1
|
Huang Y, Zhu W, Zhou J, Huang Q, Zeng G. Navigating the Evolving Landscape of Primary Hyperoxaluria: Traditional Management Defied by the Rise of Novel Molecular Drugs. Biomolecules 2024; 14:511. [PMID: 38785918 PMCID: PMC11117870 DOI: 10.3390/biom14050511] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2024] [Revised: 04/10/2024] [Accepted: 04/12/2024] [Indexed: 05/25/2024] Open
Abstract
Primary hyperoxalurias (PHs) are inherited metabolic disorders marked by enzymatic cascade disruption, leading to excessive oxalate production that is subsequently excreted in the urine. Calcium oxalate deposition in the renal tubules and interstitium triggers renal injury, precipitating systemic oxalate build-up and subsequent secondary organ impairment. Recent explorations of novel therapeutic strategies have challenged and necessitated the reassessment of established management frameworks. The execution of diverse clinical trials across various medication classes has provided new insights and knowledge. With the evolution of PH treatments reaching a new milestone, prompt and accurate diagnosis is increasingly critical. Developing early, effective management and treatment plans is essential to improve the long-term quality of life for PH patients.
Collapse
Affiliation(s)
- Yueqi Huang
- The First Affiliated Hospital, Hengyang Medical School, University of South China, Hengyang 421001, China; (Y.H.); (J.Z.)
| | - Wei Zhu
- Department of Urology and Guangdong Key Laboratory of Urology, The First Affiliated Hospital of Guangzhou Medical University, Guangzhou 510230, China;
| | - Jia Zhou
- The First Affiliated Hospital, Hengyang Medical School, University of South China, Hengyang 421001, China; (Y.H.); (J.Z.)
| | - Qiulin Huang
- The First Affiliated Hospital, Hengyang Medical School, University of South China, Hengyang 421001, China; (Y.H.); (J.Z.)
| | - Guohua Zeng
- The First Affiliated Hospital, Hengyang Medical School, University of South China, Hengyang 421001, China; (Y.H.); (J.Z.)
- Department of Urology and Guangdong Key Laboratory of Urology, The First Affiliated Hospital of Guangzhou Medical University, Guangzhou 510230, China;
| |
Collapse
|
2
|
Mandrile G, Beck B, Acquaviva C, Rumsby G, Deesker L, Garrelfs S, Gupta A, Bacchetta J, Groothoff J. Genetic assessment in primary hyperoxaluria: why it matters. Pediatr Nephrol 2023; 38:625-634. [PMID: 35695965 PMCID: PMC9842587 DOI: 10.1007/s00467-022-05613-2] [Citation(s) in RCA: 21] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/29/2022] [Revised: 04/23/2022] [Accepted: 04/29/2022] [Indexed: 01/21/2023]
Abstract
Accurate diagnosis of primary hyperoxaluria (PH) has important therapeutic consequences. Since biochemical assessment can be unreliable, genetic testing is a crucial diagnostic tool for patients with PH to define the disease type. Patients with PH type 1 (PH1) have a worse prognosis than those with other PH types, despite the same extent of oxalate excretion. The relation between genotype and clinical phenotype in PH1 is extremely heterogeneous with respect to age of first symptoms and development of kidney failure. Some mutations are significantly linked to pyridoxine-sensitivity in PH1, such as homozygosity for p.G170R and p.F152I combined with a common polymorphism. Although patients with these mutations display on average better outcomes, they may also present with CKD stage 5 in infancy. In vitro studies suggest pyridoxine-sensitivity for some other mutations, but confirmatory clinical data are lacking (p.G47R, p.G161R, p.I56N/major allele) or scarce (p.I244T). These studies also suggest that other vitamin B6 derivatives than pyridoxine may be more effective and should be a focus for clinical testing. PH patients displaying the same mutation, even within one family, may have completely different clinical outcomes. This discordance may be caused by environmental or genetic factors that are unrelated to the effect of the causative mutation(s). No relation between genotype and clinical or biochemical phenotypes have been found so far in PH types 2 and 3. This manuscript reviews the current knowledge on the genetic background of the three types of primary hyperoxaluria and its impact on clinical management, including prenatal diagnosis.
Collapse
Affiliation(s)
- Giorgia Mandrile
- Medical Genetics Unit and Thalassemia Center, San Luigi University Hospital, University of Torino, Orbassano, TO, Italy
| | - Bodo Beck
- Institute of Human Genetics, Center for Molecular Medicine Cologne, and Center for Rare and Hereditary Kidney Disease, University Hospital of Cologne, CologneCologne, Germany
| | - Cecile Acquaviva
- Service de Biochimie Et Biologie Moléculaire, Hospices Civils de Lyon, UM Pathologies Héréditaires du Métabolisme Et du Globule Rouge, Lyon, France
| | - Gill Rumsby
- Department of Clinical Biochemistry, University College London Hospitals NHS Foundation Trust | UCLH, Kintbury, UK
| | - Lisa Deesker
- Department of Pediatric Nephrology, Emma Children's Hospital, Amsterdam UMC Location University of Amsterdam, Amsterdam, Netherlands
| | - Sander Garrelfs
- Department of Pediatric Nephrology, Emma Children's Hospital, Amsterdam UMC Location University of Amsterdam, Amsterdam, Netherlands
| | - Asheeta Gupta
- Department of Nephrology, Birmingham Women's and Children's NHS Foundation Trust, Birmingham, UK
| | - Justine Bacchetta
- Reference Center for Rare Renal Diseases, Pediatric Nephrology-Rheumatology-Dermatology Unit, Hospices Civils de Lyon, Femme Mere Enfant Hospital, Lyon 1 University, Bron, France
| | - Jaap Groothoff
- Department of Pediatric Nephrology, Emma Children's Hospital, Amsterdam UMC Location University of Amsterdam, Amsterdam, Netherlands.
| |
Collapse
|
3
|
Gatticchi L, Grottelli S, Ambrosini G, Pampalone G, Gualtieri O, Dando I, Bellezza I, Cellini B. CRISPR/Cas9-mediated knock-out of AGXT1 in HepG2 cells as a new in vitro model of Primary Hyperoxaluria Type 1. Biochimie 2022; 202:110-122. [PMID: 35964771 DOI: 10.1016/j.biochi.2022.08.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2021] [Revised: 08/04/2022] [Accepted: 08/06/2022] [Indexed: 11/02/2022]
Abstract
AGXT1 encodes alanine:glyoxylate aminotransferase 1 (AGT1), a liver peroxisomal pyridoxal 5'-phosphate dependent-enzyme whose deficit causes Primary Hyperoxaluria Type 1 (PH1). PH1 is a rare disease characterized by overproduction of oxalate, first leading to kidney stones formation, and possibly evolving to life-threatening systemic oxalosis. A minority of PH1 patients is responsive to pyridoxine, while the option for non-responders is liver-kidney transplantation. Therefore, huge efforts are currently focused on the identification of new therapies, including the promising approaches based on RNA silencing recently approved. Many PH1-associated mutations are missense and lead to a variety of kinetic and/or folding defects on AGT1. In this context, the availability of a reliable in vitro disease model would be essential to better understand the phenotype of known or newly-identified pathogenic variants as well as to test novel drug candidates. Here, we took advantage of the CRISPR/Cas9 technology to specifically knock-out AGXT1 in HepG2 cells, a hepatoma-derived cell model exhibiting a conserved glyoxylate metabolism. AGXT1-KO HepG2 displayed null AGT1 expression and significantly reduced transaminase activity leading to an enhanced secretion of oxalate upon glycolate challenge. Known pathogenic AGT1 variants expressed in AGXT1-KO HepG2 cells showed alteration in both protein levels and specific transaminase activity, as well as a partial mitochondrial mistargeting when associated with a common polymorphism. Notably, pyridoxine treatment was able to partially rescue activity and localization of clinically-responsive variants. Overall, our data validate AGXT1-KO HepG2 cells as a novel cellular model to investigate PH1 pathophysiology, and as a platform for drug discovery and development.
Collapse
Affiliation(s)
- Leonardo Gatticchi
- Department of Medicine and Surgery, Physiology and Biochemistry Section, University of Perugia, 06132, Perugia, Italy
| | - Silvia Grottelli
- Department of Medicine and Surgery, Physiology and Biochemistry Section, University of Perugia, 06132, Perugia, Italy
| | - Giulia Ambrosini
- Department of Neurosciences, Biomedicine and Movement Sciences, Biochemistry Section, University of Verona, 37134, Verona, Italy
| | - Gioena Pampalone
- Department of Medicine and Surgery, Physiology and Biochemistry Section, University of Perugia, 06132, Perugia, Italy
| | - Ottavia Gualtieri
- Department of Medicine and Surgery, Physiology and Biochemistry Section, University of Perugia, 06132, Perugia, Italy
| | - Ilaria Dando
- Department of Neurosciences, Biomedicine and Movement Sciences, Biochemistry Section, University of Verona, 37134, Verona, Italy
| | - Ilaria Bellezza
- Department of Medicine and Surgery, Physiology and Biochemistry Section, University of Perugia, 06132, Perugia, Italy
| | - Barbara Cellini
- Department of Medicine and Surgery, Physiology and Biochemistry Section, University of Perugia, 06132, Perugia, Italy.
| |
Collapse
|
4
|
Dindo M, Ambrosini G, Oppici E, Pey AL, O’Toole PJ, Marrison JL, Morrison IEG, Butturini E, Grottelli S, Costantini C, Cellini B. Dimerization Drives Proper Folding of Human Alanine:Glyoxylate Aminotransferase But Is Dispensable for Peroxisomal Targeting. J Pers Med 2021; 11:jpm11040273. [PMID: 33917320 PMCID: PMC8067440 DOI: 10.3390/jpm11040273] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2021] [Revised: 03/30/2021] [Accepted: 04/02/2021] [Indexed: 12/15/2022] Open
Abstract
Peroxisomal matrix proteins are transported into peroxisomes in a fully-folded state, but whether multimeric proteins are imported as monomers or oligomers is still disputed. Here, we used alanine:glyoxylate aminotransferase (AGT), a homodimeric pyridoxal 5′-phosphate (PLP)-dependent enzyme, whose deficit causes primary hyperoxaluria type I (PH1), as a model protein and compared the intracellular behavior and peroxisomal import of native dimeric and artificial monomeric forms. Monomerization strongly reduces AGT intracellular stability and increases its aggregation/degradation propensity. In addition, monomers are partly retained in the cytosol. To assess possible differences in import kinetics, we engineered AGT to allow binding of a membrane-permeable dye and followed its intracellular trafficking without interfering with its biochemical properties. By fluorescence recovery after photobleaching, we measured the import rate in live cells. Dimeric and monomeric AGT displayed a similar import rate, suggesting that the oligomeric state per se does not influence import kinetics. However, when dimerization is compromised, monomers are prone to misfolding events that can prevent peroxisomal import, a finding crucial to predicting the consequences of PH1-causing mutations that destabilize the dimer. Treatment with pyridoxine of cells expressing monomeric AGT promotes dimerization and folding, thus, demonstrating the chaperone role of PLP. Our data support a model in which dimerization represents a potential key checkpoint in the cytosol at the crossroad between misfolding and correct targeting, a possible general mechanism for other oligomeric peroxisomal proteins.
