title: cAMP-response element-binding protein contributes to suppression of the A2A adenosine receptor promoter by mutant Huntingtin with expanded polyglutamine residues.
abstract: Huntington's disease is a neurodegenerative disease resulting from a CAG (glutamine) trinucleotide expansion in exon 1 of the Huntingtin (Htt) gene. The role of the striatum-enriched A2A adenosine receptor (A2A-R) in Huntington's disease has attracted much attention lately. In the present study, we found that expression of mutant Htt with expanded poly(Q) significantly reduced the transcript levels of the endogenous A2A-R in PC12 cells and primary striatal neurons. Cotransfection of various promoter constructs of the A2A-R gene and an expression construct of poly(Q)-expanded Htt revealed that the Htt mutant suppressed the core promoter activity of the A2A-R gene. Stimulation of the A2A-R using CGS21680, forskolin, and a constitutively active cAMP-response element-binding protein (CREB) mutant elevated the reduced promoter activity of the A2A-R gene by mutant Htt. Moreover, the effect of CGS was blocked by an A2A-R-selective antagonist (CSC), two inhibitors of protein kinase A, and two dominant negative mutants of (CREB). The protein kinase A/CREB pathway therefore is involved in regulating A2A-R promoter activity. Consistently, an atypical CRE site (TCCAGG) is located in the core promoter region of the A2A-R gene. Electrophoretic gel mobility shift assay and mutational inactivation further demonstrated the functional binding of CREB to the core promoter region and showed that expression of poly(Q)-expanded Htt abolished the binding of CREB to this site. Stimulation of the A2A-R restored the reduced CREB binding caused by the mutant and concurrently reduced mutant Htt aggregation. Collectively, the poly(Q)-expanded mutant Htt suppressed expression of the A2A-R by inhibiting its core promoter at least partially by preventing CREB binding.
authors.affiliation: Division of Neuroscience, Institute of Biomedical Sciences, Academia Sinica and Institute of Neuroscience, National Yang Ming University, Taipei 11529, Taiwan.
authors.forename: Ming-Chang
authors.initials: MC
authors.lastname: Chiang
authors.forename: Yi-Chao
authors.initials: YC
authors.lastname: Lee
authors.forename: Chuen-Lin
authors.initials: CL
authors.lastname: Huang
authors.forename: Yijuang
authors.initials: Y
authors.lastname: Chern
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D017362:Cyclic AMP Response Element-Binding Protein / Q000235:genetics / Q000378:metabolism*; D042622:DNA Repeat Expansion; D005786:Gene Expression Regulation; D006801:Humans; D000071058:Huntingtin Protein; D009419:Nerve Tissue Proteins / Q000235:genetics* / Q000378:metabolism; D009474:Neurons / Q000166:cytology / Q000378:metabolism; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism; D016716:PC12 Cells; D010455:Peptides / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D043705:Receptor, Adenosine A2A / Q000235:genetics / Q000378:metabolism*
chemical_list: D017362:Cyclic AMP Response Element-Binding Protein; C086055:HTT protein, human; C499524:Htt protein, rat; D000071058:Huntingtin Protein; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D010455:Peptides; D020033:Protein Isoforms; D043705:Receptor, Adenosine A2A; C097188:polyglutamine