Seidl K, Erck C, Buchberger A
Institute for Biochemistry and Biotechnology, Department of Cell and Molecular Biology, University of Braunschweig, Germany.
J Cell Physiol. 1998 Jul;176(1):10-21. doi: 10.1002/(SICI)1097-4652(199807)176:1<10::AID-JCP2>3.0.CO;2-B.
We have studied expression and function of neurotrophins and their receptors during myogenic differentiation of C2C12 cells, a clonal cell line derived from mouse muscle that is capable of in vitro differentiation. The genes coding for nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF) and their common low-affinity receptor p75(neurotrophin receptor) (p75NTR) were shown to be expressed in C2C12 myoblasts and downregulated during myogenic differentiation and fusion into myotubes. Cocultures with dorsal root ganglia from day 8 chick embryos revealed neurite-promoting activities of C2C12 cells that ceased with myogenic differentiation. These data suggest a temporal and developmental window for the effect of myogenic cell-derived neurotrophins on neuronal as well as on myogenic cell populations. NGF was shown to increase DNA synthesis and cell growth of C2C12 myoblasts and to enhance myogenic differentiation in this cell line. We present evidence that NGF-mediated processes take place at stages preceding myogenic differentiation. Enhanced muscle differentiation was also seen in p75NTR-overexpressing C2C12 myoblasts which maintained high levels of receptors but ceased to produce NGF during differentiation. In contrast, when exogenous NGF was present at the onset of myogenic differentiation of receptor-overexpressing cells, muscle cell development was strongly repressed. This indicates that downregulation of p75NTR is necessary for guiding myogenic cells towards terminal differentiation. Since none of the trk high-affinity neurotrophin receptors could be demonstrated in C2C12 cells, we conclude that NGF mediates its nonneurotrophic effect via its low-affinity receptor in an autocrine fashion.
我们研究了神经营养因子及其受体在C2C12细胞成肌分化过程中的表达和功能，C2C12细胞是一种源自小鼠肌肉的克隆细胞系，能够在体外分化。编码神经生长因子（NGF）、脑源性神经营养因子（BDNF）及其共同的低亲和力受体p75（神经营养因子受体）（p75NTR）的基因在C2C12成肌细胞中表达，并在成肌分化和融合为肌管的过程中下调。与第8天鸡胚背根神经节共培养显示，C2C12细胞具有促进神经突生长的活性，这种活性随着成肌分化而停止。这些数据表明，成肌细胞衍生的神经营养因子对神经元以及成肌细胞群体的影响存在一个时间和发育窗口。NGF被证明可增加C2C12成肌细胞的DNA合成和细胞生长，并增强该细胞系中的成肌分化。我们提供的证据表明，NGF介导的过程发生在成肌分化之前的阶段。在过表达p75NTR的C2C12成肌细胞中也观察到增强的肌肉分化，这些细胞在分化过程中保持高水平的受体，但停止产生NGF。相反，当在过表达受体的细胞成肌分化开始时存在外源性NGF时，肌肉细胞发育受到强烈抑制。这表明p75NTR的下调对于引导成肌细胞向终末分化是必要的。由于在C2C12细胞中未检测到任何trk高亲和力神经营养因子受体，我们得出结论，NGF通过其低亲和力受体以自分泌方式介导其非神经营养作用。
