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Sarkissian CN, Scriver PP, Prevost L, Levy HL. Charles Scriver: Epitome of the physician scientist. Mol Genet Metab 2022; 137:388-398. [PMID: 36503822 DOI: 10.1016/j.ymgme.2022.11.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/10/2022] [Revised: 10/31/2022] [Accepted: 11/01/2022] [Indexed: 11/06/2022]
Abstract
Charles Scriver is a towering figure in the medical genetics community. At 92 he can look back upon a remarkable career that established the field of biochemical genetics, a subsection of medical genetics that is translating the developments in basic genetics into the diagnoses and treatments of inherited biochemical diseases. This biographical sketch summarizes the key achievements of Dr. Scriver in research and medicine, integrating the different components of medical genetics into comprehensive provincial programs, teaching a generation of physicians and researchers, and developing worldwide collaborations. Charles has been a mighty figure in so many ways. He began his career by bringing amino acid chromatography from London to North America, thereby greatly enlarging the scope of metabolic disorders. Subsequently, his editorship of the classic Metabolic and Molecular Bases of Inherited Disease brought metabolism into genetics and established the field of biochemical genetics. He discovered a number of new diseases and was the first to recognize shared mediated amino acid transporters in the kidney, a medical breakthrough that has become a basic concept of amino acid homeostasis. He led the formation of the Quebec Network of Genetic Medicine, incorporating screening, diagnosis, counseling, treatment and research of genetic diseases, which to this day serves as a model for collaborative and comprehensive medical genetic programs internationally. He initiated the development of sapropterin (Kuvan®), the first non-dietary treatment for phenylketonuria (PKU) and helped identify the mechanism of this cofactor's action on phenylalanine hydroxylase in variants of PKU. His laboratory also led the development of phenylalanine ammonia lyase (Palynziq®), an enzyme substitution therapy that now serves as an alternative to dietary treatment for PKU. The ecosystem that Charles generated at the deBelle laboratory was collegial and highly fruitful. With the input and support of his remarkable wife Zipper, he found a way to integrate the concept of family into his work environment. Bustling with an endless series of evolving activities, he generated an inclusive setting which drew on the talents of brilliant clinical and research staff, as well as the input of patients and their families. In all these efforts, Charles managed to answer his own musings summarized in the following three questions: Who do we serve? How do we serve? Why do we serve? Charles Scriver's life is one well lived. An extraordinary physician scientist whose accomplishments are cause for pause and wonder; generating volumes of contribution which will forever seem impossible for one individual to deliver.
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Affiliation(s)
| | | | - Lynne Prevost
- Department of Biochemical Genetics, Montreal Children's Hospital, Montreal, Quebec, Canada.
| | - Harvey L Levy
- Division of Genetics and Genomics, Boston Children's Hospital, Department of Pediatrics Harvard Medical School, Boston, MA, USA.
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Effect of disease-linked mutations on the structure, function, stability and aggregation of human carbonic anhydrase II. Int J Biol Macromol 2020; 143:472-482. [DOI: 10.1016/j.ijbiomac.2019.11.012] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2019] [Revised: 10/29/2019] [Accepted: 11/04/2019] [Indexed: 11/15/2022]
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Jung-Kc K, Himmelreich N, Prestegård KS, Shi TJS, Scherer T, Ying M, Jorge-Finnigan A, Thöny B, Blau N, Martinez A. Phenylalanine hydroxylase variants interact with the co-chaperone DNAJC12. Hum Mutat 2019; 40:483-494. [PMID: 30667134 DOI: 10.1002/humu.23712] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2018] [Revised: 01/12/2019] [Accepted: 01/19/2019] [Indexed: 12/13/2022]
Abstract
DNAJC12, a type III member of the HSP40/DNAJ family, has been identified as the specific co-chaperone of phenylalanine hydroxylase (PAH) and the other aromatic amino acid hydroxylases. DNAJ proteins work together with molecular chaperones of the HSP70 family to assist in proper folding and maintenance of intracellular stability of their clients. Autosomal recessive mutations in DNAJC12 were found to reduce PAH levels, leading to hyperphenylalaninemia (HPA) in patients without mutations in PAH. In this work, we investigated the interaction of normal wild-type DNAJC12 with mutant PAH in cells expressing several PAH variants associated with HPA in humans, as well as in the Enu1/1 mouse model, homozygous for the V106A-Pah variant, which leads to severe protein instability, accelerated PAH degradation and mild HPA. We found that mutant PAH exhibits increased ubiquitination, instability, and aggregation compared with normal PAH. In mouse liver lysates, we showed that DNAJC12 interacts with monoubiquitin-tagged PAH. This form represented a major fraction of PAH in the Enu1/1 but was also present in liver of wild-type PAH mice. Our results support a role of DNAJC12 in the processing of misfolded ubiquitinated PAH by the ubiquitin-dependent proteasome/autophagy systems and add to the evidence that the DNAJ proteins are important players both for proper folding and degradation of their clients.
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Affiliation(s)
- Kunwar Jung-Kc
- Department of Biomedicine, University of Bergen, Bergen, Norway
| | | | | | | | - Tanja Scherer
- Division of Metabolism, University Children's Hospital Zürich, Zürich, Switzerland
| | - Ming Ying
- Department of Biomedicine, University of Bergen, Bergen, Norway
| | | | - Beat Thöny
- Division of Metabolism, University Children's Hospital Zürich, Zürich, Switzerland
| | - Nenad Blau
- Dietmar-Hopp-Metabolic Center, University Children's Hospital, Heidelberg, Germany.,Division of Metabolism, University Children's Hospital Zürich, Zürich, Switzerland
| | - Aurora Martinez
- Department of Biomedicine, University of Bergen, Bergen, Norway
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Zhang Y, Yuan XM, Wang YF, Jiang MM, Bi YN, Liu Y, Pu WL, Song L, Huang JY, Sun LK, Zhou ZX, Zhou K. Isopsoralen induces different subchronic toxicities and metabolomic outcomes between male and female Wistar rats. Regul Toxicol Pharmacol 2019; 103:1-9. [PMID: 30634019 DOI: 10.1016/j.yrtph.2019.01.010] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2017] [Revised: 10/19/2018] [Accepted: 01/02/2019] [Indexed: 10/27/2022]
Abstract
Isopsoralen is a major active and quality-control component of Fructus Psoraleae, but lacks a full safety evaluation. We evaluated the oral toxicity of isopsoralen in Wistar rats treated for 3 months at doses of 0, 3.5, 7.0, and 14 mg/kg. Additionally, the plasma metabolomics of isopsoralen in male and female rats treated for 3 months at doses of 0 and 14 mg/kg were investigated by gas chromatography-mass spectrometry. Many abnormalities were observed in the isopsoralen-treated rats, including suppression of body weight gain, and changes in serum biochemical parameters and visceral coefficients. Histopathological changes in liver, pancreatic, and reproductive system tissues were also observed in the isopsoralen-treated rats. The metabolomic analyses showed alterations in many metabolites (19 in female rats; 28 in male rats) after isopsoralen administration. The significant changes in these metabolites revealed metabolomic alterations in the isopsoralen-treated rats, especially in amino acid metabolism regardless of sex, including phenylalanine, tyrosine, and tryptophan biosynthesis and glycine, serine, and threonine metabolism. Furthermore, fatty acid metabolism comprised the main affected pathways in female rats, while lipid metabolism and energy metabolism were the main affected pathways in male rats.
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Affiliation(s)
- Yue Zhang
- Institute of Traditional Chinese Medicine, Tianjin University of Traditional Chinese Medicine, Tianjin, 300193, China; Tianjin State Key Laboratory of Modern Chinese Medicine, Tianjin, 300193, China; Ministry of Education Key Laboratory of Traditional Chinese Medical Formulae, Tianjin University of Traditional Chinese Medicine, Tianjin, 300193, China
| | - Xiao-Mei Yuan
- Institute of Traditional Chinese Medicine, Tianjin University of Traditional Chinese Medicine, Tianjin, 300193, China
| | - Yue-Fei Wang
- Institute of Traditional Chinese Medicine, Tianjin University of Traditional Chinese Medicine, Tianjin, 300193, China; Tianjin State Key Laboratory of Modern Chinese Medicine, Tianjin, 300193, China
| | - Miao-Miao Jiang
- Institute of Traditional Chinese Medicine, Tianjin University of Traditional Chinese Medicine, Tianjin, 300193, China; Tianjin State Key Laboratory of Modern Chinese Medicine, Tianjin, 300193, China
| | - Ya-Nan Bi
- Institute of Traditional Chinese Medicine, Tianjin University of Traditional Chinese Medicine, Tianjin, 300193, China
| | - Ying Liu
- College of Veterinary Medicine, Inner Mongolia Agricultural University, Hohhot, 010018, China
| | - Wei-Ling Pu
- Institute of Traditional Chinese Medicine, Tianjin University of Traditional Chinese Medicine, Tianjin, 300193, China
| | - Lei Song
- Institute of Traditional Chinese Medicine, Tianjin University of Traditional Chinese Medicine, Tianjin, 300193, China; Ministry of Education Key Laboratory of Traditional Chinese Medical Formulae, Tianjin University of Traditional Chinese Medicine, Tianjin, 300193, China
| | - Ju-Yang Huang
- Institute of Traditional Chinese Medicine, Tianjin University of Traditional Chinese Medicine, Tianjin, 300193, China; Ministry of Education Key Laboratory of Traditional Chinese Medical Formulae, Tianjin University of Traditional Chinese Medicine, Tianjin, 300193, China
| | - Li-Kang Sun
- Institute of Traditional Chinese Medicine, Tianjin University of Traditional Chinese Medicine, Tianjin, 300193, China; Tianjin State Key Laboratory of Modern Chinese Medicine, Tianjin, 300193, China
| | - Zhi-Xing Zhou
- Tianjin Institute of Pharmaceutical Research, Tianjin, 300193, China
| | - Kun Zhou
- Institute of Traditional Chinese Medicine, Tianjin University of Traditional Chinese Medicine, Tianjin, 300193, China; Tianjin State Key Laboratory of Modern Chinese Medicine, Tianjin, 300193, China; Ministry of Education Key Laboratory of Traditional Chinese Medical Formulae, Tianjin University of Traditional Chinese Medicine, Tianjin, 300193, China.
