A Tissue-Specific Soluble Platelet-Derived Growth Factor Receptor-beta Isoform Retains Functional Capacity

项目总结/摘要 微血管功能障碍是从阿尔茨海默病到癌症的一系列毁灭性疾病的基础。 然而，在血管相关病理中，血管维持的潜在机制变得失调， 仍在出现，推动了基于血液的诊断和生物工程治疗的发展。我们 最近发现了一种血小板源生长因子受体β（PDGFRβ）的截短型可变剪接变体 编码可溶性PDGFRβ同种型（sPDGFRβ），可能具有未来诊断和 治疗靶点受体酪氨酸激酶（RTK），如PDGFRβ，通常具有可溶性对应物， 通过选择性剪接产生，作为“诱饵”受体负调节配体诱导的信号传导 全长的受体。全长PDGFRβ由周细胞（PC）表达，以介导其募集至 产生同源配体血小板衍生生长因子BB（PDGF-1）的微血管内皮细胞（EC） BB）-其中PC促进血管稳定性并调节渗透性。然而，微血管PC密度和血管 组织和专门的血管床之间的渗透性不同，血管功能障碍通常与 PC丢失和PDGFRβ-PDGF-BB信号传导失调。因此，PDGFRβ介导的PC募集对于 血管完整性，尽管控制它的确切机制仍不清楚。最近的研究报告称， 在脑病理学情况下通过蛋白水解裂解产生的sPDGFRβ。然而，我们的数据表明， 小的sPDGFRβ在广泛的正常健康组织中通过选择性剪接产生，尽管它也 可能与疾病状态有关。我们最近阐明了sPdgfrb的完整mRNA序列， 操作和分析方法。除了在各种组织中广泛和差异表达外， 我们的初步研究结果表明，与小鼠脑中表达全长Pdgfrb（fPdgfrb）的细胞重叠， 脑实质中存在免疫标记的非血管相关sPDGFRβ蛋白信号。这些 研究结果，与相关RTK中的配体螯合的既定机制一起考虑，告知我们 PDGF-BB生物利用度受选择性剪接的sPDGFRβ调节以介导PC血管的假说 募集和调节血管渗透性。因此，使用互补的体外和体内模型，我们 建议研究sPDGFRβ结合和调节（i）PDGF-BB生物利用度，（ii）激活 全长PDGFRβ（fPDGFRβ），（iii）PC动力学，和（iv）发育中的血管形态和渗透性。我们 将研究sPDGFRβ细胞特异性和各种组织中的时空分布，以确定 其功能作用的范围。此外，我们将评估sPDGFRβ作为生物标志物和治疗的潜力。 在涉及PC丢失的血管相关病理中。这项工作将促进我们对机制的理解 基础船舶维护和完整性，并为后续合作研究奠定基础， 研究sPDGFRβ作为心血管疾病潜在的诊断工具和治疗靶点。

PROJECT SUMMARY / ABSTRACT Microvascular dysfunction underlies a wide range of devastating diseases, from Alzheimer’s Disease to cancer. However, mechanisms underlying vessel maintenance that become dysregulated in vascular-related pathologies are still emerging, fueling the advancement of blood-based diagnostics and bioengineered therapeutics. We recently identified a truncated, alternative splice variant of Platelet-Derived Growth Factor Receptor-β (PDGFRβ) that encodes a soluble PDGFRβ isoform (sPDGFRβ), which may harbor potential as a future diagnostic and therapeutic target. Receptor tyrosine kinases (RTKs), like PDGFRβ, often have soluble counterparts that are generated via alternative splicing to function as “decoy” receptors to negatively regulate ligand-induced signaling of the full-length receptor. Full-length PDGFRβ is expressed by pericytes (PCs) to mediate their recruitment to microvascular endothelial cells (ECs) producing the cognate ligand Platelet-Derived Growth Factor BB (PDGF- BB) – where PCs promote vessel stability and tune permeability. However, microvascular PC density and vessel permeability vary between tissues and specialized vascular beds, with vessel dysfunction often associated with PC loss and misregulated PDGFRβ--PDGF-BB signaling. Thus PDGFRβ-mediated PC recruitment is vital to vessel integrity, although the exact mechanisms that govern it remain unclear. Recent studies report a large sPDGFRβ produced via proteolytic cleavage in cerebral pathology scenarios. However, our data indicate that a small sPDGFRβ is generated via alternative splicing in a broad range of normal, healthy tissues, though it is also likely involved in disease states. We recently elucidated the full mRNA sequence of sPdgfrb, enabling targeted manipulation and analysis approaches. In addition to broad and differential expression across various tissues, our preliminary findings indicate overlap with full-length Pdgfrb (fPdgfrb)-expressing cells in mouse brain, and presence of immunolabled, non-vessel associated sPDGFRβ protein signal in the brain parenchyma. These findings, considered alongside established mechanisms of ligand sequestration in related RTKs, inform our hypothesis that PDGF-BB bioavailability is regulated by alternatively spliced sPDGFRβ to mediate PC-vessel recruitment and tune vessel permeability. Therefore, using complementary in vitro and in vivo models, we propose investigation of sPDGFRβ potential to bind and regulate (i) PDGF-BB bioavailability, (ii) activation of full-length PDGFRβ (fPDGFRβ), (iii) PC dynamics, and (iv) developing vessel morphology and permeability. We will investigate sPDGFRβ cell-specificity, and spatio-temporal distribution in various tissues to determine the extent of its functional role. In addition, we will assess the potential of sPDGFRβ as a biomarker and treatment in vascular-related pathologies involving PC loss. This work will advance our understanding of mechanisms underlying vessel maintenance and integrity, and lay the groundwork for follow-on collaborative studies aiming to develop sPDGFRβ as a potential diagnostic tool and therapeutic target in cardiovascular diseases.