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

背景：血脑屏障（BBB）是抵御外源物质的强大守门人，在复杂神经元活动的脑内稳态中起着重要作用。因此，为了使大多数生物活性蛋白和肽穿过血脑屏障，需要大分子受体绕过血脑屏障的限制性通透性。因此，无论是脑成像造影剂配方，还是脑穿透剂的开发，都必须达到两个分子目标：更高的靶向选择性和更好的给药效果。实现这些目标的一个合理方法是了解生物活性配体如何选择性地结合并通过血脑屏障上的特定受体进行运输。然而，特异性大分子（co）受体介导的转运之间的身份和相互依存的功能关系，使内吞作用能够进入特定的细胞内室，仍然缺乏文献记载。增加生物活性分子脑内递送的一个有吸引力的策略也是在细胞内靶向细胞器内特异性递送。因此，受体介导的配体细胞内运输/区隔过程也有待于更好地定义和理解血脑屏障。我们的研究计划的原创性：虽然肽胞吞进入脑组织发生，部分是通过血脑屏障界面的低密度脂蛋白受体相关蛋白1 (LRP1)，我们已经发现了新的补偿性适应机制，在LRP1/脑内皮细胞中，这使我们能够假设通过来自硫酸肝素蛋白聚糖和vps10p结构域受体的新大分子受体，交替胞吞过程的重要参与。我们的研究项目对技术进步的影响：通过检查脑内皮细胞和非内皮细胞类型中细胞外配体的差异内化和运输是否存在不同的尚未记录的机制，我们将在分子水平上描述细胞表面大分子受体的功能相互依赖性。因此，鉴定介导血脑屏障转胞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运输过程的研究工具，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，因为它最终将为对血脑屏障表型的更大靶向选择性提供理论依据，并有助于设计更好的脑内递送策略。因此，我们的研究项目产生的直接影响应该会激励下一代生物偶联物选择性地与我们提议研究的受体结合。

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.