Dopamine- and cAMP-regulated Phosphoprotein of 32-kDa (DARPP-32)-dependent Activation of Extracellular Signal-regulated Kinase (ERK) and Mammalian Target of Rapamycin Complex 1 (mTORC1) Signaling in Experimental Parkinsonism

Emanuela Santini,Michael Feyder,Giuseppe Gangarossa,Helen S Bateup,Paul Greengard,Gilberto Fisone

doi:10.1074/jbc.m112.388413

Abstract

Dyskinesia, a motor complication caused by prolonged administration of the antiparkinsonian drug l-3,4-dihydroxyphenylalanine (l-DOPA), is accompanied by activation of cAMP signaling and hyperphosphorylation of the dopamine- and cAMP-regulated phosphoprotein of 32 kDa (DARPP-32). Here, we show that the abnormal phosphorylation of DARPP-32 occurs specifically in medium spiny neurons (MSNs) expressing dopamine D1 receptors (D1R). Using mice in which DARPP-32 is selectively deleted in D1R-expressing MSNs, we demonstrate that this protein is required for l-DOPA-induced activation of the extracellular signal-regulated protein kinases 1 and 2 and the mammalian target of rapamycin complex 1 (mTORC1) pathways, which are implicated in dyskinesia. We also show that mutation of the phosphorylation site for cAMP-dependent protein kinase on DARPP-32 attenuates l-DOPA-induced dyskinesia and reduces the concomitant activations of ERK and mTORC1 signaling. These studies demonstrate that, in D1R-expressing MSNs, l-DOPA-induced activation of ERK and mTORC1 requires DARPP-32 and indicates the importance of the cAMP/DARPP-32 signaling cascade in dyskinesia.

Highlights

Using mice in which DARPP-32 is selectively deleted in D1 receptors (D1R)-expressing medium spiny neurons (MSNs), we demonstrate that this protein is required for L-DOPA-induced activation of the extracellular signal-regulated protein kinases 1 and 2 and the mammalian target of rapamycin complex 1 pathways, which are implicated in dyskinesia
We provide evidence demonstrating that L-DOPA increases protein kinase (PKA)/DARPP-32 signaling selectively in striatonigral MSNs and that PKA-dependent phosphorylation of DARPP-32 is implicated in L-DOPA-induced dyskinesia (LID) and in the activation of the ERK and mammalian target of rapamycin complex 1 (mTORC1) cascades associated with this condition
We utilized various transgenic mouse lines to demonstrate the existence of a link between PKA-mediated phosphorylation of DARPP-32 and the concomitant activation of ERK and mTORC1 signaling produced in the dorsal striatum by L-DOPA

Summary

Background

Using mice in which DARPP-32 is selectively deleted in D1R-expressing MSNs, we demonstrate that this protein is required for L-DOPA-induced activation of the extracellular signal-regulated protein kinases 1 and 2 and the mammalian target of rapamycin complex 1 (mTORC1) pathways, which are implicated in dyskinesia. The area preferentially innervated by the substantia nigra pars compacta, medium spiny neurons (MSNs) react to the loss of dopamine by increasing their sensitivity to dopaminergic agonists [2] This phenomenon is evident at the level of the MSNs that directly innervate the output nuclei of the basal ganglia. We provide evidence demonstrating that L-DOPA increases PKA/DARPP-32 signaling selectively in striatonigral MSNs and that PKA-dependent phosphorylation of DARPP-32 is implicated in LID and in the activation of the ERK and mTORC1 cascades associated with this condition

EXPERIMENTAL PROCEDURES

RESULTS

DISCUSSION