Aberrant amplification of A2A receptor signaling in striatal cells expressing mutant huntingtin

Huntington's disease (HD) is a neurodegenerative disorder caused by expansion of a CAG repeat in the gene encoding for Huntingtin (Htt), which results in progressive degeneration of the striatal GABAergic/enkephalin neurons. These neurons express both the A2A and D2 receptors, which stimulate and inhibit adenylyl cyclase, respectively. In this study we analyzed the possibility of an involvement of the A2A receptor and its signaling components in the pathogenesis of HD. We report here that striatal cells expressing mutant Htt exhibit increased binding affinities for the selective A2A receptor ligand 3H‐SCH‐58261. Furthermore, despite identical basal adenylyl cyclase activity in all cells, forskolin, a direct activator of this enzyme, significantly overstimulated cAMP production in mutant Htt cells with respect to parental or wild‐type Htt‐expressing cells. Michaelis‐Menten analysis of forskolin‐stimulated enzyme activity revealed a specific decrease of Km value in mutant Htt cells, indicating increased sensitivity for the substrate. Remarkably, coupling of the A2A receptor to adenylyl cyclase was also aberrantly increased. Nevertheless, in all clones, stimulation of cAMP production by 10−7 M NECA was fully counteracted by selective A2A receptor antagonists. Altogether, these data suggest that expression of mutant Htt induces an amplification of adenylyl cyclase‐transduced signals and an aberrant coupling of the A2A receptor to this transduction system. Given the involvement of adenylyl cyclase in key physiological functions, including cell growth and cell survival, we speculate that these changes may alter the susceptibility of striatal neurons to cell death and may contribute to the development of HD.

[1]  J. Cha,et al.  Transcriptional dysregulation in Huntington’s disease , 2000, Trends in Neurosciences.

[2]  He Li,et al.  Amino-terminal fragments of mutant huntingtin show selective accumulation in striatal neurons and synaptic toxicity , 2000, Nature Genetics.

[3]  A. Hackam,et al.  Inhibiting Caspase Cleavage of Huntingtin Reduces Toxicity and Aggregate Formation in Neuronal and Nonneuronal Cells* , 2000, The Journal of Biological Chemistry.

[4]  P. Greengard,et al.  Severe deficiencies in dopamine signaling in presymptomatic Huntington's disease mice. , 2000, Proceedings of the National Academy of Sciences of the United States of America.

[5]  A. Hackam,et al.  Wild-Type Huntingtin Protects from Apoptosis Upstream of Caspase-3 , 2000, The Journal of Neuroscience.

[6]  F. Cattabeni,et al.  Brain Adenosine Receptors as Targets for Therapeutic Intervention in Neurodegenerative Diseases , 1999, Annals of the New York Academy of Sciences.

[7]  B. J. Knoll,et al.  Partial agonists and G protein-coupled receptor desensitization. , 1999, Trends in pharmacological sciences.

[8]  Stephen B. Dunnett,et al.  Characterization of Progressive Motor Deficits in Mice Transgenic for the Human Huntington’s Disease Mutation , 1999, The Journal of Neuroscience.

[9]  A. Parent,et al.  Neuronal degeneration in the basal ganglia and loss of pallido-subthalamic synapses in mice with targeted disruption of the Huntington's disease gene , 1999, Brain Research.

[10]  D. Tagle,et al.  Mutant Huntingtin Expression in Clonal Striatal Cells: Dissociation of Inclusion Formation and Neuronal Survival by Caspase Inhibition , 1999, The Journal of Neuroscience.

[11]  E. Ongini,et al.  Blockade of adenosine A2A receptors by SCH 58261 results in neuroprotective effects in cerebral ischaemia in rats , 1998, Neuroreport.

[12]  P. Svenningsson,et al.  Locating the neuronal targets for caffeine , 1998 .

[13]  E. Ongini,et al.  Neuroprotection induced by stimulating A1 or blocking A2A adenosine receptors: An apparent paradox , 1998 .

[14]  E. Cattaneo,et al.  Generation and characterization of embryonic striatal conditionally immortalized ST14A cells , 1998, Journal of neuroscience research.

