Assaying Lysosomal Enzyme Activity in Dictyostelium discoideum.

Lysosomes are membrane-enclosed organelles that digest intracellular material. They contain more than 50 different enzymes that can degrade a variety of macromolecules including nucleic acids, proteins, polysaccharides, and lipids. In addition to functioning within lysosomes, lysosomal enzymes are also secreted. Alterations in the levels and activities of lysosomal enzymes dysregulates lysosomes, which can lead to the intralysosomal accumulation of biological material and the development of lysosomal storage diseases (LSDs) in humans. Dictyostelium discoideum has a long history of being used to study the trafficking and functions of lysosomal enzymes. More recently, it has been used as a model system to study several LSDs. In this chapter, we outline the methods for assessing the activity of several lysosomal enzymes in D. discoideum (α-galactosidase, ß-galactosidase, α-glucosidase, ß-glucosidase, ß-N-acetylglucosaminidase, α-mannosidase, cathepsin B, cathepsin D, cathepsin F, palmitoyl protein thioesterase 1, and tripeptidyl peptidase 1).

Extracellular vesicles from recombinant cell factories improve the activity and efficacy of enzymes defective in lysosomal storage disorders.

In the present study the use of extracellular vesicles (EVs) as vehicles for therapeutic enzymes in lysosomal storage disorders was explored. EVs were isolated from mammalian cells overexpressing alpha-galactosidase A (GLA) or N-sulfoglucosamine sulfohydrolase (SGSH) enzymes, defective in Fabry and Sanfilippo A diseases, respectively. Direct purification of EVs from cell supernatants was found to be a simple and efficient method to obtain highly active GLA and SGSH proteins, even after EV lyophilization. Likewise, EVs carrying GLA (EV-GLA) were rapidly uptaken and reached the lysosomes in cellular models of Fabry disease, restoring lysosomal functionality much more efficiently than the recombinant enzyme in clinical use. In vivo, EVs were well tolerated and distributed among all main organs, including the brain. DiR-labelled EVs were localized in brain parenchyma 1 h after intra-arterial (internal carotid artery) or intravenous (tail vein) administrations. Moreover, a single intravenous administration of EV-GLA was able to reduce globotriaosylceramide (Gb3) substrate levels in clinically relevant tissues, such kidneys and brain. Overall, our results demonstrate that EVs from cells overexpressing lysosomal enzymes act as natural protein delivery systems, improving the activity and the efficacy of the recombinant proteins and facilitating their access to organs neglected by conventional enzyme replacement therapies.

A polylysine-polyhistidine fusion peptide for lysosome-targeted protein delivery.

Cell-penetrating peptides (CPPs) can deliver payloads into cells by forming complexes with bioactive molecules via either covalent or non-covalent bonds. Previously, we reported polyhistidine (H16 peptide: HHHHHHHHHHHHHHHH-NH2) as a new CPP. This peptide is anticipated to be a valuable new carrier for drug delivery to intracellular lysosomes; the peptide can transport macromolecules into these organelles. In the present study, we examined the application of the H16 peptide as a drug delivery system (DDS) to reverse to lysosomal storage disease (LSD) in cells in vitro. LSDs are metabolic disorders caused by the loss of specific lysosomal enzymes. The majority of lysosomal enzymes are acidic proteins and we utilized this common feature for our DDS. We synthesized a polylysine-polyhistidine fusion peptide (K10H16 peptide: KKKKKKKKKKGHHHHHHHHHHHHHHHH-NH2) and developed a simple method for transporting acidic proteins into intracellular lysosomes via formation of complexes of enzymes with the K10H16 peptide by electrostatic interaction. First, we demonstrated our strategy using maltose-binding protein-fused green fluorescent protein (MBP-GFP) to model an acidic protein. The K10H16 peptide bound to MBP-GFP and transported it into intracellular lysosomes. Further, alpha-galactosidase A (GLA), one of the lysosomal enzymes associated with LSD, was also delivered to intracellular lysosomes by the peptide. The complex between K10H16 peptide and GLA restored typical proliferation to LSD cells, which otherwise grew more slowly than normal cells. These results suggest that K10H16 peptide replenished lysosomal enzyme deficiency in LSD cells. The K10H16 peptide may be useful as a DDS for LSD therapy.