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Himmelreich N, Shen N, Okun JG, Thiel C, Hoffmann GF, Blau N. Relationship between genotype, phenylalanine hydroxylase expression and in vitro activity and metabolic phenotype in phenylketonuria. Mol Genet Metab 2018; 125:86-95. [PMID: 30037505 DOI: 10.1016/j.ymgme.2018.06.011] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/25/2018] [Revised: 06/21/2018] [Accepted: 06/22/2018] [Indexed: 01/22/2023]
Abstract
Residual phenylalanine hydroxylase (PAH) activity is the main determinant of the metabolic phenotype in phenylketonuria (PKU). The genotypic heterogeneity of PKU, involving >1000 PAH variants and over 2500 different genotypes, makes genotype-based phenotype prediction challenging. While a relationship between PAH variants and the metabolic phenotype is well established, we questioned the importance of PAH expression and residual in vitro activity for the metabolic phenotype. Thirty-four PAH variants (p.F39 L, p.A47V, p.D59Y, p.I65S, p.R68G, p.R68S, p.E76G, p.A104D, p.D143G, p.R155H, p.R176L, p.V190A, p.G218 V, p.R241C, p.R243Q, p.P244L, p.R252W, p.R261Q, p.E280K, p.R297H, p.A300S, p.I306V, p.A309V, p.L311P, p.A313T, p.L348 V, p.V388 M, A403V, p.R408Q, p.R408W, p.R413P, p.D415N, p.Y417H, and p.A434D) were transiently transfected into COS-7 cells, and expression of PAH was investigated. Expression patterns were compared with in vitro PAH activity and allelic phenotype values (APVs). In vitro PAH activity was significantly higher (p < .01) in variants associated with mild hyperphenylalaninemia (PAH activity = 52.1 ± 8.5%; APV = 6.7-10.0) than that in classic PKU variants (PAH activity = 21.1 ± 7.0%; APV = 0-2.7). Mild PKU variants (PAH activity = 40.2 ± 7.6%; APV = 2.8-6.6) were not significantly different from mild hyperphenylalaninemia, but there was a difference (p < .048) compared with classic PKU phenotypes.
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Affiliation(s)
- Nastassja Himmelreich
- Center for Child and Adolescent Medicine, and Dietmar-Hopp Metabolic Center, University of Heidelberg, Heidelberg, Germany
| | - Nan Shen
- Center for Child and Adolescent Medicine, and Dietmar-Hopp Metabolic Center, University of Heidelberg, Heidelberg, Germany; Department of Rehabilitation Medicine, Xin Hua Hospital affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Jürgen G Okun
- Center for Child and Adolescent Medicine, and Dietmar-Hopp Metabolic Center, University of Heidelberg, Heidelberg, Germany
| | - Christian Thiel
- Center for Child and Adolescent Medicine, and Dietmar-Hopp Metabolic Center, University of Heidelberg, Heidelberg, Germany
| | - Georg F Hoffmann
- Center for Child and Adolescent Medicine, and Dietmar-Hopp Metabolic Center, University of Heidelberg, Heidelberg, Germany
| | - Nenad Blau
- Center for Child and Adolescent Medicine, and Dietmar-Hopp Metabolic Center, University of Heidelberg, Heidelberg, Germany.
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Li N, He C, Li J, Tao J, Liu Z, Zhang C, Yuan Y, Jiang H, Zhu J, Deng Y, Guo Y, Li Q, Yu P, Wang Y. Analysis of the genotype-phenotype correlation in patients with phenylketonuria in mainland China. Sci Rep 2018; 8:11251. [PMID: 30050108 PMCID: PMC6062512 DOI: 10.1038/s41598-018-29640-y] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2018] [Accepted: 07/13/2018] [Indexed: 11/22/2022] Open
Abstract
Mutations in the gene encoding phenylalanine hydroxylase (PAH) are associated with various degrees of phenylketonuria (PKU). The aim of our study was to define the genotype-phenotype correlations of mutations in the PAH gene that cause phenylketonuria (PKU) among the Chinese mainland population. Mutations in the PAH gene were analysed by next-generation sequencing, and a genotype-phenotype correlation analysis was performed in 1079 patients. Fifteen “null + null” genotypes, including four homoallelic and eleven heteroallelic genotypes, were clearly associated with classic PKU. Five functionally hemizygous (p.E280K, p.R252Q, p.E56D, p.S310F and p.T372R) and four compound heterozygous (p.T278I/p.S359L, p.R408W/p.R243Q, p.F161S/p.R243Q and p.F161S/p.R413P) genotypes were clearly associated with classic PKU. Ten functionally hemizygous genotypes, p.G257V, p.R158W, p.L255S, p.G247V, p.F161S, p.R158Q, p.V388M, p.I65T, p.I324N and p.R400K, were frequently associated with classic PKU. Three functionally hemizygous genotypes, p.P147L, p.I95del and p.F331S, and four compound heterozygous genotypes, p.G257V/p.R408Q, p.A434D/p.R413P, p.R243Q/p.A47E and p.R241C/p.G239D, were consistently correlated with mild PKU. Three functionally hemizygous genotypes, p.H107R, p.Q419R and p.F392I, and nine compound heterozygous genotypes (p.G312V/p.R241C, p.R243Q/p.V230I, p.R243Q/p.A403V, p.R243Q/p.Q419R, p.R243Q/p.R53H, p.R243Q/p.H107R, p.R241C/p.R408Q, p.R241C/p.H220P and p.R53H/p.R400K) were consistent with mild hyperphenylalaninaemia (MHP). Our study provides further support for the hypothesis that the PAH genotype is the main factor that determines the phenotype of PKU.
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Affiliation(s)
- Nana Li
- National Center for Birth Defect Monitoring, West China Second University Hospital, Sichuan University, Chengdu, China.,Key Laboratory of Birth Defects and Related Diseases of Women and Children (Sichuan University), Ministry of Education, Chengdu, China
| | - Chunhua He
- National Center for Birth Defect Monitoring, West China Second University Hospital, Sichuan University, Chengdu, China.,Key Laboratory of Birth Defects and Related Diseases of Women and Children (Sichuan University), Ministry of Education, Chengdu, China
| | - Jing Li
- Laboratory of Translational Medicine, Chinese PLA General Hospital, Beijing, China
| | - Jing Tao
- National Center for Birth Defect Monitoring, West China Second University Hospital, Sichuan University, Chengdu, China.,Key Laboratory of Birth Defects and Related Diseases of Women and Children (Sichuan University), Ministry of Education, Chengdu, China
| | - Zhen Liu
- National Center for Birth Defect Monitoring, West China Second University Hospital, Sichuan University, Chengdu, China.,Key Laboratory of Birth Defects and Related Diseases of Women and Children (Sichuan University), Ministry of Education, Chengdu, China
| | - Chunyan Zhang
- Laboratory of Translational Medicine, Chinese PLA General Hospital, Beijing, China
| | - Yuan Yuan
- Tianjin Medical Laboratory, BGI-Tianjin, BGI-Shenzhen, Tianjin, 300308, China
| | - Hui Jiang
- BGI-Shenzhen, Shenzhen, 518103, China.,China National GeneBank, BGI-Shenzhen, Shenzhen, 518120, China
| | - Jun Zhu
- National Center for Birth Defect Monitoring, West China Second University Hospital, Sichuan University, Chengdu, China.,Key Laboratory of Birth Defects and Related Diseases of Women and Children (Sichuan University), Ministry of Education, Chengdu, China
| | - Ying Deng
- National Center for Birth Defect Monitoring, West China Second University Hospital, Sichuan University, Chengdu, China.,Key Laboratory of Birth Defects and Related Diseases of Women and Children (Sichuan University), Ministry of Education, Chengdu, China
| | - Yixiong Guo
- National Center for Birth Defect Monitoring, West China Second University Hospital, Sichuan University, Chengdu, China.,Key Laboratory of Birth Defects and Related Diseases of Women and Children (Sichuan University), Ministry of Education, Chengdu, China
| | - Qintong Li
- Key Laboratory of Birth Defects and Related Diseases of Women and Children (Sichuan University), Ministry of Education, Chengdu, China
| | - Ping Yu
- National Center for Birth Defect Monitoring, West China Second University Hospital, Sichuan University, Chengdu, China. .,Key Laboratory of Birth Defects and Related Diseases of Women and Children (Sichuan University), Ministry of Education, Chengdu, China.
| | - Yanping Wang
- National Center for Birth Defect Monitoring, West China Second University Hospital, Sichuan University, Chengdu, China. .,Key Laboratory of Birth Defects and Related Diseases of Women and Children (Sichuan University), Ministry of Education, Chengdu, China.
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Danecka MK, Woidy M, Zschocke J, Feillet F, Muntau AC, Gersting SW. Mapping the functional landscape of frequent phenylalanine hydroxylase (PAH) genotypes promotes personalised medicine in phenylketonuria. J Med Genet 2015; 52:175-85. [PMID: 25596310 DOI: 10.1136/jmedgenet-2014-102621] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
BACKGROUND In phenylketonuria, genetic heterogeneity, frequent compound heterozygosity, and the lack of functional data for phenylalanine hydroxylase genotypes hamper reliable phenotype prediction and individualised treatment. METHODS A literature search revealed 690 different phenylalanine hydroxylase genotypes in 3066 phenylketonuria patients from Europe and the Middle East. We determined phenylalanine hydroxylase function of 30 frequent homozygous and compound heterozygous genotypes covering 55% of the study population, generated activity landscapes, and assessed the phenylalanine hydroxylase working range in the metabolic (phenylalanine) and therapeutic (tetrahydrobiopterin) space. RESULTS Shared patterns in genotype-specific functional landscapes were linked to biochemical and pharmacological phenotypes, where (1) residual activity below 3.5% was associated with classical phenylketonuria unresponsive to pharmacological treatment; (2) lack of defined peak activity induced loss of response to tetrahydrobiopterin; (3) a higher cofactor need was linked to inconsistent clinical phenotypes and low rates of tetrahydrobiopterin response; and (4) residual activity above 5%, a defined peak of activity, and a normal cofactor need were associated with pharmacologically treatable mild phenotypes. In addition, we provide a web application for retrieving country-specific information on genotypes and genotype-specific phenylalanine hydroxylase function that warrants continuous extension, updates, and research on demand. CONCLUSIONS The combination of genotype-specific functional analyses with biochemical, clinical, and therapeutic data of individual patients may serve as a powerful tool to enable phenotype prediction and to establish personalised medicine strategies for dietary regimens and pharmacological treatment in phenylketonuria.
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Affiliation(s)
- Marta K Danecka
- Department of Molecular Pediatrics, Dr. von Hauner Children's Hospital, Ludwig-Maximilians-University, Munich, Germany
| | - Mathias Woidy
- Department of Molecular Pediatrics, Dr. von Hauner Children's Hospital, Ludwig-Maximilians-University, Munich, Germany
| | - Johannes Zschocke
- Division of Human Genetics, Medical University Innsbruck, Innsbruck, Austria
| | - François Feillet
- Department of Pediatrics, Hôpital d'Enfants Brabois, CHU Nancy, Vandoeuvre les Nancy, France
| | - Ania C Muntau
- University Children's Hospital, University Medical Center Hamburg Eppendorf, Hamburg, Germany
| | - Søren W Gersting
- Department of Molecular Pediatrics, Dr. von Hauner Children's Hospital, Ludwig-Maximilians-University, Munich, Germany
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Lee Y, Stiers KM, Kain BN, Beamer LJ. Compromised catalysis and potential folding defects in in vitro studies of missense mutants associated with hereditary phosphoglucomutase 1 deficiency. J Biol Chem 2014; 289:32010-32019. [PMID: 25288802 DOI: 10.1074/jbc.m114.597914] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Recent studies have identified phosphoglucomutase 1 (PGM1) deficiency as an inherited metabolic disorder in humans. Affected patients show multiple disease phenotypes, including dilated cardiomyopathy, exercise intolerance, and hepatopathy, reflecting the central role of the enzyme in glucose metabolism. We present here the first in vitro biochemical characterization of 13 missense mutations involved in PGM1 deficiency. The biochemical phenotypes of the PGM1 mutants cluster into two groups: those with compromised catalysis and those with possible folding defects. Relative to the recombinant wild-type enzyme, certain missense mutants show greatly decreased expression of soluble protein and/or increased aggregation. In contrast, other missense variants are well behaved in solution, but show dramatic reductions in enzyme activity, with kcat/Km often <1.5% of wild-type. Modest changes in protein conformation and flexibility are also apparent in some of the catalytically impaired variants. In the case of the G291R mutant, severely compromised activity is linked to the inability of a key active site serine to be phosphorylated, a prerequisite for catalysis. Our results complement previous in vivo studies, which suggest that both protein misfolding and catalytic impairment may play a role in PGM1 deficiency.
