Lysosomal Metabolism Research Articles

A C9orf72-CARM1 axis regulates lipid metabolism under glucose starvation-induced nutrient stress.

Cells undergo metabolic adaptation during environmental changes by using evolutionarily conserved stress response programs. This metabolic homeostasis is exquisitely regulated, and its imbalance could underlie human pathological conditions. We report here that C9orf72, which is linked to the most common forms of the neurodegenerative diseases amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), is a key regulator of lipid metabolism under stress. Loss of C9orf72 leads to an overactivation of starvation-induced lipid metabolism that is mediated by dysregulated autophagic digestion of lipids and increased de novo fatty acid synthesis. C9orf72 acts by promoting the lysosomal degradation of coactivator-associated arginine methyltransferase 1 (CARM1), which in turn regulates autophagy-lysosomal functions and lipid metabolism. In ALS/FTD patient-derived neurons or tissues, a reduction in C9orf72 function is associated with dysregulation in the levels of CARM1, fatty acids, and NADPH oxidase NOX2. These results reveal a C9orf72-CARM1 axis in the control of stress-induced lipid metabolism and implicates epigenetic dysregulation in relevant human diseases.

Reduced glucocerebrosidase activity in monocytes from patients with Parkinson\u2019s disease

Missense mutations in glucocerebrosidase (GBA1) that impair the activity of the encoded lysosomal lipid metabolism enzyme (GCase) are linked to an increased risk of Parkinson’s disease. However, reduced GCase activity is also found in brain tissue from Parkinson’s disease patients without GBA1 mutations, implicating GCase dysfunction in the more common idiopathic form of Parkinson’s disease. GCase is very highly expressed in monocytes, and thus we measured GCase activity in blood samples from recently diagnosed Parkinson’s disease patients. Flow cytometry and immunoblotting assays were used to measure levels of GCase activity and protein in monocytes and lymphocytes from patients with Parkinson’s disease (n = 48) and matched controls (n = 44). Gene sequencing was performed to screen participants for GBA1 missense mutations. In the Parkinson’s disease patients, GCase activity was significantly reduced in monocytes, but not lymphocytes, compared to controls, even when GBA1 mutation carriers were excluded. Monocyte GCase activity correlated with plasma ceramide levels in the Parkinson’s disease patients. Our results add to evidence for GCase dysfunction in idiopathic Parkinson’s disease and warrant further work to determine if monocyte GCase activity associates with Parkinson’s disease progression.

Derivatization of common antidepressant drugs increases inhibition of acid sphingomyelinase and reduces induction of phospholipidosis.

In recent studies, major depressive disorder (MDD) was linked to an increase in acid sphingomyelinase (ASM) activity. Several drugs that are commonly used to treat MDD functionally inhibit the lysosomal enzyme ASM and are called functional inhibitors of ASM (FIASMAs). These drugs are classified as cationic amphiphilic drugs (CADs) that influence the catalytic activities of different lysosomal enzymes. This action results in the side effect of phospholipidosis (PLD), which describes a detrimental increase in the phospholipid content in lysosomes. FIASMAs differ only slightly in their physico-chemical properties, but their effects on ASM activity and induction of the lysosomal phospholipid content vary significantly. In this study, we systematically induced minor chemical modifications to the FIASMAs imipramine, desipramine and fluoxetine. We generated a library of 45 new CADs with slightly different log P (logarithmic partition coefficient) and pKa (logarithmic acid dissociation constant) values. The effects of the compounds on the ASM activity and lysosomal phospholipid content were assessed in cell culture assays. We identified four compounds with beneficial effects, i.e., increased ASM activity inhibition and reduced PLD induction compared with the original drugs. The compounds HT04, RH272B and RH272D outperformed the original imipramine, whereas RH281A performed better than desipramine. Thus, minor chemical variations of CADs impact lysosomal metabolism in a specific manner and can lead to antidepressant drugs with less deleterious side effects.

Lysosomal acid lipase and lipid metabolism: new mechanisms, new questions, and new therapies.

