Arginine Functionally Improves Clinically Relevant Human Galactose-1-Phosphate Uridylyltransferase (GALT) Variants Expressed in a Prokaryotic Model

Coelho, Ana Daniela; Trabuco, Matilde Cardoso; Silva, Maria João; Almeida, Isabel Tavares de; Leandro, Paula; Rivera, Isabel; Vicente, João B.

doi:10.1007/8904_2015_420

Cited by 19 publications

(18 citation statements)

References 20 publications

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“…These findings contradict the previous study on the prokaryotic model of galactosemia, in which arginine supplementation to the medium in a concentration of 25 mM partially rescued the bacterial culture expressing human GALT p.Q188R [ 13 ]. These discrepancies might stem from the high arginine concentration used in the prokaryotic model.…”

Section: Discussioncontrasting

confidence: 99%

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Arginine does not rescue p.Q188R mutation deleterious effect in classic galactosemia

Haskovic

Derks

Ploeg

et al. 2018

Orphanet J Rare Dis

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BackgroundClassic galactosemia is a rare genetic metabolic disease with an unmet treatment need. Current standard of care fails to prevent chronically-debilitating brain and gonadal complications.Many mutations in the GALT gene responsible for classic galactosemia have been described to give rise to variants with conformational abnormalities. This pathogenic mechanism is highly amenable to a therapeutic strategy based on chemical/pharmacological chaperones. Arginine, a chemical chaperone, has shown beneficial effect in other inherited metabolic disorders, as well as in a prokaryotic model of classic galactosemia.The p.Q188R mutation presents a high prevalence in the Caucasian population, making it a very clinically relevant mutation. This mutation gives rise to a protein with lower conformational stability and lower catalytic activity. The aim of this study is to assess the potential therapeutic role of arginine for this mutation.MethodsArginine aspartate administration to four patients with the p.Q188R/p.Q188R mutation, in vitro studies with three fibroblast cell lines derived from classic galactosemia patients as well as recombinant protein experiments were used to evaluate the effect of arginine in galactose metabolism. This study has been registered at https://clinicaltrials.gov (NCT03580122) on 09 July 2018. Retrospectively registered.ResultsFollowing a month of arginine administration, patients did not show a significant improvement of whole-body galactose oxidative capacity (p = 0.22), erythrocyte GALT activity (p = 0.87), urinary galactose (p = 0.52) and urinary galactitol levels (p = 0.41). Patients’ fibroblasts exposed to arginine did not show changes in GALT activity. Thermal shift analysis of recombinant p.Q188R GALT protein in the presence of arginine did not exhibit a positive effect.ConclusionsThis short pilot study in four patients homozygous for the p.Q188R/p.Q188R mutation reveals that arginine has no potential therapeutic role for galactosemia patients homozygous for the p.Q188R mutation.Electronic supplementary materialThe online version of this article (10.1186/s13023-018-0954-8) contains supplementary material, which is available to authorized users.

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Section: Discussioncontrasting

confidence: 99%

“…In vitro studies using a prokaryotic model of classic galactosemia revealed that arginine might be of potential value for a number of clinically-relevant mutations, including p.Q188R [ 13 ].…”

Section: Introductionmentioning

confidence: 99%

Arginine does not rescue p.Q188R mutation deleterious effect in classic galactosemia

Haskovic

Derks

Ploeg

et al. 2018

Orphanet J Rare Dis

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“…The latter is the more economical option based on the experience of lysosomal storage disorders (52). In support of a chaperone approach, the chemical chaperone arginine has been reported to rescue bacteria expressing the p.Gln188Arg and p.Lys285Asn variants (53). For hGALT-specific pharmacological chaperones, the dimer interface on opposite face of the active sites (40) or the divalent metal binding sites are potential pockets to be targeted for small molecule design and screening, akin to the efforts in amyotrophic lateral sclerosis (54) and transthyretin amyloidoses (55).…”

