mTORC1-TFEB pathway in degeneration of the RPE

该项目的长期目标是阐明膜贩运的调控机制。 视网膜色素上皮(RPE)细胞，并了解缺陷在视网膜这一调节中的作用 包括老年性黄斑变性(AMD)在内的疾病。RPE负责每日的删除 光感受器外段(POS)通过吞噬作用脱落，激活严密控制的过程 膜运输和细胞器运输。在我们已发表的和初步的研究中，我们发现 吞噬激活雷帕霉素机械靶点(MTOR)介导的信号通路。在……下面 生理条件下，mTOR激活是一过性的。然而，老化和退化导致了mTOR 在早晨爆发后激活变得更长。在我们新开发的RPE特异性小鼠模型中 MTORC1上游抑制子TSC1的缺失，结构性的高mTOR活性导致RPE和 光感受器退化，可能是由于膜运输失调和POS降解延迟引起的。 我们进一步发现，VPS11，膜系留复合体的一个关键成分，在 TSC1缺陷的RPE细胞可能是由于对转录因子EB(TFEB)的抑制。基于这些 新的发现，我们假设mTORC1的过度激活可以引起RPE和光感受器 由于有缺陷的膜运输而退化。增强TFEB介导的RPE表达 运输蛋白可以恢复细胞功能，防止视网膜退变表型 TSC1RPE小鼠。这一假设将通过三个具体目标进行检验。目标1是进一步描述 RPE中TSC1基因条件性敲除小鼠的视网膜表型。目标2是确定是否 MTOR过激活抑制TFEB介导的RPE细胞内转运和膜融合 VPS11表达式。目的3是确定TFEB基因疗法是否可以预防或挽救RPE 退化。拟议研究的结果有望进一步确定mTOR在 控制RPE和光感受器的相互作用。尽管抗血管内皮生长因子治疗取得了前所未有的成就 成功后，大多数AMD患者都有萎缩性形式的疾病，其病因仍在很大程度上 未知的和治疗的选择非常有限。识别mTOR下游的新目标 退化的RPE细胞可以促进治疗策略的设计，以防止或至少延缓 AMD早期的疾病进展。

The long-term goal of this project is to elucidate the mechanisms by which membrane trafficking is regulated in retinal pigment epithelium (RPE) cells, and to understand the role of defects in this regulation in retinal diseases including age-related macular degeneration (AMD). The RPE is responsible for the removal of daily shed photoreceptor outer segments (POS) by phagocytosis, which activates tightly controlled processes of membrane trafficking and organelle transport. In our published and preliminary studies, we found that phagocytosis activated signaling pathway mediated by the mechanistic target of rapamycin (mTOR). Under physiological conditions, mTOR activation was transient. Aging and degeneration, however, rendered mTOR activation to become prolonged after morning burst. In our newly developed murine model of RPE-specific deletion of mTORC1 upstream suppressor TSC1, constitutively high mTOR activity led to RPE and photoreceptor degeneration, likely caused by deregulated membrane trafficking and delayed POS degradation. We further identified VPS11, a key component of the membrane tethering complexes, was downregulated in TSC1-deficient RPE cells possibly due to inhibition on the transcription factor EB (TFEB). Based on those novel findings, we hypothesize that hyperactivation of mTORC1 can cause RPE and photoreceptor degeneration due to defective membrane trafficking. Enhancing TFEB-mediated expression of RPE trafficking proteins can restore the cellular functions and prevent the degenerative phenotype in retina of TSC1RPE mice. The hypothesis will be tested by three specific aims. Aim 1 is to further characterize the retinal phenotype of mice with conditional knockout of TSC1 in the RPE. Aim 2 is to determine whether overactivation of mTOR inhibits RPE intracellular trafficking and membrane fusion by inhibiting TFEB-mediated VPS11 expression. Aim 3 is to determine whether TFEB gene therapy can prevent or rescue RPE degeneration. Results from the proposed studies are expected to further establish the critical roles of mTOR in controlling the RPE and photoreceptor interaction. Although anti-VEGF therapy has achieved unprecedented success, the majority of AMD patients have the atrophic form of the disease whose etiology is still largely unknown and treatment options are very limited. Identifying novel targets downstream of mTOR in degenerating RPE cells can facilitate the design of therapeutic strategies to prevent or at least delay the disease progression at early stage of AMD.