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Affiliation(s)
- Yingying Lee
- Biochemistry Department, University of Missouri, Columbia, Missouri 65211
| | - Kyle M Stiers
- Biochemistry Department, University of Missouri, Columbia, Missouri 65211
| | - Bailee N Kain
- Biochemistry Department, University of Missouri, Columbia, Missouri 65211
| | - Lesa J Beamer
- Biochemistry Department, University of Missouri, Columbia, Missouri 65211.
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Réblová K, Hrubá Z, Procházková D, Pazdírková R, Pouchlá S, Zeman J, Fajkusová L. Hyperphenylalaninemia in the Czech Republic: genotype-phenotype correlations and in silico analysis of novel missense mutations. Clin Chim Acta 2013; 419:1-10. [PMID: 23357515 DOI: 10.1016/j.cca.2013.01.006] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2012] [Revised: 01/10/2013] [Accepted: 01/16/2013] [Indexed: 01/01/2023]
Abstract
BACKGROUND Hyperphenylalaninemia (HPA) is one of the most common inherited metabolic disorders caused by deficiency of the enzyme phenylalanine hydroxylase (PAH). HPA is associated with mutations in the PAH gene, which leads to reduced protein stability and/or impaired catalytic function. Currently, almost 700 different disease-causing mutations have been described. The impact of mutations on enzyme activity varies ranging from classical PKU, mild PKU, to non-PKU HPA phenotype. METHODS We provide results of molecular genetic diagnostics of 665 Czech unrelated HPA patients, structural analysis of missense mutations associated with classical PKU and non-PKU HPA phenotype, and prediction of effects of 6 newly discovered HPA missense mutations using bioinformatic approaches and Molecular Dynamics simulations. RESULTS Ninety-eight different types of mutations were indentified. Thirteen of these were novel (6 missense, 2 nonsense, 1 splicing, and 4 small gene rearrangements). Structural analysis revealed that classical PKU mutations are more non-conservative compared to non-PKU HPA mutations and that specific sequence and structural characteristics of a mutation might be critical when distinguishing between non-PKU HPA and classical PKU mutations. The greatest impact was predicted for the p.(Phe263Ser) mutation while other novel mutations p.(Asn167Tyr), p.(Thr200Asn), p.(Asp229Gly), p.(Leu358Phe), and p.(Ile406Met) were found to be less deleterious.
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Affiliation(s)
- Kamila Réblová
- Central European Institute of Technology, Masaryk University, Brno, Czech Republic.
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Naik S, Zhang N, Gao P, Fisher MT. On the design of broad based screening assays to identify potential pharmacological chaperones of protein misfolding diseases. Curr Top Med Chem 2012; 12:2504-22. [PMID: 23339304 PMCID: PMC3751797 DOI: 10.2174/1568026611212220006] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2012] [Revised: 09/18/2012] [Accepted: 09/21/2012] [Indexed: 01/11/2023]
Abstract
Correcting aberrant folds that develop during protein folding disease states is now an active research endeavor that is attracting increasing attention from both academic and industrial circles. One particular approach focuses on developing or identifying small molecule correctors or pharmacological chaperones that specifically stabilize the native fold. Unfortunately, the limited screening platforms available to rapidly identify or validate potential drug candidates are usually inadequate or slow because the folding disease proteins in question are often transiently folded and/or aggregation-prone, complicating and/or interfering with the assay outcomes. In this review, we outline and discuss the numerous platform options currently being employed to identify small molecule therapeutics for folding diseases. Finally, we describe a new stability screening approach that is broad based and is easily applicable toward a very large number of both common and rare protein folding diseases. The label free screening method described herein couples the promiscuity of the GroEL binding to transient aggregation-prone hydrophobic folds with surface plasmon resonance enabling one to rapidly identify potential small molecule pharmacological chaperones.
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Affiliation(s)
- Subhashchandra Naik
- University of Kansas Medical Center, Department of Biochemistry, Kansas City KS, USA
| | - Na Zhang
- University of Kansas, Protein Production Facility, Lawrence KS, USA
| | - Phillip Gao
- University of Kansas, Protein Production Facility, Lawrence KS, USA
| | - Mark T. Fisher
- University of Kansas Medical Center, Department of Biochemistry, Kansas City KS, USA
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11
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Sarkissian CN, Gamez A, Scott P, Dauvillier J, Dorenbaum A, Scriver CR, Stevens RC. Chaperone-like therapy with tetrahydrobiopterin in clinical trials for phenylketonuria: is genotype a predictor of response? JIMD Rep 2011; 5:59-70. [PMID: 23430918 DOI: 10.1007/8904_2011_96] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/22/2010] [Revised: 08/04/2011] [Accepted: 09/20/2011] [Indexed: 12/24/2022] Open
Abstract
Prospectively enrolled phenylketonuria patients (n=485) participated in an international Phase II clinical trial to identify the prevalence of a therapeutic response to daily doses of sapropterin dihydrochloride (sapropterin, KUVAN(®)). Responsive patients were then enrolled in two subsequent Phase III clinical trials to examine safety, ability to reduce blood Phenylalanine levels, dosage (5-20 mg/kg/day) and response, and bioavailability of sapropterin. We combined phenotypic findings in the Phase II and III clinical trials to classify study-related responsiveness associated with specific alleles and genotypes identified in the patients. We found that 17% of patients showed a response to sapropterin. The patients harbored 245 different genotypes derived from 122 different alleles, among which ten alleles were newly discovered. Only 16.3% of the genotypes clearly conferred a sapropterin-responsive phenotype. Among the different PAH alleles, only 5% conferred a responsive phenotype. The responsive alleles were largely but not solely missense mutations known to or likely to cause misfolding of the PAH subunit. However, the metabolic response was not robustly predictable from the PAH genotypes, based on the study design adopted for these clinical trials, and accordingly it seems prudent to test each person for this phenotype with a standardized protocol.
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Affiliation(s)
- Christineh N Sarkissian
- Departments of Biology, Human Genetics and Pediatrics, McGill University, Montreal, QC, Canada
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Abstract
Phenylalanine hydroxylase deficiency is an autosomal recessive disorder that results in intolerance to the dietary intake of the essential amino acid phenylalanine. It occurs in approximately 1:15,000 individuals. Deficiency of this enzyme produces a spectrum of disorders including classic phenylketonuria, mild phenylketonuria, and mild hyperphenylalaninemia. Classic phenylketonuria is caused by a complete or near-complete deficiency of phenylalanine hydroxylase activity and without dietary restriction of phenylalanine most children will develop profound and irreversible intellectual disability. Mild phenylketonuria and mild hyperphenylalaninemia are associated with lower risk of impaired cognitive development in the absence of treatment. Phenylalanine hydroxylase deficiency can be diagnosed by newborn screening based on detection of the presence of hyperphenylalaninemia using the Guthrie microbial inhibition assay or other assays on a blood spot obtained from a heel prick. Since the introduction of newborn screening, the major neurologic consequences of hyperphenylalaninemia have been largely eradicated. Affected individuals can lead normal lives. However, recent data suggest that homeostasis is not fully restored with current therapy. Treated individuals have a higher incidence of neuropsychological problems. The mainstay of treatment for hyperphenylalaninemia involves a low-protein diet and use of a phenylalanine-free medical formula. This treatment must commence as soon as possible after birth and should continue for life. Regular monitoring of plasma phenylalanine and tyrosine concentrations is necessary. Targets of plasma phenylalanine of 120-360 μmol/L (2-6 mg/dL) in the first decade of life are essential for optimal outcome. Phenylalanine targets in adolescence and adulthood are less clear. A significant proportion of patients with phenylketonuria may benefit from adjuvant therapy with 6R-tetrahydrobiopterin stereoisomer. Special consideration must be given to adult women with hyperphenylalaninemia because of the teratogenic effects of phenylalanine. Women with phenylalanine hydroxylase deficiency considering pregnancy should follow special guidelines and assure adequate energy intake with the proper proportion of protein, fat, and carbohydrates to minimize risks to the developing fetus. Molecular genetic testing of the phenylalanine hydroxylase gene is available for genetic counseling purposes to determine carrier status of at-risk relatives and for prenatal testing.
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Cerreto M, Cavaliere P, Carluccio C, Amato F, Zagari A, Daniele A, Salvatore F. Natural phenylalanine hydroxylase variants that confer a mild phenotype affect the enzyme's conformational stability and oligomerization equilibrium. BIOCHIMICA ET BIOPHYSICA ACTA 2011; 1812:1435-45. [PMID: 21820508 DOI: 10.1016/j.bbadis.2011.07.012] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2011] [Revised: 07/19/2011] [Accepted: 07/20/2011] [Indexed: 11/26/2022]
Abstract
Hyperphenylalaninemias are genetic diseases prevalently caused by mutations in the phenylalanine hydroxylase (PAH) gene. The wild-type PAH enzyme is a homotetramer regulated by its substrate, cofactor and phosphorylation. We reproduced a full-length wild-type protein and seven natural full-length PAH variants, p.I65M, p.N223Y, p.R297L, p.F382L, p.K398N, p.A403V, and p.Q419R, and analyzed their biochemical and biophysical behavior. All mutants exhibited reduced enzymatic activity, namely from 38% to 69% of wild-type activity. Biophysical characterization was performed by size-exclusion chromatography, light scattering and circular dichroism. In the purified wild-type PAH, we identified the monomer in equilibrium with the dimer and tetramer. In most mutants, the equilibrium shifted toward the dimer and most tended to form aggregates. All PAH variants displayed different biophysical behaviors due to loss of secondary structure and thermal destabilization. Specifically, p.F382L was highly unstable at physiological temperature. Moreover, using confocal microscopy with the number and brightness technique, we studied the effect of BH4 addition directly in living human cells expressing wild-type PAH or p.A403V, a mild mutant associated with BH4 responsiveness in vivo. Our results demonstrate that BH4 addition promotes re-establishment of the oligomerization equilibrium, thus indicating that the dimer-to-tetramer shift in pA403V plays a key role in BH4 responsiveness. In conclusion, we show that the oligomerization process and conformational stability are altered by mutations that could affect the physiological behavior of the enzyme. This endorses the hypothesis that oligomerization and folding defects of PAH variants are the most common causes of HPAs, particularly as regards mild human phenotypes.
