Truncated N-terminal huntingtin fragment with expanded-polyglutamine （htt552-100Q） suppresses brain-derived neurotrophic factor transcription in astrocytes  

作　　者：Linhui Wang Fang Lin Jin Wang Junchao Wu Rong Han Lujia Zhu Guoxing Zhang Marian DiFiglia Zhenghong Qin 

机构地区：[1]Department of Physiology,Soochow University School of Biology and Basic Medical Sciences,Suzhou 215123,China [2]Departrnent of Pharmacology and Laboratory of Aging and Nervous Diseases,Soochow University School of Pharmacy,Suzhou 215123,China [3]Laboratory of Neurobiology,Massachusetts General Hospital,Harvard Medical School,Charlestown,Boston,MA 02129,USA

出　　处：《Acta Biochimica et Biophysica Sinica》2012年第3期249-258,共10页生物化学与生物物理学报（英文版）

摘　　要：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 con- tributes 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 aggre- gates formed by htt552-100Q entrapped transcription factors cAMP-response element-binding protein and stimulatory protein 1, which might account for the reduc- tion of BDNF transcription. These findings suggest that mhtt552 reduces BDNF transcription in astrocytes, which might contribute to the neuronal dysfunction in HD.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 con- tributes 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 aggre- gates formed by htt552-100Q entrapped transcription factors cAMP-response element-binding protein and stimulatory protein 1, which might account for the reduc- tion of BDNF transcription. These findings suggest that mhtt552 reduces BDNF transcription in astrocytes, which might contribute to the neuronal dysfunction in HD.

关 键 词：Huntington＇s disease ASTROCYTES brainderived neurotrophic factor HUNTINGTIN TRANSCRIPTION 

分 类 号：Q421[生物学—神经生物学] Q753[生物学—生理学]