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Gaucher disease (GD) is caused by biallelic GBA1/Gba1 mutations that encode defective glucocerebrosidase (GCase). Progranulin (PGRN, encoded by GRN/Grn) is a modifier of GCase, but the interplay between PGRN and GCase, specifically GBA1/Gba1 mutations, contributing to GD severity is unclear. Mouse models were developed with various dosages of Gba1 D409V mutation against the PGRN deficiency (Grn-/-) [Grn-/-;Gba1D409V/WT (PG9Vwt), Grn-/-;Gba1D409V/D409V (PG9V), Grn-/-;Gba1D409V/Null (PG9VN)]. Disease progression in those mouse models was characterized by biochemical, pathological, transcriptomic, and neurobehavioral analyses. Compared to PG9Vwt, Grn-/-;Gba1WT/Null and Grn-/- mice that had a higher level of GCase activity and undetectable pathologies, homozygous or hemizygous D409V in PG9V or PG9VN, respectively, resulted in profound inflammation and neurodegeneration. PG9VN mice exhibited much earlier onset, shorter life span, tissue fibrosis, and more severe phenotypes than PG9V mice. Glycosphingolipid accumulation, inflammatory responses, lysosomal-autophagy dysfunction, microgliosis, retinal gliosis, as well as α-Synuclein increases were much more pronounced in PG9VN mice. Neurodegeneration in PG9VN was characterized by activated microglial phagocytosis of impaired neurons and programmed cell death due to necrosis and, possibly, pyroptosis. Brain transcriptomic analyses revealed the intrinsic relationship between D409V dosage, and the degree of altered gene expression related to lysosome dysfunction, microgliosis, and neurodegeneration in GD, suggesting the disease severity is dependent on a GCase activity threshold related to Gba1 D409V dosage and loss of PGRN. These findings contribute to a deeper understanding of GD pathogenesis by elucidating additional underlying mechanisms of interplay between PGRN and Gba1 mutation dosage in modulating GCase function and disease severity in GD and GBA1-associated neurodegenerative diseases., (© The Author(s) 2024. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Gaucher disease is a lysosomal storage disease, which happens due to mutations in GBA1 / Gba1 that encodes the enzyme termed as lysosomal acid β-glucosidase. The major function of this enzyme is to catalyze glucosylceramide (GC) into glucose and ceramide. The deficiency of this enzyme and resultant abnormal accumulation of GC cause altered function of several of the innate and adaptive immune cells. For example, augmented infiltration of T cells contributes to the increased production of pro-inflammatory cytokines, (e.g., IFNγ, TNFα, IL6, IL12p40, IL12p70, IL23, and IL17A/F). This leads to tissue damage in a genetic mouse model ( Gba1 9V/- ) of Gaucher disease. The cellular mechanism(s) by which increased tissue infiltration of T cells occurs in this disease is not fully understood. Here, we delineate role of the CXCR3 receptor and its exogenous C-X-C motif chemokine ligand 9 (CXCL9) in induction of increased tissue recruitment of CD4 + T and CD8 + T cells in Gaucher disease. Intracellular FACS staining of macrophages (Mϕs) and dendritic cells (DCs) from Gba1 9V/- mice showed elevated production of CXCL9. Purified CD4 + T cells and the CD8 + T cells from Gba1 9V/- mice showed increased expression of CXCR3. Ex vivo and in vivo chemotaxis experiments showed CXCL9 involvement in the recruitment of Gba1 9V/- T cells. Furthermore, antibody blockade of the CXCL9 receptor (CXCR3) on T cells caused marked reduction in CXCL9- mediated chemotaxis of T cells in Gba1 9V/- mice. These data implicate abnormalities of the CXCL9-CXCR3 axis leading to enhanced tissue recruitment of T cells in Gaucher disease. Such results provide a rationale for blockade of the CXCL9/CXCR3 axis as potential new therapeutic targets for the treatment of inflammation in Gaucher disease.

Substrate reduction therapy (SRT) in clinic adequately manages the visceral manifestations in Gaucher disease (GD) but has no direct effect on brain disease. To understand the molecular basis of SRT in GD treatment, we evaluated the efficacy and underlying mechanism of SRT in an immortalized neuronal cell line derived from a Gba knockout ( Gba -/- ) mouse model. Gba -/- neurons accumulated substrates, glucosylceramide, and glucosylsphingosine. Reduced cell proliferation was associated with altered lysosomes and autophagy, decreased mitochondrial function, and activation of the mTORC1 pathway. Treatment of the Gba -/- neurons with venglustat analogue GZ452, a central nervous system-accessible SRT, normalized glucosylceramide levels in these neurons and their isolated mitochondria. Enlarged lysosomes were reduced in the treated Gba -/- neurons, accompanied by decreased autophagic vacuoles. GZ452 treatment improved mitochondrial membrane potential and oxygen consumption rate. Furthermore, GZ452 diminished hyperactivity of selected proteins in the mTORC1 pathway and improved cell proliferation of Gba -/- neurons. These findings reinforce the detrimental effects of substrate accumulation on mitochondria, autophagy, and mTOR in neurons. A novel rescuing mechanism of SRT was revealed on the function of mitochondrial and autophagy-lysosomal pathways in GD. These results point to mitochondria and the mTORC1 complex as potential therapeutic targets for treatment of GD.

Competing Interests: Declaration of Competing Interest The authors declare no conflicts of interest.

Background: Enzyme replacement therapy (ERT) can positively affect the visceral manifestations of lysosomal storage diseases (LSDs). However, the exclusion of the intravenous ERT agents from the central nervous system (CNS) prevents direct therapeutic effects., Methods: Using a neuronopathic Gaucher disease (nGD) mouse model, CNS-ERT was created using a systemic, non-invasive, and CNS-selective delivery system based on nanovesicles of saposin C (SapC) and dioleoylphosphatidylserine (DOPS) to deliver to CNS cells and tissues the corrective, functional acid β-glucosidase (GCase)., Findings: Compared to free GCase, human GCase formulated with SapC-DOPS nanovesicles (SapC-DOPS-GCase) was more stable in serum, taken up into cells, mostly by a mannose receptor-independent pathway, and resulted in higher activity in GCase-deficient cells. In contrast to free GCase, SapC-DOPS-GCase nanovesicles penetrated through the blood-brain barrier into the CNS. The CNS targeting was mediated by surface phosphatidylserine (PS) of blood vessel and brain cells. Increased GCase activity and reduced GCase substrate levels were found in the CNS of SapC-DOPS-GCase-treated nGD mice, which showed profound improvement in brain inflammation and neurological phenotypes., Interpretation: This first-in-class CNS-ERT approach provides considerable promise of therapeutic benefits for neurodegenerative diseases., Funding: This study was supported by the National Institutes of Health grants R21NS 095047 to XQ and YS, R01NS 086134 and UH2NS092981 in part to YS; Cincinnati Children's Hospital Medical Center Research Innovation/Pilot award to YS and XQ; Gardner Neuroscience Institute/Neurobiology Research Center Pilot award to XQ and YS, Hematology-Oncology Programmatic Support from University of Cincinnati and New Drug State Key Project grant 009ZX09102-205 to XQ., Competing Interests: Declaration of Competing Interest The authors claim a provisional patent application has been filed on March 10, 2020. Consistent with current Cincinnati Children's Hospital Medical Center policies, the development and commercialization of this technology has been licensed to Bexion Pharmaceuticals, LLC, in which X. Qi, holds (< 5%) equity interest., (Copyright © 2020 The Authors. Published by Elsevier B.V. All rights reserved.)

