Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, University at Buffalo, 445 Pharmacy Building, Buffalo, New York, 14214-8033, USA.
Department of Internal Medicine, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, New York, USA.
AAPS J. 2021 Mar 7;23(2):40. doi: 10.1208/s12248-021-00557-1.
Therapeutic immunoglobulin G (IgG) antibodies comprise the largest class of protein therapeutics. Several factors that influence their overall disposition have been well-characterized, including target-mediated mechanics and convective flow. What remains poorly defined is the potential for non-targeted entry into various tissues or cell types by means of uptake via cell surface receptors at those sites. Megalin and cubilin are large endocytic receptors whose cooperative function plays important physiological roles at the tissues in which they are expressed. One such example is the kidney, where loss of either results in significant declines in proximal tubule protein reabsorption. Due to their diverse ligand profile and broad tissue expression, megalin and cubilin represent potential candidates for receptor-mediated uptake of IgG into various epithelia. Therefore, the objective of the current work was to determine if IgG was a novel ligand of megalin and/or cubilin. Direct binding was measured for human IgG with both megalin and the cubilin/amnionless complex. Additional work focusing on the megalin-IgG interaction was then conducted to build upon these findings. Cell uptake studies using megalin ligands for competitive inhibition or proximal tubule cells stably transduced with megalin-targeted shRNA constructs supported a role for megalin in the endocytosis of human IgG. Furthermore, a pharmacokinetic study using transgenic mice with a kidney-specific mosaic knockout of megalin demonstrated increased urinary excretion of human IgG in megalin knockout mice when compared to wild-type controls. These findings indicate that megalin is capable of binding and internalizing IgG via a high affinity interaction.
治疗性免疫球蛋白 G（IgG）抗体是最大的一类蛋白治疗药物。许多影响其总体分布的因素已得到很好的描述，包括靶向介导的机制和对流。目前仍不清楚的是，IgG 是否有可能通过细胞表面受体非靶向进入各种组织或细胞类型。巨球蛋白和 Cubilin 是大型内吞受体，它们在表达它们的组织中发挥着重要的生理作用。一个这样的例子是肾脏，其中任何一种的丧失都会导致近端小管蛋白重吸收显著下降。由于它们的配体谱多样且广泛表达于各种组织，巨球蛋白和 Cubilin 代表了 IgG 通过受体介导进入各种上皮细胞的潜在候选物。因此，目前工作的目的是确定 IgG 是否是巨球蛋白和/或 Cubilin 的新型配体。直接结合被测量为与人 IgG 巨球蛋白和 Cubilin/Amnionless 复合物。然后进行了更多的工作，重点研究了巨球蛋白-IgG 相互作用，以进一步研究这些发现。使用巨球蛋白配体进行竞争性抑制的细胞摄取研究或用巨球蛋白靶向 shRNA 构建体稳定转导的近端小管细胞支持巨球蛋白在人 IgG 内吞作用中的作用。此外，使用具有肾脏特异性巨球蛋白镶嵌敲除的转基因小鼠进行的药代动力学研究表明，与野生型对照相比，巨球蛋白敲除小鼠的人 IgG 尿排泄增加。这些发现表明，巨球蛋白能够通过高亲和力相互作用结合并内化 IgG。
