Balance between synaptic versus extrasynaptic NMDA receptor activity influences inclusions and neurotoxicity of mutant huntingtin

• Published in: Nature medicine Vol. 15; no. 12; pp. 1407 - 1413
• Main Authors: Talantova, Maria, Kaul, Marcus, Yao, Dongdong, Xia, Peng, Ehrnhoefer, Dagmar E, Zaidi, Rameez, Lipton, Stuart A, Graham, Rona K, Tong, Gary, Zhang, Dongxian, Clemente, Arjay, Okamoto, Shu-ichi, Hayden, Michael R, Pouladi, Mahmoud A, Vincent Chen, H-S
• Format: Journal Article
• Language: English
• Published: New York Nature Publishing Group US 01.12.2009; Nature Publishing Group
• Subjects: Animals; Biomedical and Life Sciences; Biomedicine; Cancer Research; Care and treatment; Causes of; Cell Death - physiology; Cell receptors; Chromosomes, Artificial, Yeast; Disease; Gene mutations; Genetic aspects; Health aspects; Huntingtin Protein; Huntington's chorea; Infectious Diseases; Memantine - pharmacology; Metabolic Diseases; Mice; Mice, Transgenic; Molecular Medicine; Mortality; Mutation; Nerve Tissue Proteins - genetics; Nerve Tissue Proteins - physiology; Neurons; Neurons - cytology; Neurons - drug effects; Neurosciences; Neurotoxicity; Nuclear Proteins - genetics; Nuclear Proteins - physiology; Patch-Clamp Techniques; Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; Receptors, N-Methyl-D-Aspartate - physiology; Synapses - physiology; Trans-Activators - physiology; Transcription Factors; Yeasts; United States
• ISSN: 1078-8956; 1546-170X
• DOI: 10.1038/nm.2056

In a mouse model of Huntington's disease, synaptic activation of NMDA receptors induces the formation of huntingtin-containing inclusions, rendering neurons more resistant to death in vivo and in vitro . In contrast, stimulation of extrasynaptic NMDA receptors increases neuronal vulnerability by preventing inclusion formation. Huntington's disease is caused by an expanded CAG repeat in the gene encoding huntingtin ( HTT ), resulting in loss of striatal and cortical neurons. Given that the gene product is widely expressed, it remains unclear why neurons are selectively targeted. Here we show the relationship between synaptic and extrasynaptic activity, inclusion formation of mutant huntingtin protein (mtHtt) and neuronal survival. Synaptic N -methyl- D -aspartate–type glutamate receptor (NMDAR) activity induces mtHtt inclusions via a T complex-1 (TCP-1) ring complex (TRiC)-dependent mechanism, rendering neurons more resistant to mtHtt-mediated cell death. In contrast, stimulation of extrasynaptic NMDARs increases the vulnerability of mtHtt-containing neurons to cell death by impairing the neuroprotective cyclic AMP response element–binding protein (CREB)–peroxisome proliferator–activated receptor-γ coactivator-1α (PGC-1α) cascade and increasing the level of the small guanine nucleotide–binding protein Rhes, which is known to sumoylate and disaggregate mtHtt. Treatment of transgenic mice expressing a yeast artificial chromosome containing 128 CAG repeats (YAC128) with low-dose memantine blocks extrasynaptic (but not synaptic) NMDARs and ameliorates neuropathological and behavioral manifestations. By contrast, high-dose memantine, which blocks both extrasynaptic and synaptic NMDAR activity, decreases neuronal inclusions and worsens these outcomes. Our findings offer a rational therapeutic approach for protecting susceptible neurons in Huntington's disease.