Mutations in LRRK2 linked to Parkinson disease sequester Rab8a to damaged lysosomes and regulate transferrin-mediated iron uptake in microglia

Mutations in leucine-rich repeat kinase 2 (LRRK2) cause autosomal dominant Parkinson disease (PD), while polymorphic LRRK2 variants are associated with sporadic PD. PD-linked mutations increase LRRK2 kinase activity and induce neurotoxicity in vitro and in vivo. The small GTPase Rab8a is a LRRK2 kinase substrate and is involved in receptor-mediated recycling and endocytic trafficking of transferrin, but the effect of PD-linked LRRK2 mutations on the function of Rab8a is poorly understood. Here, we show that gain-of-function mutations in LRRK2 induce sequestration of endogenous Rab8a to lysosomes in overexpression cell models, while pharmacological inhibition of LRRK2 kinase activity reverses this phenotype. Furthermore, we show that LRRK2 mutations drive association of endocytosed transferrin with Rab8a-positive lysosomes. LRRK2 has been nominated as an integral part of cellular responses downstream of proinflammatory signals and is activated in microglia in postmortem PD tissue. Here, we show that iPSC-derived microglia from patients carrying the most common LRRK2 mutation, G2019S, mistraffic transferrin to lysosomes proximal to the nucleus in proinflammatory conditions. Furthermore, G2019S knock-in mice show a significant increase in iron deposition in microglia following intrastriatal LPS injection compared to wild-type mice, accompanied by striatal accumulation of ferritin. Our data support a role of LRRK2 in modulating iron uptake and storage in response to proinflammatory stimuli in microglia

Sequential screening nominates the Parkinson's disease associated kinase LRRK2 as a regulator of Clathrin-mediated endocytosis

Mutations in leucine-rich repeat kinase 2 (LRRK2) are an established cause of inherited Parkinson's disease (PD). LRRK2 is expressed in both neurons and glia in the central nervous system, but its physiological function(s) in each of these cell types is uncertain. Through sequential screens, we report a functional interaction between LRRK2 and Clathrin adaptor protein complex 2 (AP2). Analysis of LRRK2 KO tissue revealed a significant dysregulation of AP2 complex components, suggesting LRRK2 may act upstream of AP2. In line with this hypothesis, expression of LRRK2 was found to modify recruitment and phosphorylation of AP2. Furthermore, expression of LRRK2 containing the R1441C pathogenic mutation resulted in impaired clathrin-mediated endocytosis (CME). A decrease in activity-dependent synaptic vesicle endocytosis was also observed in neurons harboring an endogenous R1441C LRRK2 mutation. Alongside LRRK2, several PD-associated genes intersect with membrane-trafficking pathways. To investigate the genetic association between Clathrin-trafficking and PD, we used polygenetic risk profiling from IPDGC genome wide association studies (GWAS) datasets. Clathrin-dependent endocytosis genes were found to be associated with PD across multiple cohorts, suggesting common variants at these loci represent a cumulative risk factor for disease. Taken together, these findings suggest CME is a LRRK2-mediated, PD relevant pathway.Neurological Motor Disorder

Association of Variants in the SPTLC1 Gene With Juvenile Amyotrophic Lateral Sclerosis

Importance: Juvenile amyotrophic lateral sclerosis (ALS) is a rare form of ALS characterized by age of symptom onset less than 25 years and a variable presentation.Objective: To identify the genetic variants associated with juvenile ALS.Design, Setting, and Participants: In this multicenter family-based genetic study, trio whole-exome sequencing was performed to identify the disease-associated gene in a case series of unrelated patients diagnosed with juvenile ALS and severe growth retardation. The patients and their family members were enrolled at academic hospitals and a government research facility between March 1, 2016, and March 13, 2020, and were observed until October 1, 2020. Whole-exome sequencing was also performed in a series of patients with juvenile ALS. A total of 66 patients with juvenile ALS and 6258 adult patients with ALS participated in the study. Patients were selected for the study based on their diagnosis, and all eligible participants were enrolled in the study. None of the participants had a family history of neurological disorders, suggesting de novo variants as the underlying genetic mechanism.Main Outcomes and Measures: De novo variants present only in the index case and not in unaffected family members.Results: Trio whole-exome sequencing was performed in 3 patients diagnosed with juvenile ALS and their parents. An additional 63 patients with juvenile ALS and 6258 adult patients with ALS were subsequently screened for variants in the SPTLC1 gene. De novo variants in SPTLC1 (p.Ala20Ser in 2 patients and p.Ser331Tyr in 1 patient) were identified in 3 unrelated patients diagnosed with juvenile ALS and failure to thrive. A fourth variant (p.Leu39del) was identified in a patient with juvenile ALS where parental DNA was unavailable. Variants in this gene have been previously shown to be associated with autosomal-dominant hereditary sensory autonomic neuropathy, type 1A, by disrupting an essential enzyme complex in the sphingolipid synthesis pathway.Conclusions and Relevance: These data broaden the phenotype associated with SPTLC1 and suggest that patients presenting with juvenile ALS should be screened for variants in this gene.</p

