| 1. |
- Borgkvist, Anders
(författare)
-
Molecular mechanisms underlying the actions of psychoactive drugs in the basal ganglia : focus on cannabinoids and morphine
- 2008
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis is centered on the identification of the molecular mechanisms involved in the psychomotor effects of cannabinoids and morphine. These drugs share the ability of acting at the level of the basal ganglia, a group of subcortical structures involved in the control of locomotion, as well as in cognitive and motivational aspects of motor function. In Paper I and II, we have examined the involvement of the dopamine- and cAMP-dependent phosphoprotein of 32 kDa (DARPP-32) in the motor depressant effect produced by activation of the neuronal CB1 receptor (CB1R). DARPP-32 is highly expressed in the medium spiny neurons of the striatum, which is the largest component of the basal ganglia. We found that administration of CP55,940, a selective CB1R agonist, or delta9-tetrahydrocannabinol (delta9-THC), the active component of marihuana or hashish, increased the state of phosphorylation of DARPP-32 at the cAMP-dependent protein kinase site (PKA), Thr34. Similar increases were observed with AM404, a blocker of the reuptake of endogenous cannabinoids (e.g. anandamide and 2-arachidonyl glycerol), or URB597, an inhibitor of the enzyme fatty acid amide hydrolase (FAAH), which is responsible for the degradation of endocannabinoids. The motor depressant effect (catalepsy) produced by CP55,940, was attenuated by genetic inactivation of DARPP-32. Point mutation of Thr34 on DARPP-32 produced a similar reduction in the effect of the CB1R agonist. Genetic inactivation either of dopamine D2 receptors (D2Rs) or of adenosine A2A receptors (A2ARs) reduced the phosphorylation of DARPP-32 at Thr34 and the motor depression produced by CP55,940. These data indicated that a considerable proportion of the psychomotor effect of cannabinoids is accounted for by a signaling cascade involving PKA-dependent phosphorylation of DARPP-32, achieved via CB1R-mediated modulation of D2R and A2AR transmission. In Paper III, we have examined the involvement of DARPP-32 in the short- and long-term effects of morphine. We found that acute administration of morphine increased DARPP-32 phosphorylation at Thr34 in both dorsal striatum and ventral striatum (nucleus accumbens). The ability of morphine to stimulate Thr34 phosphorylation was prevented by blockade of dopamine D1 receptors (D1Rs). Genetic inactivation of DARPP-32 or point mutation of Thr34 reduced the hyperlocomotor response to a single injection of morphine. In contrast, DARPP-32 mutant mice developed behavioral sensitization to morphine comparable to that of wild-type controls and displayed normal morphine conditioned place preference. These results demonstrated that dopamine D1R-mediated activation of the cAMP/DARPP-32 cascade in striatal MSNs is involved in the psychomotor action, but not in the rewarding properties, of morphine. Exposure to cues previously associated with intake of substances of abuse can promote drug related responses. In Paper IV, we have examined the effects of exposure to a drug-associated context on the psychomotor response to morphine. We found that the psychomotor sensitization produced by repeated administration of morphine was markedly increased in mice examined 4 weeks after the last drug injection. In addition, the withdrawal period was able to confer to the environment paired with morphine the ability to increase ERK phosphorylation in a specific compartment (i.e. the shell) of the nucleus accumbens. Using transgenic mice with enhanced green fluorescent protein (EGFP) expression under the control of the D1R (drd1a-EGFP) or D2R promoter (drd2-EGFP), we showed that context-dependent ERK phosphorylation was restricted to D1R-expressing MSNs. Furthermore, we found that this effect depended on D1R activation. This study showed that, following repeated morphine injections, a drug free period induced context-dependent phosphorylation of ERK in a discrete group of neurons within the nucleus accumbens shell. This activation was associated with enhanced psychomotor sensitization and could be implicated in context-elicited drug seeking induced by repeated exposure to drugs of abuse.
|
|
| 2. |
- Errico, Francesco, et al.
