Van Brocklyn J, Bremer E G, Yates A J
Division of Neuropathology, Ohio State University, Columbus 43210.
J Neurochem. 1993 Jul;61(1):371-4. doi: 10.1111/j.1471-4159.1993.tb03581.x.
We previously showed that gangliosides inhibit DNA synthesis in Swiss 3T3 cells stimulated with platelet-derived growth factor (PDGF) in a dose-responsive manner. This correlated with the inhibitory effects of several gangliosides (except GM3) on tyrosine phosphorylation of the PDGF receptor (PDGFR). [35S]Methionine-labeled Swiss 3T3 cells were incubated either with or without gangliosides and stimulated with PDGF, and proteins were cross-linked with bis(sulfosuccinimidyl) suberate. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that two protein bands (170 and 350 kDa) were specifically immunoprecipitated with an anti-PDGFR antibody. Using both Swiss 3T3 and human glioma U-1242MG cells, western blots with anti-PDGFR and anti-phosphotyrosine antibodies confirmed that these bands were the PDGFR monomer and dimer, respectively, and that phosphotyrosine was present in these bands only after cells were stimulated with PDGF. Of the gangliosides tested, GM1, GM2, GD1a, GD1b, GD3, and GT1b, but not GM3, inhibited the formation of the 350-kDa band. These results demonstrate that all gangliosides tested, except GM3, probably inhibit PDGF-mediated growth by preventing dimerization of PDGFR monomers. Loss of more complex gangliosides in human gliomas would permit unregulated activation of the PDGFR, contributing to uncontrolled growth stimulation. We propose that ganglioside inhibition of receptor dimerization is a novel mechanism for regulating and coordinating several trophic factor-mediated cell functions.
我们先前表明，神经节苷脂以剂量依赖的方式抑制血小板衍生生长因子（PDGF）刺激的瑞士3T3细胞中的DNA合成。这与几种神经节苷脂（GM3除外）对PDGF受体（PDGFR）酪氨酸磷酸化的抑制作用相关。将[35S]甲硫氨酸标记的瑞士3T3细胞与神经节苷脂一起或不与神经节苷脂一起孵育，并用PDGF刺激，然后用双（磺基琥珀酰亚胺基）辛二酸酯使蛋白质交联。十二烷基硫酸钠 - 聚丙烯酰胺凝胶电泳显示，两条蛋白带（170和350 kDa）被抗PDGFR抗体特异性免疫沉淀。使用瑞士3T3细胞和人胶质瘤U - 1242MG细胞，用抗PDGFR和抗磷酸酪氨酸抗体进行的蛋白质印迹证实，这些条带分别是PDGFR单体和二聚体，并且仅在细胞用PDGF刺激后这些条带中才存在磷酸酪氨酸。在所测试的神经节苷脂中，GM1、GM2、GD1a、GD1b、GD3和GT1b（但不是GM3）抑制了350 kDa条带的形成。这些结果表明，除GM3外，所有测试的神经节苷脂可能通过阻止PDGFR单体二聚化来抑制PDGF介导的生长。人胶质瘤中更复杂神经节苷脂的缺失将允许PDGFR的不受调节的激活，导致不受控制的生长刺激。我们提出神经节苷脂对受体二聚化的抑制是调节和协调几种营养因子介导的细胞功能的一种新机制。