Gaucher disease (GD) is caused by GBA1 mutations leading to functional deficiency of acid-β-glucosidase (GCase). No effective treatment is available for neuronopathic GD (nGD). A subclass of neural stem and precursor cells (NPCs) expresses VLA4 (integrin α4β1, very late antigen-4) that facilitates NPC entry into the brain following intravenous (IV) infusion. Here, the therapeutic potential of IV VLA4+NPCs was assessed for nGD using wild-type mouse green fluorescent protein (GFP)-positive multipotent induced pluripotent stem cell (iPSC)-derived VLA4+NPCs. VLA4+NPCs successfully engrafted in the nGD (4L;C*) mouse brain. GFP-positive cells differentiated into neurons, astrocytes and oligodendrocytes in the brainstem, midbrain and thalamus of the transplanted mice and significantly improved sensorimotor function and prolonged life span compared to vehicle-treated 4L;C* mice. VLA4+NPC transplantation significantly decreased levels of CD68 and glial fibrillary acidic protein, as well as TNFα mRNA levels in the brain, indicating reduced neuroinflammation. Furthermore, decreased Fluoro-Jade C and NeuroSilver staining suggested inhibition of neurodegeneration. VLA4+NPC-engrafted 4L;C* midbrains showed 35% increased GCase activity, reduced substrate [glucosylceramide (GC, -34%) and glucosylsphingosine (GS, -11%)] levels and improved mitochondrial oxygen consumption rates in comparison to vehicle-4L;C* mice. VLA4+NPC engraftment in 4L;C* brain also led to enhanced expression of neurotrophic factors that have roles in neuronal survival and the promotion of neurogenesis. This study provides evidence that iPSC-derived NPC transplantation has efficacy in an nGD mouse model and provides proof of concept for autologous NPC therapy in nGD., (© The Author(s) 2019. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Gaucher disease is caused by mutations in GBA1 encoding acid β-glucosidase (GCase). Saposin C enhances GCase activity and protects GCase from intracellular proteolysis. Structure simulations indicated that the mutant GCases, N370S (0 S), V394L (4L) and D409V(9V)/H(9H), had altered function. To investigate the in vivo function of Gba1 mutants, mouse models were generated by backcrossing the above homozygous mutant GCase mice into Saposin C deficient (C*) mice. Without saposin C, the mutant GCase activities in the resultant mouse tissues were reduced by ~50% compared with those in the presence of Saposin C. In contrast to 9H and 4L mice that have normal histology and life span, the 9H;C* and 4L;C* mice had shorter life spans. 9H;C* mice developed significant visceral glucosylceramide (GC) and glucosylsphingosine (GS) accumulation (GC»GS) and storage macrophages, but lesser GC in the brain, compared to 4L;C* mice that presents with a severe neuronopathic phenotype and accumulated GC and GS primarily in the brain. Unlike 9V mice that developed normally for over a year, 9V;C* pups had a lethal skin defect as did 0S;C* mice resembled that of 0S mice. These variant Gaucher disease mouse models presented a mutation specific phenotype and underscored the in vivo role of Saposin C in the modulation of Gaucher disease.

The complement system is well appreciated for its role as an important effector of innate immunity that is activated by the classical, lectin or alternative pathway. C5a is one important mediator of the system that is generated in response to canonical and non-canonical C5 cleavage by circulating or cell-derived proteases. In addition to its function as a chemoattractant for neutrophils and other myeloid effectors, C5a and its sister molecule C3a have concerted roles in cell homeostasis and surveillance. Through activation of their cognate G protein coupled receptors, C3a and C5a regulate multiple intracellular pathways within the mitochondria and the lysosomal compartments that harbor multiple enzymes critical for protein, carbohydrate and lipid metabolism. Genetic mutations of such lysosomal enzymes or their receptors can result in the compartmental accumulation of specific classes of substrates in this organelle summarized as lysosomal storage diseases (LSD). A frequent LSD is Gaucher disease (GD), caused by autosomal recessively inherited mutations in GBA1, resulting in functional defects of the encoded enzyme, acid β-glucosidase (glucocerebrosidase, GCase). Such mutations promote excessive accumulation of β-glucosylceramide (GC or GL1) in innate and adaptive immune cells frequently associated with chronic inflammation. Recently, we uncovered an unexpected link between the C5a and C5a receptor 1 (C5aR1) axis and the accumulation of GL1 in experimental and clinical GD. Here, we will review the pathways of complement activation in GD, its role as a mediator of the inflammatory response, and its impact on glucosphingolipid metabolism. Further, we will discuss the potential role of the C5a/C5aR1 axis in GL1-specific autoantibody formation and as a novel therapeutic target in GD., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

In Gaucher disease (GD), deficiency of lysosomal acid β-glucosidase results in a broad phenotypic spectrum that is classified into three types based on the absence (type 1 [GD1]) or presence and severity of primary central nervous system involvement (type 2 [GD2], the fulminant neuronopathic form, and type 3 [GD3], the milder chronic neuronopathic form). Enzyme replacement therapy (ERT) with imiglucerase ameliorates and prevents hematological and visceral manifestations in GD1, but data in GD3 are limited to small, single-center series. The effects of imiglucerase ERT on hematological, visceral and growth outcomes (note: ERT is not expected to directly impact neurologic outcomes) were evaluated during the first 5years of treatment in 253 children and adolescents (<18years of age) with GD3 enrolled in the International Collaborative Gaucher Group (ICGG) Gaucher Registry. The vast majority of GBA mutations in this diverse global population consisted of only 2 mutations: L444P (77%) and D409H (7%). At baseline, GD3 patients exhibited early onset of severe hematological and visceral disease and growth failure. During the first year of imiglucerase treatment, hemoglobin levels and platelet counts increased and liver and spleen volumes decreased, leading to marked decreases in the number of patients with moderate or severe anemia, thrombocytopenia, and hepatosplenomegaly. These improvements were maintained through Year 5. There was also acceleration in linear growth as evidenced by increasing height Z-scores. Despite devastating disease at baseline, the probability of surviving for at least 5years after starting imiglucerase was 92%. In this large, multinational cohort of pediatric GD3 patients, imiglucerase ERT provided a life-saving and life-prolonging benefit for patients with GD3, suggesting that, with proper treatment, many such severely affected patients can lead productive lives and contribute to society., (Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.)

To study the neuronal deficits in neuronopathic Gaucher Disease (nGD), the chronological behavioral profiles and the age of onset of brain abnormalities were characterized in a chronic nGD mouse model (9V/null). Progressive accumulation of glucosylceramide (GC) and glucosylsphingosine (GS) in the brain of 9V/null mice were observed at as early as 6 and 3 months of age for GC and GS, respectively. Abnormal accumulation of α-synuclein was present in the 9V/null brain as detected by immunofluorescence and Western blot analysis. In a repeated open-field test, the 9V/null mice (9 months and older) displayed significantly less environmental habituation and spent more time exploring the open-field than age-matched WT group, indicating the onset of short-term spatial memory deficits. In the marble burying test, the 9V/null group had a shorter latency to initiate burying activity at 3 months of age, whereas the latency increased significantly at ≥12 months of age; 9V/null females buried significantly more marbles to completion than the WT group, suggesting an abnormal response to the instinctive behavior and an abnormal activity in non-associative anxiety-like behavior. In the conditional fear test, only the 9V/null males exhibited a significant decrease in response to contextual fear, but both genders showed less response to auditory-cued fear compared to age- and gender-matched WT at 12 months of age. These results indicate hippocampus-related emotional memory defects. Abnormal gait emerged in 9V/null mice with wider front-paw and hind-paw widths, as well as longer stride in a gender-dependent manner with different ages of onset. Significantly higher liver- and spleen-to-body weight ratios were detected in 9V/null mice with different ages of onsets. These data provide temporal evaluation of neurobehavioral dysfunctions and brain pathology in 9V/null mice that can be used for experimental designs to evaluate novel therapies for nGD., Competing Interests: The authors have declared that no competing interests exist.

Gaucher disease is a lysosomal storage disease caused by defective activity of acid β-glucosidase (GCase), which leads to the accumulation of its major substrates, glucosylceramide (GlcCer) and glucosylsphingosine (GlcSph) in many cells. To modulate cellular substrate concentration in viable mouse models of Gaucher disease (Gba1 mutants), a novel mouse model was created with enhanced glycosphingolipid biosynthesis. This was accomplished by cross-breeding Gba1 mutant mice with mice expressing a transgene (GCStg) containing the mouse glucosylceramide synthase (GCS, Ugcg) cDNA driven by the ROSA promoter, yielding GCStg/Gba1 mice. The GCStg rescued Ugcg null mice from embryonic lethality. GCStg/Gba1 mice showed 2-3 fold increases in tissue GCS activity as well as accelerated GlcCer accumulation and the appearance of lipid-laden CD68 positive macrophages in visceral organs. Although GlcCer/GlcSph concentrations were elevated in the brain, there was no neurodegenerative phenotype up to 1 yr of age conceivably due to the greater residual GCase hydrolytic activity in the brains than in the visceral tissues of 9V/null mice. These studies provide 'proof of principle' for threshold substrate flux that modifies phenotypic development in Gaucher disease and other lysosomal storage diseases.

