Functional Characterization and Pharmacological Evaluation of a Novel GLA Missense Mutation Found in a Severely Affected Fabry Disease Family.

BACKGROUND: Fabry disease (FD) is a rare X-linked storage disorder resulting from the deficient activity of the lysosomal hydrolase α-galactosidase A (α-Gal A). Here we describe a 23-year-old man with FD possessing a novel mutation in the GLA gene, the evaluation of his family, and the functional characterization of the novel variant. METHODS: Two generations of a family were screened for FD by clinical symptoms and low enzymatic activity. This step was followed by DNA sequencing that showed a novel GLA missense mutation. To confirm the pathogenicity potential of the mutation, we employed site-directed polymerase chain reaction mutagenesis. GLA wild-type and mutant plasmids were transfected into mammalian cells; RNA and proteins were extracted for expression and analysis of enzymatic activity. RESULTS: The patient presents the variant p.Asn34Asp in the GLA and had several manifestations of FD since adolescence. The investigation of the deficiency of α-Gal A was initiated due to stage 4 of chronic kidney disease. All family members carrying the novel mutation presented early symptoms, including index case's mother, who received a renal transplant when she was 35 years old. In silico and in vitro analysis confirmed the pathogenic potential of the mutation p.Asn34Asp showing that the enzyme had only 4% of residual activity due to protein misfolding. The ability of the pharmacological chaperone 1-deoxygalactonojirimycin to recover the mutant was confirmed, producing 37.5% of residual activity. CONCLUSION: In this work, we present a novel missense mutation in GLA that leads to the production of a catalytically competent α-Gal A, which is degraded before its delivery to the lysosome, promoting severe manifestations of FD, with a very similar disease course in affected men and women.

Voluntary wheel running activates Akt/AMPK/eNOS signaling cascades without improving profound endothelial dysfunction in mice deficient in α-galactosidase A.

Fabry disease is caused by loss of activity of the lysosomal hydrolase α-galactosidase A (GLA). Premature life-threatening complications in Fabry patients arise from cardiovascular disease, including stroke and myocardial infarction. Exercise training has been shown to improve endothelial dysfunction in various settings including coronary artery disease. However, the effects of exercise training on endothelial dysfunction in Fabry disease have not been investigated. Gla knockout mice were single-housed in a cage equipped with a voluntary wheel (EX) or no wheel (SED) for 12 weeks. Exercised mice ran 10 km/day on average during the voluntary running intervention (VR) period. Despite significantly higher food intake in EX than SED, body weights of EX and SED remained stable during the VR period. After the completion of VR, citrate synthase activity in gastrocnemius muscle was significantly higher in EX than SED. VR resulted in greater phosphorylation of Akt (S473) and AMPK (T172) in the aorta of EX compared to SED measured by western blot. Furthermore, VR significantly enhanced eNOS protein expression and phosphorylation at S1177 by 20% and 50% in the aorta of EX when compared with SED. Similarly, plasma nitrate and nitrite levels were 77% higher in EX than SED. In contrast, measures of anti- and pro-oxidative enzymes (superoxide dismutase and p67phox subunit of NADPH oxidase) and overall oxidative stress (plasma oxidized glutathione) were not different between groups. Although the aortic endothelial relaxation to acetylcholine was slightly increased in EX, it did not reach statistical significance. This study provides the first evidence that VR improves Akt/AMPK/eNOS signaling cascades, but not endothelial function in the aorta of aged Gla deficient mice.

[The unusual couple: a clinical case of coexistence between aHUS and Fabry's disease].

Atypical hemolytic-uremic syndrome (aHUS) is a rare, potentially lethal (1-4) systemic disorder, capable of affecting both adults and children, causing thrombotic microangiopathy (TMA) (5) that leads to the formation of thrombus within small blood vessels with multiple organ failure. The pathogenesis of the aHUS is part of a sort of chronic and uncontrolled activation of the complement system by genetic mutation of some proteins usually responsible for its self-regulation (6,7). Today, the rapid diagnosis of the disease and the timely start of treatment with eculizumab, improve outcomes of renal failure, stroke and heart attack (8-10). Fabry disease is a rare tesaurismosis, X linked, due to the deficiency of the lysosomal enzyme alpha-galactosidase A (11-13), necessary for the physiological catabolism of glycosphingolipids. Multisystem clinical manifestations lead to a serious degenerative pathology. The diagnostic suspicion based on anamnesis and careful research of the symptoms and then confirmed by the enzymatic dosage of alpha galactosidase or by molecular analysis, allows the early treatment of the patient with enzyme replacement therapy, guaranteeing the resolution and/or slowing down the evolution of the disease, especially in the brain, heart and kidneys. In this report, we describe the clinical case of a patient who is a carrier of both rare diseases.

