ABSTRACT
Lysosomal enzymes degrade cellular macromolecules, while their inactivation causes human hereditary metabolic disorders. Mucopolysaccharidosis IVA (MPS IVA; Moquio A syndrome) is one of the lysosomal storage disorders caused by a defective Galactosamine-6-sulfatase (GalN6S) enzyme. In several populations, disease incidence is elevated due to missense mutations brought on by non-synonymous allelic variation in the GalN6S enzyme. Here, we studied the effect of non-synonymous single nucleotide polymorphism (nsSNPs) on the structural dynamics of the GalN6S enzyme and its binding with N-acetylgalactosamine (GalNAc) using all-atom molecular dynamics simulation and an essential dynamics approach. Consequently, in this study, we have identified three functionally disruptive mutations in domain-I and domain-II, that is, S80L, R90W, and S162F, which presumably contribute to post-translational modifications. The study delineated that both domains work cooperatively, and alteration in domain II (S80L, R90W) leads to conformational changes in the catalytic site in domain-I, while mutation S162F mainly provokes higher residual flexibility of domain II. These results show that these mutations impair the hydrophobic core, implying that Morquio A syndrome is caused by misfolding of the GalN6S enzyme. The results also show the instability of the GalN6S-GalNAc complex upon substitution. Overall, the structural dynamics resulting from point mutations give the molecular rationale for Moquio A syndrome and, more importantly, the Mucopolysaccharidoses (MPS) family of diseases, re-establishing MPS IVA as a protein-folding disease.Communicated by Ramaswamy H. Sarma.
Subject(s)
Mucopolysaccharidosis IV , Humans , Mucopolysaccharidosis IV/genetics , Acetylgalactosamine , Galactosamine , Protein Folding , SulfatasesABSTRACT
Morquio A disease (Mucopolysaccharidosis type IVA, MPS IVA) is one of the 11 mucopolysaccharidoses (MPSs), a heterogeneous group of inherited lysosomal storage disorders (LSDs) caused by deficiency in enzymes need to degrade glycosaminoglycans (GAGs). Morquio A is characterized by a decrease in N-acetylgalactosamine-6-sulfatase activity and subsequent accumulation of keratan sulfate and chondroitin 6-sulfate in cells and body fluids. As the pathophysiology of this LSD is not completely understood and considering the previous results of our group concerning oxidative stress in Morquio A patients receiving enzyme replacement therapy (ERT), the aim of this study was to investigate oxidative stress parameters in Morquio A patients at diagnosis. It was studied 15 untreated Morquio A patients, compared with healthy individuals. The affected individuals presented higher lipid peroxidation, assessed by urinary 15-F2t-isoprostane levels and no protein damage, determined by sulfhydryl groups in plasma and di-tyrosine levels in urine. Furthermore, Morquio A patients showed DNA oxidative damage in both pyrimidines and purines bases, being the DNA damage positively correlated with lipid peroxidation. In relation to antioxidant defenses, affected patients presented higher levels of reduced glutathione (GSH) and increased activity of glutathione peroxidase (GPx), while superoxide dismutase (SOD) and glutathione reductase (GR) activities were similar to controls. Our findings indicate that Morquio A patients present at diagnosis redox imbalance and oxidative damage to lipids and DNA, reinforcing the idea about the importance of antioxidant therapy as adjuvant to ERT, in this disorder.
ABSTRACT
Abstract Patients with mucopolysaccharidosis (MPS), and Morquio A syndrome (MPS IVA) in particular, often report substantial pain burden. MOR-008 was a randomized, double-blind, pilot study assessing the safety and efficacy, including impact on patient-reported pain, of 52 weeks of treatment with elosulfase alfa (at a dose of 2.0 or 4.0 mg/kg/week) in patients with Morquio A syndrome (?7 years old). Assessment of pain at baseline revealed that patients (N = 25) had a mean number of pain locations of 5.7, mean pain intensity score of 4.6 (indicative of medium pain), and a mean number of selected pain descriptors of 7.4 words. Treatment with elosulfase alfa improved subjective pain score (reduced to 3.2), pain locations (reduced by a mean of 1 location), and pain descriptor words (reduced to 4.9 words) over 1 year (52 weeks), suggesting that elosulfase alfa can reduce pain in some patients with Morquio A.
