title: Truncated N-terminal huntingtin fragment with expanded-polyglutamine (htt552-100Q) suppresses brain-derived neurotrophic factor transcription in astrocytes.
abstract: Although huntingtin (htt) can be cleaved at many sites by caspases, calpains, and aspartyl proteases, amino acid (aa) 552 was defined as a preferred site for cleavage in human Huntington disease (HD) brains in vivo. To date, the normal function of wild-type N-terminal htt fragment 1-552 aa (htt552) and its pathological roles of mutant htt552 are still unknown. Although mutant htt (mhtt) is also expressed in astrocytes, whether and how mhtt contributes to the neurodegeneration through astrocytes in HD remains largely unknown. In this study, a glia HD model, using an adenoviral vector to express wild-type htt552 (htt552-18Q) and its mutation (htt552-100Q) in rat primary cortical astrocytes, was generated to investigate the influence of htt552 on the transcription of brain-derived neurotrophic factor (BDNF). Results from enzyme linked immunosorbent assay showed that the level of BDNF in astrocyte-conditioned medium was decreased in the astrocytes expressing htt552-100Q. Quantitative real-time polymerase chain reaction demonstrated that htt552-100Q reduced the transcripts of the BDNF III and IV, hence, repressed the transcription of BDNF. Furthermore, immunofluorescence showed that aggregates formed by htt552-100Q entrapped transcription factors cAMP-response element-binding protein and stimulatory protein 1, which might account for the reduction of BDNF transcription. These findings suggest that mhtt552 reduces BDNF transcription in astrocytes, which might contribute to the neuronal dysfunction in HD.
authors.affiliation: Department of Physiology, Soochow University School of Biology and Basic Medical Sciences, Suzhou, China.
authors.forename: Linhui
authors.initials: L
authors.lastname: Wang
authors.forename: Fang
authors.initials: F
authors.lastname: Lin
authors.forename: Jin
authors.initials: J
authors.lastname: Wang
authors.forename: Junchao
authors.initials: J
authors.lastname: Wu
authors.forename: Rong
authors.initials: R
authors.lastname: Han
authors.forename: Lujia
authors.initials: L
authors.lastname: Zhu
authors.forename: Guoxing
authors.initials: G
authors.lastname: Zhang
authors.forename: Marian
authors.initials: M
authors.lastname: DiFiglia
authors.forename: Zhenghong
authors.initials: Z
authors.lastname: Qin
mesh_terms: D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D001253:Astrocytes / Q000166:cytology; D019208:Brain-Derived Neurotrophic Factor / Q000378:metabolism*; D017077:Culture Media, Conditioned / Q000494:pharmacology; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D005786:Gene Expression Regulation; D006801:Humans; D000071058:Huntingtin Protein; D008856:Microscopy, Fluorescence / Q000379:methods; D009419:Nerve Tissue Proteins / Q000737:chemistry*; D009474:Neurons / Q000166:cytology; D009687:Nuclear Proteins / Q000737:chemistry*; D010455:Peptides / Q000235:genetics*; D017434:Protein Structure, Tertiary; D051381:Rats; D017207:Rats, Sprague-Dawley; D014157:Transcription Factors / Q000378:metabolism
chemical_list: D019208:Brain-Derived Neurotrophic Factor; D017077:Culture Media, Conditioned; C086055:HTT protein, human; C499524:Htt protein, rat; D000071058:Huntingtin Protein; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D010455:Peptides; D014157:Transcription Factors; C097188:polyglutamine