Fig. 4

Highly expression or phosphorylated activation of GRP75 promotes the macropinocytosis of Tat/pGL3-Ca²⁺ nanoparticles. (A) Confocal imaging the co-uptake of Tat/pGL3-Ca²⁺-DiYO1 nanoparticles and dextran-RD (1 h) in cells with GRP75-KD or -OE. Scale bar: 10 μm. (B) Scatterplots depict the uptake level of Tat/pGL3-Ca²⁺ nanoparticles in single cell population with GRP75-KD or -OE. (C) Uptake quantitation of Tat/pGL3-Ca²⁺-DiYO1 in GRP75-KD or -OE cell population by the fluorescence microplate reader. (D) Luciferase activity of GRP75-KD or -OE cells transduced with Tat/pGL3-Ca²⁺ nanoparticles for 14 h. (E) Confocal imaging the uptake of Tat/pGL3-Ca²⁺-DiYO3 nanoparticles in Skov3 cells with GRP75-KD or transfected with EGFP-fused GRP75 constructs. Polymerized actin fibers were detected by staining with Rhodamine-phalloidin. Scale bar, 10 μm. (F) Scatterplots depict the uptake level of Tat/pGL3-Ca²⁺-DiYO3 nanoparticles in indicated cells. (G–H) Morphometric analyses of the lamellipodia and filopodia formation in indicated cells. > 60 cells were counted for each cell line or transfection. n = 3. Statistically significant differences in relation to NC (negative control) group are shown: **P < 0.01, *P < 0.05