LRRK2 kinase activity regulates synaptic vesicle trafficking and neurotransmitter release through modulation of LRRK2 macro-molecular complex.

Maria D Cirnaru,Luigi Bubacco,Michela Matteoli,Isabella Russo,Elisa Greggio,Michele Morari,Carlo Sala,Maria Passafaro,Ludovico Arcuri,Giovanni Piccoli,Antonella Marte,Francesco Longo,Luca Murru,Franco Onofri,Martina Gabrielli,Ernesto Fedele,Elisa Belluzzi

doi:10.3389/fnmol.2014.00049

Abstract

Mutations in Leucine-rich repeat kinase 2 gene (LRRK2) are associated with familial and sporadic Parkinson's disease (PD). LRRK2 is a complex protein that consists of multiple domains executing several functions, including GTP hydrolysis, kinase activity, and protein binding. Robust evidence suggests that LRRK2 acts at the synaptic site as a molecular hub connecting synaptic vesicles to cytoskeletal elements via a complex panel of protein-protein interactions. Here we investigated the impact of pharmacological inhibition of LRRK2 kinase activity on synaptic function. Acute treatment with LRRK2 inhibitors reduced the frequency of spontaneous currents, the rate of synaptic vesicle trafficking and the release of neurotransmitter from isolated synaptosomes. The investigation of complementary models lacking LRRK2 expression allowed us to exclude potential off-side effects of kinase inhibitors on synaptic functions. Next we studied whether kinase inhibition affects LRRK2 heterologous interactions. We found that the binding among LRRK2, presynaptic proteins and synaptic vesicles is affected by kinase inhibition. Our results suggest that LRRK2 kinase activity influences synaptic vesicle release via modulation of LRRK2 macro-molecular complex.

Highlights

Parkinson’s disease (PD) is an age-related neurodegenerative disease affecting 2% of the population above 65-years and is clinically characterized by bradykinesia, rigidity, and resting tremor
Given that Leucine-rich repeat kinase 2 gene (LRRK2) possesses an active kinase domain, we investigated the impact of LRRK2 kinase inhibition on synaptic activity
Our previous observations provided evidence that LRRK2 executes critical functions at the presynaptic site; given its relative position as an integral part of a presynaptic protein network, LRRK2 may serve as a molecular hub coordinating both the storage and the mobilization of Synaptic vesicles (SV) driven by activity (Piccoli et al, 2011, 2014)

Summary

Introduction

Parkinson’s disease (PD) is an age-related neurodegenerative disease affecting 2% of the population above 65-years and is clinically characterized by bradykinesia, rigidity, and resting tremor. Up to now few LRRK2 substrates have been identified in in vitro studies, but none has been convincingly proved in vivo, leaving the pathophysiological relevance of the kinase activity unclear. Several lines of evidence suggest that kinase activity is linked to LRRK2 dimerization (Greggio et al, 2008; Sen et al, 2009; Civiero et al, 2012) as well as subcellular distribution (Berger et al, 2010) and regulates binding to 14-3-3 proteins (Nichols et al, 2010). Several studies suggested that LRRK2 is part of a protein complex that influences the trafficking of synaptic vesicles belonging to the recycling pool (Shin et al, 2008; Piccoli et al, 2011; Matta et al, 2012).

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Conclusion