Probing into receptor-mediated trafficking and internalization functions of biologically active peptides

背景资料：血脑屏障（BBB）是一个强大的守门人，对外源性物质，发挥重要作用，在脑内稳态的复杂神经活动。因此，为了使大多数生物活性蛋白质和肽穿过BBB，需要大分子受体来规避BBB限制性渗透性。因此，无论是用于脑成像造影剂制剂还是在脑渗透剂的开发中，都必须实现两个分子目标：更大的靶向选择性和更好的递送功效。实现这些目标的合理方法是了解生物活性配体如何选择性地结合到BBB的特异性受体并通过其转运。然而，特定的大分子（共）受体介导的转运，使内吞作用的特定细胞内室之间的身份和相互依赖的功能关系，仍然很少记录。增加生物活性分子的脑内递送的有吸引力的策略也是将其特异性地递送到细胞内靶向的细胞器内。因此，受体介导的配体细胞内运输/区室化过程也仍有待于在BBB更好地定义和理解。我们的研究计划的独创性：虽然肽转胞吞作用进入脑组织部分是通过BBB界面的低密度脂蛋白受体相关蛋白1（LRP 1）发生的，但我们在LRP 1/脑内皮细胞中发现了新的无文献记载的代偿性适应机制，这使我们能够假设通过来自硫酸肝素蛋白聚糖的新的大分子受体，和Vps 10 p-结构域受体。我们的研究计划导致技术进步的影响：通过检查是否存在不同的，但未记录的，机制差异内化和贩运的细胞外配体在脑内皮细胞和非内皮细胞类型，我们将描绘在分子水平上的功能相互依赖的细胞表面大分子受体。鉴定介导跨血脑屏障的转胞吞作用的新大分子实体的价值是双重的：作为帮助理解基本的体外分子和细胞转运过程的研究工具，以及作为解决有效靶向血脑屏障的重要机制需求的药理学工具。我们相信，我们的研究计划是原创的，因为它最终将为BBB表型的更大靶向选择性提供理论基础，并有助于设计更好的脑内递送策略。因此，我们的研究计划产生的直接影响应该激励未来一代的生物缀合物选择性地结合我们打算研究的那些受体。

Background: The blood-brain barrier (BBB) is a formidable gatekeeper toward exogenous substances, playing an important role in brain homeostasis for complex neuronal activities. Accordingly, in order for the majority of bioactive proteins and peptides to cross the BBB, macromolecular receptors are required to circumvent the BBB restrictive permeability. Whether it is for brain imaging contrast formulations or in the development of brain penetrating agents, two molecular goals must therefore be achieved : Greater targeting selectivity and better delivery efficacy. A rational approach to attain these goals is to understand how biologically active ligands can selectively bind to and be transported through specific receptors at the BBB. The identity and interdependent functional relationship between specific macromolecular (co)receptors-mediated transport, that enable endocytosis to specific intracellular compartments, remain however poorly documented. An attractive strategy to increase the intracerebral delivery of a bioactive molecule is also to specifically deliver it within an intracellular targeted organelle. Thus, receptor-mediated ligand intracellular trafficking/compartmentation processes also remain to be better defined and understood at the BBB.******Originality of our research program: Although peptide transcytosis into brain tissue occurs, in part, via the low-density lipoprotein receptor-related protein 1 (LRP1) at the BBB interface, we have discovered novel undocumented compensatory adaptive mechanisms, in LRP1/brain endothelial cells, which allowed us to postulate for the significant involvement of alternate transcytosis processes through new macromolecular receptors from heparin sulfate proteoglycans and Vps10p-domain receptors. Impact of our research program leading to technology advancements: By examining whether different, yet undocumented, mechanisms exist for differential internalization and trafficking of extracellular ligands in both cerebral endothelial and non-endothelial cell types, we will delineate at the molecular level the functional interdependence of cell surface macromolecular receptors. The value of identifying new macromolecular entities that mediate transcytosis across the BBB is then two-fold: as research tools to help understand fundamental in vitro molecular and cellular transport processes, and as pharmacological tools to address the significant mechanistic needs to efficiently target the BBB. We are confident that our research program is original as it will ultimately provide rationale for greater targeting selectivity towards the BBB phenotype and help in the design of better intracerebral delivery strategies. As such, an immediate impact derived from our research program should inspire the future generation of bioconjugates to selectively bind to those receptors we propose to investigate.