Molecular defect of a phosphoglycerate kinase variant associated with haemolytic anaemia and neurological disorders in a large kindred

Recognition of a novel variant of phosphoglycerate kinase 1 deficiency PGK1 Galveston (c.472G > C) in a child with hemolytic anemia, neurologic dysfunction and myopathy

The enzyme phosphoglycerate kinase 1 (PGK1) catalyzes the first ATP producing reaction in the glycolysis pathway. Certain mutations to the coding gene of PGK1 present clinically with varying manifestations including hemolytic anemia, central nervous system (CNS) dysfunction and myopathy. Various PGK1 mutations have been described in the literature at the clinical and molecular level. Herein, we describe a novel case PGK1 mutation (PGK1 Galveston) in a 4-year-old boy who presented with all three manifestations. We discuss the characteristic hematopathology findings from this patient as well as provide a comparison with previously described neuroimaging findings. The variable clinical presentation of this condition along with its inherent uniqueness provide a diagnostic challenge for physicians. This presentation will add to the current body of knowledge for this condition and help guide future investigation and management.

A Mild Clinical Phenotype with Myopathic and Hemolytic Forms of Phosphoglycerate Kinase Deficiency (PGK Osaka): A Case Report and Literature Review

Phosphoglycerate kinase (PGK) deficiency is an X-linked disorder characterized by a combination of hemolytic anemia, myopathy, and brain involvement. We herein report a Japanese man who had several episodes of rhabdomyolysis but was training strenuously to be a professional boxer. Mild hemolytic anemia was noted. The enzymatic activity of PGK was significantly reduced, and a novel missense mutation, p.S62N, was identified in the PGK1 gene. A literature review revealed only one case with a mixed hemolytic and myopathic phenotype like ours. This mild phenotype indicates the complex pathophysiology of PGK deficiency and suggests the benefits of dietary control and exercise.

A Novel Missense Variant Associated with A Splicing Defect in A Myopathic Form of PGK1 Deficiency in The Spanish Population

Phosphoglycerate kinase (PGK)1 deficiency is an X-linked inherited disease associated with different clinical presentations, sometimes as myopathic affectation without hemolytic anemia. We present a 40-year-old male with a mild psychomotor delay and mild mental retardation, who developed progressive exercise intolerance, cramps and sporadic episodes of rhabdomyolysis but no hematological features. A genetic study was carried out by a next-generation sequencing (NGS) panel of 32 genes associated with inherited metabolic myopathies. We identified a missense variant in the PGK1 gene c.1114G > A (p.Gly372Ser) located in the last nucleotide of exon 9. cDNA studies demonstrated abnormalities in mRNA splicing because this change abolishes the exon 9 donor site. This novel variant is the first variant associated with a myopathic form of PGK1 deficiency in the Spanish population.

Identification of a novel variant in phosphoglycerate kinase-1 (PGK1) in an African-American child (PGK1 Detroit)

The human phosphoglycerate kinase-1 enzyme is the first of two energy generating steps in the glycolysis. Since its discovery in 1968, many pathologically mutated forms of PGK1 have been described. PGK1 is expressed in all tissues. The clinical manifestations of PGK1 deficiency are some combination of anemia, central nervous system and/or musculoskeletal manifestations. We describe a case of PGK1 in an African-American child, which to our knowledge, has never been described to date. The manifestations of PGK1-Detroit (c.1105A > C (p.Thr369Pro)) include hematologic and central nervous manifestations.

