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Plasma mutant α -galactosidase A protein and globotriaosylsphingosine level in Fabry disease

View Article: PubMed Central - PubMed

ABSTRACT

Fabry disease is an X-linked genetic disorder characterized by deficient activity of α-galactosidase A (GLA) and accumulation of glycolipids, and various GLA gene mutations lead to a wide range of clinical phenotypes from the classic form to the later-onset one. To investigate the biochemical heterogeneity and elucidate the basis of the disease using available clinical samples, we measured GLA activity, GLA protein and accumulated globotriaosylsphingosine (Lyso-Gb3), a biomarker of this disease, in plasma samples from Fabry patients. The analysis revealed that both the enzyme activity and the protein level were apparently decreased, and the enzyme activity was well correlated with the protein level in many Fabry patients. In these cases, a defect of biosynthesis or excessive degradation of mutant GLAs should be involved in the pathogenesis, and the residual protein level would determine the accumulation of Lyso-Gb3 and the severity of the disease. However, there are some exceptional cases, i.e., ones harboring p.C142Y, p.R112H and p.M296I, who exhibit a considerable amount of GLA protein. Especially, a subset of Fabry patients with p.R112H or p.M296I has been attracted interest because the patients exhibit almost normal plasma Lyso-Gb3 concentration. Structural analysis revealed that C142Y causes a structural change at the entrance of the active site. It will lead to a complete enzyme activity deficiency, resulting in a high level of plasma Lyso-Gb3 and the classic Fabry disease. On the other hand, it is thought that R112H causes a relatively large structural change on the molecular surface, and M296I a small one in a restricted region from the core to the surface, both the structural changes being far from the active site. These changes will cause not only partial degradation but also degeneration of the mutant GLA proteins, and the degenerated enzymes exhibiting small and residual activity remain and probably facilitate degradation of Lyso-Gb3 in plasma, leading to the later-onset phenotype. The results of this comprehensive analysis will be useful for elucidation of the basis of Fabry disease.

No MeSH data available.


Coloring of the atoms in the three-dimensional structure of GLA influenced by amino acid substitutions. (A) C142Y, (B) R112H, and (C) M296I. The backbone of GLA is represented as a ribbon model, and the distribution of the influenced atoms in each mutant GLA is shown. The influenced atoms are indicated as small spheres and their colors show the distances between the mutant and wild type ones, as follows: blue < 0.15 Å, 0.15 Å ≤ cyan < 0.30 Å, 0.30 Å ≤ green < 0.45 Å, 0.45 Å ≤ yellow < 0.60 Å, 0.60 Å ≤ orange < 0.75 Å, and red ≥ 0.75 Å. The substituted residues and catalytic residues are presented as a CPK model and blue spheres, respectively.
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f0020: Coloring of the atoms in the three-dimensional structure of GLA influenced by amino acid substitutions. (A) C142Y, (B) R112H, and (C) M296I. The backbone of GLA is represented as a ribbon model, and the distribution of the influenced atoms in each mutant GLA is shown. The influenced atoms are indicated as small spheres and their colors show the distances between the mutant and wild type ones, as follows: blue < 0.15 Å, 0.15 Å ≤ cyan < 0.30 Å, 0.30 Å ≤ green < 0.45 Å, 0.45 Å ≤ yellow < 0.60 Å, 0.60 Å ≤ orange < 0.75 Å, and red ≥ 0.75 Å. The substituted residues and catalytic residues are presented as a CPK model and blue spheres, respectively.

Mentions: Structural analysis was performed for the mutant GLAs in cases exhibiting a considerable plasma GLA protein level (i.e., those with C142Y, R112H, and M296I), and the results of coloring of the affected atoms in the mutant GLAs with these amino acid substitutions are shown in Fig. 4.


Plasma mutant α -galactosidase A protein and globotriaosylsphingosine level in Fabry disease
Coloring of the atoms in the three-dimensional structure of GLA influenced by amino acid substitutions. (A) C142Y, (B) R112H, and (C) M296I. The backbone of GLA is represented as a ribbon model, and the distribution of the influenced atoms in each mutant GLA is shown. The influenced atoms are indicated as small spheres and their colors show the distances between the mutant and wild type ones, as follows: blue < 0.15 Å, 0.15 Å ≤ cyan < 0.30 Å, 0.30 Å ≤ green < 0.45 Å, 0.45 Å ≤ yellow < 0.60 Å, 0.60 Å ≤ orange < 0.75 Å, and red ≥ 0.75 Å. The substituted residues and catalytic residues are presented as a CPK model and blue spheres, respectively.
© Copyright Policy - CC BY-NC-ND
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5121323&req=5

f0020: Coloring of the atoms in the three-dimensional structure of GLA influenced by amino acid substitutions. (A) C142Y, (B) R112H, and (C) M296I. The backbone of GLA is represented as a ribbon model, and the distribution of the influenced atoms in each mutant GLA is shown. The influenced atoms are indicated as small spheres and their colors show the distances between the mutant and wild type ones, as follows: blue < 0.15 Å, 0.15 Å ≤ cyan < 0.30 Å, 0.30 Å ≤ green < 0.45 Å, 0.45 Å ≤ yellow < 0.60 Å, 0.60 Å ≤ orange < 0.75 Å, and red ≥ 0.75 Å. The substituted residues and catalytic residues are presented as a CPK model and blue spheres, respectively.
Mentions: Structural analysis was performed for the mutant GLAs in cases exhibiting a considerable plasma GLA protein level (i.e., those with C142Y, R112H, and M296I), and the results of coloring of the affected atoms in the mutant GLAs with these amino acid substitutions are shown in Fig. 4.

View Article: PubMed Central - PubMed

ABSTRACT

Fabry disease is an X-linked genetic disorder characterized by deficient activity of &alpha;-galactosidase A (GLA) and accumulation of glycolipids, and various GLA gene mutations lead to a wide range of clinical phenotypes from the classic form to the later-onset one. To investigate the biochemical heterogeneity and elucidate the basis of the disease using available clinical samples, we measured GLA activity, GLA protein and accumulated globotriaosylsphingosine (Lyso-Gb3), a biomarker of this disease, in plasma samples from Fabry patients. The analysis revealed that both the enzyme activity and the protein level were apparently decreased, and the enzyme activity was well correlated with the protein level in many Fabry patients. In these cases, a defect of biosynthesis or excessive degradation of mutant GLAs should be involved in the pathogenesis, and the residual protein level would determine the accumulation of Lyso-Gb3 and the severity of the disease. However, there are some exceptional cases, i.e., ones harboring p.C142Y, p.R112H and p.M296I, who exhibit a considerable amount of GLA protein. Especially, a subset of Fabry patients with p.R112H or p.M296I has been attracted interest because the patients exhibit almost normal plasma Lyso-Gb3 concentration. Structural analysis revealed that C142Y causes a structural change at the entrance of the active site. It will lead to a complete enzyme activity deficiency, resulting in a high level of plasma Lyso-Gb3 and the classic Fabry disease. On the other hand, it is thought that R112H causes a relatively large structural change on the molecular surface, and M296I a small one in a restricted region from the core to the surface, both the structural changes being far from the active site. These changes will cause not only partial degradation but also degeneration of the mutant GLA proteins, and the degenerated enzymes exhibiting small and residual activity remain and probably facilitate degradation of Lyso-Gb3 in plasma, leading to the later-onset phenotype. The results of this comprehensive analysis will be useful for elucidation of the basis of Fabry disease.

No MeSH data available.