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14
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Loaiza A, Ronau JA, Ribbe A, Stanciu L, Burgner JW, Paul LN, Abu-Omar MM. Folding dynamics of phenylalanine hydroxylase depends on the enzyme’s metallation state: the native metal, iron, protects against aggregate intermediates. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2011; 40:959-68. [DOI: 10.1007/s00249-011-0711-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/25/2011] [Revised: 04/07/2011] [Accepted: 04/28/2011] [Indexed: 10/18/2022]
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Muntau AC, Gersting SW. Phenylketonuria as a model for protein misfolding diseases and for the development of next generation orphan drugs for patients with inborn errors of metabolism. J Inherit Metab Dis 2010; 33:649-58. [PMID: 20824346 DOI: 10.1007/s10545-010-9185-4] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/17/2010] [Revised: 07/22/2010] [Accepted: 07/26/2010] [Indexed: 11/28/2022]
Abstract
The lecture dedicated to Professor Horst Bickel describes the advances, successes, and opportunities concerning the understanding of the biochemical and molecular basis of phenylketonuria and the innovative treatment strategies introduced for these patients during the last 60 years. These concepts were transferred to other inborn errors of metabolism and led to significant reduction in morbidity and to an improvement in quality of life. Important milestones were the successful development of a low-phenylalanine diet for phenylketonuria patients, the recognition of tetrahydrobiopterin as an option to treat these individuals pharmacologically, and finally market approval of this drug. The work related to the discovery of a pharmacological treatment led metabolic researchers and pediatricians to new insights into the molecular processes linked to mutations in the phenylalanine hydroxylase gene at the cellular and structural level. Again, phenylketonuria became a prototype disorder for a previously underestimated but now rapidly expanding group of diseases: protein misfolding disorders with loss of function. Due to potential general biological mechanisms underlying these disorders, the door may soon open to a systematic development of a new class of pharmaceutical products. These pharmacological chaperones are likely to correct misfolding of proteins involved in numerous genetic and nongenetic diseases.
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Affiliation(s)
- Ania C Muntau
- Dr von Hauner Children's Hospital, Department of Molecular Pediatrics, Ludwig Maximilians University, Lindwurmstrasse 4, 80337 Munich, Germany.
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16
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Gersting SW, Staudigl M, Truger MS, Messing DD, Danecka MK, Sommerhoff CP, Kemter KF, Muntau AC. Activation of phenylalanine hydroxylase induces positive cooperativity toward the natural cofactor. J Biol Chem 2010; 285:30686-97. [PMID: 20667834 PMCID: PMC2945563 DOI: 10.1074/jbc.m110.124016] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2010] [Revised: 06/29/2010] [Indexed: 11/06/2022] Open
Abstract
Protein misfolding with loss-of-function of the enzyme phenylalanine hydroxylase (PAH) is the molecular basis of phenylketonuria in many individuals carrying missense mutations in the PAH gene. PAH is complexly regulated by its substrate L-Phenylalanine and its natural cofactor 6R-L-erythro-5,6,7,8-tetrahydrobiopterin (BH(4)). Sapropterin dihydrochloride, the synthetic form of BH(4), was recently approved as the first pharmacological chaperone to correct the loss-of-function phenotype. However, current knowledge about enzyme function and regulation in the therapeutic setting is scarce. This illustrates the need for comprehensive analyses of steady state kinetics and allostery beyond single residual enzyme activity determinations to retrace the structural impact of missense mutations on the phenylalanine hydroxylating system. Current standard PAH activity assays are either indirect (NADH) or discontinuous due to substrate and product separation before detection. We developed an automated fluorescence-based continuous real-time PAH activity assay that proved to be faster and more efficient but as precise and accurate as standard methods. Wild-type PAH kinetic analyses using the new assay revealed cooperativity of activated PAH toward BH(4), a previously unknown finding. Analyses of structurally preactivated variants substantiated BH(4)-dependent cooperativity of the activated enzyme that does not rely on the presence of l-Phenylalanine but is determined by activating conformational rearrangements. These findings may have implications for an individualized therapy, as they support the hypothesis that the patient's metabolic state has a more significant effect on the interplay of the drug and the conformation and function of the target protein than currently appreciated.
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Affiliation(s)
- Søren W. Gersting
- From the Department of Molecular Pediatrics, Dr. von Hauner Children's Hospital, Munich 80337 and
| | - Michael Staudigl
- From the Department of Molecular Pediatrics, Dr. von Hauner Children's Hospital, Munich 80337 and
| | - Marietta S. Truger
- From the Department of Molecular Pediatrics, Dr. von Hauner Children's Hospital, Munich 80337 and
| | - Dunja D. Messing
- From the Department of Molecular Pediatrics, Dr. von Hauner Children's Hospital, Munich 80337 and
| | - Marta K. Danecka
- From the Department of Molecular Pediatrics, Dr. von Hauner Children's Hospital, Munich 80337 and
| | - Christian P. Sommerhoff
- the Department of Clinical Chemistry and Clinical Biochemistry, Surgical Clinic, Ludwig-Maximilians-University, Munich 80336, Germany
| | - Kristina F. Kemter
- From the Department of Molecular Pediatrics, Dr. von Hauner Children's Hospital, Munich 80337 and
| | - Ania C. Muntau
- From the Department of Molecular Pediatrics, Dr. von Hauner Children's Hospital, Munich 80337 and
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17
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McKinney JA, Turel B, Winge I, Knappskog PM, Haavik J. Functional properties of missense variants of human tryptophan hydroxylase 2. Hum Mutat 2009; 30:787-94. [PMID: 19319927 DOI: 10.1002/humu.20956] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Tryptophan hydroxylase 2 (TPH2) catalyzes the rate-limiting step in serotonin biosynthesis in the nervous system. Several variants of human TPH2 have been reported to be associated with a spectrum of neuropsychiatric disorders such as unipolar major depression, bipolar disorder, suicidality, and attention-deficit/hyperactivity disorder (ADHD). We used three different expression systems: rabbit reticulocyte lysate, Escherichia coli, and human embryonic kidney cells, to identify functional effects of all human TPH2 missense variants reported to date. The properties of mutants affecting the regulatory domain, that is, p.Leu36Val, p.Leu36Pro, p.Ser41Tyr, and p.Arg55Cys, were indistinguishable from the wild-type (WT). Moderate loss-of-function effects were observed for mutants in the catalytic and oligomerization domains, that is, p.Pro206Ser, p.Ala328Val, p.Arg441His, and p.Asp479Glu, which were manifested via stability and solubility effects, whereas p.Arg303Trp had severely reduced solubility and was completely inactive. All variants were tested as substrates for protein kinase A and were found to have similar phosphorylation stoichiometries. A standardized assay protocol as described here for activity and solubility screening should also be useful for determining properties of other TPH2 variants that will be discovered in the future.
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18
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The Missense p.S231F Phenylalanine Hydroxylase Gene Mutation Causes Complete Loss of Enzymatic Activity In Vitro. Protein J 2009; 28:294-9. [DOI: 10.1007/s10930-009-9194-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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19
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Gersting SW, Kemter KF, Staudigl M, Messing DD, Danecka MK, Lagler FB, Sommerhoff CP, Roscher AA, Muntau AC. Loss of function in phenylketonuria is caused by impaired molecular motions and conformational instability. Am J Hum Genet 2008; 83:5-17. [PMID: 18538294 PMCID: PMC2443833 DOI: 10.1016/j.ajhg.2008.05.013] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2008] [Revised: 05/09/2008] [Accepted: 05/17/2008] [Indexed: 11/21/2022] Open
Abstract
A significant share of patients with phenylalanine hydroxylase (PAH) deficiency benefits from pharmacological doses of tetrahydrobiopterin (BH(4)), the natural PAH cofactor. Phenylketonuria (PKU) is hypothesized to be a conformational disease, with loss of function due to protein destabilization, and the restoration of enzyme function that is observed in BH(4) treatment might be transmitted by correction of protein misfolding. To elucidate the molecular basis of functional impairment in PAH deficiency, we investigated the impact of ten PAH gene mutations identified in patients with BH(4)-responsiveness on enzyme kinetics, stability, and conformation of the protein (F55L, I65S, H170Q, P275L, A300S, S310Y, P314S, R408W, Y414C, Y417H). Residual enzyme activity was generally high, but allostery was disturbed in almost all cases and pointed to altered protein conformation. This was confirmed by reduced proteolytic stability, impaired tetramer assembly or aggregation, increased hydrophobicity, and accelerated thermal unfolding--with particular impact on the regulatory domain--observed in most variants. Three-dimensional modeling revealed the involvement of functionally relevant amino acid networks that may communicate misfolding throughout the protein. Our results substantiate the view that PAH deficiency is a protein-misfolding disease in which global conformational changes hinder molecular motions essential for physiological enzyme function. Thus, PKU has evolved from a model of a genetic disease that leads to severe neurological impairment to a model of a treatable protein-folding disease with loss of function.
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Affiliation(s)
- Søren W. Gersting
- Department of Molecular Pediatrics, Children's Research Center, Dr. von Hauner Children's Hospital, Ludwig Maximilians University, 80337 Munich, Germany
| | - Kristina F. Kemter
- Department of Molecular Pediatrics, Children's Research Center, Dr. von Hauner Children's Hospital, Ludwig Maximilians University, 80337 Munich, Germany
| | - Michael Staudigl
- Department of Molecular Pediatrics, Children's Research Center, Dr. von Hauner Children's Hospital, Ludwig Maximilians University, 80337 Munich, Germany
| | - Dunja D. Messing
- Department of Molecular Pediatrics, Children's Research Center, Dr. von Hauner Children's Hospital, Ludwig Maximilians University, 80337 Munich, Germany
| | - Marta K. Danecka
- Department of Molecular Pediatrics, Children's Research Center, Dr. von Hauner Children's Hospital, Ludwig Maximilians University, 80337 Munich, Germany
| | - Florian B. Lagler
- Department of Medical Genetics, Molecular and Clinical Pharmacology, Innsbruck Medical University, 6020 Innsbruck, Austria
| | - Christian P. Sommerhoff
- Department of Clinical Chemistry and Clinical Biochemistry, Surgical Clinic, Ludwig Maximilians University, 80337 Munich, Germany
| | - Adelbert A. Roscher
- Department of Molecular Pediatrics, Children's Research Center, Dr. von Hauner Children's Hospital, Ludwig Maximilians University, 80337 Munich, Germany
| | - Ania C. Muntau
- Department of Molecular Pediatrics, Children's Research Center, Dr. von Hauner Children's Hospital, Ludwig Maximilians University, 80337 Munich, Germany
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20
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Pey AL, Stricher F, Serrano L, Martinez A. Predicted effects of missense mutations on native-state stability account for phenotypic outcome in phenylketonuria, a paradigm of misfolding diseases. Am J Hum Genet 2007; 81:1006-24. [PMID: 17924342 PMCID: PMC2265664 DOI: 10.1086/521879] [Citation(s) in RCA: 140] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2007] [Accepted: 07/25/2007] [Indexed: 12/15/2022] Open
Abstract
Phenylketonuria (PKU) is a genetic disease caused by mutations in human phenylalanine hydroxylase (PAH). Most missense mutations result in misfolding of PAH, increased protein turnover, and a loss of enzymatic function. We studied the prediction of the energetic impact on PAH native-state stability of 318 PKU-associated missense mutations, using the protein-design algorithm FoldX. For the 80 mutations for which expression analyses have been performed in eukaryote systems, in most cases we found substantial overall correlations between the mutational energetic impact and both in vitro residual activities and patient metabolic phenotype. This finding confirmed that the decrease in protein stability is the main molecular pathogenic mechanism in PKU and the determinant for phenotypic outcome. Metabolic phenotypes have been shown to be better predicted than in vitro residual activities, probably because of greater stringency in the phenotyping process. Finally, all the remaining 238 PKU missense mutations compiled at the PAH locus knowledgebase (PAHdb) were analyzed, and their phenotypic outcomes were predicted on the basis of the energetic impact provided by FoldX. Residues in exons 7-9 and in interdomain regions within the subunit appear to play an important structural role and constitute hotspots for destabilization. FoldX analysis will be useful for predicting the phenotype associated with rare or new mutations detected in patients with PKU. However, additional factors must be considered that may contribute to the patient phenotype, such as possible effects on catalysis and interindividual differences in physiological and metabolic processes.
