Department of Pharmacology, Stony Brook University, Stony Brook, New York 11794, USA.
J Neurochem. 2010 Apr;113(1):200-12. doi: 10.1111/j.1471-4159.2010.06596.x. Epub 2010 Feb 2.
Oligodendrocyte progenitor cells first proliferate to generate sufficient cell numbers and then differentiate into myelin-producing oligodendrocytes. The signal transduction mediators that underlie these events, however, remain poorly understood. The tyrosine phosphatase Shp1 has been linked to oligodendrocyte differentiation as Shp1-deficient mice show hypomyelination. The Shp1 homolog, Shp2, has recently been shown to regulate astrogliogenesis, but its role in oligodendrocyte development remains unknown. Here, we report that Shp2 protein levels were developmentally regulated in oligodendrocytes, with Shp2 phosphorylation being promoted by oligodendroglial mitogens but suppressed by laminin, an extracellular matrix protein that promotes oligodendroglial differentiation. In contrast, oligodendrocyte progenitors were found to be unresponsive to mitogens following Shp2, but not Shp1, depletion. In agreement with previous studies, Shp1 depletion led to decreased levels of myelin basic protein in differentiating oligodendrocytes, as well as reduced outgrowth of myelin membrane sheets. Shp2 depletion in contrast did not prevent oligodendrocyte differentiation but promoted expanded myelin membrane outgrowth. Taken together these data suggest that Shp1 and Shp2 have distinct functions in oligodendrocyte development: Shp2 regulates oligodendrocyte progenitor proliferation and Shp1 regulates oligodendrocyte differentiation. Adhesion to laminin may additionally provide extrinsic regulation of Shp2 activity and thus promote the transition from progenitor to differentiating oligodendrocyte.
少突胶质前体细胞首先增殖以产生足够的细胞数量,然后分化为产生髓鞘的少突胶质细胞。然而,这些事件背后的信号转导介质仍知之甚少。酪氨酸磷酸酶 Shp1 与少突胶质细胞分化有关,因为 Shp1 缺陷小鼠表现出髓鞘形成减少。最近表明,Shp1 的同源物 Shp2 调节星形胶质细胞发生,但它在少突胶质细胞发育中的作用仍不清楚。在这里,我们报告 Shp2 蛋白水平在少突胶质细胞中呈发育性调节,Shp2 磷酸化受少突胶质细胞有丝分裂原促进,但受层粘连蛋白抑制,层粘连蛋白是一种促进少突胶质细胞分化的细胞外基质蛋白。相比之下,发现少突胶质细胞祖细胞在 Shp2 耗尽后对有丝分裂原无反应,但 Shp1 耗尽后则有反应。与先前的研究一致,Shp1 耗尽导致分化中的少突胶质细胞中髓鞘碱性蛋白水平降低,以及少突胶质细胞膜片的生长减少。相比之下,Shp2 耗尽不会阻止少突胶质细胞分化,但会促进扩大的髓鞘膜生长。这些数据表明 Shp1 和 Shp2 在少突胶质细胞发育中具有不同的功能:Shp2 调节少突胶质前体细胞增殖,Shp1 调节少突胶质细胞分化。黏附到层粘连蛋白可能会额外调节 Shp2 活性,从而促进从祖细胞向分化的少突胶质细胞的转变。