Collapse
Affiliation(s)
- Mirco Dindo
- Department of Medicine and Surgery, University of Perugia, 06132 Perugia, Italy; (M.D.); (S.G.); (C.C.)
| | - Giulia Ambrosini
- Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, 37134 Verona, Italy; (G.A.); (E.O.); (E.B.)
| | - Elisa Oppici
- Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, 37134 Verona, Italy; (G.A.); (E.O.); (E.B.)
| | - Angel L. Pey
- Departamento de Química Física, Unidad de Excelencia de Química Aplicada a Biomedicina y Medioambiente e Instituto de Biotecnología, Facultad de Ciencias, Universidad de Granada, 18071 Granada, Spain;
| | - Peter J. O’Toole
- Bioscience Technology Facility, Department of Biology, University of York, York YO23 3GE, UK; (P.J.O.); (J.L.M.); (I.E.G.M.)
| | - Joanne L. Marrison
- Bioscience Technology Facility, Department of Biology, University of York, York YO23 3GE, UK; (P.J.O.); (J.L.M.); (I.E.G.M.)
| | - Ian E. G. Morrison
- Bioscience Technology Facility, Department of Biology, University of York, York YO23 3GE, UK; (P.J.O.); (J.L.M.); (I.E.G.M.)
| | - Elena Butturini
- Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, 37134 Verona, Italy; (G.A.); (E.O.); (E.B.)
| | - Silvia Grottelli
- Department of Medicine and Surgery, University of Perugia, 06132 Perugia, Italy; (M.D.); (S.G.); (C.C.)
| | - Claudio Costantini
- Department of Medicine and Surgery, University of Perugia, 06132 Perugia, Italy; (M.D.); (S.G.); (C.C.)
| | - Barbara Cellini
- Department of Medicine and Surgery, University of Perugia, 06132 Perugia, Italy; (M.D.); (S.G.); (C.C.)
- Correspondence: ; Tel.: +39-075-585-8339
| |
Collapse
|
5
|
Halbritter J. Genetics of kidney stone disease-Polygenic meets monogenic. Nephrol Ther 2021; 17S:S88-S94. [PMID: 33910705 DOI: 10.1016/j.nephro.2020.02.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2020] [Accepted: 02/03/2020] [Indexed: 11/16/2022]
Abstract
Kidney stone disease comprising nephrolithiasis and nephrocalcinosis is a clinical syndrome of increasing prevalence with remarkable heterogeneity. Stone composition, age of manifestation, rate of recurrence, and impairment of kidney function varies with underlying etiologies. While calcium-based kidney stones account for the vast majority their etiology is still poorly understood. Recent studies underline the notion that genetic susceptibility together with dietary habits constitutes the major driver of kidney stone formation. In addition to single gene (Mendelian) disorders, which are most likely underestimated in the adult population, common risk alleles explain part of the observed heritability. Interestingly, identified GWAS loci often match those of Mendelian disease genes and vice versa (CASR, SLC34A1, CYP24A1). These findings provide mechanistic links related to renal calcium homeostasis, vitamin D metabolism, and CaSR-signaling regulated by the CaSR-CLDN14-CLDN16/19 axis (paracellular Ca2+ reabsorption) and TRPV5 (transcellular Ca2+ reabsorption). Recent identification of new single gene disorders of calcium-oxalate-nephrolithiasis (SLC26A1, CLDN2) and distal renal tubular acidosis with nephrocalcinosis (FOXI1, WDR72, ATP6V1C2) enabled additional insights into the kidney-gut axis and molecular prerequisites of proper urinary acidification. Implementation of centralized patient registries on hereditary kidney stone diseases are necessary to build up well characterized cohorts for urgently needed clinical studies.
Collapse
Affiliation(s)
- Jan Halbritter
- Medical Department III, Endocrinology, Nephrology and Rheumatology, Division of Nephrology, University of Leipzig Medical Center, Leipzig, Germany.
| |
Collapse
|
6
|
Cycloserine enantiomers are reversible inhibitors of human alanine:glyoxylate aminotransferase: implications for Primary Hyperoxaluria type 1. Biochem J 2020; 476:3751-3768. [PMID: 31794008 DOI: 10.1042/bcj20190507] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2019] [Revised: 11/12/2019] [Accepted: 12/03/2019] [Indexed: 12/14/2022]
Abstract
Peroxisomal alanine:glyoxylate aminotransferase (AGT) is responsible for glyoxylate detoxification in human liver and utilizes pyridoxal 5'-phosphate (PLP) as coenzyme. The deficit of AGT leads to Primary Hyperoxaluria Type I (PH1), a rare disease characterized by calcium oxalate stones deposition in the urinary tract as a consequence of glyoxylate accumulation. Most missense mutations cause AGT misfolding, as in the case of the G41R, which induces aggregation and proteolytic degradation. We have investigated the interaction of wild-type AGT and the pathogenic G41R variant with d-cycloserine (DCS, commercialized as Seromycin), a natural product used as a second-line treatment of multidrug-resistant tuberculosis, and its synthetic enantiomer l-cycloserine (LCS). In contrast with evidences previously reported on other PLP-enzymes, both ligands are AGT reversible inhibitors showing inhibition constants in the micromolar range. While LCS undergoes half-transamination generating a ketimine intermediate and behaves as a classical competitive inhibitor, DCS displays a time-dependent binding mainly generating an oxime intermediate. Using a mammalian cellular model, we found that DCS, but not LCS, is able to promote the correct folding of the G41R variant, as revealed by its increased specific activity and expression as a soluble protein. This effect also translates into an increased glyoxylate detoxification ability of cells expressing the variant upon treatment with DCS. Overall, our findings establish that DCS could play a role as pharmacological chaperone, thus suggesting a new line of intervention against PH1 based on a drug repositioning approach. To a widest extent, this strategy could be applied to other disease-causing mutations leading to AGT misfolding.
Collapse
|
7
|
Pfanner N, Warscheid B, Wiedemann N. Mitochondrial proteins: from biogenesis to functional networks. Nat Rev Mol Cell Biol 2020; 20:267-284. [PMID: 30626975 DOI: 10.1038/s41580-018-0092-0] [Citation(s) in RCA: 541] [Impact Index Per Article: 135.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Mitochondria are essential for the viability of eukaryotic cells as they perform crucial functions in bioenergetics, metabolism and signalling and have been associated with numerous diseases. Recent functional and proteomic studies have revealed the remarkable complexity of mitochondrial protein organization. Protein machineries with diverse functions such as protein translocation, respiration, metabolite transport, protein quality control and the control of membrane architecture interact with each other in dynamic networks. In this Review, we discuss the emerging role of the mitochondrial protein import machinery as a key organizer of these mitochondrial protein networks. The preprotein translocases that reside on the mitochondrial membranes not only function during organelle biogenesis to deliver newly synthesized proteins to their final mitochondrial destination but also cooperate with numerous other mitochondrial protein complexes that perform a wide range of functions. Moreover, these protein networks form membrane contact sites, for example, with the endoplasmic reticulum, that are key for integration of mitochondria with cellular function, and defects in protein import can lead to diseases.
Collapse
Affiliation(s)
- Nikolaus Pfanner
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, Freiburg, Germany. .,CIBSS Centre for Integrative Biological Signalling Studies, University of Freiburg, Freiburg, Germany.
| | - Bettina Warscheid
- CIBSS Centre for Integrative Biological Signalling Studies, University of Freiburg, Freiburg, Germany.,Institute of Biology II, Biochemistry - Functional Proteomics, Faculty of Biology, University of Freiburg, Freiburg, Germany
| | - Nils Wiedemann
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, Freiburg, Germany. .,CIBSS Centre for Integrative Biological Signalling Studies, University of Freiburg, Freiburg, Germany.
| |
Collapse
|
8
|
Fernández-Higuero JÁ, Betancor-Fernández I, Mesa-Torres N, Muga A, Salido E, Pey AL. Structural and functional insights on the roles of molecular chaperones in the mistargeting and aggregation phenotypes associated with primary hyperoxaluria type I. ADVANCES IN PROTEIN CHEMISTRY AND STRUCTURAL BIOLOGY 2018; 114:119-152. [PMID: 30635080 DOI: 10.1016/bs.apcsb.2018.09.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
To carry out their biological function in cells, proteins must be folded and targeted to the appropriate subcellular location. These processes are controlled by a vast collection of interacting proteins collectively known as the protein homeostasis network, in which molecular chaperones play a prominent role. Protein homeostasis can be impaired by inherited mutations leading to genetic diseases. In this chapter, we focus on a particular disease, primary hyperoxaluria type 1 (PH1), in which disease-associated mutations exacerbate protein aggregation in the cell and mistarget the peroxisomal alanine:glyoxylate aminotransferase (AGT) protein to mitochondria, in part due to native state destabilization and enhanced interaction with Hsp60, 70 and 90 chaperone systems. After a general introduction of molecular chaperones and PH1, we review our current knowledge on the structural and energetic features of PH1-causing mutants that lead to these particular pathogenic mechanisms. From this perspective, and in the context of the key role of molecular chaperones in PH1 pathogenesis, we present and discuss current and future perspectives for pharmacological treatments for this disease.
Collapse
Affiliation(s)
- José Ángel Fernández-Higuero
- Biofisika Institute (CSIC, UPV/EHU) and Department of Biochemistry and Molecular Biology, Faculty of Science and Technology, University of the Basque Country (UPV/EHU), Bilbao, Spain
| | - Isabel Betancor-Fernández
- Centre for Biomedical Research on Rare Diseases (CIBERER), Hospital Universitario de Canarias, ITB, University of La Laguna, Tenerife, Spain
| | - Noel Mesa-Torres
- Department of Physical Chemistry, University of Granada, Granada, Spain
| | - Arturo Muga
- Biofisika Institute (CSIC, UPV/EHU) and Department of Biochemistry and Molecular Biology, Faculty of Science and Technology, University of the Basque Country (UPV/EHU), Bilbao, Spain
| | - Eduardo Salido
- Centre for Biomedical Research on Rare Diseases (CIBERER), Hospital Universitario de Canarias, ITB, University of La Laguna, Tenerife, Spain
| | - Angel L Pey
- Department of Physical Chemistry, University of Granada, Granada, Spain.
| |
Collapse
|
9
|
Halbritter J, Seidel A, Müller L, Schönauer R, Hoppe B. Update on Hereditary Kidney Stone Disease and Introduction of a New Clinical Patient Registry in Germany. Front Pediatr 2018; 6:47. [PMID: 29564324 PMCID: PMC5850730 DOI: 10.3389/fped.2018.00047] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/04/2018] [Accepted: 02/19/2018] [Indexed: 12/15/2022] Open
Abstract
Kidney stone disease is an increasingly prevalent condition with remarkable clinical heterogeneity, with regards to stone composition, age of manifestation, rate of recurrence, and impairment of kidney function. Calcium-based kidney stones account for the vast majority of cases, but their etiology is poorly understood, notably their genetic drivers. As recent studies indicate, hereditary conditions are most likely underestimated in prevalence, and new disease genes are constantly being identified. As a consequence, there is an urgent need of a more efficient documentation and collection of cases with underlying hereditary conditions, to better understand shared phenotypic presentation and common molecular mechanisms. By implementation of a centralized patient registry on hereditary kidney stone disease in Germany, we aim to help closing the vast knowledge gap on genetics of kidney stone disease. In this context, clinical registries are indispensable for several reasons: first, delineating better phenotype-genotype associations will allow more precise patient stratification in future clinical research studies. Second, identifying new disease genes and new mechanisms will further reduce the rate of unknown nephrolithiasis/nephrocalcinosis etiology; and third, deciphering new molecular targets will pave the way to develop drugs for recurrence prevention in severely affected families.
Collapse
Affiliation(s)
- Jan Halbritter
- Division of Nephrology, Department of Internal Medicine, University of Leipzig, Leipzig, Germany
| | - Anna Seidel
- Division of Nephrology, Department of Internal Medicine, University of Leipzig, Leipzig, Germany
| | - Luise Müller
- Division of Nephrology, Department of Internal Medicine, University of Leipzig, Leipzig, Germany
| | - Ria Schönauer
- Division of Nephrology, Department of Internal Medicine, University of Leipzig, Leipzig, Germany
| | - Bernd Hoppe
- Division of Pediatric Nephrology, University Children's Hospital, Bonn, Germany
| |
Collapse
|
10
|
Bridges RJ, Bradbury NA. Cystic Fibrosis, Cystic Fibrosis Transmembrane Conductance Regulator and Drugs: Insights from Cellular Trafficking. Handb Exp Pharmacol 2018; 245:385-425. [PMID: 29460152 DOI: 10.1007/164_2018_103] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The eukaryotic cell is organized into membrane-delineated compartments that are characterized by specific cadres of proteins sustaining biochemically distinct cellular processes. The appropriate subcellular localization of proteins is key to proper organelle function and provides a physiological context for cellular processes. Disruption of normal trafficking pathways for proteins is seen in several genetic diseases, where a protein's absence for a specific subcellular compartment leads to organelle disruption, and in the context of an individual, a disruption of normal physiology. Importantly, several drug therapies can also alter protein trafficking, causing unwanted side effects. Thus, a deeper understanding of trafficking pathways needs to be appreciated as novel therapeutic modalities are proposed. Despite the promising efficacy of novel therapeutic agents, the intracellular bioavailability of these compounds has proved to be a potential barrier, leading to failures in treatments for various diseases and disorders. While endocytosis of drug moieties provides an efficient means of getting material into cells, the subsequent release and endosomal escape of materials into the cytosol where they need to act has been a barrier. An understanding of cellular protein/lipid trafficking pathways has opened up strategies for increasing drug bioavailability. Approaches to enhance endosomal exit have greatly increased the cytosolic bioavailability of drugs and will provide a means of investigating previous drugs that may have been shelved due to their low cytosolic concentration.
