Department of Psychiatry and Behavioral Health, University of North Texas Health Science Center, TX, USA.
Matrix Biol. 2010 Jul;29(6):503-10. doi: 10.1016/j.matbio.2010.06.004. Epub 2010 Jun 23.
Hyaluronan (HA) is a glycosaminoglycan composed of N-acetylglucosamine and glucuronic acid subunits. Endocytosis is thought to play an essential role in the catabolism of HA due to the intracellular compartmentalization of the HA degrading hyaluronidase enzymes. Previous investigations have shown that keratinocytes, chondrocytes and breast tumor cell lines endocytose HA via the cell surface glycoprotein, CD44. However, other cell types endocytose HA using a CD44-independent mechanism that remains to be defined. The purpose of this study was to investigate HA endocytosis in B16-F10 melanoma cells. We found that B16-F10 melanoma cells expressed CD44 on their surfaces. Unexpectedly, CD44 did not play a role in the endocytosis of HA. Electron microscopy studies revealed that B16-F10 melanoma cells exhibited membrane ruffling, a characteristic feature of macropinocytosis, only after incubating the cells with the HA co-polymer. Moreover, B16-F10 melanoma cells endocytosed HA via macropinocytosis as assessed by drug inhibition studies and the co-localization of fluorescently labeled HA with fluorescent tracers under confocal microscopy. Based on these results, we conclude that induced macropinocytosis may provide a previously unrecognized avenue for HA endocytosis in some cell types.
透明质酸（HA）是由 N-乙酰葡萄糖胺和葡萄糖醛酸亚单位组成的糖胺聚糖。由于 HA 降解酶透明质酸酶的细胞内区室化，内吞作用被认为在 HA 的分解代谢中起重要作用。先前的研究表明，角朊细胞、软骨细胞和乳腺癌细胞系通过细胞表面糖蛋白 CD44 内吞 HA。然而，其他细胞类型通过仍有待确定的 CD44 非依赖性机制内吞 HA。本研究旨在研究 B16-F10 黑色素瘤细胞中的 HA 内吞作用。我们发现 B16-F10 黑色素瘤细胞在其表面表达 CD44。出乎意料的是，CD44 并不参与 HA 的内吞作用。电子显微镜研究显示，只有在用 HA 共聚物孵育细胞后，B16-F10 黑色素瘤细胞才会表现出细胞膜皱襞，这是巨胞饮的特征。此外，通过药物抑制研究和在共聚焦显微镜下荧光标记的 HA 与荧光示踪剂的共定位评估，B16-F10 黑色素瘤细胞通过巨胞饮作用内吞 HA。基于这些结果，我们得出结论，诱导的巨胞饮可能为某些细胞类型中的 HA 内吞提供了以前未被认识的途径。
