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Mutations in LRRK2 and GBA1 are common genetic risk factors for Parkinson’s disease (PD) and major efforts are underway to develop new therapeutics that target LRRK2 or glucocerebrosidase (GCase). Here we describe a mechanistic and therapeutic convergence of LRRK2 and GCase in neurons derived from patients with PD. We find that GCase activity was reduced in dopaminergic (DA) neurons derived from PD patients with LRRK2 mutations. Inhibition of LRRK2 kinase activity results in increased GCase activity in DA neurons with either LRRK2 or GBA1 mutations. This increase is sufficient to partially rescue accumulation of oxidized dopamine and alpha-synuclein in PD patient neurons. We have identified the LRRK2 substrate Rab10 as a key mediator of LRRK2 regulation of GCase activity. Together, these results suggest an important role of mutant LRRK2 as a negative regulator of lysosomal GCase activity. Mutations in LRRK2 and GBA1 , which encodes glucocerebrosidase (GCase), are associated with Parkinson’s disease. Here the authors show that LRRK2 is a negative regulator of lysosomal GCase activity, using dopaminergic neurons derived from iPSCs from PD patients with LRRK2 mutations.

The intracellular transport of cholesterol is subject to tight regulation. The structure of the lysosomal integral membrane protein type 2 (LIMP-2, also known as SCARB2) reveals a large cavity that traverses the molecule and resembles the cavity in SR-B1 that mediates lipid transfer. The detection of cholesterol within the LIMP-2 structure and the formation of cholesterol − like inclusions in LIMP-2 knockout mice suggested the possibility that LIMP2 transports cholesterol in lysosomes. We present results of molecular modeling, crosslinking studies, microscale thermophoresis and cell-based assays that support a role of LIMP-2 in cholesterol transport. We show that the cavity in the luminal domain of LIMP-2 can bind and deliver exogenous cholesterol to the lysosomal membrane and later to lipid droplets. Depletion of LIMP-2 alters SREBP-2-mediated cholesterol regulation, as well as LDL-receptor levels. Our data indicate that LIMP-2 operates in parallel with Niemann Pick (NPC)-proteins, mediating a slower mode of lysosomal cholesterol export. Cholesterol transport is tightly regulated in the cell and in lysosomes is regulated by NPC1/2. Here, Heybrock et al. use molecular modeling, knockout mice and cell based studies to show that LIMP-2 also mediates lysosomal cholesterol transport.

Significance Our report highlights, for the first time to our knowledge, a distinct relationship between lysosomal integral membrane protein type-2 (LIMP-2) expression, β-glucocerebrosidase (GC) activity, and clearance of α-synuclein. In LIMP-2–deficient mice, increased levels of endogenous α-synuclein led to severe neurological deficits and premature death. We found that loss of LIMP-2 reduced lysosomal GC activity, resulting in lipid storage, disturbed autophagic/lysosomal function, and α-synuclein accumulation leading to neurotoxicity of dopaminergic neurons as well as apoptotic cell death and inflammation. Furthermore, heterologous overexpression of functional LIMP-2 enhanced α-synuclein clearance and improved lysosomal activity of GC. Our results suggest that lysosomal GC activity can be influenced via its interaction with LIMP-2, which could be a promising strategy for the treatment of synucleinopathies. Mutations within the lysosomal enzyme β-glucocerebrosidase (GC) result in Gaucher disease and represent a major risk factor for developing Parkinson disease (PD). Loss of GC activity leads to accumulation of its substrate glucosylceramide and α-synuclein. Since lysosomal activity of GC is tightly linked to expression of its trafficking receptor, the lysosomal integral membrane protein type-2 (LIMP-2), we studied α-synuclein metabolism in LIMP-2–deficient mice. These mice showed an α-synuclein dosage-dependent phenotype, including severe neurological impairments and premature death. In LIMP-2–deficient brains a significant reduction in GC activity led to lipid storage, disturbed autophagic/lysosomal function, and α-synuclein accumulation mediating neurotoxicity of dopaminergic (DA) neurons, apoptotic cell death, and inflammation. Heterologous expression of LIMP-2 accelerated clearance of overexpressed α-synuclein, possibly through increasing lysosomal GC activity. In surviving DA neurons of human PD midbrain, LIMP-2 levels were increased, probably to compensate for lysosomal GC deficiency. Therefore, we suggest that manipulating LIMP-2 expression to increase lysosomal GC activity is a promising strategy for the treatment of synucleinopathies.

