Deloulme J C, Janet T, Pettmann B, Laeng P, Knoetgen M F, Sensenbrenner M, Baudier J
Centre de Neurochimie du CNRS, INSERM Unité 44, Strasbourg, France.
J Neurochem. 1992 Feb;58(2):567-78. doi: 10.1111/j.1471-4159.1992.tb09757.x.
Basic fibroblast growth factor (bFGF) is a well-characterized peptide hormone that has mitogenic activity for various cell types and elicits a characteristic set of responses on the cell types investigated. In this report we confirmed that bFGF is a potent mitogen for rat brain-derived oligodendrocyte (OL) precursor cells as well as for differentiated OL in secondary culture. bFGF was shown to induce expression of the protooncogene c-fos in OL. The role of protein kinase C (PKC) in mediating bFGF-stimulated proliferation as well as c-fos expression in OL was investigated. The PKC activator phorbol 12-myristate 13-acetate (PMA) stimulated c-fos expression but did not trigger cell proliferation. When PKC was down-regulated by pretreatment of OL with PMA for 20 h, the bFGF-mediated stimulations of OL proliferation and c-fos mRNA expression were still observed, whereas the induction of c-fos mRNA by PMA was totally inhibited. These data demonstrate that the bFGF mitogenic signaling pathway in OLs does not require PKC. On the other hand, bFGF was found to stimulate specifically the phosphorylation of a limited number of PKC substrates in oligodendroglial cells, including the MARCKS protein. The bFGF-dependent phosphorylation of MARCKS protein was totally inhibited when PKC was first down-regulated, indicating that the phosphorylation of this protein is PKC dependent. Tryptic digestion of the phosphorylated MARCKS protein revealed that bFGF stimulated specifically the phosphorylation of the MARCKS protein on a single phosphopeptide. We provide evidence that bFGF also stimulated fatty acylation of the MARCKS protein, which might explain the observed specific bFGF-dependent phosphorylation of this protein in OL. We propose that bFGF-dependent fatty acylation and phosphorylation of the MARCKS protein are not essential for the transduction of the bFGF mitogenic signal but are probably linked to differentiation processes elicited by bFGF on OL.
碱性成纤维细胞生长因子（bFGF）是一种特性明确的肽类激素，对多种细胞类型具有促有丝分裂活性，并能在被研究的细胞类型上引发一系列特征性反应。在本报告中，我们证实bFGF是大鼠脑源性少突胶质细胞（OL）前体细胞以及传代培养的分化型OL的强效促有丝分裂剂。bFGF被证明可诱导OL中原癌基因c-fos的表达。研究了蛋白激酶C（PKC）在介导bFGF刺激的OL增殖以及c-fos表达中的作用。PKC激活剂佛波酯12-肉豆蔻酸酯13-乙酸酯（PMA）刺激了c-fos表达，但未引发细胞增殖。当用PMA预处理OL 20小时使PKC下调时，仍可观察到bFGF介导的OL增殖和c-fos mRNA表达的刺激作用，而PMA对c-fos mRNA的诱导作用则被完全抑制。这些数据表明，OL中的bFGF促有丝分裂信号通路不需要PKC。另一方面，发现bFGF可特异性刺激少突胶质细胞中有限数量的PKC底物的磷酸化，包括MARCKS蛋白。当PKC首先被下调时，bFGF依赖的MARCKS蛋白磷酸化被完全抑制，表明该蛋白的磷酸化是PKC依赖性的。对磷酸化的MARCKS蛋白进行胰蛋白酶消化显示，bFGF特异性刺激了MARCKS蛋白在单个磷酸肽上的磷酸化。我们提供的证据表明，bFGF还刺激了MARCKS蛋白的脂肪酰化，这可能解释了在OL中观察到的该蛋白特异性的bFGF依赖性磷酸化。我们提出，bFGF依赖的MARCKS蛋白脂肪酰化和磷酸化对于bFGF促有丝分裂信号的转导并非必不可少，但可能与bFGF对OL引发的分化过程有关。
