Function of hCG/LH and their receptor in the mammalian nervous system

本研究以大鼠肾上腺嗜铬细胞瘤双能细胞系PC12为研究对象。为探讨人绒毛膜促性腺激素(HCG)对PC12细胞分化的影响，将野生型人促黄体激素/绒毛膜促性腺激素受体(LH/CG-R)导入PC12细胞，用稳定表达转基因的亚克隆进行实验。在PC12细胞中用hCG/LHR激活转导的LHCG-R或表达成分激活的突变型LHCG-R可引起明显的神经元分化的形态和生化改变。人绒毛膜促性腺激素的分化作用具有配体剂量和时间依赖性。Western印迹分析显示，hCG处理后，细胞外信号调节蛋白激酶(ERKs)和p38丝裂原活化蛋白激酶(MAPK)均被激活。抑制研究表明，ERK和p38MAPK信号转导通路在分化过程中都是不可或缺的。此外，磷脂酶C(PLC)途径部分参与了hCG诱导PC12的分化。这些发现暗示了hCG/Lh和Lh/Cg-R在哺乳动物神经系统神经发生中的潜在作用。我们进一步研究了hCG在髓鞘形成过程中的可能作用。髓磷脂蛋白零(P0)是周围神经系统髓鞘的主要成分，在髓鞘形成的初始阶段被诱导。人绒毛膜促性腺激素与Forskolin联合应用可显著提高体外瞬时表达黄体生成素/CG-R的小鼠雪旺细胞系P0mRNA的表达。P0蛋白表达的检测正在进行中。提示hCG可能通过诱导P0的表达而促进髓鞘形成。HCG诱导P0表达的机制可能与KROX-20等多种转录因子有关，目前正在研究中。这些研究表明，hCG/LH及其受体参与哺乳动物神经系统的发育和维持。人绒毛膜促性腺激素可能成为未来治疗急性神经损伤或神经退行性疾病的一种潜在的再生药物。

The bipotent cell line, PC12, derived from rat adrenal pheochromocytoma was used as an in vitro model for our studies. To examine the effect of human chorionic gonadotropin (hCG) on PC12 differentiation, wild type human luteinizing hormone/chorionic gonadotropin receptor (LH/CG-R) was transduced into PC12 cells and stable transgene-expressing subclones were used for experiments. Activation of transduced LH/CG-R with hCG/LH or expression of a constitutively activated mutated LH/CG-R in PC12 cells induced distinct morphological and biochemical changes characteristic of neuronal differentiation. The differentiation effect of hCG was ligand dose- and time-dependent. Western blot analysis revealed that both the extracellular signal-regulated kinases (ERKs) and p38 mitogen-activated protein kinase (MAPK) were activated after hCG treatment. Inhibitor studies showed both the ERK and p38 MAPK signal transduction pathway were indispensable for the differentiation process. In addition, the Phospholipase C (PLC) pathway was partially involved in hCG induced PC12 differentiation. These findings imply a potential role of hCG/LH and LH/CG-R in the neurogenesis of the mammalian nervous system. We further investigated the possible effect of hCG in the initiation of myelination. Myelin protein zero (P0) is the major component of the myelin sheath of the peripheral nervous system and is induced at the initial phase of myelination. hCG when combined with Forskolin dramatically increased P0 mRNA expression in a mouse Schwann cell line transiently expressing LH/CG-R in vitro. Examination of P0 protein expression is underway. The result suggests hCG may promotes myelination through inducing P0 expression. The mechanism of hCG induced P0 expression could be through several transcription factors such as krox-20 and is under investigation. These studies show that hCG/LH and its receptor participate in the development and maintenance of the mammalian nervous system. hCG could be a potential regeneration drug for future treatment of acute neural injuries or neurodegenerative disorders.