Gaucher disease: The effects of phosphatidylserine on glucocerebrosidase from normal and Gaucher fibroblasts

Summary Glucocerebroside -glucosidase (glucocerebrosidase) activity was assayed from cultured fibroblasts of normal individuals, and patients with type 1 (non-neuropathic), type 2 (acute neuropathic), and type 3 (subacute neuropathic) form of Gaucher disease. Residual glucocerebrosidase activity of patients was 8.9 to 17.4% of normal controls, and there was no clear correlation between the level of residual enzyme activity and the different clinical subtypes of the disease. When membrane-bound glucocerebrosidase activity was assayed in the presence of crude brain lipid extracts or purified phosphatidylserine, enzyme from both the normal and type 1 Gaucher fibroblasts was stimulated dramatically (35–60% by crude extracts, 85–90% by phosphatidylserine). This stimulation was not observed with fibroblast glucocerebrosidase of an infantile type 2 and two juvenile type 3 Gaucher patients. The presence of inhibitors of glucocerebrosidase in these type 2 and type 3 Gaucher cells was not detected. Contrary to the mutant enzyme from these Gaucher fibroblasts, glucocerebrosidase from fibroblasts of two adult type 3 Gaucher patients with cerebral involvement was stimulated substantially (72–85%) by phosphatidylserine. When membrane-bound glucocerebrosidase from fibroblasts of the infantile type 2 and juvenile type 3 patients was solubilized with sodium cholate (1% w/v) and delipidated, the phospholipid stimulation of enzyme activity was restored. These findings suggest that considerable clinical and biochemical heterogeneity exists among patients with neuropathic Gaucher disease and that phosphatidylserine activation cannot be used as a reliable indicator in predicting future onset of neurodegeneration in Gaucher patients. The possibility of an aberrant binding of mutant glucocerebrosidase to the lysosomal membrane in juvenile type 3 form of Gaucher disease is discussed.     

Biosynthesis and maturation of glucocerebrosidase in Gaucher fibroblasts

The biosynthesis and maturation of glucocerebrosidase were studied in fibroblasts from patients with the neurological and non-neurological forms of Gaucher disease and in control cells. In control fibroblasts the precursor of glucocerebrosidase (62-63 kDa), observed after a short pulse with [35S]methionine, was converted during the chase period to a 66-kDa intermediate form and, finally, to the 59-kDa mature protein. In fibroblasts from patients with the non-neurological phenotype of Gaucher disease (type 1) the same biosynthetic forms were seen as in control fibroblasts. These biosynthetic forms correspond to the three-banded pattern seen in control and Gaucher type 1 fibroblast extracts analysed by the immunoblotting procedure, or after electrophoresis and fluorography of extracts of such fibroblasts cultured for 5 days with [14C]leucine. The 59-kDa protein seen in type 1 fibroblasts was unstable and disappeared after a prolonged chase; this disappearance was not observed when the cells were grown in the presence of leupeptin. In fibroblasts from patients with the neurological forms of Gaucher disease (types 2 and 3) the 62.5-kDa precursor of glucocerebrosidase was present in near-normal amounts after a short pulse, but the 59-kDa form was not detected even when cells were cultured with leupeptin. These results are in accordance with the absence of the 59-kDa band in immunoblots of types 2 and 3 fibroblast extracts. Culturing of type 1, type 2 and type 3 Gaucher fibroblasts in the presence of leupeptin led to an increase in the activity of glucocerebrosidase.     

Hydrophilic iminosugar active-site-specific chaperones increase residual glucocerebrosidase activity in fibroblasts from Gaucher patients