Collapse
Affiliation(s)
- Robert J Bridges
- Department of Physiology and Biophysics, Chicago Medical School, North Chicago, IL, USA
| | - Neil A Bradbury
- Department of Physiology and Biophysics, Chicago Medical School, North Chicago, IL, USA.
| |
Collapse
|
11
|
Oppici E, Dindo M, Conter C, Borri Voltattorni C, Cellini B. Folding Defects Leading to Primary Hyperoxaluria. Handb Exp Pharmacol 2018; 245:313-343. [PMID: 29071511 DOI: 10.1007/164_2017_59] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Protein misfolding is becoming one of the main mechanisms underlying inherited enzymatic deficits. This review is focused on primary hyperoxalurias, a group of disorders of glyoxylate detoxification associated with massive calcium oxalate deposition mainly in the kidneys. The most common and severe form, primary hyperoxaluria Type I, is due to the deficit of liver peroxisomal alanine/glyoxylate aminotransferase (AGT). Various studies performed in the last decade clearly evidence that many pathogenic missense mutations prevent the AGT correct folding, leading to various downstream effects including aggregation, increased degradation or mistargeting to mitochondria. Primary hyperoxaluria Type II and primary hyperoxaluria Type III are due to the deficit of glyoxylate reductase/hydroxypyruvate reductase (GRHPR) and 4-hydroxy-2-oxoglutarate aldolase (HOGA1), respectively. Although the molecular features of pathogenic variants of GRHPR and HOGA1 have not been investigated in detail, the data available suggest that some of them display folding defects. Thus, primary hyperoxalurias can be ranked among protein misfolding disorders, because in most cases the enzymatic deficit is due to the inability of each enzyme to reach its native and functional conformation. It follows that molecules able to improve the folding yield of the enzymes involved in each disease form could represent new therapeutic strategies.
Collapse
Affiliation(s)
- Elisa Oppici
- Department of Neurosciences, Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, Strada Le Grazie 8, 37134, Verona, Italy
| | - Mirco Dindo
- Department of Neurosciences, Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, Strada Le Grazie 8, 37134, Verona, Italy
| | - Carolina Conter
- Department of Neurosciences, Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, Strada Le Grazie 8, 37134, Verona, Italy
| | - Carla Borri Voltattorni
- Department of Neurosciences, Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, Strada Le Grazie 8, 37134, Verona, Italy.
| | - Barbara Cellini
- Department of Experimental Medicine, University of Perugia, Piazzale Gambuli 1, 06132, Perugia, Italy.
| |
Collapse
|
12
|
Bhattacharya R, Rose PW, Burley SK, Prlić A. Impact of genetic variation on three dimensional structure and function of proteins. PLoS One 2017; 12:e0171355. [PMID: 28296894 PMCID: PMC5351996 DOI: 10.1371/journal.pone.0171355] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2016] [Accepted: 01/19/2017] [Indexed: 11/18/2022] Open
Abstract
The Protein Data Bank (PDB; http://wwpdb.org) was established in 1971 as the first open access digital data resource in biology with seven protein structures as its initial holdings. The global PDB archive now contains more than 126,000 experimentally determined atomic level three-dimensional (3D) structures of biological macromolecules (proteins, DNA, RNA), all of which are freely accessible via the Internet. Knowledge of the 3D structure of the gene product can help in understanding its function and role in disease. Of particular interest in the PDB archive are proteins for which 3D structures of genetic variant proteins have been determined, thus revealing atomic-level structural differences caused by the variation at the DNA level. Herein, we present a systematic and qualitative analysis of such cases. We observe a wide range of structural and functional changes caused by single amino acid differences, including changes in enzyme activity, aggregation propensity, structural stability, binding, and dissociation, some in the context of large assemblies. Structural comparison of wild type and mutated proteins, when both are available, provide insights into atomic-level structural differences caused by the genetic variation.
Collapse
Affiliation(s)
- Roshni Bhattacharya
- Bioinformatics and Medical Informatics, San Diego State University, San Diego, California, United States of America
| | - Peter W. Rose
- RCSB Protein Data Bank, San Diego Supercomputer Center, University of California San Diego, La Jolla, California, United States of America
| | - Stephen K. Burley
- RCSB Protein Data Bank, San Diego Supercomputer Center, University of California San Diego, La Jolla, California, United States of America
- RCSB Protein Data Bank, Department of Chemistry and Chemical Biology, Center for Integrative Proteomics Research, Institute for Quantitative Biomedicine, and Cancer Institute of New Jersey, Rutgers, The State University of New Jersey, Piscataway, New Jersey, United States of America
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, California, United States of America
| | - Andreas Prlić
- RCSB Protein Data Bank, San Diego Supercomputer Center, University of California San Diego, La Jolla, California, United States of America
- * E-mail:
| |
Collapse
|
13
|
Affiliation(s)
- Barbara Cellini
- Department of Neuroscience, Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, Verona (VR), Italy
| |
Collapse
|
14
|
Saryi NAA, Hutchinson JD, Al-Hejjaj MY, Sedelnikova S, Baker P, Hettema EH. Pnc1 piggy-back import into peroxisomes relies on Gpd1 homodimerisation. Sci Rep 2017; 7:42579. [PMID: 28209961 PMCID: PMC5314374 DOI: 10.1038/srep42579] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2016] [Accepted: 12/29/2016] [Indexed: 12/17/2022] Open
Abstract
Peroxisomes are eukaryotic organelles that posttranslationally import proteins via one of two conserved peroxisomal targeting signal (PTS1 or 2) mediated pathways. Oligomeric proteins can be imported via these pathways but evidence is accumulating that at least some PTS1-containing monomers enter peroxisomes before they assemble into oligomers. Some proteins lacking a PTS are imported by piggy-backing onto PTS-containing proteins. One of these proteins is the nicotinamidase Pnc1, that is co-imported with the PTS2-containing enzyme Glycerol-3-phosphate dehydrogenase 1, Gpd1. Here we show that Pnc1 co-import requires Gpd1 to form homodimers. A mutation that interferes with Gpd1 homodimerisation does not prevent Gpd1 import but prevents Pnc1 co-import. A suppressor mutation that restores Gpd1 homodimerisation also restores Pnc1 co-import. In line with this, Pnc1 interacts with Gpd1 in vivo only when Gpd1 can form dimers. Redirection of Gpd1 from the PTS2 import pathway to the PTS1 import pathway supports Gpd1 monomer import but not Gpd1 homodimer import and Pnc1 co-import. Our results support a model whereby Gpd1 may be imported as a monomer or a dimer but only the Gpd1 dimer facilitates co-transport of Pnc1 into peroxisomes.
Collapse
Affiliation(s)
- Nadal A Al Saryi
- Department of Molecular Biology and Biotechnology University of Sheffield Firth Court, Western Bank Sheffield S10 2TN United Kingdom
| | - John D Hutchinson
- Department of Molecular Biology and Biotechnology University of Sheffield Firth Court, Western Bank Sheffield S10 2TN United Kingdom
| | - Murtakab Y Al-Hejjaj
- Department of Molecular Biology and Biotechnology University of Sheffield Firth Court, Western Bank Sheffield S10 2TN United Kingdom
| | - Svetlana Sedelnikova
- Department of Molecular Biology and Biotechnology University of Sheffield Firth Court, Western Bank Sheffield S10 2TN United Kingdom
| | - Patrick Baker
- Department of Molecular Biology and Biotechnology University of Sheffield Firth Court, Western Bank Sheffield S10 2TN United Kingdom
| | - Ewald H Hettema
- Department of Molecular Biology and Biotechnology University of Sheffield Firth Court, Western Bank Sheffield S10 2TN United Kingdom
| |
Collapse
|
15
|
M'dimegh S, Omezzine A, M'barek I, Moussa A, Mabrouk S, Kaarout H, Souche G, Chemli J, Aloui S, Aquaviva-Bourdain C, Achour A, Abroug S, Bouslama A. Mutational Analysis of Agxt in Tunisian Population with Primary Hyperoxaluria Type 1. Ann Hum Genet 2016; 81:1-10. [PMID: 27935012 DOI: 10.1111/ahg.12178] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2016] [Accepted: 11/10/2016] [Indexed: 01/25/2023]
Abstract
BACKGROUND Primary hyperoxaluria type 1 (PH1) is an autosomal recessive metabolic disorder caused by inherited mutations in the AGXT gene encoding liver peroxisomal alanine:glyoxylate aminotransferase (AGT). PH1 is a clinically and genetically heterogeneous disorder. The aim of our study was to analyze and characterize the mutational spectrum of PH1 in Tunisian patients. MATERIALS AND METHODS Molecular studies of 146 Tunisian patients suspected with PH were performed by PCR/Restriction fragment length polymorphism (RFLP) to detect seven mutations described as the most common. Direct sequencing for the 11 exons was performed in patients in whom any mutation was not identified. RESULTS The genetic diagnosis of PH1 was confirmed in 62.3% of patients. The first molecular approach based on PCR/restriction enzyme test was positive in 37.6% of patients, whereas the second molecular approach based on whole gene sequencing was successful in 24% of cases. Twelve pathogenic mutations were detected in our cohort. Two mutations were novel, and five were detected for the first time in Tunisians. The three most frequent mutations were p.Ile244Thr, p.Gly190Arg, and c.33dupC, with a frequency of 43.4%, 21.4%, and 13.1%, respectively. CONCLUSION The two novel mutations detected in our study extend the spectrum of known AGXT gene mutations. The screen for the mutations identified in this study can provide a useful, cost-effective, and first-line investigation in Tunisian PH1 patients.
Collapse
Affiliation(s)
- Saoussen M'dimegh
- Biochemistry Department, Sahloul University Hospital, Sousse, Tunisia
| | - Asma Omezzine
- Biochemistry Department, Sahloul University Hospital, Sousse, Tunisia
| | - Ibtihel M'barek
- Biochemistry Department, Sahloul University Hospital, Sousse, Tunisia
| | - Amira Moussa
- Biochemistry Department, Sahloul University Hospital, Sousse, Tunisia
| | - Sameh Mabrouk
- Biochemistry Department, Sahloul University Hospital, Sousse, Tunisia
| | - Hayet Kaarout
- Internal Medicine A Department, Charles Nicolle University Hospital, Tunis, Tunisia
| | - Geneviéve Souche
- Laboratory of Inborn Metabolic Diseases, Centre de Biologie Est, Hospices Civils de Lyon, Lyon, France
| | - Jalel Chemli
- Pediatric Department, Sahloul University Hospital, Sousse, Tunisia
| | - Sabra Aloui
- Nephrology Department, Fatouma Bourguiba University Hospital, Monastir, Tunisia
| | - Cécile Aquaviva-Bourdain
- Laboratory of Inborn Metabolic Diseases, Centre de Biologie Est, Hospices Civils de Lyon, Lyon, France
| | | | - Saoussen Abroug
- Pediatric Department, Sahloul University Hospital, Sousse, Tunisia
| | - Ali Bouslama
- Biochemistry Department, Sahloul University Hospital, Sousse, Tunisia
| |
Collapse
|
16
|
Genetic defects underlying renal stone disease. Int J Surg 2016; 36:590-595. [PMID: 27838384 DOI: 10.1016/j.ijsu.2016.11.015] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2016] [Revised: 11/06/2016] [Accepted: 11/07/2016] [Indexed: 12/19/2022]
Abstract
Renal stones are common and are usually secondary to risk factors affecting the solubility of substances in the urinary tract. Primary, that is genetic, causes are rare but nevertheless are important to recognise so that appropriate treatments can be instigated and the risks to other family members acknowledged. A brief overview of the investigation of renal stones from a biochemical point of view is presented with emphasis on the problems that can arise. The genetic basis of renal stone disease caused by (i) derangement of a metabolic pathway, (ii) diversion to an insoluble product, (iii) failure of transport and (iv) renal tubular acidosis is described by reference to the disorders of adenine phosphoribosyl transferase (APRT) deficiency, primary hyperoxaluria, cystinuria and autosomal dominant distal renal tubular acidosis.