Lysosomal acid lipase (LAL), encoded by the LIPA gene, is an essential lysosomal enzyme that hydrolyzes cholesteryl ester and triglyceride delivered to the lysosome. This review highlights the novel pathophysiological role of LAL, the functional genomic discoveries of LIPA as a risk locus for coronary heart diseases (CHD), and the clinical advance in therapies for LAL deficiency. The essential role of LAL in lipid metabolism has been confirmed in human and mice with LAL deficiency. In humans, loss-of-function mutations of LIPA cause rare lysosomal disorders, Wolman disease, and cholesteryl ester storage disease, in which LAL enzyme replacement therapy has shown significant benefits in a phase 3 clinical trial. Recent studies have revealed the role of LAL-mediated lysosomal lipolysis in regulating macrophage M2 polarization, lipid mediator production, VLDL secretion, lysosomal function and autophagy, extracellular degradation of aggregated-LDL, and adipose tissue lipolysis. Genome-wide association studies and functional genomic studies have identified LIPA as a risk locus for CHD, but the causal variants and mechanisms remain to be determined. Despite years of research, our understanding of LAL is incomplete. Future studies will continue to focus on the key pathophysiological functions of LAL in health and diseases including CHD.

Changes of lysosomal membrane permeabilization and lipid metabolism in sidt2 deficient mice.

The SID1 transmembrane family member 2 (sidt2) deficient mouse model was used to investigate the function of sidt2 in lysosomal membrane permeabilization and lipid metabolism of liver tissue. The mouse model was established by Cre/LoxP technology. Enzymatic methods were used to analyze the sidt2−/− mouse serum lipids, aspartate transaminase, alanine transaminase and serum bilirubin, compared with sidt2+/+ mice. Defective lipid metabolism and damaged liver functions were observed in the sidt2−/− mice. By using hematoxylin and eosin and Oil Red O staining, changes of morphology were observed in sidt2−/− mice with optical microscopy. Transmission electron microscopy was also used. Hepatic steatosis and partial liver tissue apoptosis were observed. The tissue distribution of sidt2 protein and mRNA was measured in knockout mice. The results indicated that negligible sidt2 mRNA and protein expression were observed in sidt2−/− mice, and that sidt2−/− mice had abnormal liver functions. Transmission electron microscopy revealed membrane lipid droplets in the liver cell cytoplasm, and some apoptotic body formation. These results demonstrated that absence of the lysosomal membrane protein sidt2 led to changes in lysosomal membrane permeabilization and lipid metabolism.

Deficiency of Lysosomal Ceramide Hydrolysis Contributes to Enhanced Exosome Release and Calcification in Coronary Artery Myocytes

Ceramide has been shown to contribute to vascular calcification under different pathological conditions. However, the precise mechanism mediating this process remains unknown. The present study investigated the role of lysosomal ceramide metabolism via acid ceramidase (AC) in the regulation of exosome excretion in coronary artery myocytes (CAMs) and the possible implication in the development of calcification. In cultured CAMs from smooth muscle (SM)‐specific Asah1 (mouse code of AC gene) knock‐out mice (Asah1fl/fl/SMcre), we observed that deletion of Asah1 gene increased lysosomal ceramide level compared to their control littermates, as detected by immunostaining of ceramide co‐localized with lysosome marker lamp‐1. Treatment of CAMs from wild type mice produced similar effects to reduce lysosomal ceramide given its effect to inhibit AC activity. Alizarin Red staining showed that more remarkable calcium deposition or calcification by 1.9 folds occurred in cultured CAMs from Asah1fl/fl/SMcre mice compared to cells from their control littermates, if these cells were treated with 3 mM NaH2PO3 and atherogenic stimulator, 7‐ket. Correspondingly, CAMs from Asah1fl/fl/SMcre mice were found to have significant phenotype transition as shown by Western blot analysis, increased expression of synthetic and osteogenic markers (more vimentin and osteopontin) and decreased contractile phenotypic marker (less SM22α), and this synthetic or osteogenic phenotype was enhanced by 7‐ket treatment. Using super‐resolution imaging with Structured Illumination Microscopy (SR‐SIM), we found that 7‐ket markedly reduced colocalization of Rab‐7a (multivesicular body (MVB) marker) with lamp‐1 in 7‐ket‐treated WT CAMs by 3 folds or CAMs from Asah1fl/fl/SMcre mice by 2.5 folds, suggesting inhibition of MVB‐lysosome encountering or fusion during inhibition of AC expression and activity. Using nanoparticle tracking analysis, 7‐ket‐induced excretion of exosomes (80–140 nm in size) was found to be significantly increased in CAMs of Asah1fl/fl/SMcre mice by 2.1 folds compared to CAMs from their control littermates. These results suggest that AC‐mediated ceramide hydrolysis in lysosomes critically controls MVB fate and exosome release and that insufficient AC expression and activity may lead to enhancement of exosome release, contributing to calcium deposition or calcification in CAMs or arterial media.Support or Funding Information(supported by NIH grants HL057244, HL075316 and HL122937).This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