Key Message: Human glucocerebrosidase with vacuolar anchoring domains was targeted to protein storage vacuoles (PSVs) of Arabidopsis seeds, but unexpectedly via the Golgi complex. PSV-targeting to effectively avoid problematic N-glycans is protein dependent. Plant-specific N-glycosylation patterns elaborated within the Golgi complex are a major limitation of using plants to produce biopharmaceuticals as the presence of β1,2 xylose and/or α1,3 fucose residues on the recombinant glycoprotein can render the product immunogenic if administrated parenterally. A reporter protein fused to a vacuolar membrane targeting motif comprised of the BP-80 transmembrane domain (TMD), and the cytoplasmic tail (CT) of α-tonoplast intrinsic protein (α-TIP) is delivered to protein storage vacuoles (PSVs) of tobacco seeds by ER-derived transport vesicles that bypass the Golgi complex. This prompted us to investigate whether a pharmaceutical glycoprotein is targeted to PSVs using the same targeting sequences, thus avoiding the unwanted plant-Golgi-specific complex N-glycan modifications. The human lysosomal acid β-glucosidase (glucocerebrosidase; GCase) (EC 3.2.1.45) fused to the BP-80 TMD and α-TIP CT was produced in Arabidopsis thaliana wild-type (Col-0) seeds. The chimeric GCase became localized in PSVs but transited through the Golgi complex, as indicated by biochemical analyses of the recombinant protein's N-glycans. Our findings suggest that use of this PSV-targeting strategy to avoid problematic N-glycan maturation on recombinant therapeutic proteins is not consistently effective, as it is likely protein- and/or species-specific.

The acid β-glucosidase (glucocerbrosidase (GCase)) binding sequence to LIMP-2 (lysosomal integral membrane protein 2), the receptor for intracellular GCase trafficking to the lysosome, has been identified. Heterologous expression of deletion constructs, the available GCase crystal structures, and binding and co-localization of identified peptides or mutant GCases were used to identify and characterize a highly conserved 11-amino acid sequence, DSPIIVDITKD, within human GCase. The binding to LIMP-2 is not dependent upon a single amino acid, but the interactions of GCase with LIMP-2 are heavily influenced by Asp(399) and the di-isoleucines, Ile(402) and Ile(403). A single alanine substitution at any of these decreases GCase binding to LIMP-2 and alters its pH-dependent binding as well as diminishing the trafficking of GCase to the lysosome and significantly increasing GCase secretion. Enterovirus 71 also binds to LIMP-2 (also known as SCARB2) on the external surface of the plasma membrane. However, the LIMP-2/SCARB2 binding sequences for enterovirus 71 and GCase are not similar, indicating that LIMP-2/SCARB2 may have multiple or overlapping binding sites with differing specificities. These findings have therapeutic implications for the production of GCase and the distribution of this enzyme that is delivered to various organs., (© 2014 by The American Society for Biochemistry and Molecular Biology, Inc.)

Gaucher disease (GD) is a rare, genetic lysosomal storage disorder caused by functional defects of acid β-glucosidase that results in multiple organ dysfunction. Glycosylation of recombinant acid human β-glucosidase and exposure of terminal mannose residues are critical to the success of enzyme replacement therapy (ERT) for the treatment of visceral and hematologic manifestations in GD. Three commercially available ERT products for treatment of GD type 1 (GD1) include imiglucerase, velaglucerase alfa, and taliglucerase alfa. Imiglucerase and velaglucerase alfa are produced in different mammalian cell systems and require production glycosylation modifications to expose terminal α-mannose residues, which are needed for mannose receptor-mediated uptake by target macrophages. Such modifications add to production costs. Taliglucerase alfa is a plant cell-expressed acid β-glucosidase approved in the United States and other countries for ERT in adults with GD1. A plant-based expression system, using carrot root cell cultures, was developed for production of taliglucerase alfa and does not require additional processing for postproduction glycosidic modifications. Clinical trials have demonstrated that taliglucerase alfa is efficacious, with a well-established safety profile in adult, ERT-naïve patients with symptomatic GD1, and for such patients previously treated with imiglucerase. These included significant improvements in organomegaly and hematologic parameters as early as 6months, and maintenance of achieved therapeutic values in previously treated patients. Ongoing clinical trials will further characterize the long-term efficacy and safety of taliglucerase alfa in more diverse patient populations, and may help to guide clinical decisions for achieving optimal outcomes for patients with GD1., (Copyright © 2014 Elsevier Inc. All rights reserved.)

ABCA12 mutations disrupt the skin barrier and cause harlequin ichthyosis. We previously showed Abca12(-/-) skin has increased glucosylceramide (GlcCer) and correspondingly lower amounts of ceramide (Cer). To examine why loss of ABCA12 leads to accumulation of GlcCer, de novo sphingolipid synthesis was assayed using [(14)C]serine labeling in ex vivo skin cultures. A defect was found in β-glucocerebrosidase (GCase) processing of newly synthesized GlcCer species. This was not due to a decline in GCase function. Abca12(-/-) epidermis had 5-fold more GCase protein (n = 4, P < 0.01), and a 5-fold increase in GCase activity (n = 3, P < 0.05). As with Abca12(+/+) epidermis, immunostaining in null skin showed a typical interstitial distribution of the GCase protein in the Abca12(-/-) stratum corneum. Hence, we tested whether the block in GlcCer conversion could be circumvented by topically providing GlcCer. This approach restored up to 15% of the lost Cer products of GCase activity in the Abca12(-/-) epidermis. However, this level of barrier ceramide replacement did not significantly reduce trans-epidermal water loss function. Our results indicate loss of ABCA12 function results in a failure of precursor GlcCer substrate to productively interact with an intact GCase enzyme, and they support a model of ABCA12 function that is critical for transporting GlcCer into lamellar bodies.

Gaucher disease results from mutations in GBA1 that cause functional disruption of the encoded lysosomal enzyme, acid β-glucosidase. The consequent excess accumulation of glucosylceramide and glucosylsphingosine in lysosomes is central to the disease pathogenesis with classical involvement of macrophage (Mфs) lineage cells of visceral organs, bone, or brain. Several studies have implicated the increased secretion of chemokines and infiltration of a variety of immunological cells into tissues of Gaucher disease patients. Trafficking of immunological cells to the sites of inflammation requires the presence of chemokines. Although increases of different immunological cells and several chemokines are present in Gaucher disease, the specific chemoattractants that cause the increased influx of immunological cells are not fully defined. Here, increased levels of I-309, MCP-5, CXCL-2, CXCL-9, CXCL-10, CXCL-11, CXCL-13, and their corresponding leukocytes, i.e., MOs (monocytes), Mфs, dendritic cells (DCs), polymorphonuclear neutrophils (PMNs), and T, and B cells were identified in the circulation of mice with Gba1 mutations (D409V/null). Sera from D409V/null mice contained chemoattractants for a variety of immunological cells as shown by ex vivo chemotaxis studies and by flow cytometry. Enhanced chemotaxis towards 9V/null sera was found for 9V/null lung-, spleen-, liver-, and bone marrow-derived Mфs (CD11b(+) F480(+)), PMNs (Gr1(high) CD11b(+)), DCs (CD11c(+) CD11b(+)), T lymphocytes (CD3(+) TCRB(+)), and B lymphocytes (B220(+) CD19(+)). These data support these chemotactic factors as causative to increased tissue infiltration of leukocytes in Gaucher disease., (Published by Elsevier Inc.)

