Parkinson's disease (PD) is characterized by the progressive loss of substantia nigra dopaminergic neurons and the presence of cytoplasmic inclusions named Lewy bodies. Two missense mutations of the ␣-synuclein (␣-syn; A30P and A53T) have been described in several families with an autosomal dominant form of PD. ␣-Syn also constitutes one of the main components of Lewy bodies in sporadic cases of PD. To develop an animal model of PD, lentiviral vectors expressing different human or rat forms of ␣-syn were injected into the substantia nigra of rats. In contrast to transgenic mice models, a selective loss of nigral dopaminergic neurons associated with a dopaminergic denervation of the striatum was observed in animals expressing either wild-type or mutant forms of human ␣-syn. This neuronal degeneration correlates with the appearance of abundant ␣-syn-positive inclusions and extensive neuritic pathology detected with both ␣-syn and silver staining. Lentiviral-mediated expression of wild-type or mutated forms of human ␣-syn recapitulates the essential neuropathological features of PD. Rat ␣-syn similarly leads to protein aggregation but without cell loss, suggesting that inclusions are not the primary cause of cell degeneration in PD. Viral-mediated genetic models may contribute to elucidate the mechanism of ␣-syn-induced cell death and allow the screening of candidate therapeutic molecules.

Parkinson disease (PD) is characterized by dopaminergic neurodegeneration and intracellular inclusions of α-synuclein amyloid fibers, which are stable and difficult to dissolve. Whether inclusions are neuroprotective or pathological remains controversial, because prefibrillar oligomers may be more toxic than amyloid inclusions. Thus, whether therapies should target inclusions, preamyloid oligomers, or both is a critically important issue. In yeast, the protein-remodeling factor Hsp104 cooperates with Hsp70 and Hsp40 to dissolve and reactivate aggregated proteins. Metazoans, however, have no Hsp104 ortholog. Here we introduced Hsp104 into a rat PD model. Remarkably, Hsp104 reduced formation of phosphorylated α-synuclein inclusions and prevented nigrostriatal dopaminergic neurodegeneration induced by PD-linked α-synuclein (A30P). An in vitro assay employing pure proteins revealed that Hsp104 prevented fibrillization of α-synuclein and PD-linked variants (A30P, A53T, E46K). Hsp104 coupled ATP hydrolysis to the disassembly of preamyloid oligomers and amyloid fibers composed of α-synuclein. Furthermore, the mammalian Hsp70 and Hsp40 chaperones, Hsc70 and Hdj2, enhanced α-synuclein fiber disassembly by Hsp104. Hsp104 likely protects dopaminergic neurons by antagonizing toxic α-synuclein assemblies and might have therapeutic potential for PD and other neurodegenerative amyloidoses.

Parkinson's disease (PD) is characterized by a progressive loss of midbrain dopamine neurons and the presence of cytoplasmic inclusions called Lewy bodies. Mutations in several genes including ␣-synuclein and parkin have been linked to familial PD. The loss of parkin's E3-ligase activity leads to dopaminergic neuronal degeneration in early-onset autosomal recessive juvenile parkinsonism, suggesting a key role of parkin for dopamine neuron survival. To evaluate the potential neuroprotective role of parkin in the pathogenesis of PD, we tested whether overexpression of wild-type rat parkin could protect against the toxicity of mutated human A30P ␣-synuclein in a rat lentiviral model of PD. Animals overexpressing parkin showed significant reductions in ␣-synuclein-induced neuropathology, including preservation of tyrosine hydroxylasepositive cell bodies in the substantia nigra and sparing of tyrosine hydroxylase-positive nerve terminals in the striatum. The parkinmediated neuroprotection was associated with an increase in hyperphosphorylated ␣-synuclein inclusions, suggesting a key role for parkin in the genesis of Lewy bodies. These results indicate that parkin gene therapy may represent a promising candidate treatment for PD.gene therapy ͉ lentivirus ͉ neurodegenerative disease ͉ Lewy body ͉ neuroprotection P arkinson's disease (PD) is one of the most common neurodegenerative disorders, affecting Ϸ2% of the population over the age of 60. Loss of dopaminergic neurons in the substantia nigra pars compacta and subsequent striatal dopamine depletion causes motor impairments including akinesia, resting tremor, muscle rigidity, and gait and postural deficits. The neuropathological hallmark of PD is the appearance of proteinaceous intracellular deposits identified as Lewy bodies and Lewy neurites. Although the mechanism leading to the selective degeneration of nigral dopamine neurons in sporadic PD remains unknown, clues about the pathogenesis of familial forms of PD are emerging because of the discovery of various gene mutations. Two missense mutations in ␣-synuclein (A53T and A30P) were the first to be identified, and these are responsible for early-onset autosomal dominant PD (1, 2). The subsequent findings that ␣-synuclein is a major component of Lewy bodies in sporadic PD (3, 4) and that ␣-synuclein locus triplication causes autosomal dominant PD (5), suggest that accumulation of wild-type ␣-synuclein is sufficient to cause PD. Other PD-linked mutations in genes encoding for parkin, UCH-L1, DJ-1, and PINK1 have also been identified (6, 7).Mutations in the parkin gene are associated with autosomal recessive juvenile parkinsonism (AR-JP), a disease characterized by juvenile onset of typical parkinsonian symptoms and pathology (8). Parkin is an E3 ubiquitin ligase, and parkin mutations found in AR-JP patients lead to partial or complete loss of this activity (9). Several substrates of parkin have been identified such as CDCrel-1, synphilin-1, and o-glycosylated forms of ␣-synuclein (␣Sp22) and Pael-R (10). Both ␣Sp22 a...