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Review
. 2017 Apr:113:87-96.
doi: 10.1016/j.addr.2016.08.014. Epub 2016 Sep 6.

Investigation of endosome and lysosome biology by ultra pH-sensitive nanoprobes

Chensu Wang  1 , Tian Zhao  2 , Yang Li  2 , Gang Huang  2 , Michael A White  3 , Jinming Gao  4
Affiliations
Review

Investigation of endosome and lysosome biology by ultra pH-sensitive nanoprobes

Chensu Wang et al. Adv Drug Deliv Rev. 2017 Apr.

Abstract

Endosomes and lysosomes play a critical role in various aspects of cell physiology such as nutrient sensing, receptor recycling, protein/lipid catabolism, and cell death. In drug delivery, endosomal release of therapeutic payloads from nanocarriers is also important in achieving efficient delivery of drugs to reach their intracellular targets. Recently, we invented a library of ultra pH-sensitive (UPS) nanoprobes with exquisite fluorescence response to subtle pH changes. The UPS nanoprobes also displayed strong pH-specific buffer effect over small molecular bases with broad pH responses (e.g., chloroquine and NH4Cl). Tunable pH transitions from 7.4 to 4.0 of UPS nanoprobes cover the entire physiological pH of endocytic organelles (e.g., early and late endosomes) and lysosomes. These unique physico-chemical properties of UPS nanoprobes allowed a 'detection and perturbation' strategy for the investigation of luminal pH in cell signaling and metabolism, which introduces a nanotechnology-enabled paradigm for the biological studies of endosomes and lysosomes.

Keywords: Cell signaling; Endocytic organelles; Metabolomics; Organelle imaging; pH buffering; pH sensitive nanoprobes.

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Figures

Figure 1
Figure 1
(a) Schematic illustration of fluorescent UPS nanoprobe design. (b) Structures of the PEO-b-(PR-r-TMR) copolymers. Representative confocal microscopy images of activated UPS6.2 (c) and UPS5.3 (d) in cells with GFP-labeled early endosomes (top panel) and late endosomes/lysosomes (bottom panel) at 30 and 45 min, respectively; and schematic illustration of the selective activation of UPS6.2 in early endosomes (c, right panel) and UPS5.3 in late endosomes/lysosomes (d, right panel), respectively. Figures adapted from Ref [36] with permission from Wiley-VCH.
Figure 2
Figure 2
(a) Schematic design of UPS nanoprobes with FQs. (b) A random copolymer strategy was used to achieve an operator predetermined control of the pHt of UPS nanoprobes by the ability to continuously fine-tune the hydrophobicity of PR segments. (c) Representative library of UPS nanoprobes with 0.3 pH increment covering the physiologic range of pH 4–7.4. (d) Exemplary UPS library consisting of 10 nanoprobes spanning a wide pH range (4–7.4) and large fluorescent emissions (400−820 nm). Figures adapted from Ref [58] with permission from ACS Publications.
Figure 3
Figure 3
(a–b) Schematic of the dual-reporter nanoprobe. In the micelle state, the always-ON dyes serve as the quencher for the OFF-ON fluorophores. When the micelle is disassembled, the always-ON and OFF-ON fluorophores can fluoresce independently. (c) Fluorescent images of test tubes filled with always ON/OFF-ON UPS6.2 nanoprobes in buffers with different pH. Figures adapted from Ref [64] with permission from Nature Publishing Group.
Figure 4
Figure 4
(a) pH titration of each component of the UPS nanoprobe library. (b) Buffer capacity (β) for each component of the UPS library was plotted as a function of pH in the pH range of 4.0 to 7.4. (c) Real-time measurement of endo/lysosomal pH in HeLa cells treated with a dose of 1 mg/mL of UPS6.2, UPS5.3 and UPS4.4. (d) Working model of pH transitions required for free amino acid versus albumin-derived amino acid dependent activation of the mTORC1 signaling pathway. (e) A heatmap of relative abundance of the indicated metabolites under nutrient replete (fed) or deprived (starved) conditions. Cells were treated with UPS4.4 at the indicated doses. Figures adapted from Ref [64] with permission from Nature Publishing Group.
Figure 5
Figure 5
(a) DIC images of HBEC30 KT and HCC4017 cells with and without exposure to UPS at their effective doses. Scale bar =100 μm. (b) Caspase3/7 activity in HBEC30KT (blue), HBEC30KT KP (red), HBEC30KT KPL (green) and HCC4017 (magenta) cells was measured 72 h after exposure to the indicated doses of UPS6.2. α = 0.05, **p<0.01, ****p<0.0001. (c) Cellular ATP levels of HCC4017 treated with 1 mg/mL UPS6.2 for 72 h together with the indicated concentrations of methyl pyruvate (MP), dimethyl-2-oxoglutarate (MOG), or water (dash line). Figures adapted from Ref [64] with permission from Nature Publishing Group.
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References

    1. Maxfield FR, McGraw TE. Endocytic recycling. Nat Rev Mol Cell Biol. 2004;5:121–132. - PubMed
    1. Settembre C, Fraldi A, Medina DL, Ballabio A. Signals from the lysosome: a control centre for cellular clearance and energy metabolism. Nat Rev Mol Cell Biol. 2013;14:283–296. - PMC - PubMed
    1. Huotari J, Helenius A. Endosome maturation. EMBO J. 2011;30:3481–3500. - PMC - PubMed
    1. Casey JR, Grinstein S, Orlowski J. Sensors and regulators of intracellular pH. Nat Rev Mol Cell Biol. 2010;11:50–61. - PubMed
    1. Mukherjee S, Ghosh RN, Maxfield FR. Endocytosis. Physiol Rev. 1997;77:759–803. - PubMed