Lysosomal integral membrane protein-2 (LIMP-2/SCARB2) contributes to endosomal and lysosomal function. LIMP-2 deficiency is associated with neurological abnormalities and kidney failure and, as an acid glucocerebrosidase receptor, impacts Gaucher and Parkinson’s diseases. Here we report a crystal structure of a LIMP-2 luminal domain dimer with bound cholesterol and phosphatidylcholine. Binding of these lipids alters LIMP-2 from functioning as a glucocerebrosidase-binding monomer toward a dimeric state that preferentially binds anionic phosphatidylserine over neutral phosphatidylcholine. In cellular uptake experiments, LIMP-2 facilitates transport of phospholipids into murine fibroblasts, with a strong substrate preference for phosphatidylserine. Taken together, these biophysical and cellular studies define the structural basis and functional importance of a form of LIMP-2 for lipid trafficking. We propose a model whereby switching between monomeric and dimeric forms allows LIMP-2 to engage distinct binding partners, a mechanism that may be shared by SR-BI and CD36, scavenger receptor proteins highly homologous to LIMP-2. Lysosomal integral membrane protein-2 (LIMP-2) is a glucocerebrosidase receptor, which is linked to kidney failure and other diseases. Here the authors show that LIMP-2 is also a phospholipid receptor and present the lipid-bound structure of the LIMP-2 luminal domain dimer and discuss its lipid trafficking mechanism.

Background and Objectives: Prolonged bed rest after the resection of spinal intradural tumors is postulated to mitigate the development of cerebrospinal fluid leaks (CSFLs), which is one of the feared postoperative complications. Nonetheless, the empirical evidence supporting this conjecture remains limited and requires further investigation. The goal of the study was to investigate whether prolonged bed rest lowers the risk of CSFL after the resection of spinal intradural tumors. The primary outcome was the rate of CSFL in each cohort. Materials and Methods: To validate this hypothesis, we conducted a comparative effectiveness research (CER) study at two distinct academic neurosurgical centers, wherein diverse postoperative treatment protocols were employed. Specifically, one center adopted a prolonged bed rest regimen lasting for three days, while the other implemented early postoperative mobilization. For statistical analysis, case–control matching was performed. Results: Out of an overall 451 cases, we matched 101 patients from each center. We analyzed clinical records and images from each case. In the bed rest center, two patients developed a CSFL (n = 2, 1.98%) compared to four patients (n = 4, 3.96%) in the early mobilization center (p = 0.683). Accordingly, CSFL development was not associated with early mobilization (OR 2.041, 95% CI 0.365–11.403; p = 0.416). Univariate and multivariate analysis identified expansion duraplasty as an independent risk factor for CSFL (OR 60.33, 95% CI: 0.015–0.447; p < 0.001). Conclusions: In this CER, we demonstrate that early mobilization following the resection of spinal intradural tumors does not confer an increased risk of the development of CSFL.

Background and Objectives: The utilization of non-metallic pedicle screws and rods has become a favored approach in the management of spinal tumors. An abundance of metal artifacts improves postoperative imaging and allows for precise radiation treatment planning. Under certain conditions, a vertebral body replacement (VBR) is necessary in addition to dorsal fixation. For a long time, VBR hardware was available as titanium implants only. Recently, other non-titanium products were introduced into the market. This study compares radiotherapy planning after VBR with titanium and non-titanium materials. Materials and Methods: This is a retrospective cohort study in a single academic center setting. VBR was performed for thoracic spinal metastatic disease. Radiation plan quality was evaluated according to the criteria of the International Commission on Radiation Units and Measurements, based on postoperative CT imaging. Results: Six patients with dorsal fixation and VBR were included, half of which were treated with titanium VBR and the other half with a minimum metallic implant. In addition, patients received different dorsal fixation hardware. No difference was found in terms of radiation plan quality. With non-titanium materials, visual demarcation during radiation planning was superior. Conclusions: This is the first study in the field to comprehensively compare radiation treatment planning after VBR using different materials. With minimum metallic implants, radiotherapy planning is equal in terms of planning but superior in terms of visual demarcation in comparison to standard titanium VBR, potentially enabling more precise radiotherapy approaches.