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Affiliation(s)
- Angel L Pey
- Department of Biomedicine, University of Bergen, Bergen, Norway
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21
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Erlandsen H, Pey AL, Gámez A, Pérez B, Desviat LR, Aguado C, Koch R, Surendran S, Tyring S, Matalon R, Scriver CR, Ugarte M, Martínez A, Stevens RC. Correction of kinetic and stability defects by tetrahydrobiopterin in phenylketonuria patients with certain phenylalanine hydroxylase mutations. Proc Natl Acad Sci U S A 2004; 101:16903-8. [PMID: 15557004 PMCID: PMC534739 DOI: 10.1073/pnas.0407256101] [Citation(s) in RCA: 135] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2004] [Indexed: 11/18/2022] Open
Abstract
Phenylketonuria patients harboring a subset of phenylalanine hydroxylase (PAH) mutations have recently shown normalization of blood phenylalanine levels upon oral administration of the PAH cofactor tetrahydrobiopterin [(6R)-L-erythro-5,6,7,8-tetrahydrobiopterin (BH4)]. Several hypotheses have been put forward to explain BH4 responsiveness, but the molecular basis for the corrective effect(s) of BH4 has not been understood. We have investigated the biochemical, kinetic, and structural changes associated with BH4-responsive mutations (F39L, I65T, R68S, H170D, E178G, V190A, R261Q, A300S, L308F, A313T, A373T, V388M, E390G, P407S, and Y414C). The biochemical and kinetic characterization of the 15 mutants studied points toward a multifactorial basis for the BH4 responsiveness; the mutants show residual activity (>30% of WT) and display various kinetic defects, including increased Km (BH4) and reduced cooperativity of substrate binding, but no decoupling of cofactor (BH4) oxidation. For some, BH4 seems to function through stabilization and protection of the enzyme from inactivation and proteolytic degradation. In the crystal structures of a phenylketonuria mutant, A313T, minor changes were seen when compared with the WT PAH structures, consistent with the mild effects the mutant has upon activity of the enzyme both in vitro and in vivo. Truncations made in the A313T mutant PAH form revealed that the N and C termini of the enzyme influence active site binding. Of fundamental importance is the observation that BH4 appears to increase Phe catabolism if at least one of the two heterozygous mutations has any residual activity remaining.
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Affiliation(s)
- Heidi Erlandsen
- Department of Molecular Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
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22
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Almstedt K, Lundqvist M, Carlsson J, Karlsson M, Persson B, Jonsson BH, Carlsson U, Hammarström P. Unfolding a folding disease: folding, misfolding and aggregation of the marble brain syndrome-associated mutant H107Y of human carbonic anhydrase II. J Mol Biol 2004; 342:619-33. [PMID: 15327960 DOI: 10.1016/j.jmb.2004.07.024] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2004] [Revised: 07/01/2004] [Accepted: 07/12/2004] [Indexed: 11/23/2022]
Abstract
Most loss-of-function diseases are caused by aberrant folding of important proteins. These proteins often misfold due to mutations. The disease marble brain syndrome (MBS), known also as carbonic anhydrase II deficiency syndrome (CADS), can manifest in carriers of point mutations in the human carbonic anhydrase II (HCA II) gene. One mutation associated with MBS entails the His107Tyr substitution. Here, we demonstrate that this mutation is a remarkably destabilizing folding mutation. The loss-of-function is clearly a folding defect, since the mutant shows 64% of CO(2) hydration activity compared to that of the wild-type at low temperature where the mutant is folded. On the contrary, its stability towards thermal and guanidine hydrochloride (GuHCl) denaturation is highly compromised. Using activity assays, CD, fluorescence, NMR, cross-linking, aggregation measurements and molecular modeling, we have mapped the properties of this remarkable mutant. Loss of enzymatic activity had a midpoint temperature of denaturation (T(m)) of 16 degrees C for the mutant compared to 55 degrees C for the wild-type protein. GuHCl-denaturation (at 4 degrees C) showed that the native state of the mutant was destabilized by 9.2kcal/mol. The mutant unfolds through at least two equilibrium intermediates; one novel intermediate that we have termed the molten globule light state and, after further denaturation, the classical molten globule state is populated. Under physiological conditions (neutral pH; 37 degrees C), the His107Tyr mutant will populate the molten globule light state, likely due to novel interactions between Tyr107 and the surroundings of the critical residue Ser29 that destabilize the native conformation. This intermediate binds the hydrophobic dye 8-anilino-1-naphthalene sulfonic acid (ANS) but not as strong as the molten globule state, and near-UV CD reveals the presence of significant tertiary structure. Notably, this intermediate is not as prone to aggregation as the classical molten globule. As a proof of concept for an intervention strategy with small molecules, we showed that binding of the CA inhibitor acetazolamide increases the stability of the native state of the mutant by 2.9kcal/mol in accordance with its strong affinity. Acetazolamide shifts the T(m) to 34 degrees C that protects from misfolding and will enable a substantial fraction of the enzyme pool to survive physiological conditions.
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Affiliation(s)
- Karin Almstedt
- IFM-Department of Chemistry, Linköping University, 581 83 Linköping, Sweden
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23
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Kleppe R, Haavik J. Different stabilities and denaturation pathways for structurally related aromatic amino acid hydroxylases. FEBS Lett 2004; 565:155-9. [PMID: 15135070 DOI: 10.1016/j.febslet.2004.03.092] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2004] [Revised: 03/29/2004] [Accepted: 03/29/2004] [Indexed: 10/26/2022]
Abstract
We have compared the urea stability of the human aromatic amino acid hydroxylases (AAAHs), key enzymes involved in neurotransmitter biosynthesis and amino acid homeostasis. Tyrosine-, tryptophan- and phenylalanine hydroxylase (TH, TPH and PAH, respectively) were transiently activated at low urea concentrations and rapidly inactivated in >3 M urea. The denaturation of TH occurred through two cooperative transitions, with denaturation midpoints of 1.41+/-0.06 and 5.13+/-0.05 M urea, respectively. Partially denatured human TH (hTH) retained more of its secondary structure than human PAH (hPAH), and was found to exist as tetramers, whereas hPAH dissociated into dimers. Furthermore, the urea-induced aggregation of hPAH was 100-fold higher than for hTH. These results suggest that the denatured state properties of the AAAHs contribute significantly to the stability of these enzymes and their tolerance towards missense mutations.
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Affiliation(s)
- Rune Kleppe
- Department of Biomedicine, Division for Anatomy and Cell Biology, University of Bergen, Jonas Lies vei 91, N-5009 Bergen, Norway
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24
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Gregersen N, Bross P, Andresen BS. Genetic defects in fatty acid beta-oxidation and acyl-CoA dehydrogenases. Molecular pathogenesis and genotype-phenotype relationships. ACTA ACUST UNITED AC 2004; 271:470-82. [PMID: 14728674 DOI: 10.1046/j.1432-1033.2003.03949.x] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Mitochondrial fatty acid oxidation deficiencies are due to genetic defects in enzymes of fatty acid beta-oxidation and transport proteins. Genetic defects have been identified in most of the genes where nearly all types of sequence variations (mutation types) have been associated with disease. In this paper, we will discuss the effects of the various types of sequence variations encountered and review current knowledge regarding the genotype-phenotype relationship, especially in patients with acyl-CoA dehydrogenase deficiencies where sufficient material exists for a meaningful discussion. Because mis-sense sequence variations are prevalent in these diseases, we will discuss the implications of these types of sequence variations on the processing and folding of mis-sense variant proteins. As the prevalent mis-sense variant K304E MCAD protein has been studied intensively, the investigations on biogenesis, stability and kinetic properties for this variant enzyme will be discussed in detail and used as a paradigm for the study of other mis-sense variant proteins. We conclude that the total effect of mis-sense sequence variations may comprise an invariable--sequence variation specific--effect on the catalytic parameters and a conditional effect, which is dependent on cellular, physiological and genetic factors other than the sequence variation itself.
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Affiliation(s)
- Niels Gregersen
- Research Unit for Molecular Medicine, Aarhus University Hospital and Faculty of Health Sciences, Aarhus University, Aarhus, Denmark.
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25
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Scriver CR, Hurtubise M, Konecki D, Phommarinh M, Prevost L, Erlandsen H, Stevens R, Waters PJ, Ryan S, McDonald D, Sarkissian C. PAHdb 2003: what a locus-specific knowledgebase can do. Hum Mutat 2003; 21:333-44. [PMID: 12655543 DOI: 10.1002/humu.10200] [Citation(s) in RCA: 107] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
PAHdb, a legacy of and resource in genetics, is a relational locus-specific database (http://www.pahdb.mcgill.ca). It records and annotates both pathogenic alleles (n = 439, putative disease-causing) and benign alleles (n = 41, putative untranslated polymorphisms) at the human phenylalanine hydroxylase locus (symbol PAH). Human alleles named by nucleotide number (systematic names) and their trivial names receive unique identifier numbers. The annotated gDNA sequence for PAH is typical for mammalian genes. An annotated gDNA sequence is numbered so that cDNA and gDNA sites are interconvertable. A site map for PAHdb leads to a large array of secondary data (attributes): source of the allele (submitter, publication, or population); polymorphic haplotype background; and effect of the allele as predicted by molecular modeling on the phenylalanine hydroxylase enzyme (EC 1.14.16.1) or by in vitro expression analysis. The majority (63%) of the putative pathogenic PAH alleles are point mutations causing missense in translation of which few have a primary effect on PAH enzyme kinetics. Most apparently have a secondary effect on its function through misfolding, aggregation, and intracellular degradation of the protein. Some point mutations create new splice sites. A subset of primary PAH mutations that are tetrahydrobiopterin-responsive is highlighted on a Curators' Page. A clinical module describes the corresponding human clinical disorders (hyperphenylalaninemia [HPA] and phenylketonuria [PKU]), their inheritance, and their treatment. PAHdb contains data on the mouse gene (Pah) and on four orthologous mutant mouse models and their use (for example, in research on oral treatment of PKU with the enzyme phenylalanine ammonia lyase [EC 4.3.1.5]).
