Human synapsin I mediates the function of nuclear respiratory factor 1 in neurite outgrowth in neuroblastoma IMR-32 cells.
Nuclear respiratory factor (NRF)-1 is a transcription factor with a novel function in neurite outgrowth. Synapsin I protein is a well-known phosphoprotein in neuronal terminals and has been implicated in neuronal differentiation. Human synapsin I gene promoter has a putative NRF-1 responsive element (NRE), but it is not known whether this NRE is functional. We hypothesized that synapsin I is downstream of NRF-1 and mediates its function in neurite outgrowth. Gel electrophoretic mobility shift assays, chromatin immunoprecipitation, site-directed mutagenesis, and promoter studies indicated that NRF-1 is a positive regulator of synapsin I promoter. Exogenous NRF-1 overexpression increased synapsin I protein levels in IMR-32 and HEK293T cells. Serum deprivation, which induces neurite outgrowth in IMR-32 cells, increased the binding activity of NRF-1 to synapsin I NRE and induced alternating synapsin I protein expression. Down-regulating synapsin I expression markedly decreased the percentage of neurite-bearing cells and the length of the longest neurite in IMR-32 cells that stably or transiently overexpressed NRF-1. We conclude that the human synapsin I gene is positively regulated by NRF-1 and mediates the function of NRF-1 in neurite outgrowth.
Wang
Jen-Ling
JL
Institute of Basic Medical Sciences, National Cheng Kung University, College of Medicine, Taiwan.
Chang
Wen-Teng
WT
Tong
Chih-Wei
CW
Kohno
Kimitoshi
K
Huang
A-Min
AM
D002461:Cell Line, Transformed; D045744:Cell Line, Tumor; D047369:Chromatin Immunoprecipitation / Q000379:methods; D024202:Electrophoretic Mobility Shift Assay / Q000379:methods; D005786:Gene Expression Regulation / Q000187:drug effects / Q000235:genetics; D006801:Humans; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D016296:Mutagenesis / Q000502:physiology; D016501:Neurites / Q000187:drug effects / Q000502:physiology*; D009447:Neuroblastoma / Q000473:pathology*; D051266:Nuclear Respiratory Factor 1 / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger; D034741:RNA, Small Interfering / Q000494:pharmacology; D044967:Serum / Q000378:metabolism; D016704:Synapsins / Q000235:genetics / Q000378:metabolism*; D014162:Transfection / Q000379:methods
D051266:Nuclear Respiratory Factor 1; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D016704:Synapsins; D008156:Luciferases