title: Molecular Mechanisms of Allosteric Inhibition of Brain Glycogen Phosphorylase by Neurotoxic Dithiocarbamate Chemicals.
abstract: Dithiocarbamates (DTCs) are important industrial chemicals used extensively as pesticides and in a variety of therapeutic applications. However, they have also been associated with neurotoxic effects and in particular with the development of Parkinson-like neuropathy. Although different pathways and enzymes (such as ubiquitin ligases or the proteasome) have been identified as potential targets of DTCs in the brain, the molecular mechanisms underlying their neurotoxicity remain poorly understood. There is increasing evidence that alteration of glycogen metabolism in the brain contributes to neurodegenerative processes. Interestingly, recent studies with N,N-diethyldithiocarbamate suggest that brain glycogen phosphorylase (bGP) and glycogen metabolism could be altered by DTCs. Here, we provide molecular and mechanistic evidence that bGP is a target of DTCs. To examine this system, we first tested thiram, a DTC pesticide known to display neurotoxic effects, observing that it can react rapidly with bGP and readily inhibits its glycogenolytic activity (kinact= 1.4 × 105m-1s-1). Using cysteine chemical labeling, mass spectrometry, and site-directed mutagenesis approaches, we show that thiram (and certain of its metabolites) alters the activity of bGP through the formation of an intramolecular disulfide bond (Cys318-Cys326), known to act as a redox switch that precludes the allosteric activation of bGP by AMP. Given the key role of glycogen metabolism in brain functions and neurodegeneration, impairment of the glycogenolytic activity of bGP by DTCs such as thiram may be a new mechanism by which certain DTCs exert their neurotoxic effects.
authors.affiliation: From the Université Paris Diderot, Sorbonne Paris Cité, Unité BFA, CNRS UMR 8251, 75013 Paris, France.
authors.forename: Cécile
authors.initials: C
authors.lastname: Mathieu
authors.affiliation: From the Université Paris Diderot, Sorbonne Paris Cité, Unité BFA, CNRS UMR 8251, 75013 Paris, France.
authors.forename: Linh-Chi
authors.initials: LC
authors.lastname: Bui
authors.affiliation: From the Université Paris Diderot, Sorbonne Paris Cité, Unité BFA, CNRS UMR 8251, 75013 Paris, France.
authors.forename: Emile
authors.initials: E
authors.lastname: Petit
authors.affiliation: ESPCI ParisTech, Université Paris Sciences et Lettres, Laboratoire de Spectrométrie de Masse Biologique et Protéomique, CNRS USR, 3149 Paris, France.
authors.forename: Iman
authors.initials: I
authors.lastname: Haddad
authors.affiliation: the Sorbonne Universités, UPMC Univ Paris 06, Institut de Biologie Paris-Seine, UMR CNRS 8256, Biological Adaptation and Ageing, 75005 Paris, France.
authors.forename: Onnik
authors.initials: O
authors.lastname: Agbulut
authors.affiliation: ESPCI ParisTech, Université Paris Sciences et Lettres, Laboratoire de Spectrométrie de Masse Biologique et Protéomique, CNRS USR, 3149 Paris, France.
authors.forename: Joelle
authors.initials: J
authors.lastname: Vinh
authors.affiliation: From the Université Paris Diderot, Sorbonne Paris Cité, Unité BFA, CNRS UMR 8251, 75013 Paris, France; UFR Sciences du Vivant, Université Paris Diderot, 75013 Paris, France.
authors.forename: Jean-Marie
authors.initials: JM
authors.lastname: Dupret
authors.affiliation: From the Université Paris Diderot, Sorbonne Paris Cité, Unité BFA, CNRS UMR 8251, 75013 Paris, France; UFR Sciences du Vivant, Université Paris Diderot, 75013 Paris, France. Electronic address: fernando.rodrigues-lima@univ-paris-diderot.fr.
authors.forename: Fernando
authors.initials: F
authors.lastname: Rodrigues-Lima
mesh_terms: D006003:Glycogen / Q000378:metabolism; D025002:Glycogen Phosphorylase, Brain Form / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006801:Humans; D019636:Neurodegenerative Diseases / Q000139:chemically induced / Q000235:genetics / Q000378:metabolism; D020258:Neurotoxicity Syndromes / Q000235:genetics / Q000378:metabolism; D009498:Neurotoxins / Q000737:chemistry* / Q000633:toxicity; D013859:Thiocarbamates / Q000737:chemistry* / Q000633:toxicity
chemical_list: D009498:Neurotoxins; D013859:Thiocarbamates; D006003:Glycogen; D025002:Glycogen Phosphorylase, Brain Form
keywords: Parkinson disease; allosteric regulation; brain metabolism; carbohydrate metabolism; disulfide; glycogen; glycogen storage disease; toxicology