α-Galactosidase A-deficient rats accumulate glycosphingolipids and develop cardiorenal phenotypes of Fabry disease.

Fabry disease is an X-linked lysosomal storage disease caused by α-galactosidase A (α-Gal A) deficiency. Kidney and heart failure are frequent complications in adulthood and greatly contribute to patient morbidity and mortality. Because α-Gal A-deficient mouse models do not recapitulate cardiorenal findings observed in patients, a nonmouse model may be beneficial to our understanding of disease pathogenesis. In this study, we evaluated disease processes in a recently generated Fabry rat model. We found that male Fabry rats weighed significantly less than wild-type (WT) males, whereas female Fabry rats weighed significantly more than WT females. Whereas no difference in female survival was detected, we observed that male Fabry rats had a decreased lifespan. Skin histology revealed that inflammation and lipoatrophy may be chief disease mediators in patients. With respect to the kidney and heart, we found that both organs accumulate α-Gal A substrates, including the established biomarkers, globotriaosylceramide and globotriaosylsphingosine. Longitudinal serum and urine chemistry panels demonstrated pronounced renal tubule dysfunction, which was confirmed histologically. Mitral valve thickening was observed in Fabry rats using echocardiography. We conclude that Fabry rats recapitulate important kidney and heart phenotypes experienced by patients and can be further used to study disease mechanisms and test therapies.-Miller, J. J., Aoki, K., Mascari, C. A., Beltrame, A. K., Sokumbi, O., North, P. E., Tiemeyer, M., Kriegel, A. J., Dahms, N. M., α-Galactosidase A-deficient rats accumulate glycosphingolipids and develop cardiorenal phenotypes of Fabry disease.

Case report: is low α-Gal enzyme activity sufficient to establish the diagnosis of Fabry disease?

Fabry disease is an X-linked lysosomal storage disease due to alpha-galactosidase A (α-Gal A) deficient activity which leads to the accumulation of glucoesphingolipids, such as globotriaosilceramide. There are over 700 known mutations of the enzyme gene, and most of them cause Fabry Disease. This case report describes a hemodialysis patient with a rare and controversial GLA gene mutation, the D313Y. The medecial investigation confirmed that D313Y is an alpha-galactosidase A sequence variant that causes pseudo deficient enzyme activity in plasma but not Fabry disease. Thus, clinical symptoms that prompted Fabry disease investigation could not be attributable to Fabry disease and therefore enzyme replacement therapy was not indicated.

Case report: is low α-Gal enzyme activity sufficient to establish the diagnosis of Fabry disease? / Relato de caso: a diminuição da enzimaα-Gal l é suficiente para estabelecer o diagnóstico?

Abstract Fabry disease is an X-linked lysosomal storage disease due to alpha-galactosidase A (α-Gal A) deficient activity which leads to the accumulation of glucoesphingolipids, such as globotriaosilceramide. There are over 700 known mutations of the enzyme gene, and most of them cause Fabry Disease. This case report describes a hemodialysis patient with a rare and controversial GLA gene mutation, the D313Y. The medecial investigation confirmed that D313Y is an alpha-galactosidase A sequence variant that causes pseudo deficient enzyme activity in plasma but not Fabry disease. Thus, clinical symptoms that prompted Fabry disease investigation could not be attributable to Fabry disease and therefore enzyme replacement therapy was not indicated.