Gaucher disease is an autosomal recessive lysosomal storage disorder caused by the deficient activity of glucocerebrosidase. Accumulation of glucosylceramide, primarily in the lysosomes of cells of the reticuloendothelial system, leads to hepatosplenomegaly, anemia and skeletal lesions in type I disease, and neurologic manifestations in types II and III disease. We report herein the identification of hydrophilic active-site-specific chaperones that are capable of increasing glucocerebrosidase activity in the cultured fibroblasts of Gaucher patients. Screening of a variety of natural and synthetic alkaloid compounds showed isofagomine, N-dodecyl deoxynojirimycin, calystegines A3, B1, B2 and C1, and 1,5-dideoxy-1,5-iminoxylitol to be potent inhibitors of glucocerebrosidase. Among them, isofagomine was the most potent inhibitor of glucocerebrosidase in vitro, and the most effective active-site-specific chaperone capable of increasing residual glucocerebrosidase activity in fibroblasts established from Gaucher patients with the most prevalent Gaucher disease-causing mutation (N370S). Intracellular enzyme activity increased approximately two-fold after cells had been incubated with isofagomine, and the increase in glucocerebrosidase activity was both dose-dependent and time-dependent. Western blotting demonstrated that there was a substantial increase in glucocerebrosidase protein in cells after isofagomine treatment. Immunocytochemistry revealed an improvement in the glucocerebrosidase trafficking pattern, which overlaps that of lysosome-associated membrane protein 2 in Gaucher fibroblasts cultivated with isofagomine, suggesting that the transport of mutant glucocerebrosidase is at least partially improved in the presence of isofagomine. The hydrophilic active-site-specific chaperones are less toxic to cultured cells. These results indicate that these hydrophilic small molecules are suitable candidates for further drug development for the treatment of Gaucher disease.     

Comparative study on glucocerebrosidase in spleens from patients with Gaucher disease.

In Gaucher disease (glucosylceramide lipidosis), deficiency of glucocerebrosidase causes pathological storage of glucosylceramide, particularly in the spleen. A comparative biochemical and immunological analysis has therefore been made of glucocerebrosidase in spleens from normal subjects (n = 4) and from Gaucher disease patients with non-neuronopathic (n = 5) and neuronopathic (n = 5) phenotypes. The spleens from all Gaucher disease patients showed markedly decreased glucocerebrosidase activity. Discrimination of different phenotypes of Gaucher disease was not possible on the basis of the level of residual enzyme activity, or by measurements, using the immunopurified enzyme, of kinetic constants, pI or molecular mass forms. A severe decrease was found in the specific activity of glucocerebrosidase purified to homogeneity from the spleen of a patient with the non-neuronopathic phenotype of Gaucher disease, as compared with that of the enzyme purified from the spleen of a normal subject. This finding was confirmed by an immunological method developed for accurate assessment of the relative enzyme activity per molecule of glucocerebrosidase protein. The method revealed that the residual enzyme in the spleens of all investigated patients with a non-neuronopathic course of Gaucher disease had a more than 7-fold decreased activity of glucocerebrosidase (measured in the presence of taurocholate) per molecule of enzyme, and that the concentration of glucocerebrosidase molecules in the spleens of these patients was near normal. Observations made with immunoblotting experiments were consistent with these findings. In contrast, in the spleens of patients with neuronopathic phenotypes of Gaucher disease, the concentration of glucocerebrosidase molecules was severely decreased.     

Gaucher disease. III. Substrate specificity of glucocerebrosidase and the use of nonlabeled natural substrates for the investigation of patients.

A reproducible and convenient method for assaying glucocerebrosidase activity using the natural substrates has been developed. From the insoluble pellet fraction of cultured skin fibroblast homogenates, released glucose was measured enzymically using hexokinase coupled with the glucose-6-phosphate dehydrogenase (G6PD) and nicotinamide adenine dinucleotide phosphate (NADP) system. Optimal enzyme assay conditions required both Triton X-100 and sodium taurocholate, pH 4.8. Glucocerebrosidase activities from three patients with type 1 Gaucher disease were 17.5%, 15.8%, and 11.2% of normal (normal = 198 +/- 14 nmol/hr per mg protein, n = 3). The first patient had normal beta-glucosidase activity with the artificial fluorogenic umbelliferone substrate. Interference with the accuracy of the glucose-dependent assay system by either glycolytic or gluconeogenic enzyme activites was not detected under these experimental conditions, and when substrates with long fatty-acid chain lengths (C = 22) were used, markedly decreased glucocerebrosidase activity occurred in both normal individuals and patients. The apparent Km's for the natural substrates were 0.56 +/- 0.05 mM for controls and 2.2-3.3 mM for Gaucher fibroblasts. These data further support the hypothesis that a structurally altered and catalytically deficient enzyme is synthesized in patients with type 1 Gaucher disease and illustrate the value of the natural substrate in investigating patients.     