[15]  S. W. Davies,et al.  Altered brain neurotransmitter receptors in transgenic mice expressing a portion of an abnormal human huntington disease gene. , 1998, Proceedings of the National Academy of Sciences of the United States of America.

[16]  G. Spalluto,et al.  Design, synthesis, and biological evaluation of a second generation of pyrazolo[4,3-e]-1,2,4-triazolo[1,5-c]pyrimidines as potent and selective A2A adenosine receptor antagonists. , 1998, Journal of medicinal chemistry.

[17]  Dale E. Bredesen,et al.  Caspase Cleavage of Gene Products Associated with Triplet Expansion Disorders Generates Truncated Fragments Containing the Polyglutamine Tract* , 1998, The Journal of Biological Chemistry.

[18]  E. Ongini,et al.  [3H]‐SCH 58261 labelling of functional A2A adenosine receptors in human neutrophil membranes , 1998, British journal of pharmacology.

[19]  T. Stone,et al.  Protection against kainate-induced excitotoxicity by adenosine A2A receptor agonists and antagonists , 1998, Neuroscience.

[20]  S. W. Davies,et al.  Aggregation of huntingtin in neuronal intranuclear inclusions and dystrophic neurites in brain. , 1997, Science.

[21]  E. Ongini,et al.  Characterization of A2A adenosine receptors in human lymphocyte membranes by [3H]‐SCH 58261 binding , 1997, British journal of pharmacology.

[22]  S. W. Davies,et al.  Exon 1 of the HD Gene with an Expanded CAG Repeat Is Sufficient to Cause a Progressive Neurological Phenotype in Transgenic Mice , 1996, Cell.

[23]  K. Jacobson,et al.  Recent developments in selective agonists and antagonists acting at purine and pyrimidine receptors , 1996, Drug development research.

[24]  M. Hayden,et al.  Cleavage of huntingtin by apopain, a proapoptotic cysteine protease, is modulated by the polyglutamine tract , 1996, Nature Genetics.

[25]  G. Spalluto,et al.  Pyrazolo[4,3-e]-1,2,4-triazolo[1,5-c]pyrimidine derivatives: potent and selective A(2A) adenosine antagonists. , 1996, Journal of medicinal chemistry.

[26]  Virginia E. Papaioannou,et al.  Increased apoptosis and early embryonic lethality in mice nullizygous for the Huntington's disease gene homologue , 1995, Nature Genetics.

[27]  Barbara Cacciari,et al.  Current Developments of A2a Adenosine Receptor Antagonists , 1995, Current Medicinal Chemistry.

[28]  C A Ross,et al.  When more is less: Pathogenesis of glutamine repeat neurodegenerative diseases , 1995, Neuron.

[29]  A. Joyner,et al.  Inactivation of the mouse Huntington's disease gene homolog Hdh. , 1995, Science.

[30]  P. Singh,et al.  The in vitro pharmacology of ZM 241385, a potent, non‐xanthine, A2a selective adenosine receptor antagonist , 1995, British journal of pharmacology.

[31]  S. Floresco,et al.  Targeted disruption of the Huntington's disease gene results in embryonic lethality and behavioral and morphological changes in heterozygotes , 1995, Cell.

[32]  G Burnstock,et al.  Nomenclature and Classification of Purinoceptors* , 2005 .

[33]  U. Ungerstedt,et al.  The striopallidal neuron: a main locus for adenosine-dopamine interactions in the brain , 1993, The Journal of neuroscience : the official journal of the Society for Neuroscience.

[34]  Manish S. Shah,et al.  A novel gene containing a trinucleotide repeat that is expanded and unstable on Huntington's disease chromosomes , 1993, Cell.

[35]  J. Palacios,et al.  Adenosine A2 receptors: Selective localization in the human basal ganglia and alterations with disease , 1991, Neuroscience.

[36]  J. Penney,et al.  Differential loss of striatal projection neurons in Huntington disease. , 1988, Proceedings of the National Academy of Sciences of the United States of America.

[37]  D Rodbard,et al.  Ligand: a versatile computerized approach for characterization of ligand-binding systems. , 1980, Analytical biochemistry.

[38]  M. M. Bradford.  A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein-dye binding. , 1976, Analytical biochemistry.