Glycerophosphodiesters inhibit lysosomal phospholipid catabolism in Batten disease.

Batten disease, the most prevalent form of neurodegeneration in children, is caused by mutations in the CLN3 gene, which encodes a lysosomal transmembrane protein. CLN3 loss leads to significant accumulation of glycerophosphodiesters (GPDs), the end products of glycerophospholipid catabolism in the lysosome. Despite GPD storage being robustly observed upon CLN3 loss, the role of GPDs in neuropathology remains unclear. Here, we demonstrate that GPDs act as potent inhibitors of glycerophospholipid catabolism in the lysosome using human cell lines and mouse models. Mechanistically, GPDs bind and competitively inhibit the lysosomal phospholipases PLA2G15 and PLBD2, which we establish to possess phospholipase B activity. GPDs effectively inhibit the rate-limiting lysophospholipase activity of these phospholipases. Consistently, lysosomes of CLN3-deficient cells and tissues accumulate toxic lysophospholipids. Our work establishes that the storage material in Batten disease directly disrupts lysosomal lipid homeostasis, suggesting GPD clearance as a potential therapeutic approach to this fatal disease.

Golgi-IP, a tool for multimodal analysis of Golgi molecular content.

The Golgi is a membrane-bound organelle that is essential for protein and lipid biosynthesis. It represents a central trafficking hub that sorts proteins and lipids to various destinations or for secretion from the cell. The Golgi has emerged as a docking platform for cellular signaling pathways including LRRK2 kinase whose deregulation leads to Parkinson disease. Golgi dysfunction is associated with a broad spectrum of diseases including cancer, neurodegeneration, and cardiovascular diseases. To allow the study of the Golgi at high resolution, we report a rapid Golgi immunoprecipitation technique (Golgi-IP) to isolate intact Golgi mini-stacks for subsequent analysis of their content. By fusing the Golgi-resident protein TMEM115 to three tandem HA epitopes (GolgiTAG), we purified the Golgi using Golgi-IP with minimal contamination from other compartments. We then established an analysis pipeline using liquid chromatography coupled with mass spectrometry to characterize the human Golgi proteome, metabolome, and lipidome. Subcellular proteomics confirmed known Golgi proteins and identified proteins not previously associated with the Golgi. Metabolite profiling established the human Golgi metabolome and revealed the enrichment of uridine-diphosphate (UDP) sugars and their derivatives, which is consistent with their roles in protein and lipid glycosylation. Furthermore, targeted metabolomics validated SLC35A2 as the subcellular transporter for UDP-hexose. Finally, lipidomics analysis showed that phospholipids including phosphatidylcholine, phosphatidylinositol, and phosphatidylserine are the most abundant Golgi lipids and that glycosphingolipids are enriched in this compartment. Altogether, our work establishes a comprehensive molecular map of the human Golgi and provides a powerful method to study the Golgi with high precision in health and disease.

The temporal dynamics of Plasmodium species infection after artemisinin-based combination therapy (ACT) among asymptomatic children in the Hohoe municipality, Ghana.

BACKGROUND: The routine surveillance of asymptomatic malaria using nucleic acid-based amplification tests is essential in obtaining reliable data that would inform malaria policy formulation and the implementation of appropriate control measures. METHODS: In this study, the prevalence rate and the dynamics of Plasmodium species among asymptomatic children (n = 1697) under 5 years from 30 communities within the Hohoe municipality in Ghana were determined. RESULTS AND DISCUSSION: The observed prevalence of Plasmodium parasite infection by polymerase chain reaction (PCR) was 33.6% (571/1697), which was significantly higher compared to that obtained by microscopy [26.6% (451/1697)] (P < 0.0001). Based on species-specific analysis by nested PCR, Plasmodium falciparum infection [33.6% (570/1697)] was dominant, with Plasmodium malariae, Plasmodium ovale and Plasmodium vivax infections accounting for 0.1% (1/1697), 0.0% (0/1697), and 0.0% (0/1697), respectively. The prevalence of P. falciparum infection among the 30 communities ranged from 0.0 to 82.5%. Following artesunate-amodiaquine (AS + AQ, 25 mg/kg) treatment of a sub-population of the participants (n = 184), there was a substantial reduction in Plasmodium parasite prevalence by 100% and 79.2% on day 7 based on microscopy and nested PCR analysis, respectively. However, there was an increase in parasite prevalence from day 14 to day 42, with a subsequent decline on day 70 by both microscopy and nested PCR. For parasite clearance rate analysis, we found a significant proportion of the participants harbouring residual Plasmodium parasites or parasite genomic DNA on day 1 [65.0% (13/20)], day 2 [65.0% (13/20)] and day 3 [60.0% (12/20)] after initiating treatment. Of note, gametocyte carriage among participants was low before and after treatment. CONCLUSION: Taken together, the results indicate that a significant number of individuals could harbour residual Plasmodium parasites or parasite genomic DNA after treatment. The study demonstrates the importance of routine surveillance of asymptomatic malaria using sensitive nucleic acid-based amplification techniques.

PLA2G15 is a Lysosomal BMP Hydrolase with Ester Position Specificity and its Targeting Ameliorates Lysosomal Disease.

