Sulfated polysaccharides reduce cell-surface levels of SREC-I, and promote SREC-I internalization and colocalization with Lamp1. (A) SREC-I internalized by Ac-LDL localizes with Ac-LDL. SREC-I (green) and DAPI (blue) were examined by confocal microscopy in HUVECs incubated with Alexa 594–conjugated Ac-LDL (red) (4 μg/mL, 37°C, 1 hour), fixed, and permeabilized. Scale bar represents 20 μm. Images were acquired and processed as described for Figure 3A. (B) DS500 and fucoidan reduce cell-surface levels of SREC-I. HUVECs were incubated with polysaccharides (0-64 μg/mL, 37°C, 1 hour) and washed (1 M NaCl). SREC-I was detected by flow cytometry. Results reflect relative mean fluorescence intensities with or without stimulation. (C) Temperature-, concentration-, and time-dependent reduction of cell-surface SREC-I by DS500. HUVECs were incubated with DS500. SREC-I was detected by flow cytometry. (D) DS500 induces SREC-I internalization. SREC-I (green) and DAPI (blue) were examined by confocal microscopy in HUVECs incubated with DS500 (8 μg/mL, 37°C, 1 hour), fixed, and permeabilized. Scale bar represents 20 μm. (E) SREC-I colocalizes with Lamp1. SREC-I (green), Lamp1 (red), and DAPI (blue) were examined by confocal microscopy in HUVECs incubated with DS500 (8 μg/mL, 37°C, 1 hour), fixed, and permeabilized.