P.217 - Stabilized next-generation recombinant human acid alpha-glucosidase ATB200 clears accumulated glycogen and reverses cellular dysfunction to increase muscle strength in a mouse model of Pompe disease

Pompe disease is a rare inherited metabolic disease of impaired lysosomal glycogen metabolism due to acid alpha-glucosidase (GAA) deficiency, which leads to progressive muscle weakness. Our biochemical and histologic evaluation of muscles of Gaa knockout (KO) mice revealed extensive cellular dysfunction, as evidenced by pronounced autophagy and lysosomal proliferation and potentially altered membrane repair. To date, enzyme replacement therapy using the recombinant human GAA (rhGAA) alglucosidase alfa is the only approved treatment available for Pompe disease. While alglucosidase alfa provides some clinical benefits, the infused enzyme shows insufficient uptake into skeletal muscles. This distribution is likely due to suboptimal levels of mannose-6-phosphate (M6P), which is responsible for enzyme internalization and lysosomal targeting. ATB200 is a novel rhGAA with a significantly higher M6P content than alglucosidase alfa. The pharmacological chaperone AT2221 is also utilized to stabilize ATB200 in circulation. We compared the effects of ATB200 co-administered with AT2221 (ATB200/AT2221) to those of alglucosidase alfa in Gaa KO mice. Co-administration of ATB200/AT2221 led to significantly greater glycogen reduction in key muscles. Immunohistochemical analyses suggested that ATB200/AT2221 is more effective than alglucosidase alfa in reducing lysosomal proliferation, enhancing autophagy flux, and repairing damaged muscle fibers. Furthermore, ATB200/AT2221 improved muscle strength compared with alglucosidase alfa. Collectively, these data indicate that ATB200/AT2221 efficiently targets muscle fibers, reverses cellular dysfunction, and improves muscle function. Therefore, ATB200/AT2221 is currently being investigated in the ongoing ATB200-02 clinical trial (NCT02675465) as a potential next-generation treatment for Pompe disease.

Lipidomic and Transcriptomic Basis of Lysosomal Dysfunction in Progranulin Deficiency

SummaryDefective lysosomal function defines many neurodegenerative diseases, such as neuronal ceroid lipofuscinoses (NCL) and Niemann-Pick type C (NPC), and is implicated in Alzheimer's disease (AD) and frontotemporal lobar degeneration (FTLD-TDP) with progranulin (PGRN) deficiency. Here, we show that PGRN is involved in lysosomal homeostasis and lipid metabolism. PGRN deficiency alters lysosome abundance and morphology in mouse neurons. Using an unbiased lipidomic approach, we found that brain lipid composition in humans and mice with PGRN deficiency shows disease-specific differences that distinguish them from normal and other pathologic groups. PGRN loss leads to an accumulation of polyunsaturated triacylglycerides, as well as a reduction of diacylglycerides and phosphatidylserines in fibroblast and enriched lysosome lipidomes. Transcriptomic analysis of PGRN-deficient mouse brains revealed distinct expression patterns of lysosomal, immune-related, and lipid metabolic genes. These findings have implications for the pathogenesis of FTLD-TDP due to PGRN deficiency and suggest lysosomal dysfunction as an underlying mechanism.