Resumo Doença de Fabry (DF) é uma doença de depósito lisossômico ligada ao cromossomo X, causada pela deficiência da enzima alfa-galactosidase A (α-Gal A) que leva ao acúmulo de glicoesfingolipídeos, principalmente globotriaosilceramide. Existem mais de 700 mutações conhecidas do gene da enzima, a maioria delas são causadoras de DF. Este relato de caso descreve sobre um paciente em hemodiálise com uma mutação do gene GLA rara e controversa, a D313Y. A investigação médica confirmou que D313Y é uma variante que leva à pseudodeficiência plasmática da enzima, mas não ocasiona DF. Assim, os sintomas clínicos que induziram a investigação da doença não devem ser atribuídos à DF e, portanto, não foi indicada a terapia de reposição enzimática.

[Globosides as key players in the pathophysiology of Shiga toxin-associated acute kidney failure and Fabry disease]. / Globoside als entscheidende Mediatoren in der Pathophysiologie des Shiga-Toxin-assoziierten akuten Nierenversagens und des Morbus Fabry.

Globosides and their isomeric counterparts isoglobosides belong to the class of neutral glycosphingolipids with an as yet undefined physiological function. In the pathogenesis of human diseases, globosides play an important role as cellular receptors for Shiga toxins which are produced by certain strains of S. dysenteriae and E. coli. In order to elucidate the pathogenesis of Shiga toxin-associated kidney failure, we studied human kidney biopsies and animal models. Our work showed that in patients suffering from Shiga toxin-elicited kidney failure, no complement activation could be demonstrated by immunohistochemical analysis of kidney biopsies. Therefore, complement activation is unlikely to play a major role in mediating thrombotic microangiopathy on exposure to Shiga toxin. Moreover, analysis of the human biopsies and of a murine model of Shiga toxin-associated disease pinpointed acute tubular damage as an important and previously neglected contributor to acute kidney failure in patients infected with Shiga toxin-producing E. coli. Furthermore, globosides play a decisive role in the pathogenesis of Fabry disease which results from a decreased or absent activity of the lysosomal enzyme α-galactosidase A. The results on transgenic mice showed that in vital organs, such as the heart, kidneys and liver, it was possible to revert the phenotype of Fabry disease by eliminating the synthesis of globosides. This implicates that substrate reduction therapy through inhibition of globosides might represent a new therapeutic option for Fabry disease, all the more so as globosides seem to be dispensable.

Endothelial nitric oxide synthase uncoupling and microvascular dysfunction in the mesentery of mice deficient in α-galactosidase A.

A defect in the gene for the lysosomal enzyme α-galactosidase A (Gla) results in globotriaosylceramide (Gb3) accumulation in Fabry disease and leads to premature death from cardiac and cerebrovascular events. However, gastrointestinal symptoms are often first observed during childhood in these patients and are not well understood. In this study, we demonstrate an age-dependent microvasculopathy of the mesenteric artery (MA) in a murine model of Fabry disease (Gla-knockout mice) resulting from dysregulation of the vascular homeostatic enzyme endothelial nitric oxide synthase (eNOS). The progressive accumulation of Gb3 in the MA was confirmed by thin-layer chromatographic analysis. A total absence of endothelium-dependent dilation was observed in MAs from mice at 8 mo of age, while suppression of ACh-mediated vasodilation was evident from 2 mo of age. Endothelium-independent dilation with sodium nitroprusside was normal compared with age-matched wild-type mice. The microvascular defect in MAs from Fabry mice was endothelium-dependent and associated with suppression of the active homodimer of eNOS. Phosphorylation of eNOS at the major activation site (Ser(1179)) was significantly downregulated, while phosphorylation at the major inhibitory site (Thr(495)) was remarkably enhanced in MAs from aged Fabry mice. These profound alterations in eNOS bioavailability at 8 mo of age were observed in parallel with high levels of 3-nitrotyrosine, suggesting increased reactive oxygen species along with eNOS uncoupling in this vascular bed. Overall, the mesenteric microvessels in the setting of Fabry disease were observed to have an early and profound endothelial dysfunction associated with elevated reactive nitrogen species and decreased nitric oxide bioavailability.

Pathologic endothelial response and impaired function of circulating angiogenic cells in patients with Fabry disease.

