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

摘要 认知障碍和痴呆的危险因素针对血管系统，这种情况被称为 血管对认知障碍和痴呆（VCID）的贡献。然而，分子 导致疾病中血管功能、密度和灌注降低的机制是 不太了解。最近的工作集中在血管内皮生长因子（VEGF）， 通过VEGF受体2传递信号，是内皮细胞存活的主要因素 船舶维修。VEGF生物利用度随年龄增长而下降，导致血管功能障碍 大脑和其他器官的血管密度降低。这种影响是由于增加的水平 VEGF拮抗剂，诱饵受体VEGFR 1的可变剪接可溶形式， 称为可溶性Flt 1（sFlt 1），主要在内皮中表达。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--与以下因素有关： 细胞外基质蛋白纤连蛋白（FN）的内皮下积累增加， 血管基底膜FN有助于血管修复和完整性，但在疾病 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粘附到FN诱导选择性剪接， Flt 1转录本增加sFlt 1产量这些发现使我们提出了新的 假设FN积累和血管硬化随着年龄的增长， sFlt 1，介导脑血管稀疏并损害认知功能。上 目的是，我们将确定整合素α5β1上的机械应变如何导致Flt 1剪接， 过早的多聚腺苷酸化，确定RNA结合蛋白（RBP）负责 剪接的变化和阐明调控机制。在第二个目标中，我们将测试 以上假设在小鼠模型中，并确定治疗靶点，其阻断防止 sFlt 1生产和保护认知障碍。共同完成这些目标 通过将VCID增加的血管积聚与VCID相关， FN对sFlt 1产生的影响，确定分子机制，并确定抑制 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.