alpha-synuclein and davunetide

The formation of oligomers and aggregates of overexpressed or mutant α-synuclein play a role in the degeneration of dopaminergic neurons in Parkinson's disease by causing dysfunction of mitochondria, reflected in their disturbed mobility and production of ROS. The mode of action and mechanisms underlying this mitochondrial impairment is still unclear. We have induced stable expression of wild-type, A30P or A53T α-synuclein in neuronally differentiated SH-SY5Y neuroblastoma cells and studied anterograde and retrograde mitochondrial trafficking in this cell model for Parkinson's disease. In contrast to wild-type and A30P, A53T α-synuclein significantly inhibited mitochondrial trafficking, at first retrogradely and in a later stage anterogradely. Accordingly, A53T α-synuclein also caused the highest increase in ROS production in the dysmobilized mitochondria in comparison to wild-type or A30P α-synuclein. Treatment with NAP, the eight amino acid peptide identified as the active component of activity-dependent neuroprotective protein (ADNP), completely annihilated the adverse effects of A53T on mitochondrial dynamics. Our results reveal that A53T α-synuclein (oligomers or aggregates) leads to the inhibition of mitochondrial trafficking, which can be rescued by NAP, suggesting the involvement of microtubule disruption in the pathophysiology of Parkinson's disease.

Topics: Alanine; alpha-Synuclein; Cell Differentiation; Cell Line, Tumor; Gene Expression Regulation; Humans; Kymography; Luminescent Proteins; Membrane Potential, Mitochondrial; Microtubule-Associated Proteins; Mitochondria; Neuroblastoma; Oligopeptides; Reactive Oxygen Species; RNA, Messenger; Threonine; Transfection

In Parkinson's disease mitochondrial dysfunction can lead to a deficient ATP supply to microtubule protein motors leading to mitochondrial axonal transport disruption. Compromised axonal transport will then lead to a disorganized distribution of mitochondria and other organelles in the cell, as well as, the accumulation of aggregated proteins like alpha-synuclein. Moreover, axonal transport disruption can trigger synaptic accumulation of autophagosomes packed with damaged mitochondria and protein aggregates promoting synaptic failure. We previously observed that neuronal-like cells with an inherent mitochondrial impairment derived from PD patients contain a disorganized microtubule network, as well as, alpha-synuclein oligomer accumulation. In this work we provide new evidence that an agent that promotes microtubule network assembly, NAP (davunetide), improves microtubule-dependent traffic, restores the autophagic flux and potentiates autophagosome-lysosome fusion leading to autophagic vacuole clearance in Parkinson's disease cells. Moreover, NAP is capable of efficiently reducing alpha-synuclein oligomer content and its sequestration by the mitochondria. Most interestingly, NAP decreases mitochondrial ubiquitination levels, as well as, increases mitochondrial membrane potential indicating a rescue in mitochondrial function. Overall, we demonstrate that by improving microtubule-mediated traffic, we can avoid mitochondrial-induced damage and thus recover cell homeostasis. These results prove that NAP may be a promising therapeutic lead candidate for neurodegenerative diseases that involve axonal transport failure and mitochondrial impairment as hallmarks, like Parkinson's disease and related disorders.

Topics: Aged; alpha-Synuclein; Autophagy; Case-Control Studies; Cell Line; Female; Humans; Lysosomes; Male; Membrane Potential, Mitochondrial; Microtubules; Middle Aged; Mitochondria; Mitochondrial Diseases; Neurons; Neuroprotective Agents; Oligopeptides; Parkinson Disease; Ubiquitination; Vacuoles

Abnormal accumulation of α-synuclein is associated with several neurodegenerative disorders (synucleinopathies), including sporadic Parkinson's disease (PD). Genetic mutations and multiplication of α-synuclein cause familial forms of PD and polymorphisms in the α-synuclein gene are associated with PD risk. Overexpression of α-synuclein can impair essential functions within the cell such as microtubule-dependent transport, suggesting that compounds that act on the microtubule system may have therapeutic benefit for synucleinopathies. In this study, mice overexpressing human wildtype α-synuclein under the Thy1 promoter (Thy1-aSyn) and littermate wildtype control mice were administered daily the microtubule-interacting peptide NAPVSIPQ (NAP; also known as davunetide or AL-108) intranasally for 2 months starting at 1 month of age, in a regimen known to produce effective concentrations of the peptide in mouse brain. Motor performance, coordination, and activity were assessed at the end of treatment. Olfactory function, which is altered in PD, was measured 1 month later. Mice were sacrificed at 4.5 months of age, and their brains examined for proteinase K-resistant α-synuclein inclusions in the substantia nigra and olfactory bulb. NAP-treated Thy1-aSyn mice showed a 38% decrease in the number of errors per step in the challenging beam traversal test and a reduction in proteinase K-resistant α-synuclein inclusions in the substantia nigra compared to vehicle treated transgenics. The data indicate a significant behavioral benefit and a long lasting improvement of α-synuclein pathology following administration of a short term (2 months) NAP administration in a mouse model of synucleinopathy.

Topics: alpha-Synuclein; Animals; Behavior, Animal; Brain; Disease Models, Animal; Endopeptidase K; Female; Humans; Inclusion Bodies; Male; Mice; Mice, Inbred C57BL; Mice, Transgenic; Motor Activity; Olfactory Bulb; Oligopeptides; Parkinson Disease; Pilot Projects; Substantia Nigra