Collapse
|
17
|
Effects of interface mutations on the dimerization of alanine glyoxylate aminotransferase and implications in the mistargeting of the pathogenic variants F152I and I244T. Biochimie 2016; 131:137-148. [PMID: 27720751 DOI: 10.1016/j.biochi.2016.10.001] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2016] [Revised: 10/02/2016] [Accepted: 10/02/2016] [Indexed: 11/21/2022]
Abstract
In this work the dimerization process of the minor allelic form of human alanine glyoxylate aminotransferase, a pyridoxal 5'-phosphate enzyme, was investigated. Bioinformatic analyses followed by site-directed mutagenesis, size exclusion chromatography and catalytic activity experiments allowed us to identify Arg118, Phe238 and Phe240 as interfacial residues not essential for transaminase activity but important for dimer-monomer dissociation. The apo and the holo forms of the triple mutant R118A-Mi/F238S-Mi/F240S-Mi display a dimer-monomer equilibrium dissociation constant value at least ~260- and 31-fold larger, respectively, than the corresponding ones of AGT-Mi. In the presence of PLP, the apomonomer of the triple mutant undergoes a biphasic process: the fast phase represents the formation of an inactive PLP-bound monomer, while the slow phase depicts the monomer-monomer association that parallels the regain of transaminase activity. The latter events occur with a rate constant of ~0.02 μM-1min-1. In the absence of PLP, the apomonomer is also able to dimerize but with a rate constant value ~2700-fold lower. Thereafter, the possible interference with the dimerization process of AGT-Mi exerted by the mutated residues in the I244T-Mi and F152I-Mi variants associated with Primary Hyperoxaluria type 1 was investigated by molecular dynamics simulations. On the basis of the present and previous studies, a model for the dimerization process of AGT-Mi, I244T-Mi and F152I-Mi, which outlines the structural defects responsible for the complete or partial mistargeting of the pathogenic variants, was proposed and discussed.
Collapse
|
18
|
High throughput cell-based assay for identification of glycolate oxidase inhibitors as a potential treatment for Primary Hyperoxaluria Type 1. Sci Rep 2016; 6:34060. [PMID: 27670739 PMCID: PMC5037430 DOI: 10.1038/srep34060] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2015] [Accepted: 09/05/2016] [Indexed: 12/11/2022] Open
Abstract
Glycolate oxidase (GO) and alanine:glyoxylate aminotransferase (AGT) are both involved in the peroxisomal glyoxylate pathway. Deficiency in AGT function causes the accumulation of intracellular oxalate and the primary hyperoxaluria type 1 (PH1). AGT enhancers or GO inhibitors may restore the abnormal peroxisomal glyoxylate pathway in PH1 patients. With stably transformed cells which mimic the glyoxylate metabolic pathway, we developed an indirect glycolate cytotoxicity assay in a 1,536-well plate format for high throughput screening. This assay can be used to identify compounds that reduce indirect glycolate-induced cytotoxicity by either enhancing AGT activity or inhibiting GO. A pilot screen of 4,096 known compounds identified two membrane permeable GO inhibitors: dichromate salt and colistimethate. We also developed a GO enzyme assay using the hydrogen peroxide-Amplex red reporter system. The IC50 values of potassium dichromate, sodium dichromate, and colistimethate sodium were 0.096, 0.108, and 2.3 μM in the GO enzyme assay, respectively. Further enzyme kinetic study revealed that both types of compounds inhibit GO activity by the mixed linear inhibition. Our results demonstrate that the cell-based assay and GO enzyme assay developed in this study are useful for further screening of large compound libraries for drug development to treat PH1.
Collapse
|
19
|
Caenorhabditis elegans AGXT-1 is a mitochondrial and temperature-adapted ortholog of peroxisomal human AGT1: New insights into between-species divergence in glyoxylate metabolism. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2016; 1864:1195-1205. [PMID: 27179589 DOI: 10.1016/j.bbapap.2016.05.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2016] [Revised: 04/27/2016] [Accepted: 05/10/2016] [Indexed: 11/23/2022]
|
20
|
Braun DA, Lawson JA, Gee HY, Halbritter J, Shril S, Tan W, Stein D, Wassner AJ, Ferguson MA, Gucev Z, Fisher B, Spaneas L, Varner J, Sayer JA, Milosevic D, Baum M, Tasic V, Hildebrandt F. Prevalence of Monogenic Causes in Pediatric Patients with Nephrolithiasis or Nephrocalcinosis. Clin J Am Soc Nephrol 2016; 11:664-72. [PMID: 26787776 DOI: 10.2215/cjn.07540715] [Citation(s) in RCA: 87] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2015] [Accepted: 12/02/2015] [Indexed: 12/27/2022]
Abstract
BACKGROUND AND OBJECTIVES Nephrolithiasis is a prevalent condition that affects 10%-15% of adults in their lifetime. It is associated with high morbidity due to colicky pain, the necessity for surgical intervention, and sometimes progression to CKD. In recent years, multiple monogenic causes of nephrolithiasis and nephrocalcinosis have been identified. However, the prevalence of each monogenic gene in a pediatric renal stone cohort has not yet been extensively studied. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS To determine the percentage of cases that can be explained molecularly by mutations in one of 30 known nephrolithiasis/nephrocalcinosis genes, we conducted a high-throughput exon sequencing analysis in an international cohort of 143 individuals <18 years of age, with nephrolithiasis (n=123) or isolated nephrocalcinosis (n=20). Over 7 months, all eligible individuals at three renal stone clinics in the United States and Europe were approached for study participation. RESULTS We detected likely causative mutations in 14 of 30 analyzed genes, leading to a molecular diagnosis in 16.8% (24 of 143) of affected individuals; 12 of the 27 detected mutations were not previously described as disease causing (44.4%). We observed that in our cohort all individuals with infantile manifestation of nephrolithiasis or nephrocalcinosis had causative mutations in recessive rather than dominant monogenic genes. In individuals who manifested later in life, causative mutations in dominant genes were more frequent. CONCLUSIONS We present the first exclusively pediatric cohort examined for monogenic causes of nephrolithiasis/nephrocalcinosis, and suggest that important therapeutic and preventative measures may result from mutational analysis in individuals with early manifestation of nephrolithiasis or nephrocalcinosis.
Collapse
Affiliation(s)
| | | | - Heon Yung Gee
- Division of Nephrology, Department of Medicine and Department of Pharmacology, Brain Korea 21 PLUS Project for Medical Sciences, Yonsei University College of Medicine, Seoul, Republic of Korea
| | - Jan Halbritter
- Division of Nephrology, Department of Medicine and Division of Endocrinology/Nephrology, Department of Internal Medicine, University Clinic Leipzig, Leipzig, Germany
| | | | - Weizhen Tan
- Division of Nephrology, Department of Medicine and
| | | | - Ari J Wassner
- Division of Endocrinology, Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts
| | | | - Zoran Gucev
- Department of Pediatric Nephrology, Medical Faculty Skopje, University Children's Hospital, Skopje, Macedonia
| | | | | | | | - John A Sayer
- Institute of Genetic Medicine, International Centre for Life, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Danko Milosevic
- Department of Pediatric Nephrology, Dialysis and Transplantation, Clinical Hospital Center Zagreb, University of Zagreb Medical School, Zagreb, Croatia; and
| | | | - Velibor Tasic
- Department of Pediatric Nephrology, Medical Faculty Skopje, University Children's Hospital, Skopje, Macedonia
| | - Friedhelm Hildebrandt
- Division of Nephrology, Department of Medicine and Howard Hughes Medical Institute, Chevy Chase, Maryland
| |
Collapse
|
21
|
Vivante A, Hildebrandt F. Exploring the genetic basis of early-onset chronic kidney disease. Nat Rev Nephrol 2016; 12:133-46. [PMID: 26750453 DOI: 10.1038/nrneph.2015.205] [Citation(s) in RCA: 215] [Impact Index Per Article: 26.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
The primary causes of chronic kidney disease (CKD) in children differ from those of CKD in adults. In the USA the most common diagnostic groups of renal disease that manifest before the age of 25 years are congenital anomalies of the kidneys and urinary tract, steroid-resistant nephrotic syndrome, chronic glomerulonephritis and renal cystic ciliopathies, which together encompass >70% of early-onset CKD diagnoses. Findings from the past decade suggest that early-onset CKD is caused by mutations in any one of over 200 different monogenic genes. Developments in high-throughput sequencing in the past few years has rendered identification of causative mutations in this high number of genes feasible. Use of genetic analyses in patients with early onset-CKD will provide patients and their families with a molecular genetic diagnosis, generate new insights into disease mechanisms, facilitate aetiology-based classifications of patient cohorts for clinical studies, and might have consequences for personalized approaches to the prevention and treatment of CKD. In this Review, we discuss the implications of next-generation sequencing in clinical genetic diagnostics and the discovery of novel genes in early-onset CKD. We also delineate the resulting opportunities for deciphering disease mechanisms and the therapeutic implications of these findings.
Collapse
Affiliation(s)
- Asaf Vivante
- Department of Medicine, Boston Children's Hospital, Harvard Medical School, 300 Longwood Avenue, Boston, Massachusetts 02115, USA.,Talpiot Medical Leadership Program, Sheba Medical Center, Tel-Hashomer 52621, Israel
| | - Friedhelm Hildebrandt
- Department of Medicine, Boston Children's Hospital, Harvard Medical School, 300 Longwood Avenue, Boston, Massachusetts 02115, USA
| |
Collapse
|
22
|
Oppici E, Montioli R, Dindo M, Maccari L, Porcari V, Lorenzetto A, Chellini S, Voltattorni CB, Cellini B. The Chaperoning Activity of Amino-oxyacetic Acid on Folding-Defective Variants of Human Alanine:Glyoxylate Aminotransferase Causing Primary Hyperoxaluria Type I. ACS Chem Biol 2015; 10:2227-36. [PMID: 26161999 DOI: 10.1021/acschembio.5b00480] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The rare disease Primary Hyperoxaluria Type I (PH1) results from the deficit of liver peroxisomal alanine:glyoxylate aminotransferase (AGT), as a consequence of inherited mutations on the AGXT gene frequently leading to protein misfolding. Pharmacological chaperone (PC) therapy is a newly developed approach for misfolding diseases based on the use of small molecule ligands able to promote the correct folding of a mutant enzyme. In this report, we describe the interaction of amino-oxyacetic acid (AOA) with the recombinant purified form of two polymorphic species of AGT, AGT-Ma and AGT-Mi, and with three pathogenic variants bearing previously identified folding defects: G41R-Ma, G170R-Mi, and I244T-Mi. We found that for all these enzyme AOA (i) forms an oxime at the active site, (ii) behaves as a slow, tight-binding inhibitor with KI values in the nanomolar range, and (iii) increases the thermal stability. Furthermore, experiments performed in mammalian cells revealed that AOA acts as a PC by partly preventing the intracellular aggregation of G41R-Ma and by promoting the correct peroxisomal import of G170R-Mi and I244T-Mi. Based on these data, we carried out a small-scale screening campaign. We identified four AOA analogues acting as AGT inhibitors, even if only one was found to act as a PC. The possible relationship between the structure and the PC activity of these compounds is discussed. Altogether, these results provide the proof-of-principle for the feasibility of a therapy with PCs for PH1-causing variants bearing folding defects and provide the scaffold for the identification of more specific ligands.
