Gα_olfMutation Allows Parsing the Role of cAMP-Dependent and Extracellular Signal-Regulated Kinase-Dependent Signaling in l-3,4-Dihydroxyphenylalanine-Induced Dyskinesia

Abstract

LID, and their relationship are not known. In striatal neurons, D 1 R activates adenylyl-cyclase through G␣ olf , a protein upregulated after lesion of DA neurons in rats and in patients. We report here that increased G␣ olf levels in hemiparkinsonian mice are correlated with LID after chronic L-DOPA treatment. To determine the role of this upregulation, we performed unilateral lesion in mice lacking one allele of the Gnal gene coding for G␣ olf (Gnal ϩ/Ϫ ). Despite an increase in the lesioned striatum, G␣ olf levels remained below those of unlesioned wild-type mice. In Gnal ϩ/Ϫ mice, the lesion-induced L-DOPA stimulation of cAMP/PKA-mediated phosphorylation of GluA1 Ser845 and DARPP-32 (32 kDa DA-and cAMP-regulated phosphoprotein) Thr34 was dramatically reduced, whereas ERK activation was preserved. LID occurrence was similar in Gnal ϩ/ϩ and Gnal ϩ/Ϫ mice after a 10-d L-DOPA (20 mg/kg) treatment. Thus, in lesioned animals, G␣ olf upregulation is critical for the activation by L-DOPA of D 1 R-stimulated cAMP/PKA but not ERK signaling. Although the cAMP/PKA pathway appears to be required for LID development, our results indicate that its activation is unlikely to be the main source of LID. In contrast, the persistence of L-DOPAinduced ERK activation in Gnal ϩ/Ϫ mice supports its causal role in LID development.

Heterozygous Gnal Mice Are a Novel Animal Model with Which to Study Dystonia Pathophysiology

“…The subtle modifications of SPN spine length in Gnal ϩ/ Ϫ mice could be related to cAMP signaling alteration because synaptogenesis in young mice depends on the activation of cAMP pathway and its modulation by LRRK2 (Parisiadou et al, 2014;Kozorovitskiy et al, 2015). We also detected a reduced autophosphorylation of CaMKII␤ that might be related to a lack of inhibition of its main phosphatase, protein phosphatase 1, due to an impairment of phosphorylation of its striatal-enriched inhibitor, DARPP-32, in Gnal ϩ/ Ϫ mice (Alcacer et al, 2012). However, the link between reduced phosphorylation of CaMKII␤ and changes in spine morphology is elusive because CaMKII␤ acts on actin and possibly spine morphology independently of its kinase activity (Okamoto et al, 2007;Lin and Redmond, 2008).…”

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

“…This idea is supported by evidence indicating that inhibition of PKA prevents the ability of L-DOPA to increase ERK phosphorylation in a rat model of Parkinson disease (33). However, using a similar experimental model, it has been recently reported that a large reduction in L-DOPA-induced activation of PKA and DARPP-32 does not affect ERK phosphorylation (34). These results suggest that the ability of L-DOPA to promote ERK signaling depends on basal, rather than stimulated, PKA activity and DARPP-32 phosphorylation.…”

Chemogenetic stimulation of striatal projection neurons modulates responses to Parkinson’s disease therapy

“…We next applied the same chemogenetic approach to a unilateral mouse model of parkinsonism that is widely used for studies of striatal signaling and plasticity (22)(23)(24)(25)(26)(27)(28)(29). BAC-transgenic mice sustained 6-hydroxydopamine (6-OHDA) lesions of the nigrostriatal DA pathway on one side of the brain, and AAV-DIO-hM3Dq was injected into the DA-denervated striatum 3 weeks later.…”

“…Figure 8, C and E). Single-plane images were used to manually count the number of neurons immunoreactive for p-ERK in a blind fashion, and ImageJ 1.47m (NIH) was used to automatically count the number of nuclei positive for p-PKA substrate (22). Slice preparation for ex vivo electrophysiology.…”