Discinesia indotta dalla L-DOPA nella malattia di Parkinson: nuovi meccanismi e targets molecolari.

Understanding the molecular events guiding the correct assembly of the glutamatergic synapse is a challenge in the comprehension of the mechanisms regulating synaptic strength in physiological and pathological conditions. Indeed, the localization of ionotropic glutamate receptors, NMDA-type, in the postsynaptic density (PSD) modulates the response of the postsynaptic neuron to different stimuli, both in activity-dependent synaptic plasticity and in neurodegenerative disorders, i.e. in Parkinson Disease (PD).



The main goal of this Unit is the identification of novel strategies aimed at preventing the molecular alterations of the glutamatergic striatal synapses underlying L-DOPA-induced dyskinesia (LID). To this, we will make use of different experimental approaches to modulate NR2A-containing NMDA receptor localization at synapses in 6-OHDA-lesioned animals developing LID. In particular, we will explore the modulation of NR2A subunit abundance in striatal synapse by a newly identified NR2A-interacting protein, Rabphilin-3A. We will characterize the effect of TAT-Rph-3A peptide (disrupting Rabphilin-3A/NR2A/PSD-95 complex) on the molecular composition of the glutamatergic synapses. In addition, we will evaluate whether TAT-Rph-3A peptide will be able to restore physiological striatal synaptic plasticity as well as to normalize motor behaviour in 6-OHDA lesioned rats treated with L-DOPA (in collaboration with Unit Calabresi).



Furthermore, considering that a functional interaction between NMDA receptors and other neurotrasmitters/signalling pathways involved in basal ganglia functioning has been put forward, in collaboration with other Units involved in the project we will investigate the regulation of NMDA receptor subunit composition by activating/inhibiting some of these system within the striatum. In particular, we will address the following objectives:



°Molecular analysis of NMDA receptors in post mortem striatal samples of human PD patients (in collaboration with Hirsch)



° Identification and validation of novel therapeutic strategies to target NMDA receptors to prevent or attenuate L-DOPA-induced dyskinesia (in collaboration with Unit Calabresi)



° Analysis of synaptic localization of D1 receptor and ionotropic glutamate receptor subunits in 6-OHDA lesioned animals treated with L-DOPA in absence or presence of a new 5HT-1A/B agonist (in collaboration with Unit Carta).



° Analysis of D1/PSD-95/NMDA receptor complex modulation in 6-OHDA lesioned animals treated with L-DOPA in absence or presence of a new 5HT-1A/B agonist (in collaboration with Unit Carta).



° Role of mTORC1 activation in the modulation of the molecular composition of the excitatory striatal synapse in a mouse model of LID (in collaboration with Unit Usiello).



°Molecular analysis of NMDA receptors underlying the influence of striatal BDNF on LID (in collaboration with Unit Carta).



° Molecular effects of 17ß-estradiol (E2) signaling on the modulation of striatal function in physiological conditions and in 6-OHDA lesioned rats (in collaboration with Unit Grassi).



° Analysis of the molecular composition of the glutamatergic synapses in 6-OHDA lesioned animals treated with L-DOPA plus presynaptic 5-HT1A/B agonist plus postsynaptic cell-permeable peptide (TAT2A or TAT-Rph3A, see point 12) targeting NMDA receptor synaptic localiziation (in collaboration with Calabresi and Unit Carta).



Overall, the main outcome of the study performed by this Unit will be the identification of novel pharmacological approaches to prevent and/or rescue the molecular alterations of the glutamatergic synapses underlying L-DOPA-induced dyskinesia.