(författare)
-
The GTP-binding protein Rhes modulates dopamine signalling in striatal medium spiny neurons
- 2008
-
Ingår i: Molecular and Cellular Neuroscience. - : Elsevier BV. - 1044-7431. ; 37:2, s. 335-345
-
Tidskriftsartikel (refereegranskat)abstract
- Rhes is a small GTP-binding protein prominently localized in the striatum. Previous findings obtained in cell culture systems demonstrated an involvement of Rhes in cAMP/PKA signalling pathway, at a level proximal to the activation of heterotrimeric G-protein complex. However, its role in the striatum has been, so far, only supposed. Here we studied the involvement of Rhes in dopaminergic signalling, by employing mice with a null mutation in the Rhes gene. We demonstrated that the absence of Rhes modulates cAMP/PKA signalling in both striatopallidal and striatonigral projection neurons by increasing Golf. protein levels and, in turn, influencing motor responses challenged by dopaminergic agonist/antagonist. Interestingly, we also show that Rhes is required for a correct dopamine-mediated GTP binding, a function mainly associated to stimulation of dopamine D2 receptors. Altogether, our results indicate that Rhes is an important modulator of dopaminergic transmission in the striatum.
|
|
| 3. |
- Mastropasqua, Francesca, et al.
(författare)
-
Deficiency of the Heterogeneous Nuclear Ribonucleoprotein U locus leads to delayed hindbrain neurogenesis.
- 2023
-
Ingår i: Biology open. - : The Company of Biologists. - 2046-6390. ; 12:10
-
Tidskriftsartikel (refereegranskat)abstract
- Genetic variants affecting Heterogeneous Nuclear Ribonucleoprotein U (HNRNPU) have been identified in several neurodevelopmental disorders (NDDs). HNRNPU is widely expressed in the human brain and shows the highest postnatal expression in the cerebellum. Recent studies have investigated the role of HNRNPU in cerebral cortical development, but the effects of HNRNPU deficiency on cerebellar development remain unknown. Here, we describe the molecular and cellular outcomes of HNRNPU locus deficiency during in vitro neural differentiation of patient-derived and isogenic neuroepithelial stem cells with a hindbrain profile. We demonstrate that HNRNPU deficiency leads to chromatin remodeling of A/B compartments, and transcriptional rewiring, partly by impacting exon inclusion during mRNA processing. Genomic regions affected by the chromatin restructuring and host genes of exon usage differences show a strong enrichment for genes implicated in epilepsies, intellectual disability, and autism. Lastly, we show that at the cellular level HNRNPU downregulation leads to an increased fraction of neural progenitors in the maturing neuronal population. We conclude that the HNRNPU locus is involved in delayed commitment of neural progenitors to differentiate in cell types with hindbrain profile.
|
|
| 4. |
- Santini, Emanuela, et al.
(författare)
-
Critical involvement of cAMP/DARPP-32 and extracellular signal-regulated protein kinase signaling in L-DOPA-induced dyskinesia
- 2007
-
Ingår i: The Journal of Neuroscience. - 1529-2401. ; 27:26, s. 6995-7005
-
Tidskriftsartikel (refereegranskat)abstract
- The molecular basis of L-3,4-dihydroxyphenylalanine (L-DOPA)-induced dyskinesia (LID), one of the major hindrances in the current therapy for Parkinson's disease, is still unclear. We show that attenuation of cAMP signaling in the medium spiny neurons of the striatum, achieved by genetic inactivation of the dopamine and cAMP-regulated phosphoprotein of 32 kDa (DARPP-32), reduces LID. We also show that, in dyskinetic mice, sensitized cAMP/cAMP-dependent protein kinase/DARPP-32 signaling leads to phosphorylation/activation of the extracellular signal-regulated protein kinases 1 and 2 (ERK1/2). The increase in ERK1/2 phosphorylation associated with dyskinesia results in activation of mitogen- and stress-activated kinase-1 (MSK- 1) and phosphorylation of histone H3, two downstream targets of ERK involved in transcriptional regulation. In line with these observations, we found that c- Fos expression is abnormally elevated in the striata of mice affected by LID. Persistent enhancement of the ERK signaling cascade is implicated in the generation of LID. Thus, pharmacological inactivation of ERK1/2 achieved using SL327 (alpha-[amino[(4-aminophenyl)thio]methylene]-2-(trifluoromethyl) benzeneacetonitrile), an inhibitor of the mitogen-activated kinase/ERK kinase, MEK, during chronic L-DOPA treatment counteracts the induction dyskinesia. Together, these results indicate that a significant proportion of the abnormal involuntary movements developed in response to chronic L-DOPA are attributable to hyperactivation in striatal medium spiny neurons of a signaling pathway including sequential phosphorylation of DARPP-32, ERK1/2, MSK-1, and histone H3.
|
|