Delivery,Distribution, and Neuronal Uptake of Exogenous Mannose-Terminal Glucocerebrosidase in the Intact Rat Brain

Gaucher disease is caused by insufficient activity of the enzyme glucocerebrosidase. Great benefit has been obtained through enzyme replacement therapy for patients with type 1 (non-neuronopathic) Gaucher disease. In contrast, inconsistent effects of enzyme therapy have been observed in patients with type 3 (chronic neuronopathic) Gaucher disease, and no benefit on the lethal course of the disease occurs in patients with Type 2 (acute neuronopathic) Gaucher disease. We examined the use of convection-enhanced delivery to augment the delivery and distribution of exogenous glucocerebrosidase (m.w. 63,000) to the brain by infusing it under slight hydrostatic pressure into the striatal region of rats. The enzyme was comparatively stable under these conditions. It was distributed from the site of injection toward the cerebral cortex where it became primarily localized in neurons. These findings provide considerable incentive for the exploration of intracerebral microinfusion of enzyme to the brain of patients with metabolic storage disorders involving the CNS.     

Immunological and catalytic quantitation of splenic glucocerebrosidase from the three clinical forms of Gaucher disease.

The enzymatic activity of glucocerebrosidase in splenic extracts of the adult nonneurological form of Gaucher disease (type I) was 15% +/- 7% of normal, and the titer of enzyme cross-reacting material (ECRM) in these spleens was 54% +/- 9% of normal. The titer of ECRM in splenic extracts of tissues obtained from patients with the neurological forms of Gaucher disease (types II and III) was essentially the same as in type I Gaucher spleens (59% +/- 10% of normal), but the measurable catalytic activity of glucocerebrosidase in these spleens was substantially lower than that found in type I Gaucher spleens (2.3% +/- 0.6% of normal). Thus, the attentuated glucocerebrosidase activity in spleens from all three forms of Gaucher disease appears to stem from a structurally mutated enzyme that is altered in its catalytic efficiency and possibly in its antigenic expression.     

Immunochemical characterization of two activator proteins stimulating enzymic sphingomyelin degradation in vitro. Absence of one of them in a human Gaucher disease variant

Two nonenzymic activator proteins shown previously to strongly stimulate enzymic sphingomyelin degradation in vitro were purified from human Gaucher type 1 and control spleen. Activator A1 (molecular mass 6,500 Da) had affinity for ConA-Sepharose, while activator A2 (molecular mass 3,500 Da) did not. Monospecific antibodies to each activator protein were prepared in rabbits by immunization with protein purified from type 1 Gaucher spleen. A1 and A2 activators from Gaucher type 1 spleen were shown to be immunochemically identical to A1 and A2 activators from control spleen. However, A1 and A2 activators, whether isolated from Gaucher type 1 or control spleen, were shown to be distinct proteins. Immunochemical examination of all collected fractions during the purification revealed the existence of a third activator (molecular mass 6,000 Da), which was antigenically identical to A1 activator but had no affinity for ConA-Sepharose. The two forms of A1 activator showed similar mobility on immunoelectrophoresis differing from that of A2 activator. Fibroblast extracts from controls and patients with different variants of Gaucher disease were investigated using immunodiffusion against antisera to A1 or A2 activator. In contrast to normal and Gaucher (types 1, 2 and 3) cell extracts, those of a Gaucher patient with normal glucosylceramidase activity had no visible precipitin line towards the antiserum against the two forms of A1 activator. The lack of crossreacting material to antibodies against A1 activator was confirmed by radial immunodiffusion and rocket immunoelectrophoresis. A1 activator stimulated the basal glucosylceramidase activity 5-6 fold in fibroblasts from this patient, whereas the normal effect was only a 1.2-1.5-fold stimulation. The immunological results together with the biochemical data provide evidence for the lack of an activator protein in a variant form of human Gaucher disease for the first time.     

Electrophoresis of glucocerebrosidase from normal and Gaucher disease fibroblasts.

A polyacrylamide gel electrophoresis system for glucocerebrosidase has been developed. This method was used to characterize the glucocerebrosidase activity of normal and Gaucher disease fibroblasts; the residual glucocerebrosidase activity in adult Gaucher disease fibroblasts co-migrates with the activity from normal fibroblasts.     