Inhibition of neuronal mitochondrial complex I or lysosomal glucocerebrosidase is associated with increased dopamine and serotonin turnover

Parkinson's disease (PD) is a neurodegenerative disorder caused by loss of dopaminergic and serotoninergic signalling. A number of pathogenic mechanisms have been implicated including loss of mitochondrial function at the level of complex I, and lysosomal metabolism at the level of lysosomal glucocerebrosidase (GBA1). In order to investigate further the potential involvement of complex I and GBA1 in PD, we assessed the impact of loss of respective enzyme activities upon dopamine and serotonin turnover. Using SH-SY5Y cells, complex I deficiency was modelled by using rotenone whilst GBA1 deficiency was modelled by the use of conduritol B epoxide (CBE). Dopamine, its principal metabolites, and the serotonin metabolite 5-hydroxyindoleacetic acid (5-HIAA) in the extracellular medium were quantified by HPLC. Inhibition of complex I significantly increased extracellular concentrations of 3,4-dihydroxyphenylacetic acid (DOPAC) and 5-HIAA. Comparable results were observed with CBE. These results suggest increased monoamine oxidase activity and provide evidence for involvement of impaired complex I or GBA1 activity in the dopamine/serotonin deficiency seen in PD. Use of extracellular media may also permit relatively rapid assessment of dopamine/serotonin metabolism and permit screening of novel therapeutic agents.

Loss of spatacsin function alters lysosomal lipid clearance leading to upper and lower motor neuron degeneration

Mutations in SPG11 account for the most common form of autosomal recessive hereditary spastic paraplegia (HSP), characterized by a gait disorder associated with various brain alterations. Mutations in the same gene are also responsible for rare forms of Charcot-Marie-Tooth (CMT) disease and progressive juvenile-onset amyotrophic lateral sclerosis (ALS). To elucidate the physiopathological mechanisms underlying these human pathologies, we disrupted the Spg11 gene in mice by inserting stop codons in exon 32, mimicking the most frequent mutations found in patients. The Spg11 knockout mouse developed early-onset motor impairment and cognitive deficits. These behavioral deficits were associated with progressive brain atrophy with the loss of neurons in the primary motor cortex, cerebellum and hippocampus, as well as with accumulation of dystrophic axons in the corticospinal tract. Spinal motor neurons also degenerated and this was accompanied by fragmentation of neuromuscular junctions and muscle atrophy. This new Spg11 knockout mouse therefore recapitulates the full range of symptoms associated with SPG11 mutations observed in HSP, ALS and CMT patients. Examination of the cellular alterations observed in this model suggests that the loss of spatacsin leads to the accumulation of lipids in lysosomes by perturbing their clearance from these organelles. Altogether, our results link lysosomal dysfunction and lipid metabolism to neurodegeneration and pinpoint a critical role of spatacsin in lipid turnover.

Type 1 Diabetes: Urinary Proteomics and Protein Network Analysis Support Perturbation of Lysosomal Function.

While insulin replacement therapy restores the health and prevents the onset of diabetic complications (DC) for many decades, some T1D patients have elevated hemoglobin A1c values suggesting poor glycemic control, a risk factor of DC. We surveyed the stool microbiome and urinary proteome of a cohort of 220 adolescents and children, half of which had lived with T1D for an average of 7 years and half of which were healthy siblings. Phylogenetic analysis of the 16S rRNA gene did not reveal significant differences in gut microbial alpha-diversity comparing the two cohorts. The urinary proteome of T1D patients revealed increased abundances of several lysosomal proteins that correlated with elevated HbA1c values. In silico protein network analysis linked such proteins to extracellular matrix components and the glycoprotein LRG1. LRG1 is a prominent inflammation and neovascularization biomarker. We hypothesize that these changes implicate aberrant glycation of macromolecules that alter lysosomal function and metabolism in renal tubular epithelial cells, cells that line part of the upper urinary tract.

Quantitative Profiling of Lysosomal Lipidome by Shotgun Lipidomics.