Lysosomes catabolize lipids and other biological molecules, a function essential for cellular and organismal homeostasis. Key to lipid catabolism in the lysosome is bis(monoacylglycero)phosphate (BMP), a major lipid constituent of intralysosomal vesicles (ILVs) and a stimulator of lipid-degrading enzymes. BMP levels are altered in a broad spectrum of human conditions, including neurodegenerative diseases. Although BMP synthase was recently discovered, it has long been thought that BMP's unique stereochemistry confers resistance to acid phospholipases, a requirement for its role in the lysosome. Here, we demonstrate that PLA2G15, a major lysosomal phospholipase, efficiently hydrolyzes BMP with primary esters regardless of stereochemistry. Interestingly, we discover that BMP's unique esterification position is what confers resistance to hydrolysis. Purified PLA2G15 catabolizes most BMP species derived from cell and tissue lysosomes under acidic conditions. Furthermore, PLA2G15 catalytic activity against synthesized BMP stereoisomers with primary esters was comparable to its canonical substrates. Conversely, BMP with secondary esters is intrinsically stable in vitro and requires acyl migration for hydrolysis in lysosomes. Consistent with our biochemical data, PLA2G15-deficient tissues and cells accumulate multiple BMP species, a phenotype reversible by supplementing wildtype PLA2G15 but not its catalytically dead mutant. Increasing BMP levels by targeting PLA2G15 reverses the cholesterol accumulation phenotype in Niemann Pick Disease Type C (NPC1) patient fibroblasts and significantly ameliorate disease pathologies in NPC1-deficient mice leading to extended lifespan. Our findings establish the rules that govern the stability of BMP in the lysosome and identify PLA2G15 as a lysosomal BMP hydrolase and as a potential target for modulating BMP levels for therapeutic intervention.

The Batten disease gene product CLN5 is the lysosomal bis(monoacylglycero)phosphate synthase.

Lysosomes critically rely on bis(monoacylglycero)phosphate (BMP) to stimulate lipid catabolism, cholesterol homeostasis, and lysosomal function. Alterations in BMP levels in monogenic and complex neurodegeneration suggest an essential function in human health. However, the site and mechanism responsible for BMP synthesis have been subject to debate for decades. Here, we report that the Batten disease gene product CLN5 is the elusive BMP synthase (BMPS). BMPS-deficient cells exhibited a massive accumulation of the BMP synthesis precursor lysophosphatidylglycerol (LPG), depletion of BMP species, and dysfunctional lipid metabolism. Mechanistically, we found that BMPS mediated synthesis through an energy-independent base exchange reaction between two LPG molecules with increased activity on BMP-laden vesicles. Our study elucidates BMP biosynthesis and reveals an anabolic function of late endosomes/lysosomes.

An SPNS1-dependent lysosomal lipid transport pathway that enables cell survival under choline limitation.

Lysosomes degrade macromolecules and recycle their nutrient content to support cell function and survival. However, the machineries involved in lysosomal recycling of many nutrients remain to be discovered, with a notable example being choline, an essential metabolite liberated via lipid degradation. Here, we engineered metabolic dependency on lysosome-derived choline in pancreatic cancer cells to perform an endolysosome-focused CRISPR-Cas9 screen for genes mediating lysosomal choline recycling. We identified the orphan lysosomal transmembrane protein SPNS1 as critical for cell survival under choline limitation. SPNS1 loss leads to intralysosomal accumulation of lysophosphatidylcholine (LPC) and lysophosphatidylethanolamine (LPE). Mechanistically, we reveal that SPNS1 is a proton gradient-dependent transporter of LPC species from the lysosome for their re-esterification into phosphatidylcholine in the cytosol. Last, we establish that LPC efflux by SPNS1 is required for cell survival under choline limitation. Collectively, our work defines a lysosomal phospholipid salvage pathway that is essential under nutrient limitation and, more broadly, provides a robust platform to deorphan lysosomal gene function.

CNS Repopulation by Hematopoietic-Derived Microglia-Like Cells Corrects Progranulin deficiency.

Hematopoietic stem cell transplantation can deliver therapeutic proteins to the CNS through donor-derived hematopoietic cells that become microglia-like cells. However, using standard conditioning approaches, hematopoietic stem cell transplantation is currently limited by low and slow engraftment of microglia-like cells. We report an efficient conditioning regimen based on Busulfan and a six-day course of microglia depletion using the colony-stimulating factor receptor 1 inhibitor PLX3397. Combining Busulfan-myeloablation and transient microglia depletion results in robust, rapid, and persistent microglia replacement by bone marrow-derived microglia-like cells throughout the CNS. Adding PLX3397 does not affect neurobehavior or has adverse effects on hematopoietic reconstitution. Through single-cell RNA sequencing and high-dimensional CyTOF mass cytometry, we show that microglia-like cells are a heterogeneous population and describe six distinct subpopulations. Though most bone-marrow-derived microglia-like cells can be classified as homeostatic microglia, their gene signature is a hybrid of homeostatic/embryonic microglia and border associated-macrophages. Busulfan-myeloablation and transient microglia depletion induce specific cytokines in the brain, ultimately combining myeloid proliferative and chemo-attractive signals that act locally to repopulate microglia from outside the niche. Importantly, this conditioning approach demonstrates therapeutic efficacy in a mouse model of GRN deficiency. Transplanting wild-type bone marrow into Grn-/- mice conditioned with Busulfan plus PLX3397 results in high engraftment of microglia-like cells in the brain and retina, restoring GRN levels and normalizing lipid metabolism.