Kinase domain of LRRK2G2019S is sufficient to trigger neurodegeneration of dopaminergic neurons and increases alpha-synuclein toxicity in vivo
Creators: name: Gubinelli, Francesco
name: Cresto, Noémie
name: Marie-Claude Gaillard
name: Auregan, Gwenaëlle
name: Guillermier, Martine
name: Gardier, Camille
name: Josephine, Charlène
name: Petit, Fanny
name: Jan, Caroline
name: Gipchtein, Pauline
name: Dufour, Noëlle
name: Hantraye, Philippe
name: Liot, Géraldine
name: Bemelmans, Alexis Pierre
name: Brouillet, Emmanuel
Publisher: name: Zenodo
Year: 2019
Subjects: a-synuclein
LRRK2
Parkinson's Disease

description: Alpha-synuclein (α-syn) and leucine-rich repeat kinase 2 (LRRK2) are two proteins that play crucial roles in both sporadic and familial forms of Parkinson’s disease (PD).  Recent data suggest the existence of an interplay between these two proteins in the pathogenesis of PD.

In the present study we hypothesized that the C-terminal part of LRRK2 (DLRRK2) containing the kinase domain could behave, at least in part, as the full form of LRRK2 and trigger neurodegeneration when overexpressed using adeno associated virus (AAV) in substantia nigra pars compacta (SNc) neurons.

Our results showed that the kinase activity of DLRRK2 is similar to that of the full lenght protein, and that, at 25 weeks post injection in the rat SNc, AAV-DLRRK2<sup>G2019S</sup> led to a moderate but significant loss of dopaminergic neurons (DA) (~30%) while AAV coding for the wild type (WT) form of DLRRK2 did not.

We also investigated whether overexpression of DLRRK2<sup>G2019S </sup>could modify the toxicity of α-syn<sup>A53T</sup>. Results showed that using AAVs, the majority of DA neurons co-expressed both DLRRK2 (WT or G2019S) and α-syn<sup>A53T</sup>. Such co-expression produced greater loss of DA neurons when compared with α-syn<sup>A53T </sup>alone at the time point post-infection (15 weeks) when DLRRK2<sup>G2019S</sup> alone was not toxic. This effect was not seen with the dead kinase (DK) form of DLRRK2<sup>G2019S</sup>. Since it has been suggested that the level of expression of LRRK2<sup>G2019S</sup> may play a key role in its toxicity, we checked using quantitative confocal microscopy that WT, GS and DK forms of LRRK2 were at similar levels of expression in all the analysed conditions.

The present results suggest that overexpression of the mutant kinase domain of LRRK2 is sufficient to trigger neurodegeneration and increase α-syn<sup>A53T </sup>toxicity in DA neurons <em>in vivo</em>. The presence of LRRK2<sup>G2019S</sup> in SNc neurons could render neurons more vulnerable to α-syn in PD.
description: This work was funded by rolling grants from the CEA and the CNRS. 
The research generating these results received funding from la Fondation de France (AAP 2010-12, Engt 16819) and Association France Parkinson (2016). Francesco Gubinelli is a recipient of a PhD fellowship from the European Union Horizon 2020 Programme (H2020-MSCA-ITN-2015) under the Marie Skłodowska-Curie Innovative Training Networks and Grant Agreement No. 676408.
This work benefited from a support from the national "Translational Research Infrastructure for Biotherapies in Neurosciences" (NeurATRIS, "Investissement d'Avenir", ANR-11-INBS-0011).