Fabry disease is an X-chromosomal recessive deficiency of the lysosomal hydrolase alpha-galactosidase A (alpha-Gal). This results in an accumulation of globotriaosylceramide (GL-3) in a variety of cells often with subsequent functional impairment. Here, the impact of Fabry disease on the biology of circulating angiogenic cells (CACs) and the endothelial response to transient ischemia was investigated. Untreated patients with Fabry disease (n = 26), patients after initiation of alpha-Gal enzyme replacement therapy (ERT) (n = 16) and healthy controls (n = 26) were investigated. Endothelial function was assessed by the EndoPAT2000 device. CAC numbers were assessed by flow-cytometry, CAC function by a modified Boyden chamber assay. Fabry patients showed a pathologic endothelial response, which normalized after ERT. CACs were increased in number, but functionally impaired. Immunofluorescence and electron microscopy identified an accumulation of GL-3 in Fabry CACs. ERT attenuated CAC dysfunction and improved markers of oxidative stress response in Fabry patients via a reduction in GL-3 accumulation in vitro and in vivo. Silencing of alpha-Gal in healthy CACs impaired their migratory capacity underlining a key role of this enzyme for CAC function. CAC supernatant as well as CACs from Fabry patients impaired angiogenesis and migratory capacity of HUVECs providing a mechanistic link between CAC and endothelial dysfunction. CAC adhesion to TNF-α pre-stimulated HUVECs and tube formation was impaired by alpha-Gal knockdown. Fabry patients show a dysfunction of CAC and a pathologic endothelial response. ERT improves CAC and endothelial function and thus may attenuate development of cardiovascular disease in the long term in this patient population.

Globosides but not isoglobosides can impact the development of invariant NKT cells and their interaction with dendritic cells.

Recognition of endogenous lipid Ag(s) on CD1d is required for the development of invariant NKT (iNKT) cells. Isoglobotrihexosylceramide (iGb3) has been implicated as this endogenous selecting ligand and recently suggested to control overstimulation and deletion of iNKT cells in α-galactosidase A-deficient (αGalA(-/-)) mice (human Fabry disease), which accumulate isoglobosides and globosides. However, the presence and function of iGb3 in murine thymus remained controversial. In this study, we generate a globotrihexosylceramide (Gb3)-synthase-deficient (Gb3S(-/-)) mouse and show that in thymi of αGalA(-/-)/Gb3S(-/-) double-knockout mice, which store isoglobosides but no globosides, minute amounts of iGb3 can be detected by HPLC. Furthermore, we demonstrate that iGb3 deficiency does not only fail to impact selection of iNKT cells, in terms of frequency and absolute numbers, but also does not alter the distribution of the TCR CDR 3 of iNKT cells. Analyzing multiple gene-targeted mouse strains, we demonstrate that globoside, rather than iGb3, storage is the major cause for reduced iNKT cell frequencies and defective Ag presentation in αGalA(-/-) mice. Finally, we show that correction of globoside storage in αGalA(-/-) mice by crossing them with Gb3S(-/-) normalizes iNKT cell frequencies and dendritic cell (DC) function. We conclude that, although detectable in murine thymus in αGalA(-/-)/Gb3S(-/-) mice, iGb3 does not influence either the development of iNKT cells or their interaction with peripheral DCs. Moreover, in αGalA(-/-) mice, it is the Gb3 storage that is responsible for the decreased iNKT cell numbers and impeded Ag presentation on DCs.

Vascular dysfunction in the alpha-galactosidase A-knockout mouse is an endothelial cell-, plasma membrane-based defect.

Fabry disease results from an X-linked mutation in the lysosomal alpha-galactosidase A (Gla) gene. Defective Gla results in multi-organ accumulation of neutral glycosphingolipids (GSLs), especially in the vascular endothelium, with the major GSL accumulated being globotriaosylceramide (Gb3). Excessive endothelial Gb3 accumulation is associated with increased thrombosis, atherogenesis and endothelial dysfunction. However, the mechanism(s) by which endothelial dysfunction occurs is unclear. The purpose of the present study was to further characterize the vasculopathy associated with a murine model of Fabry disease. Vascular reactivity was performed in vessels from wild-type (Gla(+/0)) and Gla-knockout (Gla(-/0)) mice. Conscious blood pressure and heart rate were measured in Gla(+/0) and Gla(-/0) mice by telemetry. The present study demonstrates that vascular smooth muscle (VSM) contractions to phenylephrine and serotonin, but not to U46619, were blunted in Gla(-/0) mice. Endothelium-dependent contraction and receptor-mediated endothelium-dependent relaxation to acetylcholine were significantly attenuated in vessels from Gla(-/0) mice. However, receptor-independent endothelium-dependent relaxation to the calcium ionophore ionomycin remained intact in vessels from Gla(-/0) mice. Furthermore, VSM reactivity was normal in aortas from Gla(-/0) mice in the absence of endothelium. These changes in vascular function were observed without changes in whole-animal blood pressure or heart rate. These results suggest that the vasculopathy associated with Fabry disease is localized to the endothelium, despite the accumulation of GSLs throughout the vasculature.

