Saitoh O, Gallagher R E, Fukuda M
La Jolla Cancer Research Foundation, Cancer Research Center, California 92037.
Cancer Res. 1991 Jun 1;51(11):2854-62.
Promyelocytic leukemia HL-60 cells can be induced to differentiate into granulocytic cells by various agents including retinoic acid (RA), dimethyl sulfoxide, and 6-thioguanine (6-TG). Although the induced cells are no longer capable of proliferation, a few cells continue to divide in the presence of inducers, and these cells are resistant to terminal differentiation by these inducers (R. E. Gallagher, D. A. Giangiulio, C-S. Chang, C. J. Glover, and R. L. Felsted, Blood, 68: 1402-1406, 1986). The present study examined the structures of O-glycans attached to leukosialin, a major sialoglycoprotein in HL-60 cells, and the activities of glycosyltransferases involved in O-glycan synthesis. Leukosialin from RA-resistant and 6-TG-resistant HL-60 sublines migrated much more slowly than those from wild-type HL-60 cells when applied to sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The dimethyl sulfoxide-resistant HL-60 subline, on the other hand, expressed leukosialin with a molecular weight similar to wild-type HL-60 cells. RA-resistant and 6-TG-resistant HL-60 cells were found to express a significant amount of tetrasaccharides that contain no sialic acid residue, while wild-type HL-60 cells expressed mainly disialosyl hexasaccharides and contained no detectable amount of asialo-oligosaccharides. Furthermore, wild-type HL-60 cells treated with the inducers for 4 days were found to express the same saccharides present in untreated wild-type HL-60 cells, indicating that the altered O-glycans present in RA and 6-TG sublines were not caused by a direct effect of these agents but rather are intrinsically unique to these sublines. To better understand the mechanisms underlying the differences in O-glycans, the activities of four sialyltransferases were measured: Gal beta 1----3GalNAc alpha 2----3sialyltransferase, Gal beta 1----4(3) GlcNAc alpha 2----3sialyltransferase, Gal beta 1----4GlcNAc alpha 2----6sialyltransferase, and GalNAc alpha 2----6sialyltransferase. Among them, Gal beta 1----3GalNAc alpha 2----3sialyltransferase and Gal beta 1----4(3)GlcNAc alpha 2----3sialyltransferase were much lower in the RA- or 6-TG-resistant HL-60 subline than in wild-type HL-60 cells. These findings indicate that the differences in O-glycans are due to the differences in alpha 2----3sialyltransferase activities. These results strongly suggest that O-glycans associated with leukosialin may play some role in HL-60 cell differentiation.
早幼粒细胞白血病HL - 60细胞可被多种物质诱导分化为粒细胞，这些物质包括视黄酸（RA）、二甲基亚砜和6 - 硫鸟嘌呤（6 - TG）。虽然诱导后的细胞不再具有增殖能力，但仍有少数细胞在诱导剂存在的情况下继续分裂，并且这些细胞对这些诱导剂的终末分化具有抗性（R. E. 加拉格尔、D. A. 詹朱利奥、C - S. 张、C. J. 格洛弗和R. L. 费尔斯泰德，《血液》，68: 1402 - 1406, 1986）。本研究检测了与白细胞唾液酸蛋白（HL - 60细胞中的一种主要唾液酸糖蛋白）相连的O - 聚糖结构，以及参与O - 聚糖合成的糖基转移酶的活性。当应用于十二烷基硫酸钠 - 聚丙烯酰胺凝胶电泳时，来自RA抗性和6 - TG抗性HL - 60亚系的白细胞唾液酸蛋白迁移速度比来自野生型HL - 60细胞的白细胞唾液酸蛋白慢得多。另一方面，二甲基亚砜抗性HL - 60亚系表达的白细胞唾液酸蛋白分子量与野生型HL - 60细胞相似。发现RA抗性和6 - TG抗性HL - 60细胞表达大量不含唾液酸残基的四糖，而野生型HL - 60细胞主要表达二唾液酸基六糖且未检测到无唾液酸寡糖。此外，用诱导剂处理4天的野生型HL - 60细胞被发现表达与未处理的野生型HL - 60细胞中相同的糖类，这表明RA和6 - TG亚系中改变的O - 聚糖不是由这些物质的直接作用引起的，而是这些亚系所特有的。为了更好地理解O - 聚糖差异背后的机制，测量了四种唾液酸转移酶的活性：Galβ1----3GalNAcα2----3唾液酸转移酶、Galβ1----4(3)GlcNAcα2----3唾液酸转移酶、Galβ1----4GlcNAcα2----6唾液酸转移酶和GalNAcα2----6唾液酸转移酶。其中，Galβ1----3GalNAcα2----3唾液酸转移酶和Galβ1----4(3)GlcNAcα2----3唾液酸转移酶在RA或6 - TG抗性HL - 60亚系中比在野生型HL - 60细胞中低得多。这些发现表明O - 聚糖的差异是由于α2----3唾液酸转移酶活性的差异。这些结果强烈表明与白细胞唾液酸蛋白相关的O - 聚糖可能在HL - 60细胞分化中起一定作用。