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Affiliation(s)
- Charles R Scriver
- Department of Human Genetics, McGill University Health Centre, Montreal, Canada.
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26
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Pey AL, Desviat LR, Gámez A, Ugarte M, Pérez B. Phenylketonuria: genotype-phenotype correlations based on expression analysis of structural and functional mutations in PAH. Hum Mutat 2003; 21:370-8. [PMID: 12655546 DOI: 10.1002/humu.10198] [Citation(s) in RCA: 98] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
When analyzed in the context of the phenylalanine hydroxylase (PAH) three-dimensional structure, only a minority of the PKU mutations described world-wide affect catalytic residues. Consistent with these observations, recent data point to defective folding and subsequent aggregation/degradation as a predominant disease mechanism for several mutations. In this work, we use a combined approach of expression in eukaryotic cells at different temperatures and a prokaryotic system with co-expression of chaperonins to elucidate and confirm structural consequences for 18 PKU mutations. Three mutations are located in the amino terminal regulatory domain and 15 in the catalytic domain. Four mutations were found to abolish the specific activity in all conditions. Two are catalytic mutations (Y277D and E280K) and two are severe structural defects (IVS10-11G>A and L311P). All the remaining mutations (D59Y, I65T, E76G, P122Q, R158Q, G218V, R243Q, P244L, R252W, R261Q, A309V, R408Q, R408W, and Y414C) are folding defects causing reduced stability and accelerated degradation, although some of them probably affect residues involved in regulation. In these cases, we have demonstrated that the amount of mutant PAH protein and residual activity could be modulated by in vitro experimental conditions, and therefore the observed in vivo metabolic variation may be explained by interindividual variation in the quality control systems. The results derived provide an experimental framework to define the mutation severity relating genotype to phenotype. They also explain the observed inconsistencies for some mutations in patients with similar genotype and different phenotypes.
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Affiliation(s)
- Angel L Pey
- Centro de Biología Molecular Severo Ochoa, CSIC-UAM, Madrid, Spain
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Waters PJ. How PAH gene mutations cause hyper-phenylalaninemia and why mechanism matters: insights from in vitro expression. Hum Mutat 2003; 21:357-69. [PMID: 12655545 DOI: 10.1002/humu.10197] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Mutations in the human PAH gene, which encodes phenylalanine hydroxylase are associated with varying degrees of hyperphenylalaninemia (HPA). The more severe of these manifest as a classic metabolic disease--phenylketonuria (PKU). In vitro expression analysis of PAH mutations has three major applications: 1) to confirm that a disease-associated mutation is genuinely pathogenic, 2) to assess the severity of a mutation's impact, and 3) to examine how a mutation exerts its deleterious effects on the PAH enzyme, that is, to elucidate the molecular mechanisms involved. Data on expression analysis of 81 PAH mutations in multiple in vitro systems is summarized in tabular form online at www.pahdb.mcgill.ca. A review of these findings points in particular to a prevalent general mechanism that appears to play a major role in the pathogenicity of many PAH mutations. Amino acid substitutions promote misfolding of the PAH protein monomer and/or oppose the correct assembly of monomers into the native tetrameric enzyme. The resulting structural aberrations trigger cellular defenses, provoking accelerated degradation of the abnormal protein. The intracellular steady-state levels of the mutant PAH enzyme are therefore reduced, leading to an overall decrease in phenylalanine hydroxylation within cells and thus to hyperphenylalaninemia. There is considerable scope for modulation of the enzymic and metabolic phenotypes by modification of the cellular handling--folding, assembly, and degradation--of the mutant PAH protein. This has major implications, both for our understanding of genotype-phenotype correlations and for the development of novel therapeutic approaches.
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Affiliation(s)
- Paula J Waters
- deBelle Laboratory for Biochemical Genetics, Montreal Children's Hospital, Montreal, Quebec, Canada.
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28
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Wu G, Yan S. Estimation of amino acid pairs sensitive to variants in human phenylalanine hydroxylase protein by means of a random approach. Peptides 2002; 23:2085-90. [PMID: 12535686 DOI: 10.1016/s0196-9781(02)00249-8] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In this data-based theoretical analysis, we use a random approach to estimate amino acid pairs in human phenylalanine 4-hydroxylase (PAH) protein in order to determine which amino acid pairs are more sensitive to 187 variants in human PAH protein. The rationale of this study is based on our hypothesis and previous findings that the harmful variants are more likely to occur at randomly unpredictable amino acid pairs rather than at randomly predictable pairs. This is reasonable to argue as randomly predictable amino acid pairs are less likely to be deliberately evolved, whereas randomly unpredictable amino acid pairs are probably deliberately evolved in connection with protein function. 94.12% of 187 variants occurred at randomly unpredictable amino acid pairs, which accounted for 71.84% of 451 amino acid pairs in human PAH protein. The chance of a variant occurring is five times higher in randomly unpredictable amino acid pairs than in predictable pairs. Thus, randomly unpredictable amino acid pairs are more sensitive to variance in human PAH protein. The results also suggest that the human PAH protein has a natural tendency towards variants.
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Affiliation(s)
- Guang Wu
- Laboratoire de Toxicocinétique et Pharmacocinétique, Faculté de Pharmacie, Université de la Méditerranée Aix-Marseille II, Marseille, France.
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29
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Terp BN, Cooper DN, Christensen IT, Jørgensen FS, Bross P, Gregersen N, Krawczak M. Assessing the relative importance of the biophysical properties of amino acid substitutions associated with human genetic disease. Hum Mutat 2002; 20:98-109. [PMID: 12124990 DOI: 10.1002/humu.10095] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The inclusion of a mutation in a pathology-based database such as the Human Gene Mutation Database (HGMD) is a two-stage process: first, the mutation must occur at the DNA level, then it must cause a clinically detectable disease state. The likelihood of the latter step, termed the relative clinical observation likelihood (RCOL), can be regarded as a function of the structural/functional consequences of a mutation at the protein level. Following this paradigm, we modeled in silico all amino acid replacements that could potentially have arisen from an inherited single base pair substitution in five human genes encoding arylsulphatase A (ARSA), antithrombin III (SERPINC1), protein C (PROC), phenylalanine hydroxylase (PAH), and transthyretin (TTR). These proteins were chosen on the basis of 1) the availability of a crystallographic structure, and 2) a sufficiently large number of amino acid replacements being logged in HGMD. A total of 9,795 possible mutant structures were modeled and 20 different biophysical parameters assessed. Together with the HGMD-derived spectra of clinically detected mutations, these data allowed maximum likelihood estimation of RCOL profiles for the 20 parameters studied. Nine parameters (including energy difference between wild-type and mutant structures, accessibility of the mutated residue, and distance from the binding/active site) exhibited statistically significant variability in their RCOL profiles, indicating that mutation-associated changes affected protein function. As yet, however, a biological meaning could only be attributed to the RCOL profiles of solvent accessibility and, for three proteins, local energy change, disturbed geometry, and distance from the active center. The limited ability of the biophysical properties of mutations to explain clinical consequences is probably due to our current lack of understanding as to which amino acid residues are critical for protein folding. However, since the proteins examined here were unrelated, and our findings consistent, it may nevertheless prove possible to extrapolate to other proteins whose dysfunction underlies inherited disease.
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MESH Headings
- Amino Acid Substitution/genetics
- Amyloid Neuropathies, Familial/genetics
- Amyloid Neuropathies, Familial/metabolism
- Antithrombin III/chemistry
- Antithrombin III/genetics
- Antithrombin III/physiology
- Antithrombin III Deficiency/genetics
- Antithrombin III Deficiency/metabolism
- Arylsulfatases/chemistry
- Arylsulfatases/deficiency
- Arylsulfatases/genetics
- Arylsulfatases/physiology
- Biophysics/methods
- Databases, Genetic
- Databases, Protein
- Genetic Diseases, Inborn/enzymology
- Genetic Diseases, Inborn/genetics
- Genetic Diseases, Inborn/metabolism
- Genotype
- Humans
- Leukodystrophy, Metachromatic/enzymology
- Leukodystrophy, Metachromatic/genetics
- Models, Genetic
- Mutation, Missense/genetics
- Phenotype
- Phenylalanine Hydroxylase/chemistry
- Phenylalanine Hydroxylase/deficiency
- Phenylalanine Hydroxylase/genetics
- Phenylalanine Hydroxylase/physiology
- Phenylketonurias/enzymology
- Phenylketonurias/genetics
- Prealbumin/chemistry
- Prealbumin/deficiency
- Prealbumin/genetics
- Prealbumin/physiology
- Protein C/chemistry
- Protein C/genetics
- Protein C/physiology
- Protein C Deficiency/genetics
- Protein C Deficiency/metabolism
- Protein Structure, Secondary/genetics
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Affiliation(s)
- Bent N Terp
- Institute of Medical Genetics, University of Wales College of Medicine, Heath Park, Cardiff, UK
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30
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Mirisola MG, Cali F, Gloria A, Schinocca P, D'Amato M, Cassara G, Leo GD, Palillo L, Meli C, Romano V. PAH gene mutations in the Sicilian population: association with minihaplotypes and expression analysis. Mol Genet Metab 2001; 74:353-61. [PMID: 11708866 DOI: 10.1006/mgme.2001.3211] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The molecular basis of PAH deficiency in the Sicilian population is characterized by a marked heterogeneity, with 44 mutations at a single locus identified by a "gene-scanning" approach and accounting for a detection rate of 91%. The remaining 9% of PAH alleles does not bear mutations in any of the 13 exons and 24 exon/intron junctions. Three mutations IVS10nt-11 G > A, R261Q, and A300S accounted for 30.5%, whereas the remaining mutations were found at relative frequencies of less than 5% and 20 mutations were observed once only. Five mutations have been detected only in Sicilians so far. By studying the association of mutations with intragenic STR-VNTR haplotypes ("minihaplotypes"), "identity by descent" has been established for 24 mutations also detected in other populations. This finding supports the hypothesis of a multipolar origin for a large proportion of PAH mutant alleles currently detected in Sicilians. In order to improve our understanding of the clinical heterogeneity of PAH deficiency in this population, we have for the first time analyzed three missense mutations L41F, T92I, and P211T in vitro by the pCDNA3/COS-7 eukaryotic expression system and found an activity of 10, 76, and 72%, respectively, compared to normal PAH. In two HPA patients with mild PKU and mild hyperphenylalaninemia (MHP), harboring respectively L41F/R261Q and T92I/P281L genotypes, the predicted biochemical effect of these genotypes appeared to be consistent with the metabolic phenotypes. In contrast, discordant metabolic phenotypes (mild PKU and MHP) were observed in two unrelated patients bearing the same R261Q/P211T genotype, a finding which underscores the complex relationship linking genotype to phenotype in PAH deficiency. Hypotheses on the possible mechanisms responsible for the observed discordance are discussed. The spectrum of PAH gene mutations in Sicily reflects the complex demographic history of this island at the crossroad of prehistoric and historical migrations in the Mediterranean sea. The data presented in this study also add to the present knowledge on the relationship between PAH genotypes and HPA phenotype and are expected to improve PAH genotyping among individuals with hyperphenylalaninemia.
