A computational analysis of in vivo VEGFR activation by multiple co-expressed ligands.
A computational analysis of in vivo VEGFR activation by multiple co-expressed ligands.
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DOI：
10.1371/journal.pcbi.1005445
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发表时间：
2017-03
影响因子：
4.3
通讯作者：
Mac Gabhann F
中科院分区：
文献类型：
--
作者：
Clegg LE;Mac Gabhann F
血管内皮生长因子A（VEGF）的剪接异构体各自对细胞外基质（ECM）和辅助受体NRP 1具有不同的亲和力，这导致仅表达单一VEGF异构体的模型系统中的不同血管表型。ECM固定的VEGF可以直接结合并激活VEGF受体2（VEGFR 2），其位点特异性磷酸化模式与可扩散的VEGF不同。迄今为止，ECM结合改变VEGF和相关胎盘生长因子（PlGF）的同种型在体内的分布以及所产生的血管生成信号传导的方式还没有很好地理解。在这里，我们扩展了我们以前验证的VEGFR 2连接，细胞内运输和位点特异性磷酸化的细胞水平计算模型，该模型捕获了可溶性和固定化VEGF信号传导的差异，以多尺度全身框架。该计算系统药理学模型捕获ECM调节VEGF和PlGF的亚型特异性生长因子分布的能力，以及缓冲组织中游离VEGF和PlGF水平的能力。我们发现，固定化的生长因子结合VEGF受体，无论是在内皮细胞和可溶性VEGFR 1，可能是重要的信号在体内。此外，我们的模型预测，VEGF亚型特异性导致不同的配置文件的VEGFR 1和VEGFR 2结合和VEGFR 2位点特异性磷酸化在体内，由Neuropilin-1介导。这些预测的信号传导变化反映了在表达单一VEGF同种型的鼠系统中观察到的变化。模拟预测，与“配体移位假说”相反，VEGF和PlGF在生理浓度下不竞争受体结合，尽管预测PlGF在过表达10倍时略微增加VEGFR 2磷酸化。这些结果对于设计适当的治疗策略以控制再生医学应用中VEGF的可用性和信号传导至关重要。血管生成，即从现有血管系统生长新血管，对于维持健康和对损伤的反应至关重要。在缺血性疾病中，这一过程受损，但靶向关键蛋白质家族血管内皮生长因子（VEGF）的治疗未能在临床上转化。这表明需要更深入地了解血管生成信号的复杂调控。在这里，我们将先前开发和验证的VEGF家族信号转导模型转化为人类全身框架。VEGF和相关PlGF蛋白的不同剪接同种型对细胞外基质（ECM）和共受体神经纤毛蛋白-1具有不同的亲和力。使用我们的模型，我们研究了这些不同的结合特性对组织中每个亚型的分布以及随后的受体信号传导的影响。该模型预测亚型特异性受体激活，这与表达单一VEGF亚型的小鼠中观察到的血管表型一致;非ECM结合亚型导致促进细胞增殖的信号传导，而强ECM结合促进迁移信号传导并增加血管分支。这种理解对于设计操纵VEGF-ECM结合以控制生长因子递送的生物材料以及理解不同组织和疾病中VEGF家族信号传导中剪接诱导的变化至关重要。
The splice isoforms of vascular endothelial growth A (VEGF) each have different affinities for the extracellular matrix (ECM) and the coreceptor NRP1, which leads to distinct vascular phenotypes in model systems expressing only a single VEGF isoform. ECM-immobilized VEGF can bind to and activate VEGF receptor 2 (VEGFR2) directly, with a different pattern of site-specific phosphorylation than diffusible VEGF. To date, the way in which ECM binding alters the distribution of isoforms of VEGF and of the related placental growth factor (PlGF) in the body and resulting angiogenic signaling is not well-understood. Here, we extend our previous validated cell-level computational model of VEGFR2 ligation, intracellular trafficking, and site-specific phosphorylation, which captured differences in signaling by soluble and immobilized VEGF, to a multi-scale whole-body framework. This computational systems pharmacology model captures the ability of the ECM to regulate isoform-specific growth factor distribution distinctly for VEGF and PlGF, and to buffer free VEGF and PlGF levels in tissue. We show that binding of immobilized growth factor to VEGF receptors, both on endothelial cells and soluble VEGFR1, is likely important to signaling in vivo. Additionally, our model predicts that VEGF isoform-specific properties lead to distinct profiles of VEGFR1 and VEGFR2 binding and VEGFR2 site-specific phosphorylation in vivo, mediated by Neuropilin-1. These predicted signaling changes mirror those observed in murine systems expressing single VEGF isoforms. Simulations predict that, contrary to the ‘ligand-shifting hypothesis,’ VEGF and PlGF do not compete for receptor binding at physiological concentrations, though PlGF is predicted to slightly increase VEGFR2 phosphorylation when over-expressed by 10-fold. These results are critical to design of appropriate therapeutic strategies to control VEGF availability and signaling in regenerative medicine applications. Angiogenesis, the growth of new blood vessels from the existing vasculature, is critical for maintenance of health and response to injury. In ischemic disease, this process is impaired, but therapies targeting a key family of proteins, the vascular endothelial growth factors (VEGF), have failed to translate clinically. This suggests a need for deeper understanding of the complex regulation underlying angiogenic signaling. Here, we translate a previously developed and validated model of VEGF family signaling into a human, whole-body framework. The different splice isoforms of VEGF and the related PlGF proteins have different affinities for the extracellular matrix (ECM) and the co-receptor Neuropilin-1. Using our model, we examine the effect of these different binding properties on the distribution of each isoform in tissue, and subsequent receptor signaling. The model predicts isoform-specific receptor activation that is consistent with observed vascular phenotypes in mice expressing a single VEGF isoform; non-ECM-binding isoforms lead to signaling that promotes cell proliferation, while strong ECM-binding promotes migratory signaling and increased vessel branching. This understanding is critical for design of biomaterials that manipulate VEGF-ECM binding to control growth factor delivery, and for understanding of splicing-induced changes in VEGF family signaling in different tissues and in disease.