Gaucher disease type 1, an inherited lysosomal storage disorder, is caused by mutations in GBA1 leading to defective glucocerebrosidase (GCase) function and consequent excess accumulation of glucosylceramide/glucosylsphingosine in visceral organs. Enzyme replacement therapy (ERT) with the biosimilars, imiglucerase (imig) or velaglucerase alfa (vela) improves/reverses the visceral disease. Comparative transcriptomic effects (microarray and mRNA-Seq) of no ERT and ERT (imig or vela) were done with liver, lung, and spleen from mice having Gba1 mutant alleles, termed D409V/null. Disease-related molecular effects, dynamic ranges, and sensitivities were compared between mRNA-Seq and microarrays and their respective analytic tools, i.e. Mixed Model ANOVA (microarray), and DESeq and edgeR (mRNA-Seq). While similar gene expression patterns were observed with both platforms, mRNA-Seq identified more differentially expressed genes (DEGs) (∼3-fold) than the microarrays. Among the three analytic tools, DESeq identified the maximum number of DEGs for all tissues and treatments. DESeq and edgeR comparisons revealed differences in DEGs identified. In 9V/null liver, spleen and lung, post-therapy transcriptomes approximated WT, were partially reverted, and had little change, respectively, and were concordant with the corresponding histological and biochemical findings. DEG overlaps were only 8-20% between mRNA-Seq and microarray, but the biological pathways were similar. Cell growth and proliferation, cell cycle, heme metabolism, and mitochondrial dysfunction were most altered with the Gaucher disease process. Imig and vela differentially affected specific disease pathways. Differential molecular responses were observed in direct transcriptome comparisons from imig- and vela-treated tissues. These results provide cross-validation for the mRNA-Seq and microarray platforms, and show differences between the molecular effects of two highly structurally similar ERT biopharmaceuticals.

Velaglucerase alfa is a glucocerebrosidase produced by gene activation technology in a human fibroblast cell line (HT-1080), and it is indicated as an enzyme replacement therapy (ERT) for the treatment of Gaucher disease type 1 (GD1). This multicenter, open-label, 12-month study examined the safety and efficacy of velaglucerase alfa in patients with GD1 previously receiving imiglucerase. Eligible patients, ≥2 years old and clinically stable on imiglucerase therapy, were switched to velaglucerase alfa at a dose equal to their prior imiglucerase dose. Infusion durations were 1 hr every other week. Forty patients received velaglucerase alfa (18 male, 22 female; four previously splenectomized; age range 9-71 years). Velaglucerase alfa was generally well tolerated with most adverse events (AEs) of mild or moderate severity. The three most frequently reported AEs were headache (12 of 40 patients), arthralgia (9 of 40 patients), and nasopharyngitis (8 of 40 patients). No patients developed antibodies to velaglucerase alfa. There was one serious AE considered treatment-related: a grade 2 anaphylactoid reaction within 30 min of the first infusion. The patient withdrew; this was the only AE-related withdrawal. Hemoglobin concentrations, platelet counts, and spleen and liver volumes remained stable through 12 months. In conclusion, adult and pediatric patients with GD1, previously treated with imiglucerase, successfully transitioned to velaglucerase alfa, which was generally well tolerated and demonstrated efficacy over 12 months' treatment consistent with that observed in the velaglucerase alfa phase 3 clinical trial program., (Copyright © 2012 Wiley Periodicals, Inc.)

Gaucher disease results from GBA1 mutations that lead to defective acid β-glucosidase (GCase) mediated cleavage of glucosylceramide (GC) and glucosylsphingosine as well as heterogeneous manifestations in the viscera and CNS. The mutation, tissue, and age-dependent accumulations of different GC species were characterized in mice with Gba1 missense mutations alone or in combination with isolated saposin C deficiency (C*). Gba1 heteroallelism for D409V and null alleles (9V/null) led to GC excesses primarily in the visceral tissues with preferential accumulations of lung GC24∶0, but not in liver, spleen, or brain. Age-dependent increases of different GC species were observed. The combined saposin C deficiency (C*) with V394L homozygosity (4L;C*) showed major GC18:0 degradation defects in the brain, whereas the analogous mice with D409H homozygosity and C* (9H;C*) led to all GC species accumulating in visceral tissues. Glucosylsphingosine was poorly degraded in brain by V394L and D409H GCases and in visceral tissues by D409V GCase. The neonatal lethal N370S/N370S genotype had insignificant substrate accumulations in any tissue. These results demonstrate age, organ, and mutation-specific quantitative differences in GC species and glucosylsphingosine accumulations that can have influence in the tissue/regional expression of Gaucher disease phenotypes.

There is a clear need for efficient methods to produce protein therapeutics requiring mannose-termination for therapeutic efficacy. Here we report on a unique system for production of active human lysosomal acid β-glucosidase (glucocerebrosidase, GCase, EC 3.2.1.45) using seeds of the Arabidopsis thaliana complex-glycan-deficient (cgl) mutant, which are deficient in the activity of N-acetylglucosaminyl transferase I (EC 2.4.1.101). Gaucher disease is a prevalent lysosomal storage disease in which affected individuals inherit mutations in the gene (GBA1) encoding GCase. A gene cassette optimized for seed expression was used to generate the human enzyme in seeds of the cgl (C5) mutant, and the recombinant GCase was mainly accumulated in the apoplast. Importantly, the enzymatic properties including kinetic parameters, half-maximal inhibitory concentration of isofagomine and thermal stability of the cgl-derived GCase were comparable with those of imiglucerase, a commercially available recombinant human GCase used for enzyme replacement therapy in Gaucher patients. N-glycan structural analyses of recombinant cgl-GCase showed that the majority of the N-glycans (97%) were mannose terminated. Additional purification was required to remove ∼15% of the plant-derived recombinant GCase that possessed potentially immunogenic (xylose- and/or fucose-containing) N-glycans. Uptake of cgl-derived GCase by mouse macrophages was similar to that of imiglucerase. The cgl seed system requires no addition of foreign (non-native) amino acids to the mature recombinant GCase protein, and the dry transgenic seeds represent a stable repository of the therapeutic protein. Other strategies that may completely prevent plant-like complex N-glycans are discussed, including the use of a null cgl mutant.

Isofagomine (IFG) is an acid β-glucosidase (GCase) active site inhibitor that acts as a pharmacological chaperone. The effect of IFG on GCase function was investigated in GCase mutant fibroblasts and mouse models. IFG inhibits GCase with K(i) ∼30 nM for wild-type and mutant enzymes (N370S and V394L). Fibroblasts treated with IFG at μM concentrations showed enhancement of WT and mutant GCase activities and protein levels. Administration of IFG (30 mg/kg/day) to the mice homozygous for GCase mutations (V394L, D409H, or D409V) led to increased GCase activity in visceral tissues and brain extracts. IFG effects on GCase stability and substrate levels were evaluated in a mouse model (hG/4L/PS-NA) that has doxycycline-controlled human WT GCase (hGCase) expression driven by a liver-specific promoter and is also homozygous for the IFG-responsive V394L GCase. Both human and mouse GCase activity and protein levels were increased in IFG-treated mice. The liver-secreted hGCase in serum was stabilized, and its effect on the lung and spleen involvement was enhanced by IFG treatment. In 8-week IFG-treated mice, the accumulated glucosylceramide and glucosylsphingosine were reduced by 75 and 33%, respectively. Decreases of storage cells were correlated with >50% reductions in substrate levels. These results indicate that IFG stabilizes GCase in tissues and serum and can reduce visceral substrates in vivo.

Emerging genetic and clinical evidence suggests a link between Gaucher disease and the synucleinopathies Parkinson disease and dementia with Lewy bodies. Here, we provide evidence that a mouse model of Gaucher disease (Gba1(D409V/D409V)) exhibits characteristics of synucleinopathies, including progressive accumulation of proteinase K-resistant α-synuclein/ubiquitin aggregates in hippocampal neurons and a coincident memory deficit. Analysis of homozygous (Gba1(D409V/D409V)) and heterozygous (Gba1(D409V/+) and Gba1(+/-)) Gaucher mice indicated that these pathologies are a result of the combination of a loss of glucocerebrosidase activity and a toxic gain-of-function resulting from expression of the mutant enzyme. Importantly, adeno-associated virus-mediated expression of exogenous glucocerebrosidase injected into the hippocampus of Gba1(D409V/D409V) mice ameliorated both the histopathological and memory aberrations. The data support the contention that mutations in GBA1 can cause Parkinson disease-like α-synuclein pathology, and that rescuing brain glucocerebrosidase activity might represent a therapeutic strategy for GBA1-associated synucleinopathies.