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Affiliation(s)
- M G Mirisola
- Dipartimento di Biopatologia e Metodologie Biomediche, Facoltà di Medicina e Chirurgia, Università degli Studi di Palermo, Via Divisi 83, 90133 Palermo, Italy
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31
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National Institutes of Health Consensus Development Conference Statement: phenylketonuria: screening and management, October 16-18, 2000. Pediatrics 2001; 108:972-82. [PMID: 11581453 DOI: 10.1542/peds.108.4.972] [Citation(s) in RCA: 216] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
OBJECTIVE To provide health care providers, patients, and the general public with a responsible assessment of currently available data regarding screening for and management of phenylketonuria (PKU). PARTICIPANTS A nonfederal, nonadvocate, 14-member panel representing the fields of pediatrics, genetics, human development, public policy, nursing, and molecular physiology and including patient representatives. In addition, 19 experts in pediatrics, medical genetics, psychology, pediatric neurology, biochemical and molecular genetics, and gene therapy presented data to the panel and to a conference audience of 312. EVIDENCE The literature was searched using Medline for January 1980 through July 2000, and an extensive bibliography of 3394 references was provided to the panel. Experts prepared abstracts for their conference presentations with relevant citations from the literature. Scientific evidence was given precedence over clinical anecdotal experience. CONSENSUS PROCESS The panel, answering predefined questions, developed its conclusions based on the scientific evidence presented in open forum and the scientific literature. The panel composed a draft statement, which was read in its entirety and circulated to the experts and the audience for comment. Thereafter, the panel resolved conflicting recommendations and released a revised statement at the end of the conference. The panel finalized the revisions within a few weeks after the conference. The draft statement was made available on the World Wide Web immediately after its release at the conference and was updated with the panel's final revisions. The statement is available at http://consensus.nih.gov. CONCLUSIONS Genetic testing for PKU has been in place for almost 40 years and has been very successful in preventing severe mental retardation in thousands of children and adults. Metabolic control is necessary across the lifespan of individuals with PKU. A comprehensive, multidisciplinary, integrated system is needed to delivery of care to individuals with PKU. Greatly needed are consistency and coordination between screening, treatment, data collection, and patient support programs. There should be equal access to culturally sensitive, age-appropriate treatment programs. Ethically sound, specific policies for storage, ownership, and use in future studies of archived samples remaining from PKU testing should be established. Research into the pathophysiology of PKU and relationship to genetic, neural, and behavioral variation is strongly encouraged. Uniform policies must be established to remove financial barriers to the acquisition of medical foods and modified low-protein foods and to provide access to support services needed to maintain metabolic control in individuals with PKU. Research on nondietary alternative treatments for PKU is strongly encouraged. To achieve optimal statistical power and cross-cultural applicability, it will be beneficial to use data acquired via national and international collaboration.phenylketonuria, hyperphenylalanimea, phenylketonuria screening, phenylalanine-restricted diet, maternal phenylketonuria, newborn screening, phenylalanine monitoring, phenylketonuria outcomes.
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32
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Gregersen N, Andresen BS, Corydon MJ, Corydon TJ, Olsen RK, Bolund L, Bross P. Mutation analysis in mitochondrial fatty acid oxidation defects: Exemplified by acyl-CoA dehydrogenase deficiencies, with special focus on genotype-phenotype relationship. Hum Mutat 2001; 18:169-89. [PMID: 11524729 DOI: 10.1002/humu.1174] [Citation(s) in RCA: 127] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Mutation analysis of metabolic disorders, such as the fatty acid oxidation defects, offers an additional, and often superior, tool for specific diagnosis compared to traditional enzymatic assays. With the advancement of the structural part of the Human Genome Project and the creation of mutation databases, procedures for convenient and reliable genetic analyses are being developed. The most straightforward application of mutation analysis is to specific diagnoses in suspected patients, particularly in the context of family studies and for prenatal/preimplantation analysis. In addition, from these practical uses emerges the possibility to study genotype-phenotype relationships and investigate the molecular pathogenesis resulting from specific mutations or groups of mutations. In the present review we summarize current knowledge regarding genotype-phenotype relationships in three disorders of mitochondrial fatty acid oxidation: very-long chain acyl-CoA dehydrogenase (VLCAD, also ACADVL), medium-chain acyl-CoA dehydrogenase (MCAD, also ACADM), and short-chain acyl-CoA dehydrogenase (SCAD, also ACADS) deficiencies. On the basis of this knowledge we discuss current understanding of the structural implications of mutation type, as well as the modulating effect of the mitochondrial protein quality control systems, composed of molecular chaperones and intracellular proteases. We propose that the unraveling of the genetic and cellular determinants of the modulating effects of protein quality control systems may help to assess the balance between genetic and environmental factors in the clinical expression of a given mutation. The realization that the effect of the monogene, such as disease-causing mutations in the VLCAD, MCAD, and SCAD genes, may be modified by variations in other genes presages the need for profile analyses of additional genetic variations. The rapid development of mutation detection systems, such as the chip technologies, makes such profile analyses feasible. However, it remains to be seen to what extent mutation analysis will be used for diagnosis of fatty acid oxidation defects and other metabolic disorders.
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Affiliation(s)
- N Gregersen
- Research Unit for Molecular Medicine, Aarhus University Hospital and Faculty of Health Sciences, Aarhus, Denmark
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33
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Walter C, Gootjes J, Mooijer PA, Portsteffen H, Klein C, Waterham HR, Barth PG, Epplen JT, Kunau WH, Wanders RJA, Dodt G. Disorders of peroxisome biogenesis due to mutations in PEX1: phenotypes and PEX1 protein levels. Am J Hum Genet 2001; 69:35-48. [PMID: 11389485 PMCID: PMC1226046 DOI: 10.1086/321265] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2001] [Accepted: 04/17/2001] [Indexed: 01/07/2023] Open
Abstract
Zellweger syndrome (ZS), neonatal adrenoleukodystrophy (NALD), and infantile Refsum disease (IRD) are clinically overlapping syndromes, collectively called "peroxisome biogenesis disorders" (PBDs), with clinical features being most severe in ZS and least pronounced in IRD. Inheritance of these disorders is autosomal recessive. The peroxisome biogenesis disorders are genetically heterogeneous, having at least 12 different complementation groups (CGs). The gene affected in CG1 is PEX1. Approximately 65% of the patients with PBD harbor mutations in PEX1. In the present study, we used SSCP analysis to evaluate a series of patients belonging to CG1 for mutations in PEX1 and studied phenotype-genotype correlations. A complete lack of PEX1 protein was found to be associated with severe ZS; however, residual amounts of PEX1 protein were found in patients with the milder phenotypes, NALD and IRD. The majority of these latter patients carried at least one copy of the common G843D allele. When patient fibroblasts harboring this allele were grown at 30 degrees C, a two- to threefold increase in PEX1 protein levels was observed, associated with a recovery of peroxisomal function. This suggests that the G843D missense mutation results in a misfolded protein, which is more stable at lower temperatures. We conclude that the search for the factors and/or mechanisms that determine the stability of mutant PEX1 protein by high-throughput procedures will be a first step in the development of therapeutic strategies for patients with mild PBDs.
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Affiliation(s)
- Claudia Walter
- Institut für Physiologische Chemie, Abteilungen für Zellbiochemie und Systembiochemie, and Institut für Molekulare Humangenetik, Ruhr-Universität Bochum, Bochum, Germany; Departments of Clinical Chemistry, Neurology, and Pediatrics, Academic Medical Center, University of Amsterdam, Amsterdam
| | - Jeannette Gootjes
- Institut für Physiologische Chemie, Abteilungen für Zellbiochemie und Systembiochemie, and Institut für Molekulare Humangenetik, Ruhr-Universität Bochum, Bochum, Germany; Departments of Clinical Chemistry, Neurology, and Pediatrics, Academic Medical Center, University of Amsterdam, Amsterdam
| | - Petra A. Mooijer
- Institut für Physiologische Chemie, Abteilungen für Zellbiochemie und Systembiochemie, and Institut für Molekulare Humangenetik, Ruhr-Universität Bochum, Bochum, Germany; Departments of Clinical Chemistry, Neurology, and Pediatrics, Academic Medical Center, University of Amsterdam, Amsterdam
| | - Herma Portsteffen
- Institut für Physiologische Chemie, Abteilungen für Zellbiochemie und Systembiochemie, and Institut für Molekulare Humangenetik, Ruhr-Universität Bochum, Bochum, Germany; Departments of Clinical Chemistry, Neurology, and Pediatrics, Academic Medical Center, University of Amsterdam, Amsterdam
| | - Christina Klein
- Institut für Physiologische Chemie, Abteilungen für Zellbiochemie und Systembiochemie, and Institut für Molekulare Humangenetik, Ruhr-Universität Bochum, Bochum, Germany; Departments of Clinical Chemistry, Neurology, and Pediatrics, Academic Medical Center, University of Amsterdam, Amsterdam
| | - Hans R. Waterham
- Institut für Physiologische Chemie, Abteilungen für Zellbiochemie und Systembiochemie, and Institut für Molekulare Humangenetik, Ruhr-Universität Bochum, Bochum, Germany; Departments of Clinical Chemistry, Neurology, and Pediatrics, Academic Medical Center, University of Amsterdam, Amsterdam
| | - Peter G. Barth
- Institut für Physiologische Chemie, Abteilungen für Zellbiochemie und Systembiochemie, and Institut für Molekulare Humangenetik, Ruhr-Universität Bochum, Bochum, Germany; Departments of Clinical Chemistry, Neurology, and Pediatrics, Academic Medical Center, University of Amsterdam, Amsterdam
| | - Jörg T. Epplen
- Institut für Physiologische Chemie, Abteilungen für Zellbiochemie und Systembiochemie, and Institut für Molekulare Humangenetik, Ruhr-Universität Bochum, Bochum, Germany; Departments of Clinical Chemistry, Neurology, and Pediatrics, Academic Medical Center, University of Amsterdam, Amsterdam
| | - Wolf-H. Kunau
- Institut für Physiologische Chemie, Abteilungen für Zellbiochemie und Systembiochemie, and Institut für Molekulare Humangenetik, Ruhr-Universität Bochum, Bochum, Germany; Departments of Clinical Chemistry, Neurology, and Pediatrics, Academic Medical Center, University of Amsterdam, Amsterdam
| | - Ronald J. A. Wanders
- Institut für Physiologische Chemie, Abteilungen für Zellbiochemie und Systembiochemie, and Institut für Molekulare Humangenetik, Ruhr-Universität Bochum, Bochum, Germany; Departments of Clinical Chemistry, Neurology, and Pediatrics, Academic Medical Center, University of Amsterdam, Amsterdam
| | - Gabriele Dodt
- Institut für Physiologische Chemie, Abteilungen für Zellbiochemie und Systembiochemie, and Institut für Molekulare Humangenetik, Ruhr-Universität Bochum, Bochum, Germany; Departments of Clinical Chemistry, Neurology, and Pediatrics, Academic Medical Center, University of Amsterdam, Amsterdam
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Waters PJ, Scriver CR, Parniak MA. Homomeric and heteromeric interactions between wild-type and mutant phenylalanine hydroxylase subunits: evaluation of two-hybrid approaches for functional analysis of mutations causing hyperphenylalaninemia. Mol Genet Metab 2001; 73:230-8. [PMID: 11461190 DOI: 10.1006/mgme.2001.3198] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Phenylketonuria (PKU) is caused by mutations in the phenylalanine hydroxylase gene (PAH), while mutations in genes encoding the two enzymes (dihydropteridine reductase, DHPR, and pterin-4-alpha-carbinolamine dehydratase, PCD) required for recycling of its cofactor, tetrahydrobiopterin (BH(4)), cause other rarer disease forms of hyperphenylalaninemia. We have applied a yeast two-hybrid method, in which protein--protein interactions are measured by four reporter gene constructs, to the analysis of six PKU-associated PAH missense mutations (F39L, K42I, L48S, I65T, A104D, and R157N). By studying homomeric interactions between mutant PAH subunits, we show that this system is capable of detecting quite subtle aberrations in PAH oligomerization caused by missense mutations and that the observed results generally correlate with the severity of the mutation as determined by other expression systems. The mutant PAH subunits are also shown in this system to be able to interact with wild-type PAH subunits, pointing to an explanation for apparent dominant negative effects previously observed in obligate heterozygotes for PKU mutations. Based on our findings, the applications and limitations of two-hybrid approaches in understanding mechanisms by which PAH missense mutations exert their pathogenic effects are discussed. We have also used this technique to demonstrate homomeric interactions between wild-type DHPR subunits and between wild-type PCD subunits. These data provide a basis for functional studies on HPA-associated mutations affecting these enzymes.
