title: Homer1 knockdown protects dopamine neurons through regulating calcium homeostasis in an in vitro model of Parkinson's disease.
abstract: Homer1 protein is an important scaffold protein at postsynaptic density and has been demonstrated to play a central role in calcium signaling in the central nervous system. The aim of this study was to investigate the effects of Homer1 knockdown on MPP(+) induced neuronal injury in cultured dopamine (DA) neurons. We found that down-regulating Homer1 expression with specific small interfering RNA (siRNA) significantly suppressed LDH release, reduced Propidium iodide (PI) or Hoechst staining, increased the number of tyrosine hydroxylase (TH) positive cells and DA uptake, and attenuated apoptotic and necrotic cell death after MPP(+) injury. Homer1 knockdown decreased intracellular reactive oxygen species (ROS) generation through inhibition of intracellular calcium overload, but did not affect the endogenous antioxidant enzyme activities. Calcium imaging was used to examine the changes of intracellular Ca(2+) concentration ([Ca(2+)]cyt) and Ca(2+) in endoplasmic reticulum (ER) ([Ca(2+)]ER), and the results showed that Homer1 siRNA transfection attenuated ER Ca(2+) release up to 120min after MPP(+) injury. Furthermore, decrease of [Ca(2+)]cyt induced by Homer1 knockdown in MPP(+) treated neurons was further enhanced by NMDA receptor antagonists MK-801 and AP-5, but not canonical transient receptor potential (TRPC) channel antagonist SKF-96365. l-type calcium antagonist isradipine but not nimodipine further inhibited intracellular calcium overload after MPP(+) insult in Homer1 down-regulated neurons. These results suggest that Homer1 knockdown has protective effects against neuronal injury in in vitro PD model by reducing calcium overload mediated ROS generation, and this protection may be dependent at least in part on the regulatory effects on the function of calcium channels in both plasma membrane and ER.
authors.affiliation: Department of Neurosurgery, Xijing Institute of Clinical Neuroscience, Xijing Hospital, Fourth, Military Medical University, Xi'an, Shaanxi 710032, China; Department of Neurosurgery, The 123th Hospital of PLA, Bengbu, Anhui 233000, China.
authors.forename: Tao
authors.initials: T
authors.lastname: Chen
authors.forename: Yue-fan
authors.initials: YF
authors.lastname: Yang
authors.forename: Peng
authors.initials: P
authors.lastname: Luo
authors.forename: Wei
authors.initials: W
authors.lastname: Liu
authors.forename: Shu-hui
authors.initials: SH
authors.lastname: Dai
authors.forename: Xin-rui
authors.initials: XR
authors.lastname: Zheng
authors.forename: Zhou
authors.initials: Z
authors.lastname: Fei
authors.forename: Xiao-fan
authors.initials: XF
authors.lastname: Jiang
mesh_terms: D015655:1-Methyl-4-phenylpyridinium; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism; D020013:Calcium Signaling; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D016923:Cell Death; D002478:Cells, Cultured; D004298:Dopamine / Q000378:metabolism; D006706:Homeostasis; D000072233:Homer Scaffolding Proteins; D009474:Neurons / Q000378:metabolism* / Q000473:pathology*; D010302:Parkinson Disease, Secondary / Q000139:chemically induced / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: D015220:Calcium Channels; D002352:Carrier Proteins; D000072233:Homer Scaffolding Proteins; C000606624:Homer1 protein, rat; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; D015655:1-Methyl-4-phenylpyridinium; D002118:Calcium; D004298:Dopamine
keywords: Calcium channel; Endoplasmic reticulum; Homer; Parkinson's disease