Novel Targets of Rapamycin & Akt in VSMC Differentiation

描述(申请人提供)：VSMC表型的调节仍然是血管平滑肌细胞(VSMC)生物学中尚未回答的关键问题。VSMC保持着显著的可塑性，可以去分化并重新进入细胞周期，从而允许生长和愈合。然而，这种可塑性也可能导致严重的血管病变，包括再狭窄、移植失败、动脉粥样硬化和移植血管病变。值得注意的是，尽管进行了密集的研究，但调控可塑性的过程在很大程度上是未知的，几乎没有成功针对这一过程的治疗方法。随着越来越多的患者患有血管疾病，迫切需要发现新的靶点。虽然雷帕霉素类似物是有效的药物洗脱支架药物，但支架晚期血栓形成和随后需要长期抗血小板治疗的风险仍然使它们的使用复杂化。我们以前的研究表明，mTORC1抑制剂雷帕霉素促进VSMC分化，揭示了细胞类型特异性转录是mTORC1途径的一种新功能。此外，我们暗示Akt2的反馈激活是雷帕霉素诱导分化的关键。我们已经发现Akt1和Akt2在血管损伤反应中的不同作用。我们还鉴定了TET2和LMO7是调节VSMC表型的新的mTORC1调节蛋白。基于这些令人兴奋的初步结果，我们将讨论mTORC1通路通过表观遗传(TET2)和转录(LMO7)调控VSMC表型和损伤反应的总体假设，以及Akt亚型在再狭窄的病理和雷帕霉素的治疗反应中发挥不同的作用。在具体目标1中，我们将确定TET2在VSMC表型调节中的作用以及雷帕霉素是如何调节它的。在特定的目标2中，我们将确定LMO7在雷帕霉素诱导的VSMC体外分化和体内损伤反应中的作用。在具体目标3中，我们将确定Akt1和Akt1的不同作用 Akt2在血管组织损伤反应中的作用。如果我们的目标实现了，我们就会确定关键 VSMC可塑性的调节元件。了解mTORC1调节VSMC表型的关键机制将有助于心血管治疗的改进。

DESCRIPTION (provided by applicant): Regulation of VSMC phenotype remains a key unanswered question in vascular smooth muscle cell (VSMC) biology. VSMC retain a remarkable plasticity to de-differentiate and re-enter the cell cycle allowing for growth and healing. However, such plasticity can also contribute to severe vascular pathologies, including restenosis, graft failure, atherosclerosis, and transplant vasculopathy. Remarkably, despite intense study, the process regulating plasticity is largely unknown with few therapies successfully targeting this process. With the growing numbers of patients suffering from vascular disease the discovery of novel targets is urgently warranted. While rapamycin analogs are efficacious drug-eluting stent agents, the risk of late-stent thrombosis and subsequent need for long term antiplatelet therapy still complicates their use. Our previous studies have revealed that the mTORC1 inhibitor, rapamycin, promotes VSMC differentiation, revealing cell type-specific transcription as a novel function of the mTORC1 pathway. Moreover, we implicated feedback activation of Akt2 as critical for rapamycin-induced differentiation. We have discovered distinct roles for Akt1 and Akt2 in the response to vascular injury. We have also identified TET2 and LMO7 as novel mTORC1-regulated proteins that modulate VSMC phenotype. Based upon these exciting Preliminary Results we will address the overall hypothesis that the mTORC1 pathway governs VSMC phenotype and response to injury through epigenetic (TET2) and transcriptional (LMO7) regulation, and that Akt isoforms play distinct roles in the pathology of restenosis and therapeutic response to rapamycin. In Specific Aim 1, we will determine the role of TET2 in VSMC phenotypic modulation and how it is regulated by rapamycin. In Specific Aim 2, we will determine the role of LMO7 in rapamycin- induced VSMC differentiation in vitro and in response to injury in vivo. In Specific Aim 3, we will determine the differential roles of Akt1 and Akt2 in injury response in vascular tissues. If our goals are achieved, we will have identified key regulatory elements in VSMC plasticity. Understanding the critical mechanisms by which mTORC1 regulates VSMC phenotype will lead to improved cardiovascular therapeutics.