LRRK2 regulates synaptic function through BDNF signaling and actin cytoskeleton

Abstract

Parkinson’s disease (PD) is a multisystemic disorder that manifests through motor and non-motor symptoms. Motor dysfunction is the most debilitating and it is caused by the degeneration of dopamine-producing neurons in the substantia nigra pars compacta (SNpc). A body of evidence indicates that synapse demise precedes by years neuronal death. Still, early synaptic dysfunctions in PD are poorly deciphered.Here we combined literature metanalysis, proteomics and phosphoproteomics with biochemical, imaging and electrophysiological measurements in neurons, brains and synaptosomes from knockout and knockin mouse models, as well as human iPSC-derived neurons associated with the PD-kinase LRRK2.We show that phosphorylation of LRRK2 at Ser935, which controls LRRK2 subcellular localization, rapidly increases upon brain-derived neurotrophic factor (BDNF) stimulation of differentiated SH-SY5Y cells and primary mouse neurons. Affinity-purification coupled with mass spectrometry (AP-MS/MS) analysis revealed that LRRK2 interactome is significantly reshaped upon BDNF stimulation, with an interconnected network of actin cytoskeleton-associated proteins increasing their binding to LRRK2. Accordingly, LRRK2 knockout neurons exhibit decreased TrkB signaling and fail to induce BDNF-dependent spinogenesis. In vivo , one-month old Lrrk2 knockout mice display defects in spine maturation, a phenotype that disappears with age. In human iPSC-derived cortical neurons, BDNF increases the frequency of miniature excitatory post-synaptic currents (mEPSC) in wild-type but not in the presence of LRRK2 knockout, functionally supporting a distinctive role of LRRK2 in BDNF-synaptic signaling. Finally, Lrrk2 G2019S PD mutant synaptosomes display differentially phosphorylated proteins enriched in categories related to postsynaptic structural organization.Taken together, our study discloses a critical function of LRRK2 in BDNF-dependent synaptic processes and identifies the postsynaptic actin cytoskeleton as a convergent site of LRRK2 pathophysiological activity.