Rapid and long-lasting transduction of neurons by targeted recombinant virus injection into the neonatal mouse brain

Viral vectors can mediate long-term gene expression in different regions of the brain. Recombinant adeno-associated virus (rAAV) and Lenti virus (LV) have both gained prominence due to their ability to achieve specific transduction of various neuronal populations. Whilst widespread gene delivery has been obtained by targeted injection of rAAV in various brain structures, LV has also been utilized for infection of stem cell populations for cell lineage tracing. Both viral vector systems are most commonly used for gene delivery in mature brains, but the great potential of somatic gene delivery into the neonate brain has not been systematically exploited. Here we provide a systematic guideline for efficient stereotaxic virus delivery into different neuronal populations of the neonate brain. We demonstrate region specific recombination of a 'stop-floxed' Rosa26 reporter allele upon targeted injection of rAAV vectors expressing Cre-recombinase at postnatal day zero (P0). In addition, utilizing LV, we show efficient transduction of P0 subventricular zone stem cells with subsequent labeling of approximately 20% of migrating neuroblasts along the rostral migratory stream (RMS) into the olfactory bulb. In summary, we report on an optimized protocol for facile, reproducible, high-throughput virus-based gene transfer into neonatal brains of wild-type and genetically altered mice, which allows targeted transduction of different brain regions and distinct neuronal populations

Boosting chaperone-mediated autophagy in vivo mitigates α-synuclein-induced neurodegeneration

α-Synuclein levels are critical to Parkinson&apos;s disease pathogenesis. Wild-type α-synuclein is degraded partly by chaperone-mediated autophagy, and aberrant α-synuclein may act as an inhibitor of the pathway. To address whether the induction of chaperone-mediated autophagy may represent a potential therapy against α-synuclein-induced neurotoxicity, we overexpressed lysosomal-associated membrane protein 2a, the rate-limiting step of chaperone-mediated autophagy, in human neuroblastoma SH-SY5Y cells, rat primary cortical neurons in vitro, and nigral dopaminergic neurons in vivo. Overexpression of the lysosomal-associated membrane protein 2a in cellular systems led to upregulation of chaperone-mediated autophagy, decreased α-synuclein turnover, and selective protection against adenoviral-mediated wild-type α-synuclein neurotoxicity. Protection was observed even when the steady-state levels of α-synuclein were unchanged, suggesting that it occurred through the attenuation of α-synuclein-mediated dysfunction of chaperone-mediated autophagy. Overexpression of the lysosomal receptor through the nigral injection of recombinant adeno-associated virus vectors effectively ameliorated α-synuclein-induced dopaminergic neurodegeneration by increasing the survival of neurons located in the substantia nigra as well as the axon terminals located in the striatum, which was associated with a reduction in total α-synuclein levels and related aberrant species. We conclude that induction of chaperone-mediated autophagy may provide a novel therapeutic strategy in Parkinson&apos;s disease and related synucleinopathies through two different mechanisms: amelioration of dysfunction of chaperone-mediated autophagy and lowering of α-synuclein levels. © 2013 The Author (2013)

Transcriptome analysis of LRRK2 knock-out microglia cells reveals alterations of inflammatory- and oxidative stress-related pathways upon treatment with α-synuclein fibrils.

none11mixedRusso I.; Kaganovich A.; Ding J.; Landeck N.; Mamais A.; Varanita T.; Biosa A.; Tessari I.; Bubacco L.; Greggio E.; Cookson M.R.Russo, I.; Kaganovich, A.; Ding, J.; Landeck, N.; Mamais, A.; Varanita, T.; Biosa, A.; Tessari, I.; Bubacco, L.; Greggio, E.; Cookson, M. R