Section: Discussionmentioning

confidence: 99%

Molecular basis of classic galactosemia from the structure of human galactose 1-phosphate uridylyltransferase

et al. 2016

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Classic galactosemia is a potentially lethal disease caused by the dysfunction of galactose 1-phosphate uridylyltransferase (GALT). Over 300 disease-associated GALT mutations have been reported, with the majority being missense changes, although a better understanding of their underlying molecular effects has been hindered by the lack of structural information for the human enzyme. Here, we present the 1.9 Å resolution crystal structure of human GALT (hGALT) ternary complex, revealing a homodimer arrangement that contains a covalent uridylylated intermediate and glucose-1-phosphate in the active site, as well as a structural zinc-binding site, per monomer. hGALT reveals significant structural differences from bacterial GALT homologues in metal ligation and dimer interactions, and therefore is a zbetter model for understanding the molecular consequences of disease mutations. Both uridylylation and zinc binding influence the stability and aggregation tendency of hGALT. This has implications for disease-associated variants where p.Gln188Arg, the most commonly detected, increases the rate of aggregation in the absence of zinc likely due to its reduced ability to form the uridylylated intermediate. As such our structure serves as a template in the future design of pharmacological chaperone therapies and opens new concepts about the roles of metal binding and activity in protein misfolding by disease-associated mutants.

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“…Because the long-term complications of CG have not been effectively prevented, despite dietary treatment, a number of experimental studies have been conducted on the development of different treatment strategies, and some studies are still ongoing. In these studies, galactokinase inhibitors that reduce precursor production, 16 manganese-containing porphyrin compounds 17 and purple sweet potato color 18 that act as antioxidants, and arginine as a stabilizer 19 have been used, but the results should be interpreted with caution, especially given the clinical setting. A study designed to enhance residual enzyme activity showed that GALT enzyme activity was significantly increased after intraperitoneal folic acid treatment compared with the control group.…”

Section: Discussionmentioning

confidence: 99%

Folate deficiency in patients with classical galactosemia: A novel finding that needs to be considered for dietary treatments

et al. 2018

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FT. Folate deficiency in patients with classical galactosemia: A novel finding that needs to be considered for dietary treatments. Turk J Pediatr 2018; 60: 540-546. The objectives of the study were to assess folate deficiency in patients with classic galactosemia, and to determine whether folic acid supplementation has an effect on galactose-1-phosphate uridyltransferase enzyme activity. Sixty-one newborn infants diagnosed with classic galactosemia between 2010 and 2017 were retrospectively evaluated. Within this group, 48 patients with Q188R homozygous mutation alone were enrolled into the study. Serum folate concentration was studied using chemiluminescence; and in folate deficient patients, galactose-1-phosphate uridyltransferase measurements before and after folic acid supplementation (100 mg/day folic acid for 30 days) were performed using an enzymatic calorimetric measurement technique based on kinetics. The serum folate level was low (<4 ng/ml) in 12 patients (25%). The galactose-1-phosphate uridyltransferase enzyme activity after folic acid supplementation was significantly higher than the values before folic acid supplementation (1.00±0.19 U/g Hb vs. 0.74±0.23 U/g Hb, p<0.05); but was still less than the normal levels. Folate deficiency, most likely due to poor dietary intake, may develop in pediatric patients with classical galactosemia, and folic acid should be supplemented. Folic acid supplementation appears to have a low, but statistically significant, effect on galactose-1-phosphate uridyltransferase enzyme activity, but comprehensive research is needed to clarify whether there is any clinical significance.

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Arginine Functionally Improves Clinically Relevant Human Galactose-1-Phosphate Uridylyltransferase (GALT) Variants Expressed in a Prokaryotic Model

Cited by 19 publications

References 20 publications

Arginine does not rescue p.Q188R mutation deleterious effect in classic galactosemia

Arginine does not rescue p.Q188R mutation deleterious effect in classic galactosemia

Molecular basis of classic galactosemia from the structure of human galactose 1-phosphate uridylyltransferase

Folate deficiency in patients with classical galactosemia: A novel finding that needs to be considered for dietary treatments

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