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Teaching Video NeuroImages: The underrecognized diphasic dyskinesia of Parkinson disease.

ABSTRACT:

SUBMITTER: Verhagen Metman L

PROVIDER: S-EPMC5562967 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:The therapeutic benefits of L–3,4–dihydroxyphenylalanine (L-DOPA) in Parkinson’s disease (PD) patients severely diminishes with the onset of L-DOPA-induced dyskinesia (LID), a debilitating motor side effect. LID is mainly due to altered dopaminergic signaling in the striatum, a brain region that controls motor and cognitive functions. However, the molecular mechanisms that promote LID remain unclear. Here, we have reported that increased striatal RasGRP1 (also known as CalDAG-GEF-II) is instrumentally linked to the development of LID in a 6-hydroxydopamine (6-OHDA) lesioned mouse model of PD. L-DOPA treatment rapidly upregulated RasGRP1 in the dopamine-1 receptor positive neurons in the dorsal striatum. RasGRP1 deleted mice (RasGRP1–/–) had drastically diminished LID, and RasGRP1–/– mice did not interfere with the therapeutic benefits of L-DOPA. In terms of its mechanism, RasGRP1 mediated L-DOPA-induced extracellular regulated kinase (ERK), the mammalian target of rapamycin kinase (mTOR) and the cAMP/PKA pathway. RasGRP1 bind directly with and acts 2 as a guanine nucleotide exchange (GEF) for Ras-homolog-enriched in the brain (Rheb), a potent activator of mTOR, both in vitro and in the intact striatum. High-resolution tandem mass tag mass spectrometry analysis of striatal tissue revealed significant targets, such as phosphodiesterase 10a (Pde10a), Pde2a, catechol-o-methyltransferase (Comt), and glutamate decarboxylase 1 and 2 (Gad1 and Gad2), as downstream regulators of RasGRP1 that are linked to LID vulnerability. Moreover, we found that RASGRP1 protein is also upregulated predominantly in the striatum of MPTP-lesioned macaque treated with L-DOPA, emphasizing the translational potential of this protein. Collectively, the findings of this study demonstrated that RasGRP1 is a major regulator of LID in the dorsal striatum. Pharmacological or gene-depletion strategies targeting RasGRP1 may offer novel therapeutic opportunities for preventing LID in PD patients.

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Teaching Video NeuroImages: The underrecognized diphasic dyskinesia of Parkinson disease.

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