Background and Objectives: Resection of dumbbell tumors can be challenging, and facet joint sparing approaches carry the risk of incomplete resection. In contrast, additional facetectomy may allow better surgical exposure at the cost of spinal stability. The aim of this study is to compare facet-sparing and facetectomy approaches for the treatment of lumbar spine dumbbell tumors. Materials and Methods: In a cohort study setting, we analyzed Eden type 2 and 3 tumors operated in our department. Conventional facet-sparing microsurgical or facetectomy approaches with minimally invasive fusions were performed according to individual surgeons’ preference. Primary outcomes were extent of resection and tumor progression over time. Secondary outcomes were perioperative adverse events. Results: Nineteen patients were included. Nine patients were operated on using a facet-sparing technique. Ten patients underwent facetectomy and fusion. While only one patient (11%) in the facet-sparing group experienced gross total resection (GTR), this was achieved for all patients in the facetectomy group (100%). The relative risk (RR) for incomplete resection in the facet-sparing cohort was 18.7 (95% CI 1.23–284.047; p = 0.035). In addition, time to progression was shorter in the facet-sparing cohort (p = 0.022) and all patients with a residual tumor underwent a second resection after a median follow-up time of 42 months (IQR 25–66). Conclusions: Minimally invasive resection of lumbar Eden type 2 and 3 dumbbell tumors including facetectomy in combination with instrumentation appears to be safe and superior to the facet-sparing approach in terms of local tumor control.

Background and Objectives: Spinal intramedullary hemangioblastomas (SIMH) are benign vascular lesions that are pathological hallmarks of von Hippel-Lindau disease (vHL) and constitute the third most common intramedullary neoplasm in adults. So far, maximal and safe resection is the first choice of treatment. However, as SIMH show no malignant transformation, it remains unclear whether surgical resection is beneficial for all patients. Materials and Methods: We retrospectively analyzed the surgical outcomes of 27 patients who were treated between 2014 and 2022 at our neurosurgical department and investigated potential risk factors that influence the surgical outcome. Pre- and postoperative neurological status were classified according to the McCormick scale. Furthermore, surgical quality indicators, such as length of hospital stay (LOS; days), 90-day readmissions, nosocomial infections, and potential risk factors that might influence the surgical outcome, such as tumor size and surgical approach, have been analyzed. In addition to that, patients were asked to fill out the EQ-5D-3L questionnaire to assess their quality of life after surgery. Results: Surgery on SIMH patients that display no or minor neurological deficits (McCormick scale I or II) is associated with a favorable postoperative outcome and overall higher quality of life compared to those patients that already suffer from severe neurological deficits (McCormick scale III or IV). Conclusion: Early surgical intervention prior to the development of severe neurological deficits may offer a better neurological outcome and quality of life.

The role of membrane potential in most intracellular organelles remains unexplored because of the lack of suitable tools. Here, we describe Voltair, a fluorescent DNA nanodevice that reports the absolute membrane potential and can be targeted to organelles in live cells. Voltair consists of a voltage-sensitive fluorophore and a reference fluorophore for ratiometry, and acts as an endocytic tracer. Using Voltair, we could measure the membrane potential of different organelles in situ in live cells. Voltair can potentially guide the rational design of biocompatible electronics and enhance our understanding of how membrane potential regulates organelle biology. A DNA-based voltmeter non-invasively measures the membrane potential of organelles.