Fig. 2
From: Assessing the potential of bacterial signal peptides for radiopharmaceutical applications
Characterization of the FITC labelled signal peptide for time-dependent binding, stability, endocytosis and uptake. (a) Time course of the binding of f-MVPIK(FITC)I to the FPR1 receptor on transiently transfected HEK293T cells. Left upper panel: representative confocal images of the fluorescent peptide only. Left lower panel: magnification of the indicated section displaying the colocalization between the bound peptide and the total cell number using Hoechst 33,342 that stains cell nuclei. Right: mean values of total fluorescence normalized to total cell number. Error bars denote SD, n = 3; N = 9 (** P = 0.005), (*** P = 0.0001), (**** P < 0.0001). Scale bar = 166 μm. (b) Left: Representative binding of f-MVPI(FITC)I to the cell surface of FPR1 transfected HEK293T cells. Right: mean values of total fluorescence normalized to total cell number. Error bars denote SD, n = 3; N = 9 (** P = 0.0002 for 0.5 h) and (** P = 0.0002 for 4 h). Scale bar = 166 μm. (c) Confocal microscopy images demonstrated that the ligand f-MVPIK(FITC)I triggers FPR1 endocytosis in HEK293T transfected with FPR1. Concentration-endocytosis curves of HEK293T cells transfected with mock, FPR1, and FPR2, respectively. Error bars denote SD, n = 3; N = 9. Scale bar = 100 μm. (d) Uptake of f-MVPIK(FITC) in FPR1 expressing HEK293T cells Living cells were incubated with 1 µM f-MVPIK(FITC) for 0.5 h and then rinsed with 1 × PBS. Images were taken after 24, 48, and 72 h. Error bars denote SD, n = 3; N = 9 (* P = 0.01), (**** P < 0.0001). Scale bar = 166 μm.
