Targeting kidney proximal tubules by protein nanocages via glomerular filtration

Nature exploits cage-like proteins for a variety of biological purposes from molecular packaging and cargo delivery to catalysis. These cage-like proteins are of immense importance in nanomedicine due to their propensity to self-assemble from simple identical building blocks to highly-ordered architecture and the design flexibility afforded by protein engineering. However, delivery of protein nanocages to the renal tubules remains a major challenge because of the glomerular filtration barrier, which effectively excludes conventional size nanocages. Here we show that DNA-binding Protein from Starved cells (Dps)—the extremely small archaeal antioxidant nanocage—is able to cross the glomerular filtration barrier and is endocytosed by the renal proximal tubules. Using a model of endotoxemia, we present an example of the way in which proximal tubule-selective Dps nanocage can limit the degree of endotoxin-induced kidney injury. This was accomplished by amplifying the endogenous antioxidant property of Dps with addition of a dinuclear manganese cluster. Dps is the first-in-class, protein cage nanoparticle that can be targeted to renal proximal tubules through glomerular filtration. In addition to its therapeutic potential, chemical and genetic engineering of Dps will offer a novel nanoplatform to advance our understanding of the physiology and pathophysiology of glomerular filtration and tubular endocytosis. Overall design: C57BL/6J male mice were subjected to vehicle (control), Dps (18 mg/kg iv), or MnDps (18 mg/kg iv) for indicated durations.