Parkinson's disease (PD), an adult neurodegenerative disorder, has been clinically linked to the lysosomal storage disorder Gaucher disease (GD), but the mechanistic connection is not known. Here, we show that functional loss of GD-linked glucocerebrosidase (GCase) in primary cultures or human iPS neurons compromises lysosomal protein degradation, causes accumulation of α-synuclein (α-syn), and results in neurotoxicity through aggregation-dependent mechanisms. Glucosylceramide (GlcCer), the GCase substrate, directly influenced amyloid formation of purified α-syn by stabilizing soluble oligomeric intermediates. We further demonstrate that α-syn inhibits the lysosomal activity of normal GCase in neurons and idiopathic PD brain, suggesting that GCase depletion contributes to the pathogenesis of sporadic synucleinopathies. These findings suggest that the bidirectional effect of α-syn and GCase forms a positive feedback loop that may lead to a self-propagating disease. Therefore, improved targeting of GCase to lysosomes may represent a specific therapeutic approach for PD and other synucleinopathies., (Copyright © 2011 Elsevier Inc. All rights reserved.)

Objective: Heterozygous mutations in the GBA1 gene elevate the risk of Parkinson disease and dementia with Lewy bodies; both disorders are characterized by misprocessing of α-synuclein (SNCA). A loss in lysosomal acid-β-glucosidase enzyme (GCase) activity due to biallelic GBA1 mutations underlies Gaucher disease. We explored mechanisms for the gene's association with increased synucleinopathy risk., Methods: We analyzed the effects of wild-type (WT) and several GBA mutants on SNCA in cellular and in vivo models using biochemical and immunohistochemical protocols., Results: We observed that overexpression of all GBA mutants examined (N370S, L444P, D409H, D409V, E235A, and E340A) significantly raised human SNCA levels to 121 to 248% of vector control (p < 0.029) in neural MES23.5 and PC12 cells, but without altering GCase activity. Overexpression of WT GBA in neural and HEK293-SNCA cells increased GCase activity, as expected (ie, to 167% in MES-SNCA, 128% in PC12-SNCA, and 233% in HEK293-SNCA; p < 0.002), but had mixed effects on SNCA. Nevertheless, in HEK293-SNCA cells high GCase activity was associated with SNCA reduction by ≤32% (p = 0.009). Inhibition of cellular GCase activity (to 8-20% of WT; p < 0.0017) did not detectably alter SNCA levels. Mutant GBA-induced SNCA accumulation could be pharmacologically reversed in D409V-expressing PC12-SNCA cells by rapamycin, an autophagy-inducer (≤40%; 10μM; p < 0.02). Isofagomine, a GBA chaperone, showed a related trend. In mice expressing two D409Vgba knockin alleles without signs of Gaucher disease (residual GCase activity, ≥20%), we recorded an age-dependent rise of endogenous Snca in hippocampal membranes (125% vs WT at 52 weeks; p = 0.019). In young Gaucher disease mice (V394Lgba+/+//prosaposin[ps]-null//ps-transgene), which demonstrate neurological dysfunction after age 10 weeks (GCase activity, ≤10%), we recorded no significant change in endogenous Snca levels at 12 weeks of age. However, enhanced neuronal ubiquitin signals and axonal spheroid formation were already present. The latter changes were similar to those seen in three week-old cathepsin D-deficient mice., Interpretation: Our results demonstrate that GBA mutants promote SNCA accumulation in a dose- and time-dependent manner, thereby identifying a biochemical link between GBA1 mutation carrier status and increased synucleinopathy risk. In cell culture models, this gain of toxic function effect can be mitigated by rapamycin. Loss in GCase activity did not immediately raise SNCA concentrations, but first led to neuronal ubiquitinopathy and axonal spheroids, a phenotype shared with other lysosomal storage disorders., (Copyright © 2011 American Neurological Association.)

Gaucher disease type 1 is caused by the defective activity of the lysosomal enzyme, acid beta-glucosidase (GCase). Regular infusions of purified recombinant GCase are the standard of care for reversing hematologic, hepatic, splenic, and bony manifestations. Here, similar in vitro enzymatic properties, and in vivo pharmacokinetics and pharmacodynamics (PK/PD) and therapeutic efficacy of GCase were found with two human GCases, recombinant GCase (CHO cell, imiglucerase, Imig) and gene-activated GCase (human fibrosarcoma cells, velaglucerase alfa, Vela), in a Gaucher mouse, D409V/null. About 80+% of either enzyme localized to the liver interstitial cells and <5% was recovered in spleens and lungs after bolus i.v. injections. Glucosylceramide (GC) levels and storage cell numbers were reduced in a dose (5, 15 or 60 U/kg/wk) dependent manner in livers (60-95%) and in spleens ( approximately 10-30%). Compared to Vela, Imig (60 U/kg/wk) had lesser effects at reducing hepatic GC (p = 0.0199) by 4 wks; this difference disappeared by 8 wks when nearly WT levels were achieved by Imig. Anti-GCase IgG was detected in GCase treated mice at 60 U/kg/wk, and IgE mediated acute hypersensitivity and death occurred after several injections of 60 U/kg/wk (21% with Vela and 34% with Imig). The responses of GC levels and storage cell numbers in Vela- and Imig-treated Gaucher mice at various doses provide a backdrop for clinical applications and decisions.

Gaucher disease is caused by defective acid beta-glucosidase (GCase) function. Saposin C is a lysosomal protein needed for optimal GCase activity. To test the in vivo effects of saposin C on GCase, saposin C deficient mice (C-/-) were backcrossed to point mutated GCase (V394L/V394L) mice. The resultant mice (4L;C*) began to exhibit CNS abnormalities approximately 30 days: first as hindlimb paresis, then progressive tremor and ataxia. Death occurred approximately 48 days due to neurological deficits. Axonal degeneration was evident in brain stem, spinal cord and white matter of cerebellum accompanied by increasing infiltration of the brain stem, cortex and thalamus by CD68 positive microglial cells and activation of astrocytes. Electron microscopy showed inclusion bodies in neuronal processes and degenerating cells. Accumulation of p62 and Lamp2 were prominent in the brain suggesting the impairment of autophagosome/lysosome function. This phenotype was different from either V394L/V394L or C-/- alone. Relative to V394L/V394L mice, 4L;C* mice had diminished GCase protein and activity. Marked increases (20- to 30-fold) of glucosylsphingosine (GS) and moderate elevation (1.5- to 3-fold) of glucosylceramide (GC) were in 4L;C* brains. Visceral tissues had increases of GS and GC, but no storage cells were found. Neuronal cells in thick hippocampal slices from 4L;C* mice had significantly attenuated long-term potentiation, presumably resulting from substrate accumulation. The 4L;C* mouse mimics the CNS phenotype and biochemistry of some type 3 (neuronopathic) variants of Gaucher disease and is a unique model suitable for testing pharmacological chaperone and substrate reduction therapies, and investigating the mechanisms of neuronopathic Gaucher disease.

Saposins A, B, C and D are derived from a common precursor, prosaposin (psap). The few patients with saposin C deficiency develop a Gaucher disease-like central nervous system (CNS) phenotype attributed to diminished glucosylceramide (GC) cleavage activity by acid beta-glucosidase (GCase). The in vivo effects of saposin C were examined by creating mice with selective absence of saposin C (C-/-) using a knock-in point mutation (cysteine-to-proline) in exon 11 of the psap gene. In C-/- mice, prosaposin and saposins A, B and D proteins were present at near wild-type levels, but the saposin C protein was absent. By 1 year, the C-/- mice exhibited weakness of the hind limbs and progressive ataxia. Decreased neuromotor activity and impaired hippocampal long-term potentiation were evident. Foamy storage cells were observed in dorsal root ganglion and there was progressive loss of cerebellar Purkinje cells and atrophy of cerebellar granule cells. Ultrastructural analyses revealed inclusions in axonal processes in the spinal cord, sciatic nerve and brain, but no excess of multivesicular bodies. Activated microglial cells and astrocytes were present in thalamus, brain stem, cerebellum and spinal cord, indicating regional pro-inflammatory responses. No storage cells were found in visceral organs of these mice. The absence of saposin C led to moderate increases in GC and lactosylceramide (LacCer) and their deacylated analogues. These results support the view that saposin C has multiple roles in glycosphingolipid (GSL) catabolism as well as a prominent function in CNS and axonal integrity independent of its role as an optimizer/stabilizer of GCase.

