Regulation of Flt 1 Splicing by Fibronectin and Integrin Signaling During Aging

摘要 认知障碍和痴呆症的危险因素针对血管系统，这种情况被称为 血管对认知损害和痴呆的贡献(VCID)。然而，分子 疾病中导致血管功能、密度和灌注量降低的机制是 人们对此知之甚少。最近的工作集中在血管内皮生长因子(VEGF)， 它通过血管内皮生长因子受体2传递信号，是内皮细胞存活的主要贡献者 和船舶维护。血管内皮生长因子的生物利用度随着年龄的增长而下降，导致血管功能障碍 并降低大脑和其他器官中的血管密度。这种效果是由于水平增加所致。 血管内皮生长因子拮抗剂，诱骗受体VEGFR1的选择性剪接的可溶性形式， 称为可溶性Flt1(SFlt1)，主要在内皮细胞表达。有趣的是，上述风险 血管疾病的因素--年龄、糖尿病、高血压和血管损伤--与 血管内皮细胞外基质蛋白纤维连接蛋白(FN)在内皮下的积聚增加 血管基底膜。FN有助于血管修复和完整性，但在疾病中 环境会导致炎症和功能障碍。初步数据显示，在 高底物硬度，细胞通过整合素α5β1与FN黏附诱导选择性剪接 Flt1转录本增加sFlt1产量这些发现促使我们提出了这本小说 假设FN的积累和血管的僵硬随着年龄的增长而增加 SFlt1，它介导大脑中的血管稀疏并损害认知功能。在第一个 目的：我们将确定整合素α5β1上的机械应变是如何导致Flt1剪接和 过早的多聚腺苷化，鉴定负责的RNA结合蛋白 剪接和阐明调控机制的变化。在第二个目标中，我们将测试 在小鼠模型中进行上述假设，并确定其阻断阻止的治疗靶点 SFlt1的产生并保护其免受认知损伤。总之，这些目标的实现 将为VCID提供新的分子洞察力，通过将血管堆积增加与 FN对sFlt1的产生，确定分子机制，并找出抑制方法 这一途径限制了与VCID危险因素相关的血管稀疏和认知能力下降。

Abstract Risk factors for cognitive impairment and dementia target the vasculature, a condition known as Vascular contributions to Cognitive Impairment & Dementia (VCID). However, the molecular mechanisms that result in reduced vascular function, density and perfusion in disease are poorly understood. Recent work has focused on vascular endothelial growth factor (VEGF), which signals through VEGF receptor 2, and is a major contributor to endothelial cell survival and vessel maintenance. VEGF bioavailability declines with age, leading to vascular dysfunction and reduced vessel density in the brain and other organs. This effect is due to increased levels of a VEGF antagonist, an alternatively spliced soluble form of the decoy receptor VEGFR1, termed soluble Flt1 (sFlt1), primarily expressed in the endothelium. Interestingly, the above risk factors for vascular disease – age, diabetes, hypertension and vascular injury – are linked to increased subendothelial accumulation of the extracellular matrix protein fibronectin (FN) in vascular basement membrane. FN contributes to vessel repair and integrity but in disease settings can drive inflammation and dysfunction. Preliminary data show that, under conditions of high substrate stiffness, cell adhesion to FN through integrin α5β1 induces alternative splicing of the Flt1 transcript to increase sFlt1 production These findings lead us to propose the novel hypothesis that FN accumulation and vessel stiffening with age drives increased production of sFlt1, which mediates vascular rarefaction in the brain and impairs cognitive function. In the first Aim, we will determine how mechanical strain on integrin α5β1 leads to Flt1 splicing and premature polyadenylation, identifying the RNA-binding proteins (RBPs) responsible for the change in splicing and elucidating mechanisms of regulation. In the second Aim, we will test the above hypothesis in mouse models and identify therapeutic targets whose blockade prevents sFlt1 production and protects from cognitive impairment. Together, the completion of these aims will provide new molecular insights into VCID by linking the increased vascular accumulation of FN to the production of sFlt1, determining molecular mechanisms, and identifying ways to inhibit this pathway to limit vascular rarefaction and cognitive decline associated with VCID risk factors.