Background: In Alzheimer’s Disease (AD), about one-third of the risk genes identified by GWAS encode proteins that function predominantly in the endocytic pathways. Among them, the Ras and Rab Interactor 3(RIN3) is a guanine nucleotide exchange factor (GEF) for the Rab5 small GTPase family and has been implicated to be a risk factor for both late onset AD (LOAD) and sporadic early onset AD (sEOAD). However, how RIN3 is linked to AD pathogenesis is currently undefined.Methods: Quantitative PCR and immunoblotting were used to measure the RIN3 expression level in mouse brain tissues and cultured basal forebrain cholinergic neuron (BFCNs). Immunostaining was used to define subcellular localization of RIN3 and to visualize endosomal changes in cultured primary BFCNs and PC12 cells. Recombinant flag-tagged RIN3 protein was purified from HEK293T cells and was used to define RIN3-interactomes by mass spectrometry. RIN3-interacting partners were validated by co-immunoprecipitation, immunofluorescence and yeast two hybrid assays. Live imaging of primary neurons was used to examine axonal transport of amyloid precursor protein (APP) and β-secretase 1 (BACE1). Immunoblotting was used to detect protein expression, processing of APP and phosphorylated forms of Tau.Results: We have shown that RIN3 mRNA level was significantly increased in the hippocampus and cortex of APP/PS1 mouse brain. Basal forebrain cholinergic neurons (BFCNs) cultured from E18 APP/PS1 mouse embryos also showed increased RIN3 expression accompanied by early endosome enlargement. In addition, via its proline rich domain, RIN3 recruited BIN1(bridging integrator 1) and CD2AP (CD2 associated protein), two other AD risk factors, to early endosomes. Interestingly, overexpression of RIN3 or CD2AP promoted APP cleavage to increase its carboxyl terminal fragments (CTFs) in PC12 cells. Upregulation of RIN3 or the neuronal isoform of BIN1 increased phosphorylated Tau level. Therefore, upregulation of RIN3 expression promoted accumulation of APP CTFs and increased phosphorylated Tau. These effects by RIN3 was rescued by the expression of a dominant negative Rab5 (Rab5^S34N) construct. Our study has thus pointed to that RIN3 acts through Rab5 to impact endosomal trafficking and signaling.Conclusion: RIN3 is significantly upregulated and correlated with endosomal dysfunction in APP/PS1 mouse. Through interacting with BIN1 and CD2AP, increased RIN3 expression alters axonal trafficking and procession of APP. Together with our previous studies, our current work has thus provided important insights into the role of RIN3 in regulating endosomal signaling and trafficking.

OBJECTIVE: Surgical procedures involving deep brain stimulation (DBS) of the globus pallidus internus (GPi) or subthalamic nucleus (STN) are well-established treatments for isolated dystonia. However, selection of the best stimulation target remains a matter of debate. The authors’ objective was to compare the effectiveness of DBS of the GPi and the STN in patients with isolated dystonia.METHODS: In this matched retrospective cohort study, the authors searched an institutional database for data on all patients with isolated dystonia who had undergone bilateral implantation of DBS electrodes in either the GPi or STN in the period from January 30, 2014, to June 30, 2017. Standardized assessments of dystonia and health-related quality of life using the Burke-Fahn-Marsden Dystonia Rating Scale (BFMDRS) and SF-36 were conducted before and at 1, 6, and 12 months after surgery. No patients were lost to the 6-month follow-up; 5 patients were lost to the 12-month follow-up.RESULTS: Both GPi (14 patients) and STN (16 patients) stimulation produced significant improvement in dystonia and quality of life in all 30 patients found in the database search. At the 1-month follow-up, however, the percentage improvement in the BFMDRS total movement score was significantly (p = 0.01) larger after STN DBS (64%) than after GPi DBS (48%). At the 12-month follow-up, the percentage improvement in the axis subscore was significantly (p = 0.03) larger after GPi DBS (93%) than after STN DBS (83%). Also, the total amount of electrical energy delivered was significantly (p = 0.008) lower with STN DBS than with GPi DBS (124 ± 52 vs 192 ± 65 μJ, respectively).CONCLUSIONS: The GPi and STN are both effective targets in alleviating dystonia and improving quality of life. However, GPi stimulation may be better for patients with axial symptoms. Moreover, STN stimulation may produce a larger clinical response within 1 month after surgery and may have a potential economic advantage in terms of lower battery consumption.