Gaucher disease is a lysosomal storage disease caused by mutations in acid beta-glucosidase (GCase) leading to defective hydrolysis and accumulation of its substrates. Two L-type calcium channel (LTCC) blockers-verapamil and diltiazem-have been reported to modulate endoplasmic reticulum (ER) folding, trafficking, and activity of GCase in human Gaucher disease fibroblasts. Similarly, these LTCC blockers were tested with cultured skin fibroblasts from homozygous point-mutated GCase mice (V394L, D409H, D409V, and N370S) with the effect of enhancing of GCase activity. Correspondingly, diltiazem increased GCase protein and facilitated GCase trafficking to the lysosomes of these cells. The in vivo effects of diltiazem on GCase were evaluated in mice homozygous wild-type (WT), V394L and D409H. In D409H homozygotes diltiazem (10 mg/kg/d via drinking water or 50-200 mg/kg/d intraperitoneally) had minor effects on increasing GCase activity in brain and liver (1.2-fold). Diltiazem treatment (10 mg/kg/d) had essentially no effect on WT and V394L GCase protein or activity levels (<1.2-fold) in liver. These results show that LTCC blockers had the ex vivo effects of increasing GCase activity and protein in the mouse fibroblasts, but these effects did not translate into similar changes in vivo even at very high drug doses.

Activation of protein kinase C (PKC) promotes the salvage pathway of ceramide formation, and acid sphingomyelinase has been implicated, in part, in providing substrate for this pathway (Zeidan, Y. H., and Hannun, Y. A. (2007) J. Biol. Chem. 282, 11549-11561). In the present study, we examined whether acid beta-glucosidase 1 (GBA1), which hydrolyzes glucosylceramide to form lysosomal ceramide, was involved in PKC-regulated formation of ceramide from recycled sphingosine. Glucosylceramide levels declined after treatment of MCF-7 cells with a potent PKC activator, phorbol 12-myristate 13-acetate (PMA). Silencing GBA1 by small interfering RNAs significantly attenuated acid glucocerebrosidase activity and decreased PMA-induced formation of ceramide by 50%. Silencing GBA1 blocked PMA-induced degradation of glucosylceramide and generation of sphingosine, the source for ceramide biosynthesis. Reciprocally, forced expression of GBA1 increased ceramide levels. These observations indicate that GBA1 activation can generate the source (sphingosine) for PMA-induced formation of ceramide through the salvage pathway. Next, the role of PKCdelta, a direct effector of PMA, in the formation of ceramide was determined. By attenuating expression of PKCdelta, cells failed to trigger PMA-induced alterations in levels of ceramide, sphingomyelin, and glucosylceramide. Thus, PKCdelta activation is suggested to stimulate the degradation of both sphingomyelin and glucosylceramide leading to the salvage pathway of ceramide formation. Collectively, GBA1 is identified as a novel source of regulated formation of ceramide, and PKCdelta is an upstream regulator of this pathway.

Activation of protein kinase C (PKC) by the phorbol ester (phorbol 12-myristate 13-acetate) induces ceramide formation through the salvage pathway involving, in part, acid beta-glucosidase 1 (GBA1), which cleaves glucosylceramide to ceramide. Here, we examine the role of the GBA1-ceramide pathway, in regulating a pro-inflammatory pathway initiated by PKC and leading to activation of p38 and induction of interleukin 6 (IL-6). Inhibition of ceramide formation by fumonisin B1 or down-regulation of PKCdelta potentiated PMA-induced activation of p38 in human breast cancer MCF-7 cells. Similarly, knockdown of GBA1 by small interfering RNAs or pharmacological inhibition of GBA1 promoted further activation of p38 after PMA treatment, implicating the GBA1-ceramide pathway in the termination of p38 activation. Knockdown of GBA1 also evoked the hyperproduction of IL-6 in response to 4beta phorbol 12-myristate 13-acetate. On the other hand, increasing cellular ceramide with cell-permeable ceramide treatment resulted in attenuation of the IL-6 response. Importantly, silencing the delta isoform of the p38 family significantly attenuated the hyperproduction of IL-6. Reciprocally, p38delta overexpression induced IL-6 biosynthesis. Thus, the GBA1-ceramide pathway is suggested to play an important role in terminating p38delta activation responsible for IL-6 biosynthesis. Furthermore, the p38delta isoform was identified as a novel and predominant target of ceramide signaling as well as a regulator of IL-6 biosynthesis.

The hydrolysis of glucosylceramide by acid beta-glucosidase proceeds via a two-step, double displacement mechanism that includes cleavage of the O-beta-glucosidic bond, enzyme-glucosylation and, then, enzyme-deglucosylation. Two residues that may impact this cycle are N370 and E235. The N370S mutant enzyme is very common in Gaucher disease type 1 patients. Homology and crystal data predictions suggested that E235 is the acid/base catalyst in the hydrolytic reaction. Here, the roles of N370 and E235 in hydrolysis were explored using mutant proteins with selected amino acid substitutions. Heterologously expressed enzymes were characterized using inhibitors, activators, and alternative substrates to gain insight into the effects on the glucosylation (single turnover) and deglucosylation (transglucosylation) steps in catalysis. Specific substitutions at N370 selectively altered only the glucosylation step whereas N370S altered this and the deglucosylation steps. To provide functional data to support E235 as the acid/base catalyst, progress curves with poor substrates with more acidic leaving groups were used in the presence and absence of azide as an exogenous nucleophile. The restoration of E235G activity to nearly wild-type levels was achieved using azide with 2,4-dinitrophenyl-beta-glucoside as substrate. The loss of the acidic arm of the pH optimum activity curve of E235G provided additional functional support for E235 as the acid/base in catalysis. This study provides insight into the function of these residues in acid beta-glucosidase active site function.

Purpose: To determine whether enzyme therapy with imiglucerase/alglucerase demonstrates dose-response relationships with doses and disease parameters used in routine clinical practice for Gaucher disease type 1 patients., Methods: Analyses included all patients with Gaucher disease type 1 on enzyme therapy and with intact spleens in the large observational database of the International Collaborative Gaucher Group Gaucher Registry. Propensity scoring was used to match patients between enzyme therapy dose groups categorized as Group A (5 U to <29 U/kg/2 weeks), Group B (29 U to <48 U/kg/2 weeks), Group C (48 U to <75 U/kg/2 weeks). Hemoglobin concentration, platelet count, and hepatic and splenic volumes were assessed after initiation of enzyme therapy using nonlinear mixed effects models. The maximal effect (Emax) and half-time to Emax (T50) of enzyme therapy for each parameter were compared across dosing groups., Results: Propensity score matching resulted in three comparable groups of 122 patients each (enzyme therapy in Groups A, B, and C). Dose-response relationships were found with regard to Emax and T50 over 96 months for each disease parameter., Conclusions: Enzyme therapy with imiglucerase/alglucerase displays a dose-dependent improvement in hematological and visceral parameters in Gaucher disease type 1 patients. Group C displayed greater treatment effects than Groups A or B. Propensity score matching and nonlinear mixed effects model analyses provide a prototype for assessment of treatment outcomes based on observational data from international rare disease registries.

Gaucher's disease continues to be a model for applications of molecular medicine to clinical delineation, diagnosis, and treatment. Analyses of several thousand affected individuals have broadened the range of the pan-ethnic disease variants, provided initial genotype and phenotype correlations, and established the effectiveness of enzyme therapy. Large numbers of affected individuals worldwide have provided insight into the effect of disease variation related to ethnic origin, prognosis, and outcome. The ability to safely and effectively use enzyme therapy to inhibit or reverse visceral-disease progression and involvement has provided impetus for design of new enzyme therapies, and creation of substrate depletion and pharmacological chaperone strategies. Such innovations could provide interventions that are effective for neuronopathic variants and, potentially, could be more cost effective than other treatments. These developments are novel, clinically important, advancements for patients with other lysosomal storage diseases and genetic diseases.