Slowly progressive leukodystrophy in an adolescent male with phosphoglycerate kinase deficiency

We report the case of an 18-year-old man with a phosphoglycerate kinase (PGK) deficiency who had slowly progressive leukodystrophy during adolescence. The patient had a history of severe neonatal jaundice, hemolytic crisis with rhabdomyolysis triggered by febrile viral infections, dysarthria, and intellectual disability during early childhood. Clumsiness in walking and writing became obvious at ∼10years of age. Evaluations performed by us on the 18-year-old patient confirmed the presence of pyramidal tract signs, increased muscle tone, and generalized dystonia. Brain magnetic resonance (MR) imaging revealed leukodystrophy in the periventricular white matter, posterior limbs of the internal capsule, dorsal pons, and middle cerebellar peduncles. Compared to MR images acquired at 9years of age, MR images acquired at 18years of age showed that the white matter atrophy had progressed. The PGK deficiency was diagnosed by identifying a known missense mutation in PGK1 (c.1060G>C) through comprehensive target capture sequencing and by observing low PGK activity in his red blood cells. The patient underwent a ketogenic diet for 2weeks, which we expected would increase adenosine triphosphate levels through sources other than the PGK-associated glycolytic pathway. The diet was not tolerated owing to the unexpected emergence of hemolysis. Hemolytic anemia, neurological dysfunction, and myopathy are often associated with PGK deficiencies. However, leukodystrophy as a symptom of PGK deficiency has not been reported previously. Our case highlights the progressive nature of the neurological complications related to PGK deficiencies. Therefore, long-term follow-up is recommended, even if neurological impairments are not obvious during childhood.

A novel PGK1 mutation associated with neurological dysfunction and the absence of episodes of hemolytic anemia or myoglobinuria

Phosphoglycerate kinase (PGK) deficiency affects three different organs: red blood cells (RBC), the central nervous system, and muscles. Next-generation sequencing identified a hemizygous PGK1 mutation (p.V217I) in a 16-year-old Japanese male patient presenting with intellectual disability and episodes of muscle weakness of unknown etiology. Enzymatic analysis demonstrated slightly lower RBC-PGK activity and compensatory increases of other glycolysis enzymes. This is the first PGK1 mutation found through next-generation sequencing.

A negative waveform in the scotopic response in a patient with phosphoglycerate kinase deficiency: a visual electrophysiology report

PURPOSE

Phosphoglycerate kinase (PGK) deficiency is an X-linked neurometabolic genetic disorder with variable systemic manifestations. So far, only one patient with retinal anomalies has been reported, but no visual electrophysiology findings were described. We report the first description of visual electrophysiology in a child with PGK deficiency. This provides further information for the site of involvement in the eye.

METHOD

A case history of a nine-year-old boy with PGK deficiency is reported.

RESULTS

This patient was diagnosed with PGK deficiency by screening soon after birth, as his mother was a known carrier of a PGK gene mutation. A bone marrow transplant was performed at the age of 9 months. He had two episodes of encephalopathy following the transplant but no acute episode of haemolysis. From the age of 6 years, his vision has been deteriorating. Visual electrophysiology results identified retinal involvement involving both rod and cone dysfunction. The visual evoked potential was normal.

CONCLUSIONS

Retinal dystrophy may be one of the clinical manifestations of phosphoglycerate kinase deficiency.

Insulin and mTOR Pathway Regulate HDAC3-Mediated Deacetylation and Activation of PGK1

Phosphoglycerate kinase 1 (PGK1) catalyzes the reversible transfer of a phosphoryl group from 1, 3-bisphosphoglycerate (1, 3-BPG) to ADP, producing 3-phosphoglycerate (3-PG) and ATP. PGK1 plays a key role in coordinating glycolytic energy production with one-carbon metabolism, serine biosynthesis, and cellular redox regulation. Here, we report that PGK1 is acetylated at lysine 220 (K220), which inhibits PGK1 activity by disrupting the binding with its substrate, ADP. We have identified KAT9 and HDAC3 as the potential acetyltransferase and deacetylase, respectively, for PGK1. Insulin promotes K220 deacetylation to stimulate PGK1 activity. We show that the PI3K/AKT/mTOR pathway regulates HDAC3 S424 phosphorylation, which promotes HDAC3-PGK1 interaction and PGK1 K220 deacetylation. Our study uncovers a previously unknown mechanism for the insulin and mTOR pathway in regulation of glycolytic ATP production and cellular redox potential via HDAC3-mediated PGK1 deacetylation.

