Mason P W, Bigbee J W, DeVries G H
Department of Biochemistry and Molecular Biophysics, Medical College of Virginia, Virginia Commonwealth University, Richmond 23298.
J Cell Biol. 1989 Feb;108(2):607-11. doi: 10.1083/jcb.108.2.607.
Proliferation of Schwann cells is one of the first events that occurs after contact with a growing axon. To further define the distribution and properties of this axonal mitogen, we have (a) cocultured cerebellar granule cells, which lack glial ensheathment in vivo with Schwann cells; and (b) exposed Schwann cell cultures to isolated granule cell membranes. Schwann cells cocultured with granule cells had a 30-fold increase in the labeling index over Schwann cells cultured alone, suggesting that the mitogen is located on the granule cell surface. Inhibition of granule cell proteoglycan synthesis caused a decrease in the granule cells' ability to stimulate Schwann cell proliferation. Membranes isolated from cerebellar granule cells when added to Schwann cell cultures caused a 45-fold stimulation in [3H]thymidine incorporation. The granule cell mitogenic signal was heat and trypsin sensitive and did not require lysosomal processing by Schwann cells to elicit its proliferative effect. The ability of granule cells and their isolated membranes to stimulate Schwann cell proliferation suggests that the mitogenic signal for Schwann cells is a ubiquitous factor present on all axons regardless of their ultimate state of glial ensheathment.
雪旺细胞增殖是其与生长中的轴突接触后最早发生的事件之一。为了进一步明确这种轴突有丝分裂原的分布和特性，我们进行了以下实验：(a) 将在体内缺乏神经胶质包被的小脑颗粒细胞与雪旺细胞进行共培养；(b) 将雪旺细胞培养物暴露于分离的颗粒细胞膜。与单独培养的雪旺细胞相比，与颗粒细胞共培养的雪旺细胞标记指数增加了30倍，这表明有丝分裂原位于颗粒细胞表面。抑制颗粒细胞蛋白聚糖合成会导致颗粒细胞刺激雪旺细胞增殖的能力下降。从小脑颗粒细胞分离的膜加入雪旺细胞培养物后，可使[3H]胸腺嘧啶核苷掺入增加45倍。颗粒细胞有丝分裂信号对热和胰蛋白酶敏感，且不需要雪旺细胞进行溶酶体处理来引发其增殖效应。颗粒细胞及其分离的膜刺激雪旺细胞增殖的能力表明，雪旺细胞的有丝分裂信号是一种存在于所有轴突上的普遍因子，无论其最终的神经胶质包被状态如何。
