Expression of the insulin-like growth factor 1 receptor (IGF-1R) in breast cancer cells: evidence for a regulatory role of dolichyl phosphate in the transition from an intracellular to an extracellular IGF-1 pathway
Expression of the insulin-like growth factor 1 receptor (IGF-1R) in breast cancer cells: evidence for a regulatory role of dolichyl phosphate in the transition from an intracellular to an extracellular IGF-1 pathway
复制标题
DOI：
10.1093/glycob/9.6.571
复制
发表时间：
1999-06-01
期刊：
影响因子：
4.3
通讯作者：
Larsson, O
中科院分区：
文献类型：
--
作者：
Dricu, A;Kanter, L;Larsson, O
在这项研究中，我们提供了证据表明，在雌激素非依赖性乳腺癌细胞的细胞表面IGF-1 R的低表达是由于磷酸长链甘油酯的从头合成速率低。对雌激素受体阴性乳腺癌细胞系MDA 231进行了分析，与之相比，黑色素瘤细胞系SK-MEL-2表达大量质膜结合的IGF-1 R，尽管MDA 231细胞具有很少或没有IGF-LR的表面表达，但它们表达功能性（即，通过测量[H-3]甲羟戊酸掺入到磷酸长羟乙酯中，我们可以证明磷酸长羟乙酯合成的速率在MDA 231细胞中比在SK-MEL-2中低得多。细胞此外，IGF-1 R α亚基的N-连接糖基化在黑素瘤细胞中高8倍。在MDA 231细胞中加入磷酸长羟乙酯后，IGF-1 R的N-连接糖基化显著增加，这又与IGF-1 R大量易位至质膜相关，如通过IGF-1结合分析和质膜蛋白的Western印迹所测定。磷酸多脂刺激的受体被证明是生物化学活性的，因为它们表现出自磷酸化。在正常条件下，在细胞表面表达非常少的IGF-1 R的MDA 231细胞不被抗体生长阻滞（α IR-3）阻断IGF-1与IGF-1 R的结合，然而，在用磷酸长萜酯处理后，导致IGF-1 R的高细胞表面表达，α IR-3有效地阻断了MDA 231细胞的生长。考虑到乳腺癌细胞产生IGF-1并表现出细胞内结合的事实，我们的数据表明，从头合成的磷酸长酯的水平可能是细胞是否使用细胞内或细胞外自分泌IGF-1途径的关键。
In this study we provide evidence that the low expression of IGF-1R at the cell surface of estrogen-independent breast cancer cells is due to a low rate of de novo synthesis of dolichyl phosphate, The analyses were performed on the estrogen receptor-negative breast cancer cell line MDA231 and, in comparison, the melanoma cell line SK-MEL-2, which expresses a high number of plasma membrane-bound IGF-1R, Whereas the MDA231 cells had little or no surface expression of IGF-LR, they expressed functional (i.e., ligand-binding) intracellular receptors, By measuring the incorporation of [H-3]mevalonate into dolichyl phosphate, we could demonstrate that the rate of dolichyl phosphate synthesis was considerably lower in MDA231 cells than in SK-MEL-2. cells. Furthermore, N-linked glycosylation of the alpha-subunit of IGF-1R was 8-fold higher in the melanoma cells. Following addition of dolichyl phosphate to MDA231 cells, N-linked glycosylation of IGF-1R was drastically increased, which in turn was correlated to a substantial translocation of IGF-1R to the plasma membrane, as assayed by IGF-1 binding analysis and by Western blotting of plasma membrane proteins. The dolichyl phosphate-stimulated receptors were proven to be biochemically active since they exhibited autophosphorylation, Under normal conditions MDA231 cells, expressing very few IGF-1R at the cell surface, were not growth-arrested by an antibody (alpha IR-3) blocking the binding of IGF-1 to IGF-1R, However, after treatment with dolichyl phosphate, leading to a high cell surface expression of IGF-1R, alpha IR-3 efficiently blocked MDA231 cell growth. Taken together with the fact that the breast cancer cells produce IGF-1 and exhibit intracellular binding, our data suggest that the level of de novo-synthesized dolichyl phosphate may be critical for whether the cells will use an intracellular or an extracellular autocrine IGF-1 pathway.