Protein Stability, Folding and Misfolding in Human PGK1 Deficiency

Conformational diseases are often caused by mutations, altering protein folding and stability in vivo. We review here our recent work on the effects of mutations on the human phosphoglycerate kinase 1 (hPGK1), with a particular focus on thermodynamics and kinetics of protein folding and misfolding. Expression analyses and in vitro biophysical studies indicate that disease-causing mutations enhance protein aggregation propensity. We found a strong correlation among protein aggregation propensity, thermodynamic stability, cooperativity and dynamics. Comparison of folding and unfolding properties with previous reports in PGKs from other species suggests that hPGK1 is very sensitive to mutations leading to enhance protein aggregation through changes in protein folding cooperativity and the structure of the relevant denaturation transition state for aggregation. Overall, we provide a mechanistic framework for protein misfolding of hPGK1, which is insightful to develop new therapeutic strategies aimed to target native state stability and foldability in hPGK1 deficient patients.

Molecular insights on pathogenic effects of mutations causing phosphoglycerate kinase deficiency

Phosphoglycerate kinase (PGK) catalyzes an important ATP-generating step in glycolysis. PGK1 deficiency is an uncommon X-linked inherited disorder, generally characterized by various combinations of non-spherocytic hemolytic anemia, neurological dysfunctions, and myopathies. Patients rarely exhibit all three clinical features. To provide a molecular framework to the different pathological manifestations, all known mutations were reviewed and 16 mutant enzymes, obtained as recombinant forms, were functionally and structurally characterized. Most mutations heavily affect thermal stability and to a different extent catalytic efficiency, in line with the remarkably low PGK activity clinically observed in the patients. Mutations grossly impairing protein stability, but moderately affecting kinetic properties (p.I47N, p.L89P, p.C316R, p.S320N, and p.A354P) present the most homogeneous correlation with the clinical phenotype. Patients carrying these mutations display hemolytic anemia and neurological disorders, and,except for p.A354P variant, no myopaty. Variants highly perturbed in both catalytic efficiency (p.G158V, p.D164V, p.K191del, D285V, p.D315N, and p.T378P) and heat stability (all, but p.T378P) result to be mainly associated with myopathy alone. Finally, mutations faintly affecting molecular properties (p.R206P, p.E252A, p.I253T, p.V266M, and p.D268N) correlate with a wide spectrum of clinical symptoms. These are the first studies that correlate the clinical symptoms with the molecular properties of the mutant enzymes. All findings indicate that the different clinical manifestations associated with PGK1 deficiency chiefly depend on the distinctive type of perturbations caused by mutations in the PGK1 gene, highlighting the need for determination of the molecular properties of PGK variants to assist in prognosis and genetic counseling. However, the clinical symptoms can not be understood only on the bases of molecular properties of the mutant enzyme. Different (environmental, metabolic, genetic and/or epigenetic) intervening factors can contribute toward the expression of PGK deficient clinical phenotypes.

Enzymatic and metabolic characterization of the phosphoglycerate kinase deficiency associated with chronic hemolytic anemia caused by the PGK-Barcelona mutation

Recently, we reported a new mutation of phosphoglycerate kinase (PGK), called PGK-Barcelona, which causes chronic hemolytic anemia associated with progressive neurological impairment. We found a 140T→A substitution that produces an Ile46Asn change located at the N-domain of the enzyme and we suggested that the decrease of the PGK activity is probably related to a loss of enzyme stability. In this paper, by analyzing whole hemolysates and cloned enzymes, we show that both enzymes possess similar kinetic properties (although some differences are observed in the Km values) and the same electrophoretic mobility. However, PGK-Barcelona has higher thermal instability. Therefore, we confirm that the decrease of the red blood cell (RBC) PGK activity caused by the PGK-Barcelona mutation is more closely related to a loss of enzyme stability than to a decrease of enzyme catalytic function. Furthermore, we have measured the levels of glycolytic metabolites and adenine nucleotides in the RBC from controls and from the patient. The increase of 2,3-bisphosphoglycerate and the decrease of ATP RBC levels are the only detected metabolic changes that could cause hemolytic anemia.