Lysosomal sulfatases: a growing family.

Sulfatases constitute a family of enzymes that specifically act in the hydrolytic degradation of sulfated metabolites by removing sulfate monoesters from various substrates, particularly glycolipids and glycosaminoglycans. A common essential feature of all known eukaryotic sulfatases is the posttranslational modification of a critical cysteine residue in their active site by oxidation to formylglycine (FGly), which is mediated by the FGly-generating enzyme in the endoplasmic reticulum and is indispensable for catalytic activity. The majority of the so far described sulfatases localize intracellularly to lysosomes, where they act in different catabolic pathways. Mutations in genes coding for lysosomal sulfatases lead to an accumulation of the sulfated substrates in lysosomes, resulting in impaired cellular function and multisystemic disorders presenting as lysosomal storage diseases, which also cover the mucopolysaccharidoses and metachromatic leukodystrophy. Bioinformatics analysis of the eukaryotic genomes revealed, besides the well described and long known disease-associated sulfatases, additional genes coding for putative enzymes with sulfatases activity, including arylsulfatase G as well as the arylsulfatases H, I, J and K, respectively. In this article, we review current knowledge about lysosomal sulfatases with a special focus on the just recently characterized family members arylsulfatase G and arylsulfatase K.

Pompe Disease: New Developments in an Old Lysosomal Storage Disorder.

Pompe disease, also known as glycogen storage disease type II, is caused by the lack or deficiency of a single enzyme, lysosomal acid alpha-glucosidase, leading to severe cardiac and skeletal muscle myopathy due to progressive accumulation of glycogen. The discovery that acid alpha-glucosidase resides in the lysosome gave rise to the concept of lysosomal storage diseases, and Pompe disease became the first among many monogenic diseases caused by loss of lysosomal enzyme activities. The only disease-specific treatment available for Pompe disease patients is enzyme replacement therapy (ERT) which aims to halt the natural course of the illness. Both the success and limitations of ERT provided novel insights in the pathophysiology of the disease and motivated the scientific community to develop the next generation of therapies that have already progressed to the clinic.

Allosteric regulation of lysosomal enzyme recognition by the cation-independent mannose 6-phosphate receptor.

The cation-independent mannose 6-phosphate receptor (CI-MPR, IGF2 receptor or CD222), is a multifunctional glycoprotein required for normal development. Through the receptor's ability to bind unrelated extracellular and intracellular ligands, it participates in numerous functions including protein trafficking, lysosomal biogenesis, and regulation of cell growth. Clinically, endogenous CI-MPR delivers infused recombinant enzymes to lysosomes in the treatment of lysosomal storage diseases. Although four of the 15 domains comprising CI-MPR's extracellular region bind phosphorylated glycans on lysosomal enzymes, knowledge of how CI-MPR interacts with ~60 different lysosomal enzymes is limited. Here, we show by electron microscopy and hydroxyl radical protein footprinting that the N-terminal region of CI-MPR undergoes dynamic conformational changes as a consequence of ligand binding and different pH conditions. These data, coupled with X-ray crystallography, surface plasmon resonance and molecular modeling, allow us to propose a model explaining how high-affinity carbohydrate binding is achieved through allosteric domain cooperativity.

The natural history of Type 1 infantile GM1 gangliosidosis: A literature-based meta-analysis.