Globus pallidus internus (GPi) deep brain stimulation (DBS) is widely used in patients with isolated dystonia; however, its use remains controversial in patients with acquired dystonia and cerebral palsy. We report the first case of a cerebral palsy patient, who failed to recover 2 years after GPi DBS; DBS was administered on both superior cerebellar peduncles (SCPs) and dentate nuclei (DNs). The monopolar stimulation results suggested that DBS was better administered via the SCPs than via the DNs. At six months follow-up, the patient exhibited a significant improvement of dystonia and spasticity, as well as in her quality of life. SCP DBS may be a potential treatment for cerebral palsy patients with dystonia and spasticity who do not respond well to GPi DBS.

Decreased DJ‐1 protein impairs antioxidative activity of neurons and plays an important role in the occurrence of Parkinson's disease (PD). We have previously identified hsa‐miR‐4639‐5p as the post‐transcriptional regulator of DJ‐1. Increased expression of hsa‐miR‐4639‐5p reduced DJ‐1 level and increased oxidative stress leading to neuronal death. Therefore, understanding the detailed mechanisms by which hsa‐miR‐4639‐5p expression is regulated will not only facilitate diagnosis but also inform the pathogenesis of PD. We examined hsa‐miR‐4639‐5 in either the plasma or exosomes derived from the central nervous system (CNS) neurons of PD patients and healthy controls. We showed that CNS‐derived exosomes gave rise to the increased plasma hsa‐miR‐4639‐5p in PD patients, pointing to hsa‐miR‐4639‐5p dysregulation in the brain of PD patients. Using a dual‐luciferase assay and a CRISPR‐Cas9 system, we identified a core promoter of hsa‐miR‐4639 (−560 to −275 upstream the transcriptional starting site) of the gene for myosin regulatory light chain interacting protein. A polymorphism in the core promoter (rs760632 G>A) could enhance hsa‐miR‐4639‐5p expression and increase PD risk. Furthermore, using MethylTarget™ assay, ChIP‐qPCR, and specific inhibitors, we demonstrated that hsa‐miR4639‐5p expression was regulated by HDAC11‐mediated histone acetylation but not DNA methylation/demethylation. Taken together, our study provides evidence that hsa‐miR‐4639‐5p is a potential diagnostic marker and therapeutic target for PD. Interventions targeting hsa‐miR‐4639‐5p might represent a novel therapy to promote healthy aging.

Background: Epidemiological studies have revealed increased Parkinson’s disease (PD) risk among individuals exposed to pesticides like 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). MPTP is frequently used to induce PD-like symptoms in research models by disrupting mitochondrial complex I (CI) function and causing dopaminergic neuronal loss in the nigrostriatal region. However, the pathway(s) through which MPTP impairs mitochondrial CI function remain to be elucidated. In this study, we aim to identify the molecular mechanisms through which MPTP modulates CI function and define the specific subunits of mitochondrial CI affected by MPTP. Methods: Male mice encompassing either wild-type Sirt3 or Sirt3 K223R de-SUMOylation mutation, were intraperitoneally injected with either MPTP or saline. In vitro experiments were conducted using the SH-SY5Y cell line with or without the Sirt3 de-SUMOylation mutation. Movement performance, mitochondrial function, and protein acetylation were evaluated. Results: MPTP exposure, both in vitro and in vivo, disrupted the AMPK–SENP1–Sirt3 axis, leading to impairment of mitochondrial function. Specifically, MPTP suppressed activation of AMPK, impeding the entry of SENP1 into the mitochondria. The lack of mitochondrial SENP1 resulted in increased levels of SUMOylated Sirt3, which inhibited its deacetylase activity. This led to a significant increase in the acetylation of CI subunits NDUFS3 and NDUFA5, which resulted in reduced CI activity and inhibition of mitochondrial function, and eventually dopaminergic neuronal death. In this pathway, sustained deSUMOylation mutation of Sirt3 (K223R in mice, K288R in humans) mitigated the impact of MPTP on mitochondrial dysregulation, as well as dopaminergic neuronal death and behavioral deficits. Conclusion: The disordered AMPK-SENP1-Sirt3 pathway plays a crucial role in the MPTP-induced CI dysfunction and PD-like phenotype, which provide valuable insights into the mechanisms of PD pathogenesis.