Genetic studies have implicated the neuronal ubiquitin C-terminal hydrolase (UCH) protein UCH-L1 in Parkinson's disease (PD) pathogenesis. Moreover, the function of UCH-L1 may be lost in the brains of PD and Alzheimer's disease patients. We have previously reported that the UCH-L1 polymorphic variant S18Y, potentially protective against PD in population studies, demonstrates specific antioxidant functions in cell culture. Albeit genetic, biochemical and neuropathological data support an association between UCH-L1, PD, synaptic degeneration and oxidative stress, the relationship between the dopaminergic system and UCH-L1 status remains obscure. In the current study, we have examined the dopaminergic system of mice lacking endogenous UCH-L1 protein (gracile axonal dystrophy mice). Our findings show that the lack of wild-type (WT) UCH-L1 does not influence to any significant degree the dopaminergic system at baseline or following injections of the neurotoxin methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Furthermore, using a novel intrastriatal adenoviral injection protocol, we have found that mouse nigral neurons retrogradely transduced with S18Y UCH-L1, but not the WT protein, are significantly protected against MPTP toxicity. Overall, these data provide evidence for an antioxidant and neuroprotective effect of the S18Y variant of UCH-L1, but not of the WT protein, in the dopaminergic system, and may have implications for the pathogenesis of PD or related neurodegenerative conditions, in which oxidative stress might play a role.
"The cDNAs encoding wt ASYN and Enhanced Green Fluorescent Protein (EGFP) were cloned into a modified version of the PENTR.GD entry vector and introduced into the pAd/PL-DEST Gateway vector (Invitrogen, Carlsbad, CA). Second generation E1, E3, and E2a- deleted recombinant human serotype 5 adenoviruses (rAd) were generated as described previously (Xilouri et al., 2012). The following titers were obtained, expressed as viral particles (vp)/μl: 2.8 × 10 8 vp/μl for rAd-ASYN and 1.43 × 10 9 vp/μl for rAd-EGFP. "
[Show abstract][Hide abstract] ABSTRACT: In the present study, we investigated the role of the main intracellular energy sensor, AMP-activated protein kinase (AMPK), in the in vitro neurotoxicity of α-synuclein (ASYN), one of the key culprits in the pathogenesis of Parkinson's disease. The loss of viability in retinoic acid-differentiated SH-SY5Y human neuroblastoma cells inducibly overexpressing wild-type ASYN was associated with the reduced activation of AMPK and its activator LKB1, as well as AMPK target Raptor. ASYN-overexpressing rat primary neurons also displayed lower activity of LKB1/AMPK/Raptor pathway. Restoration of AMPK activity by metformin or AICAR reduced the in vitro neurotoxicity of ASYN overexpression, acting independently of the prosurvival kinase Akt or the induction of autophagic response. The conditioned medium from ASYN-overexpressing cells, containing secreted ASYN, as well as dopamine-modified or nitrated recombinant ASYN oligomers, all inhibited AMPK activation in differentiated SH-SY5Y cells and reduced their viability, but not in the presence of metformin or AICAR. The RNA interference-mediated knockdown of AMPK increased the sensitivity of SH-SY5Y cells to the harmful effects of secreted ASYN. AMPK-dependent protection from extracellular ASYN was also observed in rat neuron-like pheochromocytoma cell line PC12. These data demonstrate the protective role of AMPK against the toxicity of both intracellular and extracellular ASYN, suggesting that modulation of AMPK activity may be a promising therapeutic strategy in Parkinson's disease.
Neurobiology of Disease 11/2013; 63. DOI:10.1016/j.nbd.2013.11.002 · 5.08 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: α-Synuclein levels are critical to Parkinson's disease pathogenesis. Wild-type α-synuclein is degraded partly by chaperone-mediated autophagy, and aberrant α-synuclein may act as an inhibitor of the pathway. To address whether the induction of chaperone-mediated autophagy may represent a potential therapy against α-synuclein-induced neurotoxicity, we overexpressed lysosomal-associated membrane protein 2a, the rate-limiting step of chaperone-mediated autophagy, in human neuroblastoma SH-SY5Y cells, rat primary cortical neurons in vitro, and nigral dopaminergic neurons in vivo. Overexpression of the lysosomal-associated membrane protein 2a in cellular systems led to upregulation of chaperone-mediated autophagy, decreased α-synuclein turnover, and selective protection against adenoviral-mediated wild-type α-synuclein neurotoxicity. Protection was observed even when the steady-state levels of α-synuclein were unchanged, suggesting that it occurred through the attenuation of α-synuclein-mediated dysfunction of chaperone-mediated autophagy. Overexpression of the lysosomal receptor through the nigral injection of recombinant adeno-associated virus vectors effectively ameliorated α-synuclein-induced dopaminergic neurodegeneration by increasing the survival of neurons located in the substantia nigra as well as the axon terminals located in the striatum, which was associated with a reduction in total α-synuclein levels and related aberrant species. We conclude that induction of chaperone-mediated autophagy may provide a novel therapeutic strategy in Parkinson's disease and related synucleinopathies through two different mechanisms: amelioration of dysfunction of chaperone-mediated autophagy and lowering of α-synuclein levels.
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