INTRODUCTION: Type 1 GM1 gangliosidosis is an ultra-rare, rapidly fatal lysosomal storage disorder, with life expectancy of <3 years of age. To date, only one prospective natural history study of limited size has been reported. Thus, there is a need for additional research to provide a better understanding of the progression of this disease. We have leveraged the past two decades of medical literature to conduct the first comprehensive retrospective study characterizing the natural history of Type 1 GM1 gangliosidosis. OBJECTIVES: The objectives of this study were to establish a large sample of patients from the literature in order to identify: 1) clinically distinguishing factors between Type 1 and Type 2 GM1 gangliosidosis, 2) age at first symptom onset, first hospital admission, diagnosis, and death, 3) time to onset of common clinical findings, and 4) timing of developmental milestone loss. METHODS: PubMed was searched with the keyword "GM1 Gangliosidosis" and for articles from the year 2000 onwards. A preliminary review of these results was conducted to establish subtype classification criteria for inclusion of only Type 1 patients, resulting in 44 articles being selected to generate the literature dataset of 154 Type 1 GM1 gangliosidosis patients. Key clinical events of these patient cases were recorded from the articles. RESULTS: Comprehensive subtyping criteria for Type 1 GM1 gangliosidosis were created, and clinical events, including onset, diagnosis, death, and symptomology, were mapped over time. In this dataset, average age of diagnosis was 8.7 months, and average age of death was 18.9 months. DISCUSSION: This analysis demonstrates the predictable clinical course of this disease, as almost all patients experienced significant multi-organ system dysfunction and neurodevelopmental regression, particularly in the 6- to 18-month age range. Patients were diagnosed at a late age relative to disease progression, indicating the need for improved public awareness and screening. CONCLUSION: This study highlights the significant burden of illness in this disease and provides critical natural history data to drive earlier diagnosis, inform clinical trial design, and facilitate family counseling.

Proteostasis regulators modulate proteasomal activity and gene expression to attenuate multiple phenotypes in Fabry disease.

The lysosomal storage disorder Fabry disease is characterized by a deficiency of the lysosomal enzyme α-Galactosidase A. The observation that missense variants in the encoding GLA gene often lead to structural destabilization, endoplasmic reticulum retention and proteasomal degradation of the misfolded, but otherwise catalytically functional enzyme has resulted in the exploration of alternative therapeutic approaches. In this context, we have investigated proteostasis regulators (PRs) for their potential to increase cellular enzyme activity, and to reduce the disease-specific accumulation of the biomarker globotriaosylsphingosine in patient-derived cell culture. The PRs also acted synergistically with the clinically approved 1-deoxygalactonojirimycine, demonstrating the potential of combination treatment in a therapeutic application. Extensive characterization of the effective PRs revealed inhibition of the proteasome and elevation of GLA gene expression as paramount effects. Further analysis of transcriptional patterns of the PRs exposed a variety of genes involved in proteostasis as potential modulators. We propose that addressing proteostasis is an effective approach to discover new therapeutic targets for diseases involving folding and trafficking-deficient protein mutants.

Enzyme replacement therapy for mucopolysaccharidoses; past, present, and future.

Mucopolysaccharidoses (MPS) are a group of lysosomal storage disorders, which lack an enzyme corresponding to the specific type of MPS. Enzyme replacement therapy (ERT) has been the standard therapeutic option for some types of MPS because of the ability to start immediate treatment with feasibility and safety and to improve prognosis. There are several disadvantages for current ERT, such as limited impact to the brain and avascular cartilage, weekly or biweekly infusions lasting 4-5 h, the immune response against the infused enzyme, a short half-life, and the high cost. Clinical studies of ERT have shown limited efficacy in preventing or resolving progression in neurological, cardiovascular, and skeletal diseases. One focus is to penetrate the avascular cartilage area to at least stabilize, if not reverse, musculoskeletal diseases. Although early intervention in some types of MPS has shown improvements in the severity of skeletal dysplasia and stunted growth, this limits the desired effect of ameliorating musculoskeletal disease progression to young MPS patients. Novel ERT strategies are under development to reach the brain: (1) utilizing a fusion protein with monoclonal antibody to target a receptor on the BBB, (2) using a protein complex from plant lectin, glycan, or insulin-like growth factor 2, and (3) direct infusion across the BBB. As for MPS IVA and VI, bone-targeting ERT will be an alternative to improve therapeutic efficacy in bone and cartilage. This review summarizes the effect and limitations on current ERT for MPS and describes the new technology to overcome the obstacles of conventional ERT.