Myopathy and parkinsonism in phosphoglycerate kinase deficiency

A 25-year-old man with exertional myoglobinuria had no evidence of hemolytic anemia, but he had severe parkinsonism that was responsive to levodopa. Phosphoglycerate kinase (PGK) activity was markedly decreased in muscle, and molecular analysis of the PGK1 gene identified the p.T378P mutation that was recently reported in a patient with isolated myopathy. This case reinforces the concept that PGK deficiency is a clinically heterogeneous disorder and raises the question of a relationship between PGK deficiency and idiopathic juvenile Parkinson disease.

Myopathic form of phosphoglycerate kinase (PGK) deficiency: a new case and pathogenic considerations

We describe an 18-year-old man with muscle cramps and recurrent exertional myoglobinuria, without hemolytic anemia or brain dysfunction. Phosphoglycerate kinase (PGK) deficiency was documented in muscle and erythrocytes and molecular analysis of the PGK1 gene identified a novel mutation, T378P. This is the ninth case presenting with isolated myopathy, whereas most other patients show hereditary non-spherocytic hemolytic anemia alone or associated with brain dysfunction, and a few patients have myopathy plus brain involvement. Although the diverse tissue involvement in PGK deficiency remains unclear, all mutations in myopathic patients tend to cluster in the C terminal domain, adjacent to the substrate-binding pocket. This may lead to a failure in the closure of the N terminal and C terminal domains and loss of stability due to lack of inter-domain communication during the catalytic process.

PGK deficiency

Phosphoglycerate kinase (PGK) deficiency is one of the relatively uncommon causes of hereditary non-spherocytic haemolytic anaemia (HNSHA). The gene encoding the erythrocyte enzyme PGK1, is X-linked. Mutations of this gene may cause chronic haemolysis with or without mental retardation and they may cause myopathies, often with episodes of myoglobinuria, or a combination of these clinical manifestations. Twenty-six families have been described and in 20 of these the mutations are known. The reason for different clinical manifestations of mutations of the same gene remains unknown.

Monoclonal anti-double-stranded DNA antibodies cross-react with phosphoglycerate kinase 1 and inhibit the expression and production of IL-2 in activated Jurkat T cell line

Anti-double strand DNA antibodies (anti-dsDNA) involve in lupus nephritis. However, their role in tissue damage mechanism remains unclear. In this study, a 45-kDa cognate antigen of anti-dsDNA monoclonal antibodies 9D7 was identified by two-dimensional gel electrophoresis and determined to be human phosphoglycerate kinase 1 (PGK-1) by MALDI-TOF analysis. The binding of 9D7 to PGK-1 was not affected by DNase I but was inhibited by thymus dsDNA. Human SLE sera with high anti-dsDNA titers had a high affinity with PGK. In activated Jurkat T cells, 9D7 decreased the PGK-1 mRNA production and IL-2 promoter activity. Reduction in IL-2 gene expression and protein production were observed in the 9D7-treated cells. Because PGK-1 deficiency may cause mental tardy and hemolytic anemia, interaction between anti-dsDNA and PGK-1 may be important in lupus pathogenesis. Moreover, reduction in IL-2 production by anti-dsDNA suggests their role in increasing infection rate and decreasing proper generation of activation-induced cell death.

