of Cbl E3 ubiquitin ligase activity negatively regulates receptor tyrosine kinase (RTK) signaling and CM proliferation, while increased Cbl interaction with PI3K mediates CM survival and proliferation and improves cardiac regeneration and function. In aim 1, we will determine the effects of gain- and loss-of-Cbl function on CM proliferation during post-natal heart development. In aim 2, we will investigate the impact of Cbl expression in CM proliferation following MI in both neonate and adult mice. Finally, aim 3 will define the molecular mechanisms by which Cbl affects CM proliferation and cardiac regeneration in neonatal and adult heart. The proposed experiments will provide new insights into the mechanisms whereby Cbl modulates CM proliferation and differentiation in neonatal and adult heart after MI and use our new understanding of Cbl function to uncover new approaches to enhance cardiac repair/regeneration post-MI.