Saposin B derives from the multi-functional precursor, prosaposin, and functions as an activity enhancer for several glycosphingolipid (GSL) hydrolases. Mutations in saposin B present in humans with phenotypes resembling metachromatic leukodystrophy. To gain insight into saposin B's physiological functions, a specific deficiency was created in mice by a knock-in mutation of an essential cysteine in exon 7 of the prosaposin locus. No saposin B protein was detected in the homozygotes (B-/-) mice, whereas prosaposin, and saposins A, C and D were at normal levels. B-/- mice exhibited slowly progressive neuromotor deterioration and minor head tremor by 15 months. Excess hydroxy and non-hydroxy fatty acid sulfatide levels were present in brain and kidney. Alcian blue positive (sulfatide) storage cells were found in the brain, spinal cord and kidney. Ultrastructural analyses showed lamellar inclusion material in the kidney, sciatic nerve, brain and spinal cord tissues. Lactosylceramide (LacCer) and globotriaosylceramide (TriCer) were increased in various tissues of B-/- mice supporting the in vivo role of saposin B in the degradation of these lipids. CD68 positive microglial cells and activated GFAP positive astrocytes showed a proinflammatory response in the brains of B-/- mice. These findings delineate the roles of saposin B for the in vivo degradation of several GSLs and its primary function in maintenance of CNS function. B-/- provide a useful model for understanding the contributions of this saposin to GSL metabolism and homeostasis.

Genetic and chemically induced neuronopathic mouse models of Gaucher disease were developed to facilitate understanding of the reversibility and/or progression of CNS involvement. The lethality of the skin permeability barrier defect of the complete gene knock out [gba, (glucocerebrosidase) GCase] was avoided by conditional reactivation of a low activity allele (D409H) in keratinocytes (kn-9H). In kn-9H mice, progressive CNS disease and massive glucosylceramide storage in tissues led to death from CNS involvement by the age of 14 days. Conduritol B epoxide (CBE, a covalent inhibitor of GCase) treatment (for 8-12 days) of wild type, D409H, D409V or V394L homozygotes recapitulated the CNS phenotype of the kn-9H mice with seizures, tail arching, shaking, tremor, quadriparesis, extensive neuronal degeneration loss and apoptosis, and death by the age of 14 days. Minor CNS abnormalities occurred after daily CBE injections of 100 mg/kg/day for 6 doses, but neuronal degeneration was progressive and glucosylceramide storage persisted in D409V homozygotes in the 2 to 5 months after CBE cessation; wild type and D409H mice had persistent neurological damage without progression. The persistent CNS deterioration, histologic abnormalities, and glucosylceramide storage in the CBE-treated D409V mice revealed a threshold level of GCase activity necessary for the prevention of progression of CNS involvement.

The effect of enzyme replacement therapy (ERT) on bone crisis and bone pain was investigated in patients with Gaucher disease (GD) type 1 followed over 4 years. Data from the International Collaborative Gaucher Group Gaucher Registry were used. Only patients with bone crisis and/or bone pain data for 1 year prior to ERT, and for each of 3 years after the start of ERT, were included. Bone crises were reported in 17% of patients during the year before starting ERT. The frequencies of bone crises decreased to 5%, <1% and 3% for 1, 2, and 3 years after initiation of treatment, respectively (p < 0.0001). Bone pain followed a similar pattern of response. Bone pain was reported in 49% of patients the year before treatment and decreased to 30% in the first year, 29% in the second year, and 30% in the third year of ERT (p < 0.0001). ERT is associated with a reduction in bone crisis and bone pain in patients with GD type 1 . This study shows that significant improvements in symptoms of skeletal disease are achievable clinical outcomes and treatment goals in GD type 1.

A 5-year-old male with Gaucher's disease type 3 developed progressive mesenteric and mediastinal lymphadenopathy over 12 months, despite enzyme replacement therapy, contributing to the development of a protein-losing enteropathy. These complications are unique, indicating poorly accessible, differentially responsive compartments in patients with Gaucher's disease who are receiving enzyme therapy.

Type 1 Gaucher disease, the most common lysosomal storage disorder, results from deficiency of glucocerebrosidase causing pathologic accumulation of glucocerebroside. The disease is characterized by marked variation in age of onset and degree of anemia, thrombocytopenia, hepatosplenomegaly, and skeletal disease. Most published data on Gaucher disease come from populations with large proportions of Ashkenazi-Jewish patients, who tend to have less severe disease. We compared selected demographic, clinical, and genetic parameters for Brazilian (N = 221) and rest-of-world (N = 1477) type 1 Gaucher disease patients entered into the ICGG Gaucher Registry since 1991. We also compared Brazilian patients to non-Ashkenazi rest-of-world patients (N = 692) to determine if differences were the result of fewer Brazilian Ashkenazi-Jewish patients (0.5% vs 45.0%). The Brazilian cohort differed significantly (p < 0.05) from the rest-of-world and rest-of-world non-Ashkenazi cohort, respectively, in the following measures: higher proportion of females (59.7% vs 50.4% and 49.7%), lower mean age at diagnosis (17.1 vs 24.1 and 18.8), and higher proportions of patients with anemia (55.5% vs 29.9% and 35.7%), bone pain (57.7% vs 33.7% and 35%), bone crises (16.1% vs 6.5% and 7.4%), and lytic lesions (17.0% vs 7.6% and 7.4%). The most common genotype in Brazil was N370S/L444P (c1448T-->C/c1226A-->C) (46.8% versus 16.3% and 25.7%). These data highlight the genetic and phenotypic heterogeneity among geographic populations of type 1 Gaucher patients and suggest that as a group, Brazilian patients may have a more aggressive form of the disease than rest-of-world patients. The findings also emphasize the need for caution in making generalizations about Gaucher disease across demographic groups.

Enzyme therapies for lysosomal storage diseases have developed over the past decade into the standard-of-care for affected patients. Such therapy for Gaucher disease has been the prototype, using natural source or recombinant forms of human acid beta-glucosidase (GCase). In Gaucher disease, macrophages are the repository for the pathological lipid and the target for delivery of GCase. The macrophage mannose receptor provides a Trojan horse for intracellular delivery of intravenously administered GCase (man-GCase) with mannosyl-terminated oligosaccharide chains. Passage through several hostile compartments (e.g., plasma) leads to inefficient delivery of man-GCase to macrophage lysosomes. However, regular infusions of man-GCase re-establishes health in affected patients. Similar results are being obtained in several other lysosomal storage diseases. Evolving gene and chaperone approaches provide alternative treatment strategies.

The reversibility and regression of histological and biochemical findings in a mouse model of Gaucher disease (4L/PS-NA) was evaluated using a liver-enriched activator protein promoter control of a tetracycline-controlled transcriptional activation-responsive human acid beta-glucosidase (hGCase) transgenic system. 4L/PS-NA has the acid beta-glucosidase (GCase) V394L/V394L (4L) point mutation combined with hypomorphic ( approximately 6% wild-type) expression of the mouse prosaposin transgene (PS-NA). The hGCase/4L/PS-NA had exclusive liver expression of hGCase controlled by doxycycline (DOX). In the absence of DOX, hGCase was secreted from liver at levels of approximately 120 microg/ml serum with only approximately 8% of full activity, following exposure to pH 7.4 in serum. The hGCase activity and protein were detected in cells of the liver (massive), lung, and spleen, but not the brain. The visceral tissue storage cells and glucosylceramide (GC) accumulation in hGCase/4L/PS-NA were decreased from that in 4L/PS-NA mice. Turning off hGCase expression with dietary DOX led to reaccumulation of storage cells and of GC in liver, lung, and spleen, and macrophage activation in those tissues. This study demonstrates that conditionally expressed hGCase supplemented the existing mutant mouse GCase to control visceral substrate accumulation in vivo.

Background: Gaucher disease is the most common of the lysosomal storage disorders. The primary manifestation is the accumulation of glucosylceramide (GL-1) in the macrophages of liver and spleen (Gaucher cells), due to a deficiency in the lysosomal hydrolase glucocerebrosidase (GC). A Gaucher mouse model (D409V/null) exhibiting reduced GC activity and accumulation of GL-1 was used to evaluate adeno-associated viral (AAV)-mediated gene therapy., Methods: A recombinant AAV8 serotype vector bearing human GC (hGC) was administered intravenously to the mice. The levels of hGC in blood and tissues were determined, as were the effects of gene transfer on the levels of GL-1. Histopathological evaluation was performed on liver, spleen and lungs., Results: Vector administration to pre-symptomatic Gaucher mice resulted in sustained hepatic secretion of hGC at levels that prevented GL-1 accumulation and the appearance of Gaucher cells in the liver, spleen and lungs. AAV administration to older mice with established disease resulted in normalization of GL-1 levels in the spleen and liver and partially reduced that in the lung. Analysis of the bronchoalveolar lavage fluid (BALF) from treated mice showed significant correction of the abnormal cellularity and cell differentials. No antibodies to the expressed hGC were detected following a challenge with recombinant enzyme suggesting the animals were tolerized to human enzyme., Conclusions: These data demonstrate the effectiveness of AAV-mediated gene therapy at preventing and correcting the biochemical and pathological abnormalities in a Gaucher mouse model, and thus support the continued consideration of this vector as an alternative approach to treating Gaucher disease., (Copyright 2006 John Wiley & Sons, Ltd.)

