Intracellular Trafficking Network of Protein Nanocapsules: Endocytosis, Exocytosis and Autophagy

Abstract

The inner membrane vesicle system is a complex transport system that includes endocytosis, exocytosis and autophagy. However, the details of the intracellular trafficking pathway of nanoparticles in cells have been poorly investigated. Here, we investigate in detail the intracellular trafficking pathway of protein nanocapsules using more than 30 Rab proteins as markers of multiple trafficking vesicles in endocytosis, exocytosis and autophagy. We observed that FITC-labeled protein nanoparticles were internalized by the cells mainly through Arf6-dependent endocytosis and Rab34-mediated micropinocytosis. In addition to this classic pathway: early endosome (EEs)/late endosome (LEs) to lysosome, we identified two novel transport pathways: micropinocytosis (Rab34 positive)-LEs (Rab7 positive)-lysosome pathway and EEs-liposome (Rab18 positive)-lysosome pathway. Moreover, the cells use slow endocytosis recycling pathway (Rab11 and Rab35 positive vesicles) and GLUT4 exocytosis vesicles (Rab8 and Rab10 positive) transport the protein nanocapsules out of the cells. In addition, protein nanoparticles are observed in autophagosomes, which receive protein nanocapsules through multiple endocytosis vesicles. Using autophagy inhibitor to block these transport pathways could prevent the degradation of nanoparticles through lysosomes. Using Rab proteins as vesicle markers to investigation the detail intracellular trafficking of the protein nanocapsules, will provide new targets to interfere the cellular behaver of the nanoparticles, and improve the therapeutic effect of nanomedicine.

Size-dependent Effects of Gold Nanoparticles on Osteogenic Differentiation of Human Periodontal Ligament Progenitor Cells

“…The 45 nm AuNPs were chosen since they exhibited the best pro-osteogenic effect among the three sizes. 3-MA blocks the formation of autophagosome by inhibiting the class III phosphatidylinositol 3-kinase, and CQ inhibits autophagy at a later step by blocking the degradation of autolysosome 45, 47. Both 3-MA and CQ significantly reversed the osteogenesis enhanced by 45 nm AuNPs, suggesting the pro-osteogenic effect of 45 nm AuNPs was related to the activation of autophagy, which is consistent with the previous studies 19-23.…”

Understanding the translocation mechanism of PLGA nanoparticles across round window membrane into the inner ear: a guideline for inner ear drug delivery based on nanomedicine

“…Most NPs, such as PLGA NPs, micelles, chitosan NPs, and microgels, can be entrapped by this classical degradation system. 29 Nevertheless, the cytoplasm of RWM is not the destination of NPs. NPs should escape from lysosomes, and as many NPs as possible should move across the RWM into the perilymph.…”

Crosstalk between Autophagy and Nanomaterials: Internalization, Activation, Termination

“…The binding complex, UVRAG–Beclin1, activates Class III PI3K to elicit both endosome and autophagy pathway. A recent report demonstrates that the bovine serum albumin nanocapsules (nBSA) are internalized into cell through the Rab34‐regulated macropinocytosis and Arf6‐mediated clathrin‐ and caveolae‐independent endocytosis, which also illustrates the crosstalk relationship between endocytosis and autophagy . It was shown that the internalized nBSA led to the elevated level of LC3‐II and were degraded by autophagy pathway.…”

“…They are perfect vesicle markers for investigating the details of intracellular trafficking pathway of the NMs. For examples, Rab5 involving in endocytic internalization and early endosomes' fusion is an early endosome marker, Rab7 relating to control late endocytic trafficking is a late endosome maker, and Rab9 participates in cargo recycling from endosomes to the trans‐Golgi network . Additionally, Rab proteins also play a vital role in the mediation of autophagic process .…”