Galactomannan hydrolysis and mannose metabolism in Cellvibrio mixtus.

Galactomannan hydrolysis results from the concerted action of microbial endo-mannanases, manosidases and alpha-galactosidases and is a mechanism of intrinsic biological importance. Here we report the identification of a gene cluster in the aerobic soil bacterium Cellvibrio mixtus encoding enzymes involved in the degradation of this polymeric substrate. The family 27 alpha-galactosidase, termed CmAga27A, preferentially hydrolyse galactose containing polysaccharides. In addition, we have characterized an enzyme with epimerase activity, which might be responsible for the conversion of mannose into glucose. The role of the identified enzymes in the hydrolysis of galactomannan by aerobic bacteria is discussed.

Characterisation of an alpha-galactosidase with potential relevance to ripening related texture changes.

alpha-Galactosidase (EC 3.2.1.22) from ripe papaya (Carica papaya L.) fruit was fractionated by a combination of ion exchange and gel filtration chromatography into three forms, viz., alpha-galactosidase 1, 2 and 3. The predominant isoform, alpha-gal 2, was probably a tetramer with a native molecular mass of about 170 kDa and 52 kDa-sized subunits and an estimated pI of 7.3. The subunit's N-terminal amino acid sequence shared high identity (97%) with the deduced sequence of a papaya cDNA clone encoding a putative alpha-galactosidase PAG2 as well as with an Ajuga reptans L. GGT1 clone encoding a galactan: galactan galactosyltransferase (66%). During ripening, alpha-galactosidase activity increased concomitantly with firmness loss and this increase was largely ascribed to alpha-gal 2. The protein level of alpha-gal 2 as estimated by immunoblot was low in developing fruits and generally increased with ripening. alpha-Galactosidase 2 also had the ability to markedly catalyse increased pectin solubility and depolymerisation while the polymers were still structurally attached to the cell walls mimicking, in part, the changes that occur during ripening. The close correlation between texture changes, alpha-gal 2 activity and protein levels as well as capability to modify intact cell walls suggest that the enzyme might contribute to papaya fruit softening during ripening. The purported mechanism of alpha-gal 2 action as a softening enzyme was discussed in terms of its functional capacity as a glycanase or perhaps, as a transglycosylase.

[Anderson-Fabry's disease: diagnostic problems, therapeutic relevance, and clinical experience in the treatment of the disease with enzyme replacement therapy in nephropathic patients]. / Malattia di Anderson-Fabry: problematiche diagnostiche, attualità terapeutiche ed esperienza clinica nel trattamento della malattia con terapia enzimatica sostitutiva in pazienti nefropatici.

Aim of this study was to confirm the initial results of a clinical trial on the treatment of Fabry's disease carried out in 13 Italian Nephrology Units. Fabry's disease is a rare, X-linked inherited disease, characterized by a-galactosidase (a-GAL) deficiency, a lysosomial enzymatic activity that results in the accumulation of neutral glycosphingolipids in the endothelial cells of the whole body, and causes painful crises, acroparesthesiae, angiokeratomas, corneal and lens dystrophy, and progressive damage to kidneys, heart and central nervous system, as well as potentially leading to death. The present availability of the recombinant form of a-GAL allows us to prevent or stop the long-term complications of this disease. A clinical trial, generously supported by Genzyme, was started on February 2001. In this trial 20 patients affected by Fabry's disease were periodically treated with agalsidase-beta, the commercial form of the enzyme. The initial results of the trial have indicated that the drug is capable of reducing both the number and intensity of painful crises, improving the patient's sensation of well-being, thus suggesting that this therapeutic approach might theoretically increase life expectancy in these patients.