Parkinson's disease is a movement disorder characterized by death of dopaminergic substantia nigra (SN) neurons and brain accumulation of α-synuclein. The tyrosine kinase Abl is activated in neurodegeneration. Here, we show that lentiviral expression of α-synuclein in the mouse SN leads to Abl activation (phosphorylation) and lentiviral Abl expression increases α-synuclein levels, in agreement with Abl activation in PD brains. Administration of the tyrosine kinase inhibitor nilotinib decreases Abl activity and ameliorates autophagic clearance of α-synuclein in transgenic and lentiviral gene transfer models. Subcellular fractionation shows accumulation of α-synuclein and hyper-phosphorylated Tau (p-Tau) in autophagic vacuoles in α-synuclein expressing brains, but nilotinib enhances protein deposition into the lysosomes. Nilotinib is used for adult leukemia treatment and it enters the brain within US Food and Drug Administration approved doses, leading to autophagic degradation of α-synuclein, protection of SN neurons and amelioration of motor performance. These data suggest that nilotinib may be a therapeutic strategy to degrade α-synuclein in PD and other α-synucleinopathies.

Background: TDP-43 pathology and the role of E3 ubiquitin ligases are increasingly recognized in neurodegeneration. Results: Parkin ubiquitinates TDP-43 and forms a multiprotein complex with HDAC6 to sequester TDP-43 in cytosol. Conclusion: Parkin E3 ubiquitin ligase activity promotes TDP-43 inclusion formation and nuclear translocation. Significance: Parkin-TDP-43 interaction may be exploited as a therapeutic strategy in ALS/FTLD pathology.

Tyrosine kinase inhibitors (TKIs) are effective therapies for leukaemia. Alzheimer is a neurodegenerative disease characterized by accumulation of β-amyloid (plaques) and hyper-phosphorylated Tau (tangles). Here we show that AD animals have high levels of insoluble parkin and decreased parkin-Beclin-1 interaction, while peripheral administration of TKIs, including Nilotinib and Bosutinib, increases soluble parkin leading to amyloid clearance and cognitive improvement. Blocking Beclin-1 expression with shRNA or parkin deletion prevents tyrosine kinase (TK) inhibition-induced amyloid clearance, suggesting that functional parkin-Beclin-1 interaction mediates amyloid degradation. Isolation of autophagic vacuoles (AVs) in AD mouse brain shows accumulation of parkin and amyloid, consistent with previous results in AD brains, while Bosutinib and Nilotinib increase parkin-Beclin-1 interaction and result in protein deposition in the lysosome. These data suggest that decreased parkin solubility impedes parkin-Beclin-1 interaction and amyloid clearance. We identified two FDA-approved anti-cancer drugs as potential treatment for AD.Two FDA-approved tyrosine kinase inhibitor drugs, Bosutinib and Nilotinib, are shown to ameliorate Alzheimer's disease pathology in mouse models by increasing soluble parkin and leading to amyloid clearance and cognitive improvement.

Alzheimer’s disease (AD) is a neurodegenerative disorder associated with amyloid accumulation and autophagic changes. Parkin is an E3 ubiquitin ligase involved in proteasomal and autophagic clearance. We previously demonstrated decreased parkin solubility and interaction with the key autophagy enzyme Beclin-1 in AD, but tyrosine kinase inhibition restored parkin-Beclin-1 interaction. In the current studies we determined the mechanisms of Nilotinib-induced parkin-Beclin-1 interaction, which leads to amyloid clearance. Nilotinib increased endogenous parkin levels and ubiquitination, which may enhance parkin recycling via the proteasome, leading to increased activity and interaction with Beclin-1. Parkin solubility was decreased and autophagy was altered in amyloid expressing mice, suggesting that amyloid stress affects parkin stability, leading to failure of protein clearance via the lysosome. Isolation of autophagic vacuoles revealed amyloid and parkin accumulation in autophagic compartments but Nilotinib decreased insoluble parkin levels and facilitated amyloid deposition into lysosomes in wild type, but not parkin−/− mice, further underscoring an essential role for endogenous parkin in amyloid clearance. These results suggest that Nilotinib boosts the autophagic machinery, leading to increased level of endogenous parkin that undergoes ubiquitination and interacts with Beclin-1 to facilitate amyloid clearance. These data suggest that Nilotinib-mediated autophagic changes may trigger parkin response via increased protein levels, providing a therapeutic strategy to reduce Aβ and Tau in AD.

Poly(ADP-ribose) polymerase-1 (PARP-1) is an intracellular sensor of DNA strand breaks and plays a critical role in cellular responses to DNA damage. In normally functioning cells, PARP-1 enzymatic activity has been linked to the alterations in chromatin structure associated with gene expression. However, the molecular determinants for PARP-1 recruitment to specific sites in chromatin in the absence of DNA strand breaks remain obscure. Using gel shift and enzymatic footprinting assays and atomic force microscopy, we show that PARP-1 recognizes distortions in the DNA helical backbone and that it binds to three-and four-way junctions as well as to stably unpaired regions in double-stranded DNA. PARP-1 interactions with non-B DNA structures are functional and lead to its catalytic activation. DNA hairpins, cruciforms, and stably unpaired regions are all effective co-activators of PARP-1 auto-modification and poly(ADP-ribosyl)ation of histone H1 in the absence of free DNA ends. Enzyme kinetic analyses revealed that the structural features of non-B form DNA co-factors are important for PARP-1 catalysis activated by undamaged DNA. K 0.5 constants for DNA co-factors, which are structurally different in the degree of base pairing and spatial DNA organization, follow the order: cruciform < hairpin < < loop. DNA structure also influenced the reaction rate; when a hairpin was substituted with a stably unpaired region, the maximum reaction velocity decreased almost 2-fold. These data suggest a link between PARP-1 binding to non-B DNA structures in genome and its function in the dynamics of local modulation of chromatin structure in the normal physiology of the cell.Poly(ADP-ribose) polymerization is a post-translation protein modification that utilizes an ADP-ribosyl moiety from NAD ϩ to form branched polymers of up to 200 ADP-ribose units, which are attached via glutamic acid residues to the nuclear acceptor proteins. The best understood member of the superfamily of poly(ADP-ribose) polymerases (1) is PARP-1, 1 whose activity is largely accounted for by this type of nuclear protein modification (2). PARP-1 is an abundant zinc fingercontaining nuclear protein present at ϳ1 enzyme/50 nucleosomes. It has high affinity for damaged DNA and becomes catalytically active upon binding to double-and singlestranded DNA breaks (3). PARP-1 activation leads to modification of nuclear proteins including itself (auto-modification reaction) with a very strong polyanion, poly(ADP-ribose). This modification has a profound effect on the structure and function of the acceptor proteins. Based on these properties, PARP-1 has long been regarded as an intracellular sensor of DNA strand breaks, and its function has been considered in context with the cellular responses to genotoxic stress, in particular DNA damage repair and apoptosis (4 -7).In undamaged cells, recruitment of PARP-1 to the chromatin-modifying complex leads to a dramatic and localized perturbation of histone-DNA contacts (8, 9), allowing DNA to be accessible to regulatory factors, t...