Uptake of Mannose-Terminal Glucocerebrosidase in Cultured Human Cholinergic and Dopaminergic Neuron Cell Lines

Enzyme replacement therapy has been shown to be particularly effective for patients with type 1 (non-neuronopathic) Gaucher disease. However, intravenously administered glucocerebrosidase does not reverse or halt the progression of brain damage in patients with type 2 (acute neuronopathic) Gaucher disease. A previous investigation revealed that intracerebral infusion of mannose-terminal glucocerebrosidase was safe in experimental animals. The enzyme had a comparatively long half-life in the brain. It was transported by convection from the site of infusion along white matter fiber tracts to the cerebral cortex where it was endocytosed by neurons. In anticipation of intracerebral administration of mannose-terminal glucocerebrosidase to patients with type 2 Gaucher disease, it was important to learn the mechanism involved in its cellular uptake. We therefore compared the endocytosis of this enzyme by J774 macrophage cells with that in two human neuronal cell lines and a human astrocyte cell line. Mannose-terminal glucocerebrosidase was taken up by cholinergic LA-N-2 cells, but to a much lower extent than by macrophages. Considerably less of the enzyme was endocytosed by dopaminergic SH-SY5Y cells. It was not taken up by NHA astrocytes. The findings provide encouragement for an exploration of intracerebral administration of glucocerebrosidase in patients with type 2 Gaucher disease.     

Gene therapy of Gaucher's and Fabry's diseases: current status and prospects

Gaucher disease and Fabry disease are lysosomal storage disorders characterized by the accumulation of sphingolipids. In both cases, the goal of gene therapy is to permanently provide tissues with enzyme levels allowing to avoid storage of the undigested substrates. Different gene therapy strategies must however be designed as Gaucher disease is due to a deficiency in the membrane-associated enzyme glucocerebrosidase, whereas Fabry disease is caused by a deficiency in the soluble enzyme alpha-galactosidase. Indeed, a soluble enzyme can be provided to tissues is trans by gene-modified cells whereas gene transfer has to target the most affected cells in the case of membrane-bound enzymes. Thus, in non-neurological Gaucher disease (type 1), the hematopoietic tissue has to be targeted as the deficiency affects the monocyte/macrophage lineage. Following promising preclinical studies, clinical protocols have been initiated to explore the feasibility and safety of retroviral transfer of the glucocerebrosidase gene into CD34+ cells from patients with type 1 Gaucher disease. Although gene-marked cells were detected in vivo, the level of corrected cells was very low, a finding indicating that improved vectors along with partial myeloablation may be necessary. Here, lentiviral vectors should enable more gene transduction into the hematopoietic target cells. As concerns the diffuse neurological lesions in types 2 and 3 of Gaucher disease, they will probably be especially difficult to target by gene therapy because of the non soluble nature of glucocerebrosidase. Finally, over the last few years, Fabry disease has become a compelling target for gene therapy as an etiology-based treatment strategy. Indeed, several recent studies aiming at creating a large in vivo source of alpha-galactosidase have yielded positive long-term results in the Fabry knock-out mouse model.     

Properties of beta-glucosidase in cultured skin fibroblasts from controls and patients with Gaucher disease.

Membrane-bound beta-glucosidase from cultured skin fibroblasts can be solubilized in an active form by treatment of membrane preparations with a mixture of Triton X-100 and sodium taurocholate. Several properties of the solubilized enzyme have been studied in fibroblasts from normal, healthy individuals and from 14 patients with different clinical forms of Gaucher disease. The patients studied were classified as follows: group 1 consisted of 10 chronic patients, all (with one exception) of Ashkenazi Jewish origin; group 2 consisted of three black American patients with severe visceral symptoms, manifest from early childhood, but with no apparent neurological involvement; and group 3 consisted of a single white patient with the classical infantile form of the disease. Specific beta-glucosidase activity ranged from 6.6% to 16.5% mean control value in group 1 patients and from 4.1% to 5.8% in groups 2 and 3. When compared with the enzyme from control fibroblasts, the enzyme from chronic Gaucher patients (group 1) was more rapidly inactivated at 50 degrees C, had an altered pH curve, was less effectively inhibited by deoxycorticosterone-beta-glucoside, and was more effectively inhibited by deoxycorticosterone. The enzyme from patients in groups 2 and 3 was qualitatively indistinguishable from the control enzyme in terms of these parameters. No differences in Km (4-methylumbelliferyl-beta-glucoside) or sedimentation coefficient were found between the beta-glucosidases from control and Gaucher cells. The results demonstrate that cells from Ashkenazi Jewish patients with the chronic form of Gaucher disease contain a structurally altered form of beta-glucosidase. This enzyme differs both from normal beta-glucosidase and from the residual enzyme in patients of different ethnic origin and with clinically more severe forms of the disease.     