The identification of a recurrent phosphoglycerate kinase mutation associated with chronic haemolytic anaemia and neurological dysfunction in a family from USA

Phosphoglycerate kinase (PGK) deficiency is a rare X-linked disease that is characterised by mild to severe haemolytic anaemia, rhabdomyolysis, and variable defects in the central nervous system. In a white American family, two sons presented with haemolytic anaemia, seizures, and developmental delay. The diagnosis of PGK deficiency was made based on the remarkably low (<5% of normal) erythrocyte PGK enzyme activity level and the identification of a missense (c. 491A --> T) PGK1 gene mutation. This mutation results in an Asp164Val amino acid substitution, which has previously been designated PGK-Amiens and PGK-New York. The two new patients have the full clinical syndrome of PGK deficiency including haemolytic anaemia, developmental delay and seizures, and in the proband, hemiplegic migraines, retinal dystrophy and muscle fatigue. The PGK-Amiens/New York mutation had previously been found in a French patient and also in a large Chinese-Australian kindred, indicating that either the c. 91A --> T mutation is a recurrent mutation or that there is shared ancestry between the patients that have been identified so far with the mutation. Haplotype analysis of the c. 91A --> T mutation indicated that this was a recurrent mutation.

Two new phosphoglycerate kinase mutations associated with chronic haemolytic anaemia and neurological dysfunction in two patients from Spain

We report two previously undescribed mutations of the phosphoglycerate kinase gene (PGK1) leading to enzyme deficiency. In both cases, the patients were of Spanish origin and they exhibited a severe life-long chronic haemolytic anaemia associated with progressive neurological impairment. Sequence analysis of the first patient's entire PGK1 gene found a novel missense mutation (140T > A). This mutation caused an amino acid change of Ile to Asn at 46th position from the NH(2)-terminal serine residue (Ile46Asn), which has been called PGK-Barcelona based on the place of origin of the patient. In the second patient, a G to A transversion was discovered at nucleotide 958 (958G > A). This caused a Ser319Asn amino acid substitution. Since this mutation had not been previously described, the provisional name of PGK-Murcia was given to this deficient enzyme. The crystal structure of porcine PGK was used as a molecular model to investigate how these mutations may affect enzyme structure and function. In both cases, the mutations did not modify any of the PGK binding sites for ATP or 3PG, so their consequence is related to a loss of enzyme stability rather than a decrease of enzyme catalytic function.

A novel missense mutation (1060G --> C) in the phosphoglycerate kinase gene in a Japanese boy with chronic haemolytic anaemia, developmental delay and rhabdomyolysis

We report the case of a 3-year-old Japanese boy with phosphoglycerate kinase 1 (PGK1) deficiency (Online Mendelian Inheritance in Man entry 311800). The patient had anaemia and jaundice at birth, necessitating exchange transfusions for 2 d. After one red blood cell transfusion at age 2 months, his Hb level was 8-9 g/dl, his reticulocyte counts were 300-500 x 109/l, and his total bilirubin level was 25.65-42.75 micro mol/l. The patient suffered two episodes of respiratory infection-associated haemolytic crisis and rhabdomyolysis during early infancy. At age 3.0 years, his developmental milestones (developmental quotients measured using the Tsumori-Inage methods) score was 49% (normal 74-131%), and his height was below average by -2.0 standard deviations. The diagnosis of PGK1 deficiency was made based on his remarkably low (< 10% of normal) erythrocyte PGK enzyme activity level and the identification of a novel missense (1060G-->C) PGK1 gene mutation. This mutation results in the Ala-353Pro amino acid substitution, which has been designated PGK Kyoto. The patient developed the full clinical symptoms of PGK1 deficiency including haemolytic anaemia, myopathy, central nervous system disorder and growth retardation, which is unusual.

