PD is a common neurodegenerative disease with both motor and non-motor symptoms. The main pathological changes of PD are the loss of dopaminergic neurons, the formation of Lewy bodies containing alpha-synuclein (α-syn) in the substantia nigra (SN) and decreased dopamine content in the striatum. Although factors such as iron deposition, mitochondrial dysfunction and α-syn accumulation are reported to participate in the pathogenesis of PD, the precise mechanisms have not been fully elucidated. The ubiquitin-proteasome system (UPS) is the main system for the degradation of intracellular proteins. Dysfunction of UPS has been implicated in the pathogenesis of PD (Kim et al., 2021; Stefanis et al., 2019; Sun et al., 2023).

In UPS, E3 ubiquitin ligases play an essential role in catalyzing the ubiquitination of targeted substrates. Nedd4 family interacting protein 1 (Ndfip1), also known as Nedd4 WW-domain binding protein 5 (N4WBP5), is an adapter protein that can interact with several Nedd4 family E3s, and then recruit E3 ligases to ubiquitinate target proteins (Mund and Pelham, 2009). It has been reported that the expression of Ndfip1 increased in surviving neurons in response to cerebral ischemia or reperfusion injury, suggesting that Ndfip1-mediated ubiquitination might be involved in its protective effects on neurons (Goh et al., 2014; Lackovic et al., 2012; Sang et al., 2006). An analysis of Affymetrix HG-Focus array from the Gene Expression Omnibus (GEO) database (GSE20333) showed that the expression of Ndfip1 decreased in the cases of sporadic PD compared to controls (Supplementary Fig. 1). This provides evidence for the possible involvement of Ndfip1 in PD. Our previous study has demonstrated that Ndfip1 protected SH-SY5Y cells against rotenone-induced neurotoxicity by inhibiting the upregulation of a-syn (Liu et al., 2020). Ndfip1 also prevented MPP+-induced apoptosis in MES23.5 dopaminergic cells (Liu et al., 2015). These results suggest that Ndfip1 showed neuroprotective effects on dopaminergic neurons in PD. However, its protective effects and possible mechanisms in animal models of PD are not known.

MPTP is widely used to induce PD animal model in vivo, which exhibits significant movement disorders with loss of dopaminergic neurons in the SN (Mustapha and Mat Taib, 2021). MPTP is metabolized to MPP+, which inhibits mitochondrial Complex I and induces free radical production in vivo (Langston, 2017). Therefore, MPTP-induced C57BL/6 J mice and MPP+-treated human neuroblastoma SH-SY5Y cells were chosen to study the neuroprotective effects and possible mechanisms of Ndfip1 in PD. In this study, we verified the low expression of Ndfip1 in MPTP-induced C57BL/6 J mice and MPP+-treated SH-SY5Y cells. Then we first revealed that high expression of Ndfip1 improved MPTP-induced motor dysfunction and antagonized the loss of dopaminergic neurons in the SN of MPTP-induced PD mice. In addition, we have shown that high expression of Ndfip1 restored MPP+-induced mitochondrial dysfunction and regulated ferroptosis via decreasing the expression of voltage-dependent anion-selective channel 1/2 (VDAC1/2) and long-chain acyl-CoA synthetase 4 (ACSL4). Taken together, our data disclosed Ndfip1 as a novel neuroprotective factor and proposed a new regulatory mechanism of Ndfip1 on mitochondrial dysfunction and ferroptosis. This provides new insights into the pathogenesis of PD and treatment strategies for PD.