Recent studies have illuminated novel roles of lysosomes that go far beyond simple catabolism and function in the coordination of cellular metabolism and signaling. Promising therapeutic strategies emerge from knowledge in the molecular mechanisms and physiological roles of lipid metabolism in lysosomes. Global monitoring of the function and dysregulation of lysosomal lipid metabolism requires a methodology that resolves the complexity of lysosomal lipidome by quantitatively detecting hundreds of lipid species of diverse physicochemical properties. We describe here a detailed protocol that couples isolation of superparamagnetic iron dextran-loaded lysosomes from cultured mammalian cell lines with quantitative mass spectrometry-based shotgun lipidomics.

Loss of Cathepsin B and L Leads to Lysosomal Dysfunction, NPC-Like Cholesterol Sequestration and Accumulation of the Key Alzheimer's Proteins

Proper function of lysosomes is particularly important in neurons, as they cannot dilute accumulated toxic molecules and aggregates by cell division. Thus, impairment of lysosomal function plays an important role in neuronal degeneration and in the pathogenesis of numerous neurodegenerative diseases. In this work we analyzed how inhibition and/or loss of the major lysosomal proteases, the cysteine cathepsins B and L (CtsB/L), affects lysosomal function, cholesterol metabolism and degradation of the key Alzheimer's disease (AD) proteins. Here, we show that cysteine CtsB/L, and not the aspartyl cathepsin D (CtsD), represent a major lysosomal protease(s) that control lysosomal function, intracellular cholesterol trafficking and AD-like amyloidogenic features. Intriguingly, accumulation of free cholesterol in late endosomes/lysosomes upon CtsB/L inhibition resembled a phenotype characteristic for the rare neurodegenerative disorder Niemann-Pick type C (NPC). CtsB/L inhibition and not the inhibition of CtsD led to lysosomal impairment assessed by decreased degradation of EGF receptor, enhanced LysoTracker staining and accumulation of several lysosomal proteins LC3II, NPC1 and NPC2. By measuring the levels of NPC1 and ABCA1, the two major cholesterol efflux proteins, we showed that CtsB/L inhibition or genetic depletion caused accumulation of the NPC1 in lysosomes and downregulation of ABCA1 protein levels and its expression. Furthermore, we revealed that CtsB/L are involved in degradation of the key Alzheimer’s proteins: amyloid-β peptides (Aβ) and C-terminal fragments of the amyloid precursor protein (APP) and in degradation of β-secretase (BACE1). Our results imply CtsB/L as major regulators of lysosomal function and demonstrate that CtsB/L may play an important role in intracellular cholesterol trafficking and in degradation of the key AD proteins. Our findings implicate that enhancing the activity or levels of CtsB/L could provide a promising and a common strategy for maintaining lysosomal function and for preventing and/or treating neurodegenerative diseases.

Trehalose Alters Subcellular Trafficking and the Metabolism of the Alzheimer-associated Amyloid Precursor Protein

The disaccharide trehalose is commonly considered to stimulate autophagy. Cell treatment with trehalose could decrease cytosolic aggregates of potentially pathogenic proteins, including mutant huntingtin, α-synuclein, and phosphorylated tau that are associated with neurodegenerative diseases. Here, we demonstrate that trehalose also alters the metabolism of the Alzheimer disease-related amyloid precursor protein (APP). Cell treatment with trehalose decreased the degradation of full-length APP and its C-terminal fragments. Trehalose also reduced the secretion of the amyloid-β peptide. Biochemical and cell biological experiments revealed that trehalose alters the subcellular distribution and decreases the degradation of APP C-terminal fragments in endolysosomal compartments. Trehalose also led to strong accumulation of the autophagic marker proteins LC3-II and p62, and decreased the proteolytic activation of the lysosomal hydrolase cathepsin D. The combined data indicate that trehalose decreases the lysosomal metabolism of APP by altering its endocytic vesicular transport.

Tracheobronchial stents in mucopolysaccharidosis

IntroductionThe mucopolysaccharidoses are a group of hereditary disorders pathologically characterized by tissue accumulation of glycosaminoglycans due to deficient lysosomal metabolism which often leads to progressive airway stenosis and respiratory insufficiency. Relentless and treatment-refractory narrowing of the lower airways with ensuing severe limitation of quality of life is a challenging problem in mucopolysaccharidoses. Case reportsWe report 2 cases of MPS (Hunter's and Maroteaux-Lamy's syndrome resp.) in whom tracheal stents were placed to relieve severe tracheal obstruction. The first patient could be weaned from mechanical ventilation after stent placement but showed significant long-term stent-related morbidity. The second patient suffered a severe procedure-related complication due to positioning problems typical for MPS. ConclusionsVery good short-term success can be achieved with airway stent placement in patients with MPS and severe lower airway stenosis but a high risk of severe complications and important long-term morbidity have to be weighed against potential individual benefit.