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Affiliation(s)
- P J Waters
- deBelle Laboratory for Biochemical Genetics, Montreal Children's Hospital, Quebec, Canada.
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35
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Gjetting T, Petersen M, Guldberg P, Güttler F. Missense mutations in the N-terminal domain of human phenylalanine hydroxylase interfere with binding of regulatory phenylalanine. Am J Hum Genet 2001; 68:1353-60. [PMID: 11326337 PMCID: PMC1226122 DOI: 10.1086/320604] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2001] [Accepted: 04/06/2001] [Indexed: 11/03/2022] Open
Abstract
Hyperphenylalaninemia due to a deficiency of phenylalanine hydroxylase (PAH) is an autosomal recessive disorder caused by >400 mutations in the PAH gene. Recent work has suggested that the majority of PAH missense mutations impair enzyme activity by causing increased protein instability and aggregation. In this study, we describe an alternative mechanism by which some PAH mutations may render PAH defective. Database searches were used to identify regions in the N-terminal domain of PAH with homology to the regulatory domain of prephenate dehydratase (PDH), the rate-limiting enzyme in the bacterial phenylalanine biosynthesis pathway. Naturally occurring N-terminal PAH mutations are distributed in a nonrandom pattern and cluster within residues 46-48 (GAL) and 65-69 (IESRP), two motifs highly conserved in PDH. To examine whether N-terminal PAH mutations affect the ability of PAH to bind phenylalanine at the regulatory domain, wild-type and five mutant (G46S, A47V, T63P/H64N, I65T, and R68S) forms of the N-terminal domain (residues 2-120) of human PAH were expressed as fusion proteins in Escherichia coli. Binding studies showed that the wild-type form of this domain specifically binds phenylalanine, whereas all mutations abolished or significantly reduced this phenylalanine-binding capacity. Our data suggest that impairment of phenylalanine-mediated activation of PAH may be an important disease-causing mechanism of some N-terminal PAH mutations, which may explain some well-documented genotype-phenotype discrepancies in PAH deficiency.
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Affiliation(s)
- T Gjetting
- The John F. Kennedy Institute, DK-2600 Glostrup, Denmark
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36
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Gregersen N, Bross P, Andrese BS, Pedersen CB, Corydon TJ, Bolund L. The role of chaperone-assisted folding and quality control in inborn errors of metabolism: protein folding disorders. J Inherit Metab Dis 2001; 24:189-212. [PMID: 11405340 DOI: 10.1023/a:1010319001722] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Molecular chaperones are present in the various compartments of the cell and assist the folding of newly synthesized proteins. Compared to wild-type proteins, missense mutant proteins are generally synthesized in a normal fashion, but may be impaired in their folding. A broad array of diseases that are due to misfolding of mutant proteins may be labelled conformational diseases: aggregation diseases, such as Alzheimer disease; diseases caused by negative dominance from misfolded structural proteins, such as hypertrophic cardiomyopathy; and disorders where the misfolded protein is degraded by intracellular proteases. Many metabolic disorders belong to this last category, where the so-called protein quality control systems, comprising chaperones and proteases, attempt to eliminate folding intermediates or misfolded proteins. On the basis of in vitro experiments with a limited number of missense mutations identified in patients with phenylalanine hydroxylase and fatty acid oxidation deficiencies, we discuss the cellular fate of missense mutant proteins. We find that the balance between folding to functional conformers, retention (holding) and degradation of folding intermediates or misfolded proteins is dependent on the nature of the mutation and on the efficiency of the quality control. For example, low temperature may promote formation of functional conformers, while elevated temperature usually promotes retention and degradation. We conclude that disorders caused by many missense mutations are complex diseases in which the mutation itself is a necessary major primary component, but that its effect may be modified by cellular conditions and possibly by genetic variations in the quality control systems. We suggest that this new knowledge about cell handling may open new avenues of understanding of the cell pathology and treatment of patients with metabolic disorders.
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Affiliation(s)
- N Gregersen
- Research Unit for Molecular Medicine, Aarhus University Hospital and Faculty of Health Sciences, Aarhus University, Denmark
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37
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Abstract
Archibald Edward Garrod introduced a paradigm, new for its day, in medicine: Biochemistry is dynamic and different from the static nature of organic chemistry. It led him to think about metabolic pathways and to recognize that variation in Mendelian heredity could explain an 'inborn error of metabolism'. At the time, Garrod had no idea about the nature of a gene. Genes are now well understood, genomes are being described for one organism after another (including H. sapiens) and it is understood that genomes 'speak biochemistry (not phenotype)'. Accordingly, in the era of genomics, biochemistry and physiology become the bases of functional genomics and it is possible to appreciate why 'nothing in biology makes sense without evolution' (and nothing in medicine will make sense without biology). Mendelian, biochemical and molecular genetics together have revealed what lies behind the four canonical inborn errors described by Garrod (albinism, alkaptonuria, cystinuria and pentosuria). Both older and newer ideas in genetics, new tools for applying them, and renewed respect for the clinician-scientist will enhance our understanding of the human biological variation that accounts for variant states of health and overt disease; an 'unsimple' phenotype (phenylketonuria) is used to illustrate in some detail. What can be known and what ought to be done with knowledge about human genetics to benefit individuals, families and communities (society) is both opportunity and challenge.
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Affiliation(s)
- C R Scriver
- Department of Human Genetics, McGill University and McGill University Health Centre, Montreal, Quebec, Canada.
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Gjetting T, Petersen M, Guldberg P, Güttler F. In vitro expression of 34 naturally occurring mutant variants of phenylalanine hydroxylase: correlation with metabolic phenotypes and susceptibility toward protein aggregation. Mol Genet Metab 2001; 72:132-43. [PMID: 11161839 DOI: 10.1006/mgme.2000.3118] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Phenylalanine hydroxylase (PAH) is a homotetrameric enzyme that catalyzes the conversion of phenylalanine to tyrosine, the rate-limiting step of phenylalanine disposal in humans. Primary dysfunction of PAH caused by mutations in the PAH gene results in hyperphenylalaninemia, which may impair cognitive development unless corrected by dietary restriction of phenylalanine. The mechanism(s) by which PAH missense mutations cause enzyme impairment has been studied in detail only in a small number of cases, but existing evidence points to a major role of enhanced proteolytic degradation due to aberrant folding of mutant polypeptides. We have used two heterologous in vitro expression systems (a mammalian cell-free transcription-translation system and the pET system of Escherichia coli) to examine 34 mutations that have been associated with PAH deficiency in the Danish population. These mutations represent a broad range of amino acid substitutions, functional enzyme domains, and metabolic phenotypes. In both systems, residual in vitro activities correlated broadly with metabolic phenotypes, however, with significant discrepancies. Analysis of E. coli extracts by nondenaturing polyacrylamide gel electrophoresis and storage experiments showed that (i) in general, mutations in the N-terminal regulatory domain are associated with relatively stable proteins compared to most mutations in the central catalytic domain, and (ii) for mutations in the catalytic domain, high levels of protein aggregation do not always correspond with a severe phenotype. Our data support and extend previous evidence that PAH mutations exert their pathogenic effects by several distinct mechanisms that may operate individually or in concert.
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Affiliation(s)
- T Gjetting
- The John F. Kennedy Institute, Glostrup, Denmark
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39
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Gámez A, Pérez B, Ugarte M, Desviat LR. Expression analysis of phenylketonuria mutations. Effect on folding and stability of the phenylalanine hydroxylase protein. J Biol Chem 2000; 275:29737-42. [PMID: 10875932 DOI: 10.1074/jbc.m003231200] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Phenylketonuria is an autosomal recessive human genetic disease caused by mutations in the phenylalanine hydroxylase (PAH) gene. In the present work we have used different expression systems to reveal folding defects of the PAH protein caused by phenylketonuria mutations L348V, S349L, and V388M. The amount of mutant proteins and/or the residual activity can be rescued by chaperonin co-overexpression in Escherichia coli or growth at low temperature in COS cells. Thermal stability profiles and degradation time courses of PAH expressed in E. coli show that the mutant proteins are less stable than the wild-type enzyme, also confirmed by pulse-chase experiments using a coupled in vitro transcription-translation system. Size exclusion chromatography shows altered oligomerization, partially corrected with chaperonins coexpression, except for the S349L mutant protein, which is recovered as inactive aggregates. PAH subunit interaction is affected in the S349L protein, as demonstrated in a mammalian two-hybrid assay. In conclusion, serine 349, located in the three-dimensional structure lining the active site and involved in the structural maintenance of the iron binding site, is essential for the structural stability and assembly and also for the catalytic properties of the PAH enzyme, whereas the L348V and V388M mutations affect the folding properties and stability of the protein. The experimental modulation of mutant residual activity provides a potential explanation for the existing inconsistencies in the genotype-phenotype correlations.
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Affiliation(s)
- A Gámez
- Centro de Biologia Molecular Severo Ochoa, Consejo Superior de Investigaciones Cientificas-Universidad Autónoma de Madrid, 28049 Madrid, Spain
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