Collapse
Affiliation(s)
- Elisa Oppici
- Department
of Life Sciences and Reproduction, Section of Biological Chemistry, University of Verona, Strada Le Grazie 8 37134 Verona, Italy
| | - Riccardo Montioli
- Department
of Life Sciences and Reproduction, Section of Biological Chemistry, University of Verona, Strada Le Grazie 8 37134 Verona, Italy
| | - Mirco Dindo
- Department
of Life Sciences and Reproduction, Section of Biological Chemistry, University of Verona, Strada Le Grazie 8 37134 Verona, Italy
| | - Laura Maccari
- Siena Biotech S.p.A., Strada
del Petriccio e Belriguardo, 35 53100 Siena, Italy
| | - Valentina Porcari
- Siena Biotech S.p.A., Strada
del Petriccio e Belriguardo, 35 53100 Siena, Italy
| | - Antonio Lorenzetto
- Department
of Life Sciences and Reproduction, Section of Biological Chemistry, University of Verona, Strada Le Grazie 8 37134 Verona, Italy
| | - Sara Chellini
- Siena Biotech S.p.A., Strada
del Petriccio e Belriguardo, 35 53100 Siena, Italy
| | - Carla Borri Voltattorni
- Department
of Life Sciences and Reproduction, Section of Biological Chemistry, University of Verona, Strada Le Grazie 8 37134 Verona, Italy
| | - Barbara Cellini
- Department
of Life Sciences and Reproduction, Section of Biological Chemistry, University of Verona, Strada Le Grazie 8 37134 Verona, Italy
| |
Collapse
|
23
|
Ben-Shalom E, Frishberg Y. Primary hyperoxalurias: diagnosis and treatment. Pediatr Nephrol 2015; 30:1781-91. [PMID: 25519509 DOI: 10.1007/s00467-014-3030-1] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/31/2014] [Revised: 11/21/2014] [Accepted: 12/02/2014] [Indexed: 01/22/2023]
Abstract
Primary hyperoxalurias (PH) comprise a group of three distinct metabolic diseases caused by derangement of glyoxylate metabolism in the liver. Recent years have seen advances in several aspects of PH research. This paper reviews current knowledge of the genetic and biochemical basis of PH, the specific epidemiology and clinical presentation of each type, and therapeutic approaches in different disease stages. Potential future specific therapies are discussed.
Collapse
Affiliation(s)
- Efrat Ben-Shalom
- Division of Pediatric Nephrology, Shaare Zedek Medical Center, P.O.Box 3235, Jerusalem, Israel
| | | |
Collapse
|
24
|
Montioli R, Oppici E, Dindo M, Roncador A, Gotte G, Cellini B, Borri Voltattorni C. Misfolding caused by the pathogenic mutation G47R on the minor allele of alanine:glyoxylate aminotransferase and chaperoning activity of pyridoxine. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2015; 1854:1280-9. [DOI: 10.1016/j.bbapap.2015.07.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2015] [Accepted: 07/03/2015] [Indexed: 12/22/2022]
|
25
|
Liver peroxisomal alanine:glyoxylate aminotransferase and the effects of mutations associated with Primary Hyperoxaluria Type I: An overview. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2015; 1854:1212-9. [PMID: 25620715 DOI: 10.1016/j.bbapap.2014.12.029] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2014] [Revised: 12/19/2014] [Accepted: 12/20/2014] [Indexed: 11/21/2022]
Abstract
Liver peroxisomal alanine:glyoxylate aminotransferase (AGT) (EC 2.6.1.44) catalyses the conversion of l-alanine and glyoxylate to pyruvate and glycine, a reaction that allows glyoxylate detoxification. Inherited mutations on the AGXT gene encoding AGT lead to Primary Hyperoxaluria Type I (PH1), a rare disorder characterized by the deposition of calcium oxalate crystals primarily in the urinary tract. Here we describe the results obtained on the biochemical features of AGT as well as on the molecular and cellular effects of polymorphic and pathogenic mutations. A complex scenario on the molecular pathogenesis of PH1 emerges in which the co-inheritance of polymorphic changes and the condition of homozygosis or compound heterozygosis are two important factors that determine the enzymatic phenotype of PH1 patients. All the reported data represent relevant steps toward the understanding of genotype/phenotype correlations, the prediction of the response of the patients to the available therapies, and the development of new therapeutic approaches. This article is part of a Special Issue entitled: Cofactor-dependent proteins: evolution, chemical diversity and bio-applications.
Collapse
|
26
|
Lage MD, Pittman AMC, Roncador A, Cellini B, Tucker CL. Allele-specific characterization of alanine: glyoxylate aminotransferase variants associated with primary hyperoxaluria. PLoS One 2014; 9:e94338. [PMID: 24718375 PMCID: PMC3981788 DOI: 10.1371/journal.pone.0094338] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2014] [Accepted: 03/13/2014] [Indexed: 11/19/2022] Open
Abstract
Primary Hyperoxaluria Type 1 (PH1) is a rare autosomal recessive kidney stone disease caused by deficiency of the peroxisomal enzyme alanine: glyoxylate aminotransferase (AGT), which is involved in glyoxylate detoxification. Over 75 different missense mutations in AGT have been found associated with PH1. While some of the mutations have been found to affect enzyme activity, stability, and/or localization, approximately half of these mutations are completely uncharacterized. In this study, we sought to systematically characterize AGT missense mutations associated with PH1. To facilitate analysis, we used two high-throughput yeast-based assays: one that assesses AGT specific activity, and one that assesses protein stability. Approximately 30% of PH1-associated missense mutations are found in conjunction with a minor allele polymorphic variant, which can interact to elicit complex effects on protein stability and trafficking. To better understand this allele interaction, we functionally characterized each of 34 mutants on both the major (wild-type) and minor allele backgrounds, identifying mutations that synergize with the minor allele. We classify these mutants into four distinct categories depending on activity/stability results in the different alleles. Twelve mutants were found to display reduced activity in combination with the minor allele, compared with the major allele background. When mapped on the AGT dimer structure, these mutants reveal localized regions of the protein that appear particularly sensitive to interactions with the minor allele variant. While the majority of the deleterious effects on activity in the minor allele can be attributed to synergistic interaction affecting protein stability, we identify one mutation, E274D, that appears to specifically affect activity when in combination with the minor allele.
Collapse
Affiliation(s)
| | | | - Alessandro Roncador
- Department of Life Sciences and Reproduction, Section of Biological Chemistry, University of Verona, Verona, Italy
| | - Barbara Cellini
- Department of Life Sciences and Reproduction, Section of Biological Chemistry, University of Verona, Verona, Italy
| | - Chandra L. Tucker
- Department of Biology, Duke University, Durham, NC, USA
- Department of Pharmacology, University of Colorado Denver School of Medicine, Aurora, CO, USA
- * E-mail:
| |
Collapse
|
27
|
The chaperone role of the pyridoxal 5′-phosphate and its implications for rare diseases involving B6-dependent enzymes. Clin Biochem 2014; 47:158-65. [DOI: 10.1016/j.clinbiochem.2013.11.021] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2013] [Revised: 11/28/2013] [Accepted: 11/30/2013] [Indexed: 02/06/2023]
|
28
|
Kanoun H, Jarraya F, Hadj Salem I, Mahfoudh H, Chaabouni Y, Makni F, Hachicha J, Fakhfakh F. A double mutation in AGXT gene in families with primary hyperoxaluria type 1. Gene 2013; 531:451-6. [DOI: 10.1016/j.gene.2013.08.083] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2013] [Accepted: 08/26/2013] [Indexed: 11/26/2022]
|
29
|
Oppici E, Roncador A, Montioli R, Bianconi S, Cellini B. Gly161 mutations associated with Primary Hyperoxaluria Type I induce the cytosolic aggregation and the intracellular degradation of the apo-form of alanine:glyoxylate aminotransferase. Biochim Biophys Acta Mol Basis Dis 2013; 1832:2277-88. [PMID: 24055001 DOI: 10.1016/j.bbadis.2013.09.002] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2013] [Revised: 09/05/2013] [Accepted: 09/06/2013] [Indexed: 11/18/2022]
Abstract
Primary Hyperoxaluria Type I (PH1) is a severe rare disorder of metabolism due to inherited mutations on liver peroxisomal alanine:glyoxylate aminotransferase (AGT), a pyridoxal 5'-phosphate (PLP)-dependent enzyme whose deficiency causes the deposition of calcium oxalate crystals in the kidneys and urinary tract. PH1 is an extremely heterogeneous disease and there are more than 150 disease-causing mutations currently known, most of which are missense mutations. Moreover, the molecular mechanisms by which missense mutations lead to AGT deficiency span from structural, functional to subcellular localization defects. Gly161 is a highly conserved residue whose mutation to Arg, Cys or Ser is associated with PH1. Here we investigated the molecular bases of the AGT deficit caused by Gly161 mutations with expression studies in a mammalian cellular system paired with biochemical analyses on the purified recombinant proteins. Our results show that the mutations of Gly161 (i) strongly reduce the expression levels and the intracellular half-life of AGT, and (ii) make the protein in the apo-form prone to an electrostatically-driven aggregation in the cell cytosol. The coenzyme PLP, by shifting the equilibrium from the apo- to the holo-form, is able to reduce the aggregation propensity of the variants, thus partly decreasing the effect of the mutations. Altogether, these results shed light on the mechanistic details underlying the pathogenicity of Gly161 variants, thus expanding our knowledge of the enzymatic phenotypes leading to AGT deficiency.
Collapse
Affiliation(s)
- Elisa Oppici
- Department of Life Sciences and Reproduction, Section of Biological Chemistry, University of Verona, Strada Le Grazie 8 37134 Verona, Italy
| | | | | | | | | |
Collapse
|
30
|
Protein homeostasis defects of alanine-glyoxylate aminotransferase: new therapeutic strategies in primary hyperoxaluria type I. BIOMED RESEARCH INTERNATIONAL 2013; 2013:687658. [PMID: 23956997 PMCID: PMC3730394 DOI: 10.1155/2013/687658] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/28/2013] [Accepted: 05/23/2013] [Indexed: 11/30/2022]
Abstract
Alanine-glyoxylate aminotransferase catalyzes the transamination between L-alanine and glyoxylate to produce pyruvate and glycine using pyridoxal 5′-phosphate (PLP) as cofactor. Human alanine-glyoxylate aminotransferase is a peroxisomal enzyme expressed in the hepatocytes, the main site of glyoxylate detoxification. Its deficit causes primary hyperoxaluria type I, a rare but severe inborn error of metabolism. Single amino acid changes are the main type of mutation causing this disease, and considerable effort has been dedicated to the understanding of the molecular consequences of such missense mutations. In this review, we summarize the role of protein homeostasis in the basic mechanisms of primary hyperoxaluria. Intrinsic physicochemical properties of polypeptide chains such as thermodynamic stability, folding, unfolding, and misfolding rates as well as the interaction of different folding states with protein homeostasis networks are essential to understand this disease. The view presented has important implications for the development of new therapeutic strategies based on targeting specific elements of alanine-glyoxylate aminotransferase homeostasis.
Collapse
|
31
|
Fargue S, Lewin J, Rumsby G, Danpure CJ. Four of the most common mutations in primary hyperoxaluria type 1 unmask the cryptic mitochondrial targeting sequence of alanine:glyoxylate aminotransferase encoded by the polymorphic minor allele. J Biol Chem 2012; 288:2475-84. [PMID: 23229545 DOI: 10.1074/jbc.m112.432617] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The gene encoding the liver-specific peroxisomal enzyme alanine:glyoxylate aminotransferase (AGT, EC. 2.6.1.44) exists as two common polymorphic variants termed the "major" and "minor" alleles. The P11L amino acid replacement encoded by the minor allele creates a hidden N-terminal mitochondrial targeting sequence, the unmasking of which occurs in the hereditary calcium oxalate kidney stone disease primary hyperoxaluria type 1 (PH1). This unmasking is due to the additional presence of a common disease-specific G170R mutation, which is encoded by about one third of PH1 alleles. The P11L and G170R replacements interact synergistically to reroute AGT to the mitochondria where it cannot fulfill its metabolic role (i.e. glyoxylate detoxification) effectively. In the present study, we have reinvestigated the consequences of the interaction between P11L and G170R in stably transformed CHO cells and have studied for the first time whether a similar synergism exists between P11L and three other mutations that segregate with the minor allele (i.e. I244T, F152I, and G41R). Our investigations show that the latter three mutants are all able to unmask the cryptic P11L-generated mitochondrial targeting sequence and, as a result, all are mistargeted to the mitochondria. However, whereas the G170R, I244T, and F152I mutants are able to form dimers and are catalytically active, the G41R mutant aggregates and is inactive. These studies open up the possibility that all PH1 mutations, which segregate with the minor allele, might also lead to the peroxisome-to-mitochondrion mistargeting of AGT, a suggestion that has important implications for the development of treatment strategies for PH1.
