mGluR5 promotes the differentiation of rat neural progenitor cells into cholinergic neurons and activation of extracellular signal-related protein kinases Lingyu Zhao a,b, *, Qian Jiao a, *, Chen Huang b , Ni Hou b , Xinlin Chen a , Jianshui Zhang a , Pengbo Yang a , Xi Xu c , Tusheng Song b and Yong Liu a Metabotropic glutamate receptors (mGluRs) regulate neurogenesis in the mammalian central nervous system during development and throughout adulthood. However, the mechanisms remain unknown. The present study was aimed at investigating the effect of mGluR5 on the differentiation of rat neural progenitor cells (NPCs) into neurons as well as the underlying molecular mechanisms. NPCs were treated with mGluR5 agonist (RS)-2-chloro-5-hydroxyphenylglycine (CHPG), mGluR5 siRNA, and antagonist 6-methyl-2-(phenylethynyl) pyridine hydrochloride (MPEP), respectively. Three different subtypes of neurons (cholinergic, GABAergic, and dopaminergic neurons) were evaluated, and the activation of signaling pathways of mitogen-activated protein kinases was determined. Results showed that CHPG caused rat NPCs to differentiate into neurons, whereas mGluR5 siRNA and MPEP inhibited the cell differentiation. The proportion of cholinergic neurons increased with CHPG treatment and decreased after siRNA or MPEP treatment, whereas there were no significant changes in the proportions of GABAergic and dopaminergic neurons after treatment. The phosphorylated ERK1/2 levels increased after CHPG treatment and decreased after siRNA or MPEP treatment. In conclusion, our findings showed that mGluR5 caused rat NPCs to differentiate into cholinergic neurons by activating ERKs, suggesting that mGluR5 may play a significant role in the mechanism and treatment of degenerative diseases such as Alzheimer’s disease. NeuroReport 25:427–434  c 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins. NeuroReport 2014, 25:427–434 Keywords: central nervous system, dopaminergic neurons, GABAergic neurons, mitogen-activated protein kinases, neurogenesis a Institute of Neurobiology, b Department of Genetics and Cell Biology, Environment and Genes Related to Diseases Key Laboratory of Education Ministry, Xi’an Jiaotong University College of Medicine and c Department of Anatomy, Xi’an Medical University, Xi’an, People’s Republic of China Correspondence to Yong Liu, MD, PhD, Institute of Neurobiology, Xi’an Jiaotong University College of Medicine, Xi’an, Shaanxi 710061, People’s Republic of China Tel/fax: + 86 29 8265 5080; e-mail: liuy5599@mail.xjtu.edu.cn *Lingyu Zhao and Qian Jiao contributed equally to the writing of this article. Received 29 August 2013 accepted 29 January 2014 Introduction Neural progenitor cells (NPCs) are multipotent and self- renewing cells present in the mammalian central nervous system (CNS) during development and throughout adulthood. These cells have the potential ability to differentiate into different neural lineages such as neurons, astrocytes, and oligodendrocytes [1]. NPCs can be isolated from embryonic and adult brain, and expanded as neurospheres in culture in the presence of basic fibroblast growth factor and epidermal growth factor [2]. In the last decade, NPC-based therapies have been repaired successfully for CNS diseases and are considered very effective for the improvement in neurologic function in nerve injury, brain ischemia, and neurodegenerative disorders [3]. Nevertheless, a key question in cell transplantation and regenerative thera- pies is how NPCs repair injured neurons. To elucidate the mechanisms, it is necessary to investigate NPC differ- entiation and the cellular biology processes. Glutamate is a major excitatory neurotransmitter in the CNS that may contribute toward neurogenesis by activating ionotropic glutamate receptors (iGluRs) and metabotropic glutamate receptors (mGluRs) [4]. In brain injuries that involve glutamate excitotoxicity, such as brain ischemia and epilepsy, glutamate receptor signaling might regulate the neurogenesis in response to the injuries. mGluRs, including eight subtypes termed mGluR1–8, are coupled with G proteins. mGluR5 activates phospholipase C and acts on phosphatidylino- sitol bisphosphate, causing the increase in two second messengers: inositol trisphosphate and diacylglycerol [4]. This neurotransmitter was found expressed in zones of active neurogenesis in the embryonic and postnatal rat brain, and might specifically support the survival of NPCs differentiating into neurons [5]. The results of many studies suggest that mGluR5 might play a very important role in regulating NPC differentiation in the develop- ment of CNS or after brain injury [5,6]. Tian et al. [7] reported that the activation of mGluR7 might promote the differentiation of NPCs into neurons by influencing phosphorylation of RAS/mitogen-activated protein kinase (MAPK)-signaling pathways. Extracellular signal-related protein kinase (ERK) is a main member of the MAPK family and a potential downstream mediator Cellular, molecular and developmental neuroscience 427 0959-4965  c 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins DOI: 10.1097/WNR.0000000000000134 Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.