In situ radiation-inactivation size of fibroblast membrane-bound acid beta-glucosidase in Gaucher type 1, type 2 and type 3 disease

The radiation-inactivation size of membrane-bound acid beta-glucosidase in cultured skin fibroblasts of four normal individuals, five Gaucher type 1 (non-neuropathic), four Gaucher type 2 (acute neuropathic) and three Gaucher type 3 (sub-acute neuropathic) patients was determined using the radiation-inactivation method. The radiation-inactivation size of the enzyme in the control, Gaucher type 2 and Gaucher type 3 fibroblasts ranged from 94 000 to 128 800, and no statistical significant difference was found in the enzyme size between the normal and Gaucher cells nor among the Gaucher type 2 and type 3 cells. Contrary to the normal, Gaucher type 2 and Gaucher type 3 enzyme, the radiation-inactivation size of membrane-bound acid beta-glucosidase in all of the Gaucher type 1 fibroblasts tested is significantly higher, ranging from 158 400 to 235 300. The size of the control lysosomal enzyme, sphingomyelinase, also determined by the radiation-inactivation method in fibroblasts of normal individuals and patients with the three Gaucher subtypes, was between 70 000 and 74 500 and indistinguishable from each other. Since the molecular weight of acid beta-glucosidase subunit determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis was about 60 000 (Pentchev, P.G., Brady, R.O., Hibbert, S.P., Gal, A.E. and Shapiro, C. (1973) J. Biol. Chem. 248, 5256-5261), the above data suggest that: (i) the normal fibroblast enzyme, as well as the Gaucher type 2 and type 3 mutant enzyme, in the membrane-bound form, exists as a dimer; (ii) the underlying biochemical and genetic defect in non-neuropathic (type 1) and neuropathic (type 2 and type 3) Gaucher disease is very different from each other; and (iii) subunit interaction of the mutant enzyme may be present in Gaucher type 1 fibroblasts, resulting in the formation of a higher-molecular-weight aggregate.     

A new glucocerebrosidase-gene missense mutation responsible for neuronopathic Gaucher disease in Japanese patients.

We have identified a new T-to-A single-base substitution at nucleotide 3548 (in the genomic sequence) in exon 6 in the glucocerebrosidase gene from a patient with Gaucher disease type 3. This mutation caused a substitution of isoleucine for phenylalanine at amino acid residue 213 (of 497 residues in the mature protein). By in vitro expression study in cultured mammalian cells, this mutation resulted in deficient activity of glucocerebrosidase. By allele-specific oligonucleotide hybridization of selectively PCR-amplified DNA from eight unrelated Japanese Gaucher disease patients, this mutant allele was observed in other neuronopathic Japanese Gaucher disease patients, in moderately frequent occurrence (three of six neuronopathic patients). This observation suggests that this allele was one of severe [corrected] alleles which were related to the development of neurological manifestations of Gaucher disease.     

Characterization of glucocerebrosidase in peripheral blood cells and cultured blastoid cells

We have characterized glucocerebrosidase in various cell types of peripheral blood of control subjects and in cultured human blastoid cells. The intracellular level of glucocerebrosidase in cultured blastoid cells (10-30 nmol substrate hydrolyzed/h.mg protein) resembles closely values observed for leukocyte cell types and various tissues and is significantly lower than that observed in cultured fibroblasts (150-500 nmol substrate hydrolyzed/h.mg protein). Glucocerebrosidase is extracted from leukocyte cell types and cultured blastoid cells almost exclusively in a monomeric, nonactivated form with enzymatic properties identical to those of the tissue enzyme. In contrast, extracts of platelets are rich in an aggregated, activated form of the enzyme. Glucocerebrosidase in blood cells and cultured blastoid cells is heterogeneous with respect to Mr and pI due to a heterogeneous oligosaccharide composition of the enzyme. The different forms seen represent intermediates in the biosynthesis and maturation of the enzyme. Blastoid cells should thus be an attractive model system for studying the natural history of glucocerebrosidase in a cell type related to those cells involved in the pathology of Gaucher disease.     

Heterogeneity in human acid beta-glucosidase revealed by cellulose-acetate electrophoresis