A phosphoglycerate kinase mutant (PGK Herlev; D285V) in a Danish patient with isolated chronic hemolytic anemia: mechanism of mutation and structure-function relationships

Phosphoglycerate kinase (PGK) is a X-linked enzyme that plays a key role in the glycolytic pathway. Twelve different variants have already been reported. We describe a new PGK variant, PGK Herlev (Asp 285-->Val), in a 69-year-old Danish patient with isolated chronic hemolysis but who had no neurological or muscular disorders. The description of the mutation is based upon PCR amplification of specific regions of the PGK gene, followed by direct sequencing. Although observed in a male patient, this mutated X-linked gene is expressed partially, i.e., both normal and substituted nucleotides are present at the same position in a ratio of approximately 1:9. The most likely explanation for this observation is based on the occurrence of a somatic mutation of the PGK gene. The relationship of structure to function in PGK Herlev, as well as in all known variants, was examined by the use of a computer model based on the known spatial structure of the yeast and horse enzymes. Such an approach can be generalized to any other protein that has been crystallized and for which x-ray diffraction data are available in a species closely related to man.

Other erythrocyte enzyme deficiencies associated with non-haematological symptoms: phosphoglycerate kinase and phosphofructokinase deficiency

Phosphoglycerate kinase (PGK) deficiency is associated with hereditary haemolytic anaemia and often with central nervous system dysfunction and/or myopathy. Twenty-three families have been discovered with this condition. Nine have manifested both symptoms, six only haemolysis, and seven central nervous system dysfunction and/or myopathy without haemolysis; one case is asymptomatic. Among them, the structural abnormalities of 14 mutants, including 11 missense mutations, 1 gene deletion, 1 gene insertion, and 1 splicing mutation, have been identified. The correlation between the phenotypic and structural differences in PGK deficiency remains to be defined. Splenectomy obviates transfusion in most patients but does not correct the haemolytic disorder. Phosphofructokinase (PFK) deficiency is associated with myopathy and/or haemolysis. More than half reported had the typical features of glycogen storage disease type VII (Tarui disease). The other cases exhibited myopathy alone, haemolytic anaemia alone, or no clinical symptom at all. Eight missense, 1 nonsense, 1 frameshift and 5 splicing mutations have been determined in the PFK-M gene. In classic PFK-M deficiency, the avoidance of undue exertion is the key to prevent muscle symptoms.

Red blood cell enzymes and their clinical application

Red blood cell enzyme activities are measured mainly to diagnose hereditary nonspherocytic hemolytic anemia associated with enzyme anomalies. At least 15 enzyme anomalies associated with hereditary hemolytic anemia have been reported. Some nonhematologic disease can also be diagnosed by the measurement of red blood cell enzyme activities in the case in which enzymes of red blood cells and the other organs are under the same genetic control. Progress in molecular biology has provided a new perspective. Techniques such as the polymerase chain reaction and single-strand conformation polymorphism analysis have greatly facilitated the molecular analysis of erythroenzymopathies. These studies have clarified the correlation between the functional and structural abnormalities of the variant enzymes. In general, the mutations that induce an alteration of substrate binding site and/or enzyme instability might result in markedly altered enzyme properties and severe clinical symptoms.

A phosphoglycerate kinase mutant (PGK Herlev; D285V) in a Danish patient with isolated chronic hemolytic anemia: mechanism of mutation and structure-function relationships

Phosphoglycerate kinase (PGK) is a X-linked enzyme that plays a key role in the glycolytic pathway. Twelve different variants have already been reported. We describe a new PGK variant, PGK Herlev (Asp 285-->Val), in a 69-year-old Danish patient with isolated chronic hemolysis but who had no neurological or muscular disorders. The description of the mutation is based upon PCR amplification of specific regions of the PGK gene, followed by direct sequencing. Although observed in a male patient, this mutated X-linked gene is expressed partially, i.e., both normal and substituted nucleotides are present at the same position in a ratio of approximately 1:9. The most likely explanation for this observation is based on the occurrence of a somatic mutation of the PGK gene. The relationship of structure to function in PGK Herlev, as well as in all known variants, was examined by the use of a computer model based on the known spatial structure of the yeast and horse enzymes. Such an approach can be generalized to any other protein that has been crystallized and for which x-ray diffraction data are available in a species closely related to man.