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Background: Cerebral dopamine neurotrophic factor (CDNF) is a promising therapeutic agent for treating Parkinson disease. Results: We determined the solution structure of CDNF and demonstrated its neuroprotective effects against insults caused by ␣-synuclein oligomers. Conclusion:We identified structural features of CDNF that might correspond with its physiological activity. Significance: This work strengthens the therapeutic relevance of using CDNF to treat neurodegenerative diseases.

A molecular hallmark in Parkinson's disease (PD) pathogenesis are a-synuclein aggregates. Cerebral dopamine neurotrophic factor (CDNF) is an atypical growth factor that is mostly resident in the endoplasmic reticulum but exerts its effects both intracellularly and extracellularly. One of the beneficial effects of CDNF can be protecting neurons from the toxic effects of a-synuclein. Here, we investigated the effects of CDNF on a-synuclein aggregation in vitro and in vivo. We found that CDNF directly interacts with a-synuclein with a K D = 23 ± 6 nM and reduces its auto-association. Using nuclear magnetic resonance (NMR) spectroscopy, we identified interaction sites on the CDNF protein. Remarkably, CDNF reduces the neuronal internalization of a-synuclein fibrils and induces the formation of insoluble phosphorylated a-synuclein inclusions. Intra-striatal CDNF administration alleviates motor deficits in rodents challenged with a-synuclein fibrils, though it did not reduce the number of phosphorylated a-synuclein inclusions in the substantia nigra. CDNF's beneficial effects on rodent behavior appear not to be related to the number of inclusions formed in the current context, and further study of its effects on the aggregation mechanism in vivo are needed. Nonetheless, the interaction of CDNF with a-synuclein, modifying its aggregation, spreading, and associated behavioral alterations, provides novel insights into the potential of CDNF as a therapeutic strategy in PD and other synucleinopathies.