Figure 4.

FFN246 is a VMAT2 substrate. A) Overview schematic of VMAT2-dependent uptake into a HEK cell expressing active vesicular monoamine transporter on intracellular acidic compartments. FFN246 enters the cytosol via passive diffusion, driven by VMAT2-mediated uptake into acidic vesicles, resulting in the bright, punctate staining shown in representative image D. B) Schematic of VMAT2-independent uptake into VMAT2-HEK cells. Inhibition of VMAT2 by dihydrotetrabenazine, DTBZ (E) or reserpine (F) significantly decreased cell uptake of the probe and the punctate staining pattern (p < 0.0001, n = 3). Null-transfected HEK cells yielded similarly dim, non-punctate labeling (G) (p < 0.0001, n = 3). C) VMAT2-dependent vesicular loading was quantified as normalized puncta intensity (number of puncta multiplied by average fluorescence of the puncta) normalized to total cell area across the field. Scale bar, 10 μm.