Cellulose-acetate gel electrophoresis, a technique commonly used for the separation of human acid hydrolases, was applied to study heterogeneity in acid beta-glucosidase (EC 3.2.1.45). With this technique, three forms of beta-glucosidase were distinguishable in extracts of several tissues. The most anodic beta-glucosidase activity (band 3) represents the broad-specificity beta-glucosidase that is not deficient in Gaucher disease and is not inhibited by conduritol B-epoxide (CBE). The beta-glucosidase activity was deficient in Gaucher disease. A third beta-glucosidase activity with an intermediate mobility (band 2) was also inhibited by CBE and deficient in Gaucher disease. Band 1 and band 2 beta-glucosidase thus represent different forms of glucocerebrosidase. By adding phosphatidylserine and sphingolipid activator protein (SAP-2), monomeric glucocerebrosidase could be completely converted into a form that comigrated with band 2 beta-glucosidase of tissue extracts. The addition of phosphatidylserine only also resulted in a changed mobility of the monomeric enzyme, but the migration in this case differed from that of band 2 beta-glucosidase of tissue extracts. The electrophoretic profile of beta-glucosidase activity of tissue extracts changed upon ethanol/chloroform extraction: the two glucocerebrosidase forms were converted into a band with a mobility identical to that of band 1 beta-glucosidase. Our findings indicate that the interaction of glucocerebrosidase with phospholipid and SAP-2 has major effects on the mobility of the enzyme in the cellulose-acetate gel electrophoresis system. The findings with the cellulose-acetate gel electrophoretic system are discussed in relation to the heterogeneity in glucocerebrosidase observed with sucrose density gradient analysis, immunochemical methods and isoelectric focussing studies.     

Substrate reduction therapy: clinical evaluation in type 1 Gaucher disease

Glycosphingolipid (GSL) lysosomal storage disorders are inherited enzyme deficiencies that result in pathological lysosomal accumulation of glycolipids, with widespread clinical consequences. Type 1 Gaucher disease is the commonest of these; the deficient enzyme in this condition is glucocerebrosidase. Clinical manifestations include hepatosplenomegaly, thrombocytopenia, anaemia, recurrent infections and skeletal lesions. The condition can be treated with intravenous enzyme replacement therapy (ERT). Substrate reduction therapy is a new approach in which glycolipid accumulation is counteracted not by replacing the deficient enzyme but by reducing the substrate level to better balance residual activity of the deficient enzyme. Miglustat is an inhibitor of glucosylceramide synthase, a key enzyme in GSL synthesis. Oral administration of miglustat to patients with type 1 Gaucher disease attenuates the synthesis of glucocerebroside, the substrate of the deficient glucocerebrosidase. In the first clinical study, patients with type 1 Gaucher disease who had enlargement of the liver or spleen and (if present) the spleen at baseline received 12 months treatment with oral miglustat. There were mean decreases in liver and spleen volumes of 12% (7.9-16.4, p < 0.001) and 19% (14.3-23.7, p < 0.001), respectively. Mean haemoglobin increased by 0.26 g dl(-1) (-0.5-0.57, not statistically significant) and platelet count by 8.3 x 10(9) l(-1) (1.9-14.7, p = 0.014).     

The human glucocerebrosidase gene has two functional ATG initiator codons.

Gaucher disease is due to a deficiency in the activity of the enzyme glucocerebrosidase. Glucocerebrosidase is a lysosomal enzyme that presumably requires a signal peptide for transport across the membrane of the rough endoplasmic reticulum and glycosylation for transport into lysosomes. Human glucocerebrosidase cDNA contains two potential ATG start codons in its long open reading frame. The signal peptides that are initiated from each ATG are quite different in their hydrophobicity. We demonstrate that either ATG can function independently to produce active glucocerebrosidase enzyme in cultured fibroblasts. The glucocerebrosidase activity produced from translation products initiated at either ATG is found predominantly in the lysosomes.     

Progress and potential of non-inhibitory small molecule chaperones for the treatment of Gaucher disease and its implications for Parkinson disease

Gaucher disease, caused by pathological mutations GBA1, encodes the lysosome-resident enzyme glucocerebrosidase, which cleaves glucosylceramide into glucose and ceramide. In Gaucher disease, glucocerebrosidase deficiency leads to lysosomal accumulation of substrate, primarily in cells of the reticulo-endothelial system. Gaucher disease has broad clinical heterogeneity, and mutations in GBA1 are a risk factor for the development of different synucleinopathies. Insights into the cell biology and biochemistry of glucocerebrosidase have led to new therapeutic approaches for Gaucher disease including small chemical chaperones. Such chaperones facilitate proper enzyme folding and translocation to lysosomes, thereby preventing premature breakdown of the enzyme in the proteasome. This review discusses recent progress in developing chemical chaperones as a therapy for Gaucher disease, with implications for the treatment of synucleinopathies. It focuses on the development of non-inhibitory glucocerebrosidase chaperones and their therapeutic advantages over inhibitory chaperones, as well as the challenges involved in identifying and validating chemical chaperones.