Collapse
Affiliation(s)
- Sonia Fargue
- Department of Cell and Developmental Biology, University College London, London WC1E 6BT, United Kingdom
| | | | | | | |
Collapse
|
32
|
Abstract
The eukaryotic cell is organized into membrane-covered compartments that are characterized by specific sets of proteins and biochemically distinct cellular processes. The appropriate subcellular localization of proteins is crucial because it provides the physiological context for their function. In this Commentary, we give a brief overview of the different mechanisms that are involved in protein trafficking and describe how aberrant localization of proteins contributes to the pathogenesis of many human diseases, such as metabolic, cardiovascular and neurodegenerative diseases, as well as cancer. Accordingly, modifying the disease-related subcellular mislocalization of proteins might be an attractive means of therapeutic intervention. In particular, cellular processes that link protein folding and cell signaling, as well as nuclear import and export, to the subcellular localization of proteins have been proposed as targets for therapeutic intervention. We discuss the concepts involved in the therapeutic restoration of disrupted physiological protein localization and therapeutic mislocalization as a strategy to inactivate disease-causing proteins.
Collapse
Affiliation(s)
- Mien-Chie Hung
- Department of Molecular and Cellular Oncology, The University of Texas M. D. Anderson Cancer Center, Houston, TX 77030, USA
| | | |
Collapse
|
33
|
Montioli R, Fargue S, Lewin J, Zamparelli C, Danpure CJ, Borri Voltattorni C, Cellini B. The N-terminal extension is essential for the formation of the active dimeric structure of liver peroxisomal alanine:glyoxylate aminotransferase. Int J Biochem Cell Biol 2011; 44:536-46. [PMID: 22198249 DOI: 10.1016/j.biocel.2011.12.007] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2011] [Revised: 11/26/2011] [Accepted: 12/06/2011] [Indexed: 10/14/2022]
Abstract
Alanine:glyoxylate aminotransferase (AGT) is a pyridoxal-phosphate (PLP)-dependent enzyme. Its deficiency causes the hereditary kidney stone disease primary hyperoxaluria type 1. AGT is a highly stable compact dimer and the first 21 residues of each subunit form an extension which wraps over the surface of the neighboring subunit. Naturally occurring and artificial amino acid replacements in this extension create changes in the functional properties of AGT in mammalian cells, including relocation of the enzyme from peroxisomes to mitochondria. In order to elucidate the structural and functional role of this N-terminal extension, we have analyzed the consequences of its removal using a variety of biochemical and cell biological methods. When expressed in Escherichia coli, the N-terminal deleted form of AGT showed the presence of the protein but in an insoluble form resulting in only a 10% soluble yield as compared to the full-length version. The purified soluble fraction showed reduced affinity for PLP and greatly reduced catalytic activity. Although maintaining a dimer form, it was highly prone to self-aggregation. When expressed in a mammalian cell line, the truncated construct was normally targeted to peroxisomes, where it formed large stable but catalytically inactive aggregates. These results suggest that the N-terminal extension plays an essential role in allowing AGT to attain its correct conformation and functional activity. The precise mechanism of this effect is still under investigation.
Collapse
Affiliation(s)
- Riccardo Montioli
- Department of Life Sciences and Reproduction, Section of Biological Chemistry, University of Verona, Strada Le Grazie 8, 37134 Verona, Italy
| | | | | | | | | | | | | |
Collapse
|
34
|
Tompa P, Rose GD. The Levinthal paradox of the interactome. Protein Sci 2011; 20:2074-9. [PMID: 21987416 DOI: 10.1002/pro.747] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2011] [Revised: 09/22/2011] [Accepted: 09/23/2011] [Indexed: 02/06/2023]
Abstract
The central biological question of the 21st century is: how does a viable cell emerge from the bewildering combinatorial complexity of its molecular components? Here, we estimate the combinatorics of self-assembling the protein constituents of a yeast cell, a number so vast that the functional interactome could only have emerged by iterative hierarchic assembly of its component sub-assemblies. A protein can undergo both reversible denaturation and hierarchic self-assembly spontaneously, but a functioning interactome must expend energy to achieve viability. Consequently, it is implausible that a completely "denatured" cell could be reversibly renatured spontaneously, like a protein. Instead, new cells are generated by the division of pre-existing cells, an unbroken chain of renewal tracking back through contingent conditions and evolving responses to the origin of life on the prebiotic earth. We surmise that this non-deterministic temporal continuum could not be reconstructed de novo under present conditions.
Collapse
Affiliation(s)
- Peter Tompa
- VIB Department of Structural Biology, Vrije Universiteit Brussel, Brussels, Belgium.
| | | |
Collapse
|
35
|
Benhaj Mbarek I, Abroug S, Omezzine A, Zellama D, Achour A, Harbi A, Bouslama A. Selected AGXT gene mutations analysis provides a genetic diagnosis in 28% of Tunisian patients with primary hyperoxaluria. BMC Nephrol 2011; 12:25. [PMID: 21612638 PMCID: PMC3123632 DOI: 10.1186/1471-2369-12-25] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2010] [Accepted: 05/25/2011] [Indexed: 11/16/2022] Open
Abstract
Background Primary hyperoxaluria type I (PH1) is a rare genetic disorder characterized by allelic and clinical heterogeneity. Four mutations (G170R, 33_34insC, I244T and F152I) account for more than 50% of PH1 alleles and form the basis for diagnostic genetic screening for PH1. We aimed to analyze the prevalence of these specific mutations causing PH1, and to provide an accurate tool for diagnosis of presymptomatic patients as well as for prenatal diagnosis in the affected families. Methods Polymerase chain reaction/Restriction Fragment Length Polymorphism, were used to detect the four mutations in the AGXT gene in DNA samples from 57 patients belonging to 40 families. Results Two mutations causing PH1 were detected in 24 patients (42.1%), with a predominance of the I244T mutation (68% of patients) and 33_34insC (in the remaining 32%). In 92% of cases, mutated alleles were in homozygous state. The presented clinical features were similar for the two mutations. The age of onset was heterogeneous with a higher frequency of the pediatric age. In 58.3% of cases, the presentation corresponded to advanced renal disease which occurred early (< 5 years) in the two mutations. In adolescents, only the I244T mutation was detected (41.1%). I244T and 33_34insC mutations were observed in adult patients, with 17.6% and 12.5% respectively. Conclusion Limited mutation analysis can provide a useful first line investigation for PH1. I244T and 33_34insC presented 28.2% of identified mutations causing disease in our cohort. This identification could provide an accurate tool for prenatal diagnosis in the affected families, for genetic counselling and for detection of presymptomatic individuals.
Collapse
|
36
|
Mitochondrial targeting of human NADH dehydrogenase (ubiquinone) flavoprotein 2 (NDUFV2) and its association with early-onset hypertrophic cardiomyopathy and encephalopathy. J Biomed Sci 2011; 18:29. [PMID: 21548921 PMCID: PMC3117770 DOI: 10.1186/1423-0127-18-29] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2010] [Accepted: 05/06/2011] [Indexed: 11/10/2022] Open
Abstract
Background NADH dehydrogenase (ubiquinone) flavoprotein 2 (NDUFV2), containing one iron sulfur cluster ([2Fe-2S] binuclear cluster N1a), is one of the core nuclear-encoded subunits existing in human mitochondrial complex I. Defects in this subunit have been associated with Parkinson's disease, Alzheimer's disease, Bipolar disorder, and Schizophrenia. The aim of this study is to examine the mitochondrial targeting of NDUFV2 and dissect the pathogenetic mechanism of one human deletion mutation present in patients with early-onset hypertrophic cardiomyopathy and encephalopathy. Methods A series of deletion and point-mutated constructs with the c-myc epitope tag were generated to identify the location and sequence features of mitochondrial targeting sequence for NDUFV2 in human cells using the confocal microscopy. In addition, various lengths of the NDUFV2 N-terminal and C-terminal fragments were fused with enhanced green fluorescent protein to investigate the minimal region required for correct mitochondrial import. Finally, a deletion construct that mimicked the IVS2+5_+8delGTAA mutation in NDUFV2 gene and would eventually produce a shortened NDUFV2 lacking 19-40 residues was generated to explore the connection between human gene mutation and disease. Results We identified that the cleavage site of NDUFV2 was located around amino acid 32 of the precursor protein, and the first 22 residues of NDUFV2 were enough to function as an efficient mitochondrial targeting sequence to carry the passenger protein into mitochondria. A site-directed mutagenesis study showed that none of the single-point mutations derived from basic, hydroxylated and hydrophobic residues in the NDUFV2 presequence had a significant effect on mitochondrial targeting, while increasing number of mutations in basic and hydrophobic residues gradually decreased the mitochondrial import efficacy of the protein. The deletion mutant mimicking the human early-onset hypertrophic cardiomyopathy and encephalopathy lacked 19-40 residues in NDUFV2 and exhibited a significant reduction in its mitochondrial targeting ability. Conclusions The mitochondrial targeting sequence of NDUFV2 is located at the N-terminus of the precursor protein. Maintaining a net positive charge and an amphiphilic structure with the overall balance and distribution of basic and hydrophobic amino acids in the N-terminus of NDUFV2 is important for mitochondrial targeting. The results of human disease cell model established that the impairment of mitochondrial localization of NDUFV2 as a mechanistic basis for early-onset hypertrophic cardiomyopathy and encephalopathy.
Collapse
|
37
|
Cellini B, Montioli R, Voltattorni CB. Human liver peroxisomal alanine:glyoxylate aminotransferase: characterization of the two allelic forms and their pathogenic variants. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2010; 1814:1577-84. [PMID: 21176891 DOI: 10.1016/j.bbapap.2010.12.005] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/14/2010] [Revised: 12/06/2010] [Accepted: 12/10/2010] [Indexed: 11/15/2022]
Abstract
The hepatic peroxisomal alanine:glyoxylate aminotransferase (AGT) is a pyridoxal 5'-phosphate (PLP)-enzyme whose deficiency is responsible for Primary Hyperoxaluria Type 1 (PH1), an autosomal recessive disorder. In the last few years the knowledge of the characteristics of AGT and the transfer of this information into some pathogenic variants have significantly contributed to the improvement of the understanding at the molecular level of the PH1 pathogenesis. In this review, the spectroscopic features, the coenzyme's binding affinity, the steady-state kinetic parameters as well as the sensitivity to thermal and chemical stress of the two allelic forms of AGT, the major (AGT-Ma) and the minor (AGT-Mi) allele, have been described. Moreover, we summarize the characterization obtained by means of biochemical and bioinformatic analyses of the following PH1-causing variants in the recombinant purified forms: G82E associated with the major allele, F152I encoded on the background of the minor allele, and the G41 mutants which co-segregate either with the major allele (G41R-Ma and G41V-Ma) or with the minor allele (G41R-Mi). The data have been correlated with previous clinical and cell biology results, which allow us to (i) highlight the functional differences between AGT-Ma and AGT-Mi, (ii) identify the structural and functional molecular defects of the pathogenic variants, (iii) improve the correlation between the genotype and the enzymatic phenotype, (iv) foresee or understand the molecular basis of the responsiveness to pyridoxine treatment of patients bearing these mutations, and (v) pave the way for new treatment strategies. This article is part of a Special Issue entitled: Pyridoxal Phospate Enzymology.