Characteristics of Pompe disease in China: a report from the Pompe registry.

BACKGROUND: Pompe disease is a rare, progressive, autosomal recessive lysosomal storage disorder caused by mutations in the acid α-glucosidase gene. This is the first report of Chinese patients from the global Pompe Registry. Chinese patients enrolled in the Registry ( ClinicalTrials.gov , NCT00231400) between Jan 2013 and 2 Sep 2016 with late onset Pompe disease (LOPD; presentation after 12 months of age or presentation at ≤12 months without cardiomyopathy) were included. Data analyses were descriptive. RESULTS: Of the 59 Chinese patients included, 86.4% had never received enzyme replacement therapy (ERT). The age at symptom onset and diagnosis was 14.9 (12.35) and 22.1 (10.08) years, which is younger than previous reports of LOPD patients from the rest of the world (28.4 [18.86] and 34.9 [20.03], respectively). The most common diagnosis methods were enzyme assay (79.7%) and/or DNA analysis (61.0%). Of the 36 patients diagnosed using DNA analysis, 31 had standardized variant data and among these patients the most common mutations were c.2238G > C (n = 18, 58.1%) and c.2662G > T (n = 5, 16.1%). Chinese LOPD patients appeared to have worse lung function versus patients from the rest of the world, indicated by lower forced vital capacity (37.2 [14.00]% vs. 63.5 [26.71]%) and maximal expiratory and inspiratory pressure (27.9 [13.54] vs. 51.0 [38.66] cm H2O, and 29.4 [12.04] vs. 70.5 [52.78] cm H2O). CONCLUSIONS: Compared with patients from the rest of the world, Chinese patients with LOPD appeared to have younger age at symptom onset and diagnosis, lower lung function, and the majority had not received ERT. The most common mutations were c.2238G > C and c.2662G > T.

Advances in the Development of Pharmacological Chaperones for the Mucopolysaccharidoses.

The mucopolysaccharidoses (MPS) are a group of 11 lysosomal storage diseases (LSDs) produced by mutations in the enzymes involved in the lysosomal catabolism of glycosaminoglycans. Most of the mutations affecting these enzymes may lead to changes in processing, folding, glycosylation, pH stability, protein aggregation, and defective transport to the lysosomes. It this sense, it has been proposed that the use of small molecules, called pharmacological chaperones (PCs), can restore the folding, trafficking, and biological activity of mutated enzymes. PCs have the advantages of wide tissue distribution, potential oral administration, lower production cost, and fewer issues of immunogenicity than enzyme replacement therapy. In this paper, we will review the advances in the identification and characterization of PCs for the MPS. These molecules have been described for MPS II, IVA, and IVB, showing a mutation-dependent enhancement of the mutated enzymes. Although the results show the potential of this strategy, further studies should focus in the development of disease-specific cellular models that allow a proper screening and evaluation of PCs. In addition, in vivo evaluation, both pre-clinical and clinical, should be performed, before they can become a real therapeutic strategy for the treatment of MPS patients.

Lysosomal storage disorders affecting the heart: a review.

