Figure 2: Proteasome–MSNPN complexes are transported into cells through endocytosis.
From: Direct cellular delivery of human proteasomes to delay tau aggregation
(a) Fluorescent microscope images of HeLa cells after treatment with TAMRA-labelled MSNPN alone or with proteasome–MSNPN complexes (1:50) for 24 h. Counterstained with DAPI. Bars indicate 10 μm in length. (b) As in a except that TEM images were taken. Arrows indicate MSNPN localized to the cytoplasm. (c) As in a except that proteasome–MSNPN complex uptake was blocked by various endocytosis inhibitors including genistein, chlorpromazine, and nocodazole. Bars indicate 10 μm in length. (d) Quantification of flow cytometry analysis, which measures intracellular fluorescence signals from MSNPN in the presence of endocytosis inhibitors. Bars represent the mean of percent values relative to the signal at normal conditions ±s.d. from three independent experiments. *P<0.01 (one-way analysis of variance with Bonferroni’s multiple comparison test). NS, no significance (P>0.05). See Supplementary Fig. 9a for the representative histogram. (e) As in Fig. 1e except that proteasome–MSNPN complexes (1:50) under various pH conditions were used for the suc-LLVY-AMC assay. (f) The composition and activity of proteasomes before and after pH changes were determined by native polyacrylamide gel electrophoresis, followed by visualization using in-gel suc-LLVY-AMC staining.