Collapse
Affiliation(s)
- Barbara Cellini
- Dipartimento di Scienze della Vita e della Riproduzione, Sezione di Chimica Biologica, Facoltà di Medicina e Chirurgia, Università degli Studi di Verona, Strada Le Grazie, 8 37134 Verona, Italy
| | | | | |
Collapse
|
38
|
Role of low native state kinetic stability and interaction of partially unfolded states with molecular chaperones in the mitochondrial protein mistargeting associated with primary hyperoxaluria. Amino Acids 2010; 41:1233-45. [PMID: 21103899 DOI: 10.1007/s00726-010-0801-2] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2010] [Accepted: 10/28/2010] [Indexed: 10/18/2022]
Abstract
The G170R variant of the alanine:glyoxylate aminotransferase (AGT) is the most common pathogenic allele associated to primary hyperoxaluria type I (PH1), leading to mitochondrial mistargeting when combined with the P11L and I340M polymorphisms (minor allele; AGT(LM)). In this work, we have performed a comparative analysis on the conformation, unfolding energetics and interaction with molecular chaperones between AGT(wt), AGT(LM) and AGT(LRM) (G170R in the minor allele) proteins. Our results show that these three variants share similar conformational and functional properties as folded dimers. However, kinetic stability analyses showed a ≈1,000-fold increased unfolding rate for apo-AGT(LRM) compared to apo-AGT(wt), as well as a reduced folding efficiency upon expression in Escherichia coli. Pyridoxal 5'-phosphate (PLP)-binding provided a 4-5 orders of magnitude enhancement of the kinetic stability for all variants, suggesting a role for kinetic stabilization in pyridoxine-responsive PH1. Conformational studies at mild acidic pH and moderate guanidium concentrations showed the formation of a molten-globule-like unfolding intermediate in all three variants, which do not reactivate to the native state and strongly interact with Hsc70 and Hsp90 chaperones. Additional expression analyses in a mammalian cell-free system at neutral pH showed enhanced interaction of AGT(LRM) with Hsc70 and Hsp90 proteins compared to AGT(wt), suggesting kinetic trapping of the mutant by chaperones along the folding process. Overall, our results suggest that mitochondrial mistargeting of AGT(LRM) may involve the presentation of AGT partially folded states to the mitochondrial import machinery by molecular chaperones, which would be facilitated by the low native state kinetic stability (partially corrected by PLP binding) and kinetic trapping during folding of the AGT(LRM) variant with molecular chaperones.
Collapse
|
39
|
Wang W, Shen P, Thiyagarajan S, Lin S, Palm C, Horvath R, Klopstock T, Cutler D, Pique L, Schrijver I, Davis RW, Mindrinos M, Speed TP, Scharfe C. Identification of rare DNA variants in mitochondrial disorders with improved array-based sequencing. Nucleic Acids Res 2010; 39:44-58. [PMID: 20843780 PMCID: PMC3017602 DOI: 10.1093/nar/gkq750] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
A common goal in the discovery of rare functional DNA variants via medical resequencing is to incur a relatively lower proportion of false positive base-calls. We developed a novel statistical method for resequencing arrays (SRMA, sequence robust multi-array analysis) to increase the accuracy of detecting rare variants and reduce the costs in subsequent sequence verifications required in medical applications. SRMA includes single and multi-array analysis and accounts for technical variables as well as the possibility of both low- and high-frequency genomic variation. The confidence of each base-call was ranked using two quality measures. In comparison to Sanger capillary sequencing, we achieved a false discovery rate of 2% (false positive rate 1.2 × 10−5, false negative rate 5%), which is similar to automated second-generation sequencing technologies. Applied to the analysis of 39 nuclear candidate genes in disorders of mitochondrial DNA (mtDNA) maintenance, we confirmed mutations in the DNA polymerase gamma POLG in positive control cases, and identified novel rare variants in previously undiagnosed cases in the mitochondrial topoisomerase TOP1MT, the mismatch repair enzyme MUTYH, and the apurinic-apyrimidinic endonuclease APEX2. Some patients carried rare heterozygous variants in several functionally interacting genes, which could indicate synergistic genetic effects in these clinically similar disorders.
Collapse
Affiliation(s)
- Wenyi Wang
- Stanford Genome Technology Center, Stanford University, Palo Alto, CA 94304, USA.
| | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
40
|
Djordjevic S, Zhang X, Bartlam M, Ye S, Rao Z, Danpure CJ. Structural implications of a G170R mutation of alanine:glyoxylate aminotransferase that is associated with peroxisome-to-mitochondrion mistargeting. Acta Crystallogr Sect F Struct Biol Cryst Commun 2010; 66:233-6. [PMID: 20208150 PMCID: PMC2833026 DOI: 10.1107/s1744309109054645] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2009] [Accepted: 12/18/2009] [Indexed: 11/10/2022]
Abstract
In a subset of patients with the hereditary kidney-stone disease primary hyperoxaluria type 1 (PH1), the liver-specific enzyme alanine:glyoxylate aminotransferase (AGT) is mistargeted from peroxisomes to mitochondria. This is a consequence of the combined presence of the common P11L polymorphism and a disease-specific G170R mutation. In this paper, the crystal structure of mutant human AGT containing the G170R replacement determined at a resolution of 2.6 A is reported. The crystal structure of AGT consists of an intimate dimer in which an extended N-terminal segment of 21 amino acids from one subunit wraps as an elongated irregular coil around the outside of the crystallographic symmetry-related subunit. In addition to the N-terminal segment, the monomer structure contains a large domain of 261 amino acids and a small C-terminal domain of 110 amino acids. Comparison of the mutant AGT structure and that of wild-type normal AGT shows that the two structures are almost identical, with a backbone-atom r.m.s. deviation of 0.34 A. However, evidence of significant local structural changes in the vicinity of the G170R mutation might be linked to the apparent decrease in protein stability.
Collapse
Affiliation(s)
- Snezana Djordjevic
- Structural and Molecular Biology, University College London, Gower Street, London WC1E 6BT, England
| | - Xiaoxuan Zhang
- Cell and Developmental Biology, University College London, Gower Street, London WC1E 6BT, England
| | - Mark Bartlam
- College of Life Sciences, Nankai University, Tianjin 300071, People’s Republic of China
| | - Sheng Ye
- Laboratory of Structural Biology, Tsinghua University, Beijing 100084, People’s Republic of China
| | - Zihe Rao
- College of Life Sciences, Nankai University, Tianjin 300071, People’s Republic of China
- Laboratory of Structural Biology, Tsinghua University, Beijing 100084, People’s Republic of China
| | - Christopher J. Danpure
- Cell and Developmental Biology, University College London, Gower Street, London WC1E 6BT, England
| |
Collapse
|
41
|
Hopper ED, Pittman AMC, Fitzgerald MC, Tucker CL. In vivo and in vitro examination of stability of primary hyperoxaluria-associated human alanine:glyoxylate aminotransferase. J Biol Chem 2008; 283:30493-502. [PMID: 18782763 DOI: 10.1074/jbc.m803525200] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Primary hyperoxaluria type I is a severe kidney stone disease caused by mutations in the protein alanine:glyoxylate aminotransferase (AGT). Many patients have mutations in AGT that are not deleterious alone but act synergistically with a common minor allele polymorphic variant to impair protein folding, dimerization, or localization. Although studies suggest that the minor allele variant itself is destabilized, no direct stability studies have been carried out. In this report, we analyze AGT function and stability using three approaches. First, we describe a yeast complementation growth assay for AGT, in which we show that human AGT can substitute for function of yeast Agx1 and that mutations associated with disease in humans show reduced growth in yeast. The reduced growth of minor allele mutants reflects reduced protein levels, indicating that these proteins are less stable than wild-type AGT in yeast. We further examine stability of AGT alleles in vitro using two direct methods, a mass spectrometry-based technique (stability of unpurified proteins from rates of H/D exchange) and differential scanning fluorimetry. We also examine the effect of known ligands pyridoxal 5'-phosphate and aminooxyacetic acid on stability. Our work establishes that the minor allele is destabilized and that pyridoxal 5'-phosphate and aminooxyacetic acid binding significantly stabilizes both alleles. To our knowledge, this is the first work that directly measures relative stabilities of AGT variants and ligand complexes. Because previous studies suggest that stabilizing compounds (i.e. pharmacological chaperones) may be effective for treatment of primary hyperoxaluria, we propose that the methods described here can be used in high throughput screens for compounds that stabilize AGT mutants.
Collapse
Affiliation(s)
- Erin D Hopper
- Department of Biology and Chemistry, Duke University, Durham, North Carolina 27708, USA
| | | | | | | |
Collapse
|
42
|
MacKenzie JA, Payne RM. Mitochondrial protein import and human health and disease. Biochim Biophys Acta Mol Basis Dis 2006; 1772:509-23. [PMID: 17300922 PMCID: PMC2702852 DOI: 10.1016/j.bbadis.2006.12.002] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2006] [Revised: 12/06/2006] [Accepted: 12/07/2006] [Indexed: 12/31/2022]
Abstract
The targeting and assembly of nuclear-encoded mitochondrial proteins are essential processes because the energy supply of humans is dependent upon the proper functioning of mitochondria. Defective import of mitochondrial proteins can arise from mutations in the targeting signals within precursor proteins, from mutations that disrupt the proper functioning of the import machinery, or from deficiencies in the chaperones involved in the proper folding and assembly of proteins once they are imported. Defects in these steps of import have been shown to lead to oxidative stress, neurodegenerative diseases, and metabolic disorders. In addition, protein import into mitochondria has been found to be a dynamically regulated process that varies in response to conditions such as oxidative stress, aging, drug treatment, and exercise. This review focuses on how mitochondrial protein import affects human health and disease.
Collapse
Affiliation(s)
- James A MacKenzie
- Department of Biological Sciences, 133 Piez Hall, State University of New York at Oswego, Oswego, NY 13126, USA.
| | | |
Collapse
|
43
|
Coulter-Mackie MB, Lian Q. Consequences of missense mutations for dimerization and turnover of alanine:glyoxylate aminotransferase: study of a spectrum of mutations. Mol Genet Metab 2006; 89:349-59. [PMID: 16971151 DOI: 10.1016/j.ymgme.2006.07.013] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/09/2006] [Revised: 07/31/2006] [Accepted: 07/31/2006] [Indexed: 11/29/2022]
Abstract
Alanine:glyoxylate aminotransferase (AGT) is a liver peroxisomal enzyme, deficiency of which results in primary hyperoxaluria type 1 (PH1). More than 65 PH1-related mutations are now documented in the AGT gene (AGXT), of which about 50% are missense. We have generated a spectrum of 15 missense changes including the most common PH1 mutation, G170R, and expressed them on the appropriate background of the major or minor allele, in an Escherichia coli overexpression system and in a rabbit reticulocyte transcription/translation system. We have investigated their effects on enzyme activity, dimerization, aggregation, and turnover. The effect of pyridoxal phosphate (PLP) on dimerization and stability was also investigated. Although all 15 mutant AGTs were expressed as intact proteins in E. coli, only three: G41R and G41V on the major allele, and the common mutation G170R, resulted in significant amounts of enzymatic activity. Dimerization failure was a frequent observation (13/15) except for G41V and D183N. Dimerization was poor with S187F but was substantially improved with PLP. Proteasome-mediated protein degradation was observed for all the mutations except G41R on the major allele, G41V, D183N, G170R, and S218L. Increases in the stability of the mutant enzymes in the presence of PLP were small; however, G41R on the minor allele showed a direct relationship between its half life and the concentration of PLP. The minor allele AGT product and many of the mutants were subject to a limited non-proteasomal proteolytic cleavage when ATP was depleted.
