Konopski Z, Fandrem J, Seljelid R, Eskeland T
Department of Experimental Pathology and Anatomy, University of Tromsø, Norway.
J Interferon Cytokine Res. 1995 Jul;15(7):597-603. doi: 10.1089/jir.1995.15.597.
We previously demonstrated that soluble animated beta-1,3-D-glucan (AG) is internalized after binding to a specific beta-glucan receptor on macrophages. Internalization, but not binding, of AG is reduced when the macrophages are treated with IFN-gamma. Because our data indicated that AG is taken up by macrophages through beta-glucan receptor-mediated endocytosis, we wanted to characterize further the inhibitory effect of IFN-gamma on endocytosis. We compared the internalization of AG and neutral red (NR). NR is internalized by macrophages through fluid-phase endocytosis. AG and NR showed a similar influx/efflux pattern. The initial rate of accumulation was much larger for AG than for NR, however, probably because of the involvement of the beta-glucan receptor in the uptake of AG. Internalized AG was associated with membranes of the endocytic vesicles and formed characteristic rings on confocal laser scanning microscopy (CLSM) images. Both the influx and efflux of AG and NR was inhibited by treatment of macrophages with IFN-gamma. Phorbol myristate acetate (PMA) added to the cell cultures increased the accumulation of AG and NR and reversed the inhibitory effect of IFN-gamma. The effect of PMA was dependent on functionally intact microfilaments and microtubules. CLSM showed that the accumulated AG was localized mostly in small vesicles (size < 2 microns) in IFN-gamma-treated cells, in large and small vesicles in untreated cells, and mostly in large vesicles (size > 2 microns) in PMA-treated cells. In conclusion, IFN-gamma inhibits both the beta-glucan receptor-mediated endocytosis of AG and the fluid-phase endocytosis of NR, probably by inhibiting the formation of large vesicles.
我们之前证明，可溶性活性β-1,3-D-葡聚糖（AG）在与巨噬细胞上的特定β-葡聚糖受体结合后被内化。当巨噬细胞用IFN-γ处理时，AG的内化而非结合会减少。因为我们的数据表明AG通过β-葡聚糖受体介导的内吞作用被巨噬细胞摄取，所以我们想进一步表征IFN-γ对内吞作用的抑制效果。我们比较了AG和中性红（NR）的内化情况。NR通过液相内吞作用被巨噬细胞内化。AG和NR显示出相似的流入/流出模式。然而，AG的初始积累速率比NR大得多，这可能是因为β-葡聚糖受体参与了AG的摄取。内化的AG与内吞小泡的膜相关，并在共聚焦激光扫描显微镜（CLSM）图像上形成特征性环。用IFN-γ处理巨噬细胞会抑制AG和NR的流入和流出。添加到细胞培养物中的佛波酯肉豆蔻酸酯（PMA）增加了AG和NR的积累，并逆转了IFN-γ的抑制作用。PMA的作用依赖于功能完整的微丝和微管。CLSM显示，在IFN-γ处理的细胞中，积累的AG大多定位于小泡（尺寸<2微米）中，在未处理的细胞中定位于大小泡中，而在PMA处理的细胞中大多定位于大泡（尺寸>2微米）中。总之，IFN-γ可能通过抑制大泡的形成来抑制AG的β-葡聚糖受体介导的内吞作用和NR的液相内吞作用。