Lysosomal storage disorders (LSD) comprise a group of diseases caused by a deficiency of lysosomal enzymes, membrane transporters or other proteins involved in lysosomal biology. Lysosomal storage disorders result from an accumulation of specific substrates, due to the inability to break them down. The diseases are classified according to the type of material that is accumulated; for example, lipid storage disorders, mucopolysaccharidoses and glycoproteinoses. Cardiac disease is particularly important in lysosomal glycogen storage diseases (Pompe and Danon disease), mucopolysaccharidoses and in glycosphingolipidoses (Anderson-Fabry disease). Various disease manifestations may be observed including hypertrophic and dilated cardiomyopathy, coronary artery disease and valvular diseases. Endomyocardial biopsies can play an important role in the diagnosis of these diseases. Microscopic features along with ancillary tests like special stains and ultrastructural studies help in the diagnosis of these disorders. Diagnosis is further confirmed based upon enzymatic and molecular genetic analysis. Emerging evidence suggests that Enzyme replacement therapy (ERT) substantially improves many of the features of the disease, including some aspects of cardiac involvement. The identification of these disorders is important due to the availability of ERT, the need for family screening, as well as appropriate patient management and counseling.

Utility of amniotic fluid chitotriosidase in the prenatal diagnosis of lysosomal storage disorders.

OBJECTIVE: Plasma chitotriosidase is a documented biomarker for certain lysosomal storage disorders. However, its clinical utility for prenatal samples is not elucidated yet. METHODS: We have established Reference intervals for amniotic fluid chitotriosidase using control amniotic fluids (n = 47) and compared the activity with amniotic fluids affected by lysosomal storage disorders (n = 25). RESULTS: The reference interval established was 0-6.76 nmol/h/ml. The amniotic fluids affected with LSDs exhibited elevation of chitotriosidase. The area under the curve (AUC) of receiver operating characteristic curve for affected vs. healthy was 0.987 indicating 98.6% accuracy of chitotriosidase in identifying pregnancies affected with LSDs. Among the different LSDs, Gaucher (202.00 ±â€¯35.27 nmol/h/ml) and Niemann-pick A/B (60.33 ±â€¯21.59 nmol/h/ml) showed very high levels of chitotriosidase. CONCLUSION: Amniotic fluid chitotriosidase has the potential to serve as a diagnostic marker for lysosomal storage disorders, more specifically for Gaucher and Niemann-Pick A/B.

A Glycoengineered Enzyme with Multiple Mannose-6-Phosphates Is Internalized into Diseased Cells to Restore Its Activity in Lysosomes.

In this study we developed an efficient method to prepare glycoengineered ß-N-acetylhexosaminidase containing multiple mannose-6-phosphates (M6Ps) by combining genetic code expansion with bioorthogonal ligation techniques. We found that multiple M6P-conjugated enzymes were produced with a high efficiency by using combined techniques. Importantly, glycoengineered enzymes entered lysosomes of patient-derived primary cells, which lack endogenous lysosomal ß-N-acetylhexosaminidase, more readily than commercialized human ß-hexosaminidase. Moreover, glycoengineered enzymes successfully removed GM2-ganglioside stored in lysosomes of diseased cells, indicating that its activity is restored in diseased cells. We also synthesized and applied a lysosome-targeting fluorogenic substrate to monitor endogenous and supplemental glycoengineered ß-N-acetylhexosaminidase activities in lysosomes. The results of this study indicate that the present strategy, which relies on genetic code expansion and bioorthogonal ligation techniques, is highly attractive to generate multi-M6P-containing lysosomal enzymes that can be used to study lysosomal storage disorders associated with lysosomal enzyme deficiencies.

Early prenatal diagnosis of lysosomal storage disorders by enzymatic and molecular analysis.