Collapse
Affiliation(s)
- M B Coulter-Mackie
- Department of Pediatrics, University of British Columbia, Children's and Women's Health Centre, Vancouver, BC, Canada
| | | |
Collapse
|
44
|
Danpure CJ. Primary hyperoxaluria type 1: AGT mistargeting highlights the fundamental differences between the peroxisomal and mitochondrial protein import pathways. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2006; 1763:1776-84. [PMID: 17027096 DOI: 10.1016/j.bbamcr.2006.08.021] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2006] [Revised: 08/01/2006] [Accepted: 08/18/2006] [Indexed: 10/24/2022]
Abstract
Primary hyperoxaluria type 1 (PH1) is an atypical peroxisomal disorder, as befits a deficiency of alanine:glyoxylate aminotransferase (AGT), which is itself an atypical peroxisomal enzyme. PH1 is characterized by excessive synthesis and excretion of the metabolic end-product oxalate and the progressive accumulation of insoluble calcium oxalate in the kidney and urinary tract. Disease in many patients is caused by a unique protein trafficking defect in which AGT is mistargeted from peroxisomes to mitochondria, where it is metabolically ineffectual, despite remaining catalytically active. Although the peroxisomal import of human AGT is dependent upon the PTS1 import receptor PEX5p, its PTS1 is exquisitely specific for mammalian AGT, suggesting the presence of additional peroxisomal targeting information elsewhere in the AGT molecule. This and many other functional peculiarities of AGT are probably a consequence of its rather chequered evolutionary history, during which much of its time has been spent being a mitochondrial, rather than a peroxisomal, enzyme. Analysis of the molecular basis of AGT mistargeting in PH1 has thrown into sharp relief some of the fundamental differences between the requirements of the peroxisomal and mitochondrial protein import pathways, particularly the properties of peroxisomal and mitochondrial matrix targeting sequences and the different conformational limitations placed upon importable cargos.
Collapse
Affiliation(s)
- Christopher J Danpure
- Department of Biology, University College London, Gower Street, London WC1E 6BT, UK.
| |
Collapse
|
45
|
Léon S, Goodman JM, Subramani S. Uniqueness of the mechanism of protein import into the peroxisome matrix: transport of folded, co-factor-bound and oligomeric proteins by shuttling receptors. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2006; 1763:1552-64. [PMID: 17011644 DOI: 10.1016/j.bbamcr.2006.08.037] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2006] [Revised: 08/18/2006] [Accepted: 08/23/2006] [Indexed: 11/30/2022]
Abstract
Based on earlier suggestions that peroxisomes may have arisen from endosymbionts that later lost their DNA, it was expected that protein transport into this organelle would have parallels to systems found in other organelles of endosymbiont origin, such as mitochondria and chloroplasts. This review highlights three features of peroxisomal matrix protein import that make it unique in comparison with these other subcellular compartments - the ability of this organelle to transport folded, co-factor-bound and oligomeric proteins, the dynamics of the import receptors during the matrix protein import cycle and the existence of a peroxisomal quality-control pathway, which insures that the peroxisome membrane is cleared of cargo-free receptors.
Collapse
Affiliation(s)
- Sébastien Léon
- Section of Molecular Biology, Division of Biological Sciences, University California, Room 3230 Bonner Hall, 9500 Gilman Drive, UC San Diego, La Jolla, CA 92093-0322, USA
| | | | | |
Collapse
|
46
|
Monico CG, Rossetti S, Olson JB, Milliner DS. Pyridoxine effect in type I primary hyperoxaluria is associated with the most common mutant allele. Kidney Int 2005; 67:1704-9. [PMID: 15840016 DOI: 10.1111/j.1523-1755.2005.00267.x] [Citation(s) in RCA: 128] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
BACKGROUND Pyridoxine (VB6) response in type I primary hyperoxaluria (PHI) is variable, with nearly equal numbers of patients showing partial to complete reductions in oxaluria, and resistance. Because high urine oxalate concentrations cause stones and renal injury, reduction in urine oxalate excretion is deemed favorable. Mechanisms of VB6 action on hepatic alanine:glyoxylate aminotransferase (AGT), the deficient enzyme in PHI, and VB6 dose response have not been well-characterized. METHODS Sequencing or restriction site-generating polymerase chain reaction (PCR) was used for c.508 genotyping in 23 PHI patients. Pre- and post-VB6 24-hour urine oxalate excretion and VB6 dose were ascertained by retrospective chart review. RESULTS There were six c.508 G>A homozygotes (AA), eight heterozygotes (GA), and nine patients lacking this change (GG). Pre-VB6 urine oxalate excretion was 152 +/- 39, 203 +/- 68 and 206 +/- 74 mg/1.73 m(2)/24 hours, respectively, and did not differ [AA vs. GA (P= 0.07); AA vs. GG (P= 0.07); GA vs. GG, (P= 0.47)]. Post-VB6 urine oxalate excretion was normal in AA (pre- vs. post-VB6) (P < 0.001), partially reduced in GA (P < 0.001), and unchanged in GG (P= 0.06). Urine oxalate excretion attenuation was similar for VB6 doses (mg/kg/day) of 1 to 4.9, 5 to 9.9, and 10 to 14.9 in AA (P= 0.41, P= 0.28, and P= 0.11, respectively) and GA (P= 0.42, P= 0.39, and P= 0.30, respectively) during follow-up. CONCLUSION Presence of the c.508 G>A allele confers VB6 response in PHI and VB6 doses of 5 mg/kg/day appear sufficient. c.508 genotyping can be used to predict VB6 response and guide treatment in PHI. [c represents cDNA sequence where nucleotide position +1 corresponds to the adenine (A) of the translation start codon ATG. Equivalent positions based on 5' UTR nucleotide numbering are as follows: c.508 G>A = G630A (Gly170Arg), c.32 C>T = C154T (Pro11Leu), and c.454 T>A = T576A (Phe152Ile)], yields highest residual AGT activity. To test whether VB6 response might be attributable to this allele, we performed c.508 genotyping.
Collapse
Affiliation(s)
- Carla G Monico
- Mayo Clinic College of Medicine, Mayo Clinic Foundation, Rochester, Minnesota 55905, USA.
| | | | | | | |
Collapse
|
47
|
Huber PAJ, Birdsey GM, Lumb MJ, Prowse DTR, Perkins TJ, Knight DR, Danpure CJ. Peroxisomal Import of Human Alanine:glyoxylate Aminotransferase Requires Ancillary Targeting Information Remote from Its C Terminus. J Biol Chem 2005; 280:27111-20. [PMID: 15911627 DOI: 10.1074/jbc.m502719200] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Although human alanine:glyoxylate aminotransferase (AGT) is imported into peroxisomes by a Pex5p-dependent pathway, the properties of its C-terminal tripeptide (KKL) are unlike those of any other type 1 peroxisomal targeting sequence (PTS1). We have previously suggested that AGT might possess ancillary targeting information that enables its unusual PTS1 to work. In this study, we have attempted to locate this information and to determine whether or not it is a characteristic of all vertebrate AGTs. Using the two-hybrid system, we show that human AGT interacts with human Pex5p in mammalian cells, but not yeast cells. Using (immuno)fluorescence microscopic analysis of the distribution of various constructs expressed in COS cells, we show the following. 1) The putative ancillary peroxisomal targeting information (PTS1A) in human AGT is located entirely within the smaller C-terminal structural domain of 110 amino acids, with the sequence between Val-324 and Ile-345 being the most likely candidate region. 2) The PTS1A is present in all mammalian AGTs studied (human, rat, guinea pig, rabbit, and cat), but not amphibian AGT (Xenopus). 3) The PTS1A is necessary for peroxisomal import of human, rabbit, and cat AGTs, but not rat and guinea pig AGTs. We speculate that the internal PTS1A of human AGT works in concert with the C-terminal PTS1 by interacting with Pex5p indirectly with the aid of a yet-to-be-identified mammal-specific adaptor molecule. This interaction might reshape the tetratricopeptide repeat domain allosterically, enabling it to accept KKL as a functional PTS1.
Collapse
Affiliation(s)
- Pia A J Huber
- Department of Biology, University College London, Gower Street, London WC1E 6BT, United Kingdom
| | | | | | | | | | | | | |
Collapse
|
48
|
Danpure CJ. Molecular etiology of primary hyperoxaluria type 1: new directions for treatment. Am J Nephrol 2005; 25:303-10. [PMID: 15961951 DOI: 10.1159/000086362] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2005] [Accepted: 05/04/2005] [Indexed: 01/10/2023]
Abstract
Primary hyperoxaluria type 1 (PH1) is a rare autosomal-recessive disorder caused by a deficiency of the liver-specific enzyme alanine:glyoxylate aminotransferase (AGT). AGT deficiency results in increased synthesis and excretion of the metabolic end-product oxalate and deposition of insoluble calcium oxalate in the kidney and urinary tract. Classic treatments for PH1 have tended to address the more distal aspects of the disease process (i.e. the symptoms rather than the causes). However, advances in the understanding of the molecular etiology of PH1 over the past decade have shifted attention towards the more proximal aspects of the disease process (i.e. the causes rather than the symptoms). The determination of the crystal structure of AGT has enabled the effects of some of the most important missense mutations in the AGXT gene to be rationalised in terms of AGT folding, dimerization and stability. This has opened up new possibilities for the design pharmacological agents that might counteract the destabilizing effects of these mutations and which might be of use for the treatment of a potentially life-threatening and difficult-to-treat disease.
Collapse
|
49
|
Coulter-Mackie MB, Lian Q, Wong SG. Overexpression of human alanine:glyoxylate aminotransferase in Escherichia coli: renaturation from guanidine–HCl and affinity for pyridoxal phosphate co-factor. Protein Expr Purif 2005; 41:18-26. [PMID: 15802217 DOI: 10.1016/j.pep.2004.11.004] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2004] [Revised: 11/09/2004] [Indexed: 11/30/2022]
Abstract
Alanine:glyoxylate aminotransferase-1 (AGT) is a human liver peroxisomal enzyme whose deficiency results in, primary hyperoxaluria type 1 (PH1), a fatal metabolic disease. AGT requires a pyridoxal phosphate (PLP) co-factor in its active site. The AGT gene usually exists in one of two polymorphic forms, the major and minor alleles. We describe here an overexpression system for normal and mutant variants of human AGT in Escherichia coli BL21 (DE3) pLysS. We have extracted functional AGT from inclusion bodies using guanidine-HCl. Denaturation and re-folding of the overexpressed AGT after guanidine-HCl treatment produces high yields of biologically active protein and provides a strategy for generating an apoenzyme to investigate PLP-binding. K(M)s for PLP were determined by reconstitution of the apoenzyme. Successful folding was independent of the presence of PLP. The K(M) for PLP for minor allele AGT was significantly higher than that for major allele AGT. This decreased affinity could be attributed to I340M, a polymorphism associated with the minor allele. G170R, located on the minor allele and the most common PH1 mutation, had no effect on the affinity for PLP. PH1 mutations, G41V and G41R, showed enhanced activity after re-folding. We suggest that the renaturation/re-folding and reconstitution strategies provide an approach for studying the maturation of AGT under optimal conditions and in isolation from cellular quality control and chaperoning processes. Furthermore, our data show that mutations with serious consequences in vivo may not be inherently catalytically inactive and may be rescuable.
Collapse
|
50
|
Chevalier-Porst F, Rolland MO, Cochat P, Bozon D. Maternal isodisomy of the telomeric end of chromosome 2 is responsible for a case of primary hyperoxaluria type 1. Am J Med Genet A 2005; 132A:80-3. [PMID: 15580638 DOI: 10.1002/ajmg.a.30375] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Primary hyperoxaluria type 1 (PH1) is an autosomal recessive disorder of glyoxylate metabolism, in which excessive oxalates are formed by the liver and excreted by the kidneys, causing a wide spectrum of disease, ranging from renal failure in infancy to mere renal stones in late adulthood. This disease is caused by a deficiency of alanine:glyoxylate aminotransferase (AGT), which is encoded by a single copy gene, AGXT, located in 2q37.3. We identified an apparently homozygous, loss-of-function, mutation in a patient; the gene defect was present in the heterozygous mother but not in the patient's father. We performed a microsatellite repeat analysis using 13 specific chromosome 2 markers and non-chromosome 2 minisatellites. Six specific chromosome 2 markers showed an apparently homozygous maternal inheritance while four showed a biparental transmission consistent with paternity (confirmed by minisatellite analysis). Quantitative PCR of AGXT exons 1 and 3 on the patient's and parents genomic DNA revealed the presence of two copies of the gene. This is the first case of PH1 caused by segmental maternal isodisomy of 2q37.3.
Collapse
|