ABSTRACT
Mucopolysaccharidosis VI (MPS VI) is an autosomal recessive inborn error of metabolism caused by mutations in the arylsulfatase B gene (ARSB) and consequent deficient activity of ARSB, a lysosomal enzyme. We present here the results of a study undertaken to identify the mutations in ARSB in MPS VI patients in India. Around 160 ARSB mutations, of which just 4 are from India, have been reported in the literature. Our study covered nine MPS VI patients from eight families. Both familial mutations were found in seven families, and only one mutation was found in one family. Seven mutations were found - four novel (p.G38_G40del3, p.C91R, p.L98R and p.R315P), two previously reported from India (p.D53N and p.W450C), and one reported from outside India (p.R160Q). One mutation, p.W450C, was present in two families, and the other six mutations were present in one family each. Analysis of the molecular structure of the enzyme revealed that most of these mutations either cause loss of an active site residue or destabilize the structure of the enzyme. The only previous study on mutations in ARSB in Indian MPS VI patients, by Kantaputra et al. 2014 [1], reported four novel mutations of which two (p.D53N and p.W450C) were found in our study as well. Till date, nine mutations have been reported from India, through our study and the Kantaputra study. Eight out of these nine mutations have been found only in India. This suggests that the population studied by us might have its own typical set of mutations, with other populations equally likely to have their own set of mutations.
ABSTRACT
Se presenta el caso de un paciente de 16 años de edad, con el diagnostico de mucopolisacaridosis (MPS) tipo IV-A, con una breve revisión teórica del curso y progresión crónica de esta enfermedad multi-sistémica, que se manifiesta con amplia signo sintomatología, hallazgos de laboratorio y anomalías radiológicas. El objetivo es documentar el caso y difundir a la comunidad médica boliviana, la importancia de los errores innatos del metabolismo, consideradas enfermedades "raras", que a criterio nuestro, sufren un sub-diagnóstico debido a las pocas publicaciones científicas sobre el tema en el medio.
We report the case of a patient 16 years old with a diagnosis of mucopolysaccharidosis (MPS) type IV- A, with a brief theoretical review of chronic course and progression of this multisystem disease, which manifests with extensive signs symptoms, findings are presented, with laboratory and radiological reported abnormalities. The aim is to document the event and communicated to Bolivian medical community, the importance of inborn errors of metabolism, considered "rare" diseases, which in our opinion; suffer a sub- diagnosis because of the few Bolivian scientific publications on the topic.
Subject(s)
Mucopolysaccharidosis IV/diagnosis , Mucopolysaccharidosis IV/pathologyABSTRACT
Introducción: la Mucopolisacaridosis tipo IV A (OMIM #253000), es una enfermedad autosómica recesiva que pertenece al grupo de enfermedades de depósito lisosomal, esta fue descrita inicialmente por Luis Morquio, cuya etiología es la deficiencia de la enzima N-acetil-galactosamina-6-sulfato sulfatasa, favoreciendo el depósito intracelular de queratán sulfato y condroitin-6-sulfato, llevando al espectro de manifestaciones clínicas que caracterizan este síndrome como son: baja talla, anormalidades vertebrales, opacidades corneales, inteligencia conservada, entre otras. Mediante radiografía de tórax y de extremidades inferiores se pueden observar las vértebras ovoides o en cuña y alteraciones en huesos largos, respectivamente. Objetivo: revisar sobre las generalidades de la MPS IV A, sus características clínicas, complicaciones, los estudios genéticos, la asesoría genética y su manejo preventivo. Conclusiones: las pruebas de laboratorio como el test de cloruro de cetilpiridinio o la albúmina ácida son esenciales para el diagnóstico. En cuanto al tratamiento hasta la fecha no existe una terapia de reemplazo enzimático por ello los cuidados son preventivos, y el manejo de estas personas debe ser interdisciplinario (medicina, nutrición, psicología, entre otros).
Background: mucopolysaccharidosis IV A (OMIM # 253000), belongs to the group of lysosomal storage diseases, this was first described by Luis Morquio, whose etiology is a deficiency of the enzyme N-acetylgalactosamine-6-sulfate sulfatase, favoring the deposit intracellular queratán sulfate and chondroitin-6-sulfate, leading to the spectrum of clinical manifestations that characterize this syndrome are short stature, vertebral abnormalities, corneal opacities, preserved intelligence, among others. X-ray can see the vertebrae ovoid or wedge, and alterations in long bones. Objetive: make a general overview of MPS IV A, its clinical features, complications, genetic testing, genetic counseling and preventive management. Conclusions: laboratory tests as test test cetylpyridinium chloride or acid albumin essential for diagnosis. As for treatment to date there is no enzyme replacement therapy are therefore preventive care, and management of these people should be interdisciplinary (medicine, nutrition, psychology, etc.).