Combined incubation of cadmium, docosahexaenoic and eicosapentaenoic acid results in increased uptake of cadmium and elevated docosapentaenoic acid content in hepatocytes in vitro.

BackgroundHuman hepatocellular cells Hep G2 were used to mimic and investigate the effect of the intake of cadmium (Cd2+) contaminated fish on cytotoxicity, fatty acid (FA) and phospholipid class composition.MethodsCells were incubated with a combination of Cd2+ and eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) fish specific FA.ResultsWe measured a significant increased proportion of EPA and DHA in the treated cells compared to the control line confirming the uptake. While doses of 25 μM DHA showed to be toxic to the cells, repeated short term incubations (2 h) at lower doses resulted in an increased uptake of DHA. The resarzurin assay, evaluating cell viability, showed a significant decrease in cell viability between Cd2+ incubation time and, further, the pre-incubation with BSA-FA complex resulted in significantly increased cell viability. On the metabolic level, increased concentrations of EPA and DHA resulted in an increased proportion of docosapentaenoic acid (DPA) which indicated an increased metabolism. Also 24-h combined incubations of 5 μM Cd2+ and EPA and DHA showed a significant increase DPA in the total lipid fraction of the cells. In addition, incubation with 5 μM Cd2+ for 24 h also decreased the total cardiolipin (CL) fraction from the identified phospholipids.ConclusionsWe confirmed that the applied FA were taken up by the cells. A combination of EPA, DHA and Cd2+ influenced lysosomal integrity, cell viability and lipid metabolism in the cells. The most important finding is that DHA and EPA reduced the detrimental effect of Cd2+ on cell viability. The exact effects and kinetics behind our observations still need further evaluation.

Triglyceride Regulation of Lysosomal Cholesterol in THP-1 Macrophages

The central question I investigated in my research this semester was how the cholesterol and triglyceride metabolic pathways interact in macrophages when cholesterol levels are high. What factors prevent or enhance macrophage ability to regulate cholesterol metabolism? We have preliminary evidence that excessive cholesterol accumulation in macrophages alters triglyceride metabolism in these cells. When cellular cholesterol levels are normal, the primary site of triglyceride hydrolysis is on the surface of the macrophage. There, lipases hydrolyze triglycerides within triglyceride-rich lipoproteins to glycerol and fatty acids. The fatty acids are carried across the cell membrane into the cytoplasm. In the cytoplasm, the fatty acids can be utilized to make triglycerides, phospholipids and cholesteryl esters. Cholesterol influences how the cell breaks down triglycerides. If cholesterol levels are high then triglyceride metabolism tends to occur more frequently in the lysosome. In contrast, when the cells have excess cholesterol, particularly within their lysosomes, the surface hydrolysis is suppressed and lipoproteins are taken up by endocytosis and delivered to lysosomes for hydrolysis. The effect of inhibiting the surface lipolysis was evaluated to determine the impact on intracellular cholesterol and triglyceride levels. The data indicates that the presence of triglyceride restores lysosomal metabolism of cholesterol.

αvβ5 Integrin/FAK/PGC-1α Pathway Confers Protective Effects on Retinal Pigment Epithelium.