Acid beta-glucosidase (GCase) is a 497-amino acid, membrane-associated lysosomal exo-beta-glucosidase whose defective activity leads to the Gaucher disease phenotypes. To move toward a structure/function map for disease mutations, 52 selected single amino acid substitutions were introduced into GCase, expressed in an insect cell system, purified, and characterized for basic kinetic, stability, and activator response properties. The variant GCases from Gaucher disease patients and selected variant GCases from the mouse had decreased relative k(cat) and differential effects on active site binding and/or attachment of mechanism-based covalent (conduritol B epoxide) or reversible (deoxynojirimycin derivatives) inhibitors. A defect in negatively charged phospholipid activation was present in the majority of variant GCases but was increased in two, N370S and V394L. Deficits in saposin C enhancement of k(cat) were present in variant GCases involving residues 48-122, whereas approximately 2-fold increases were obtained with the L264I GCase. About 50% of variant GCases each had wild-type or increased sensitivity to in vitro cathepsin D digestion. Mapping of these properties onto the crystal structures of GCase indicated wide dispersion of functional properties that can affect catalytic function and stability. Site-directed mutagenesis of cysteine residues showed that the disulfide bonds, Cys(4)-Cys(16) and Cys(18)-Cys(23), and a free Cys(342) were essential for activity; the free Cys(126) and Cys(248) were not. Relative k(cat) was highly sensitive to a His substitution at Arg(496) but not at Arg(495). These studies and high phylogenetic conservation indicate localized and general structural effects of Gaucher disease mutations that were not obvious from the nature of the amino acid substitution, including those predicted to be nondisruptive (e.g. Val --> Leu). These results provide initial studies for the engineering of variant GCases and, potentially, molecular chaperones for therapeutic use.

Gaucher disease is a common lysosomal storage disease caused by a defect of acid beta-glucosidase (GCase). The optimal in vitro hydrolase activity of GCase requires saposin C, an activator protein that derives from a precursor, prosaposin. To develop additional models of Gaucher disease and to test in vivo effects of saposin deficiencies, mice expressing low levels (4--45% of wild type) of prosaposin and saposins (PS-NA) were backcrossed into mice with specific point mutations (V394L/V394L or D409H/D409H) of GCase. The resultant mice were designated 4L/PS-NA and 9H/PS-NA, respectively. In contrast to PS-NA mice, the 4L/PS-NA and 9H/PS-NA mice displayed large numbers of engorged macrophages and nearly exclusive glucosylceramide (GC) accumulation in the liver, lung, spleen, thymus, and brain. Electron microscopy of the storage cells showed the characteristic tubular storage material of Gaucher cells. Compared with V394L/V394L mice, 4L/PS-NA mice that expressed 4--6% of wild-type prosaposin levels had approximately 25--75% decreases in GCase activity and protein in liver, spleen, and fibroblasts. These results imply that reduced saposin levels increased the instability of V394L or D409H GCases and that these additional decreases led to large accumulations of GC in all tissues. These models mimic a more severe Gaucher disease phenotype and could be useful for therapeutic intervention studies.

We investigated 10 unrelated Chinese patients with type 2 Gaucher disease and performed ex vivo expression for the novel mutations to characterize their functional defects. These patients were diagnosed by enzymatic assays and clinicopathologic features over the past five years in a national centre in China. Genomic DNA was sequenced by a two-stage PCR approach for mutations in the functional GBA gene. Novel mutations were expressed with baculovirus-transfected Sf21 cells. Six novel mutations were found (in traditional nomenclature): P122L, Y363C, N382K, L383R, L385P, and M416V. Review of reported mutations indicated clustering of type 2 mutations in three regions of the GBA gene. Expression of novel mutations revealed that the enzyme defect could arise from one of two mechanisms: loss of catalytic activity (Y363C and M416V) or enzyme instability (P122L and N382K).

Gaucher disease is an autosomal recessively inherited disease caused by mutations at the acid beta-glucosidase (GCase) locus (GBA). To develop viable models of Gaucher disease, point mutations (pmuts), encoding N370S, V394L, D409H, or D409V were introduced into the mouse GCase (gba) locus. DNA sequencing verified each unique pmut. Mutant GCase mRNAs were near wild-type (WT) levels. GCase activities were reduced to 2 to 25% of WT in liver, lung, spleen, and cultured fibroblasts from pmut/pmut or pmut/null mice. The corresponding brain GCase activities were approximately 25% of WT. N370S homozygosity was lethal in the neonatal period. For the other pmut mice, a few storage cells appeared in the spleen at > or =7 months (D409H or D409V homozygotes) or > or =1 year (V394L homozygotes). V394L/null, D409H/null, or D409V/null mice showed scattered storage cells in spleen at approximately 3 to 4 months. Occasional storage cells (sinusoidal cells) were present in liver. In D409V/null mice, large numbers of Mac-3-positive storage cells (ie, macrophages) accumulated in the lung. Glycosphingolipid analyses showed varying rates of progressive glucosylceramide accumulation in visceral organs of pmut/pmut or pmut/null mice, but not in brain. These GCase-deficient mice provide tools for gaining insight into the pathophysiology of Gaucher disease and developing improved therapies.

Saposins (A, B, C, and D) are small sphingolipid activator proteins that are derived by proteolytic processing of a common precursor, prosaposin. In the lysosomal sphingolipid degradation pathway, acid beta-glucosidase (GCase) requires saposin C for optimal in vitro and in vivo hydrolysis of glucocerebroside. The deficiency of prosaposin/saposins (PS-/-) in humans and mice leads to a decrease of GCase activity in selected tissues. Concordant decreases (>50%) of GCase protein and in vitro activity were detected in extracts of cultured fibroblasts and hepatocytes from PS-/- mice and human prosaposin-deficient fibroblasts. GCase RNA in the PS-/- cells was at wild-type levels. Compared with that in wild-type cells (t(1/2) >24 h), the GCase protein in the PS-/- cells had a faster disappearance rate (t(1/2) approximately 1 h in mouse and approximately 8 h in human) as determined by metabolic labeling and immunoprecipitation with anti-GCase antibodies. Treatment of PS-/- cells with leupeptin, an inhibitor of cysteine proteases, led to significant increases (approximately 2-fold) in GCase protein and in vitro activity. Loading saposin C to human PS-/- fibroblasts resulted in an enhancement of GCase protein and in vitro activity. Saposin D loading had no effect. These data indicate that saposin C is required for GCase resistance to proteolytic degradation in the cell. Thus, diminished in vivo GCase activity would be greater than expected only from the lack of GCase activation by saposin C. These results indicate a new property for saposin C, an anti-proteolytic protective function toward GCase.

Gaucher disease, a common lysosomal storage disorder, is associated with mutations at the acid beta-glucosidase (GCase) locus. Two affected individuals are described to share a common mutant allele, but manifest different clinical categorical phenotypes. A 57-year-old female, with Gaucher disease type 1 and Cherokee ancestry, was homozygous for a rare mutant allele encoding Lys79Asn (K79N). A 2-year-old Caucasian male, with Gaucher disease type 3 and Cherokee ancestry, was a heteroallelic homozygote for this same allele (K79N) and a novel complex mutation (null allele). The shared alleles were identical as determined by complete gene sequencing, suggesting a founder effect. The discrepant phenotypes (types 1 and 3) in these two patients provide support for a threshold of residual activity necessary to "protect" the central nervous system (CNS) from the pathogenic effects of Gaucher disease, indicating an allele dose-effect. Designation of genotype associations with specific phenotypes must be assessed with this perspective., (Copyright 2003 Wiley-Liss, Inc.)