ABSTRACT
There is no treatment for the neurodegenerative disorder Huntington disease (HD). Cystamine is a candidate drug; however, the mechanisms by which it operates remain unclear. We show here that cystamine increases levels of the heat shock DnaJ-containing protein 1b (HSJ1b) that are low in HD patients. HSJ1b inhibits polyQ-huntingtin-induced death of striatal neurons and neuronal dysfunction in Caenorhabditis elegans. This neuroprotective effect involves stimulation of the secretory pathway through formation of clathrin-coated vesicles containing brain-derived neurotrophic factor (BDNF). Cystamine increases BDNF secretion from the Golgi region that is blocked by reducing HSJ1b levels or by overexpressing transglutaminase. We demonstrate that cysteamine, the FDA-approved reduced form of cystamine, is neuroprotective in HD mice by increasing BDNF levels in brain. Finally, cysteamine increases serum levels of BDNF in mouse and primate models of HD. Therefore, cysteamine is a potential treatment for HD, and serum BDNF levels can be used as a biomarker for drug efficacy.
Subject(s)
Brain-Derived Neurotrophic Factor/biosynthesis , Brain/metabolism , Cystamine/chemistry , Cystamine/metabolism , Cysteamine/chemistry , HSP40 Heat-Shock Proteins/physiology , Huntington Disease/metabolism , Molecular Chaperones/physiology , Transglutaminases/metabolism , Aged , Animals , Caenorhabditis elegans , Humans , Macaca , Mice , Mice, Transgenic , Middle Aged , Neuroprotective Agents/pharmacology , Rats , Rats, Sprague-DawleyABSTRACT
In the search for neuroprotective factors in Huntington's disease, we found that insulin growth factor 1 via activation of the serine/threonine kinase Akt/PKB is able to inhibit neuronal death specifically induced by mutant huntingtin containing an expanded polyglutamine stretch. The IGF-1/Akt pathway has a dual effect on huntingtin-induced toxicity, since activation of this pathway also results in a decrease in the formation of intranuclear inclusions of mutant huntingtin. We demonstrate that huntingtin is a substrate of Akt and that phosphorylation of huntingtin by Akt is crucial to mediate the neuroprotective effects of IGF-1. Finally, we show that Akt is altered in Huntington's disease patients. Taken together, these results support a potential role of the Akt pathway in Huntington's disease.