PurposeTo elucidate the mechanism of the induction of peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) by photoreceptor outer segments (POS) and its effects on retinal pigment epithelium (RPE).MethodsPGC-1α upregulation by POS was confirmed in ARPE-19 cells and in RPE ex vivo. To elucidate the mechanism, siRNAs against β5 integrin, CD36, Mer tyrosine kinase (MerTK), and Atg5, blocking antibodies against CD36 and MerTK, and a specific inhibitor for focal adhesion kinase (FAK) were used. We examined the effect of POS-induced PGC-1α upregulation on the levels of reactive oxygen species (ROS), mitochondrial biogenesis, senescence-associated β-galactosidase (SA-β-gal) after H2O2 treatment, and lysosomal activity. Lysosomal activity was evaluated through transcriptional factor EB and its target genes, and the activity of cathepsin D. Lipid metabolism after POS treatment was assessed using Oil Red O and BODIPY C11. RPE phenotypes of PGC-1α-deficient mice were examined.ResultsPOS-induced PGC-1α upregulation was suppressed by siRNA against β5 integrin and a FAK inhibitor. siRNAs and blocking antibodies against CD36 and MerTK enhanced the effect of POS on PGC-1α. The upregulation of PGC-1α increased the levels of mRNA for antioxidant enzymes and stimulated mitochondrial biogenesis, decreased ROS levels, and reduced SA-β-gal staining in H2O2-treated ARPE-19 cells. PGC-1α was critical for lysosomal activity and lipid metabolism after POS treatment. PGC-1α-deficient mice demonstrated an accumulation of type 2 lysosomes in RPE, thickening of Bruch’s membrane, and poor choriocapillaris vasculature.ConclusionsThe binding, but not the internalization of POS confers protective effects on RPE cells through the αvβ5 integrin/FAK/PGC-1α pathway.

Gaucher disease and comorbidities: B-cell malignancy and parkinsonism.

Data emerging from the International Collaborative Gaucher Group (ICGG) Gaucher Registry together with other contemporary clinical surveys have revealed a close association between Gaucher disease and non-Hodgkin's B-cell lymphoma and myeloma and Gaucher disease and Parkinson's disease. Several possible explanations for increased B-cell proliferation and neoplasia in Gaucher disease have been proposed, including the possible influence of sphingosine (derived from the extra lysosomal metabolism of glucosylceramide), gene modifiers, splenectomy and immune system deregulation induced by cytokines, chemokines, and hydrolases released from Gaucher cells. Parkinson's disease is frequently seen in the otherwise-healthy relatives of Gaucher disease patients leading to the finding that GBA mutations represent a genetic risk factor for Parkinson's disease. The mechanism of the association between GBA mutations and Parkinson's disease has yet to be elucidated but the pathogenesis appears distinct from that of Gaucher disease. Several pathogenic pathways have been proposed including lysosomal and/or mitochondrial dysfunction. The effect of Gaucher disease specific therapies on the incidence of cancer or Parkinson's disease are not clear and will likely be evaluated in future ICGG Gaucher Registry studies.

Activation of Peroxisome Proliferator-activated Receptor α Induces Lysosomal Biogenesis in Brain Cells: IMPLICATIONS FOR LYSOSOMAL STORAGE DISORDERS

Lysosomes are ubiquitous membrane-enclosed organelles filled with an acidic interior and are central to the autophagic, endocytic, or phagocytic pathway. In contrast to its classical function as the waste management machinery, lysosomes are now considered to be an integral part of various cellular signaling processes. The diverse functionality of this single organelle requires a very complex and coordinated regulation of its activity with transcription factor EB (TFEB), a master regulator of lysosomal biogenesis, at its core. However, mechanisms by which TFEB is regulated are poorly understood. This study demonstrates that gemfibrozil, an agonist of peroxisome proliferator-activated receptor (PPAR) α, alone and in conjunction with all-trans-retinoic acid is capable of enhancing TFEB in brain cells. We also observed that PPARα, but not PPARβ and PPARγ, is involved in gemfibrozil-mediated up-regulation of TFEB. Reporter assay and chromatin immunoprecipitation studies confirmed the recruitment of retinoid X receptor α, PPARα, and PGC1α on the PPAR-binding site on the Tfeb promoter as well. Subsequently, the drug-mediated induction of TFEB caused an increase in lysosomal protein and the lysosomal abundance in cell. Collectively, this study reinforces the link between lysosomal biogenesis and lipid metabolism with TFEB at the crossroads. Furthermore, gemfibrozil may be of therapeutic value in the treatment of lysosomal storage disorders in which autophagy-lysosome pathway plays an important role.