OBJECTIVE: To report the 4-year experience of early prenatal diagnosis of lysosomal storage disorders (LSDs) at a center in mainland China. METHOD: Forty-seven pregnancies affected with LSDs were assed using enzymes and/or molecular studies. Prenatal studies were performed on 43 uncultured chorionic villi (CV) samples, two amniotic fluid samples, and two umbilical cord blood samples. RESULTS: Of the 47 fetuses, 23 (48.9%) were determined to normal, 13 (27.7%) to be carriers, and 11 (23.4%) diagnosed as affected. In this cohort, mucopolysaccharidoses (MPS) type II was the most common LSD, followed by Pompe disease and then metachromatic leucodystrophy. In the 17 MPS II cases, the four affected fetuses showed MPS II enzyme activity expression levels of 1.4% to 6.7%, while the enzyme activity levels of the 13 normal fetuses ranged from 72% to 240.4%. In the seven Pompe cases, three fetuses were normal with Pompe enzyme activity expression levels of 20%, 38.8%, and 77.3%, while four carrier pregnancies showed enzyme activity levels of 17.5%, 17.5%, 33.4%, and 13.8%, respectively. CONCLUSION: Based on different enzyme properties in uncultured CV, different prenatal diagnostic strategies should be adopted for MPS II and Pompe disease. Combining enzyme assay and molecular studies in uncultured CV improves the reliability of prenatal diagnosis of LSDs.

Genotypic-phenotypic features and enzyme replacement therapy outcome in patients with mucopolysaccharidosis VI from Turkey.

Mucopolysaccharidosis type VI (MPS VI) is a lysosomal storage disorder (LSD) characterized by a chronic, progressive course with multiorgan involvement. In our study, clinical, biochemical, molecular findings, and response to enzyme replacement therapy (ERT) for at least 6 months were evaluated in 20 patients with MPS VI. Treatment effects on clinical findings such as liver and spleen sizes, cardiac and respiratory parameters, visual and auditory changes, joints' range of motions, endurance tests and changes in urinary glycosaminoglycan excretions, before and after ERT were analyzed. ERT caused increased physical endurance and decreased urinary dermatan sulfate/chondroitin sulfate ratios. Changes in growth parameters, cardiac, respiratory, visual, auditory findings, and joint mobility were not significant. All patients and parents reported out an increased quality of life, which were not correlated with clinical results. The most prevalent mutation was p.L321P, accounting for 58.8% of the mutant alleles and two novel mutations (p.G79E and p.E390 K) were found. ERT was a safe but expensive treatment for MPS VI, with mild benefits in severely affected patients. Early treatment with ERT is mandatory before many organs and systems are involved.

An improved purification method for the lysosomal storage disease protein ß-glucuronidase produced in CHO cells.

Human ß-glucuronidase (GUS; EC 3.2.1.31) is a lysosomal enzyme that catalyzes the hydrolysis of ß-d-glucuronic acid residues from the non-reducing termini of glycosaminoglycans. Impairment in GUS function leads to the metabolic disorder mucopolysaccharidosis type VII, also known as Sly syndrome. We produced GUS from a CHO cell line grown in suspension in a 15 L perfused bioreactor and developed a three step purification procedure that yields ∼99% pure enzyme with a recovery of more than 40%. The method can be completed in two days and has the potential to be integrated into a continuous manufacturing scheme.

Recommendations on clinical trial design for treatment of Mucopolysaccharidosis Type III.

BACKGROUND: Mucopolysaccharidosis type III is a progressive, neurodegenerative lysosomal storage disorder for which there is currently no effective therapy. Though numerous potential therapies are in development, there are several challenges to conducting clinical research in this area. We seek to make recommendations on the approach to clinical research in MPS III, including the selection of outcome measures and trial endpoints, in order to improve the quality and impact of research in this area. RESULTS: An international workshop involving academic researchers, clinical experts and industry groups was held in June 2015, with presentations and discussions on disease pathophysiology, biomarkers, potential therapies and clinical outcome measures. A set of recommendations was subsequently prepared by a working group and reviewed by all delegates. We present a series of 11 recommendations regarding the conduct of clinical research, outcome measures and management of natural history data in Mucopolysaccharidosis type III. CONCLUSIONS: Improving the quality of clinical research in Mucopolysaccharidosis type III will require an open, collaborative and systematic approach between academic researchers, clinicians and industry. Natural history data should be published as soon as possible and ideally collated in a central repository. There should be agreement on outcome measures and instruments for evaluation of clinical outcomes to maximise the effectiveness of current and future clinical research.