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O'Neill AG, Burrell AL, Zech M, Elpeleg O, Harel T, Edvardson S, Mor-Shaked H, Rippert AL, Nomakuchi T, Izumi K, Kollman JM. Neurodevelopmental disorder mutations in the purine biosynthetic enzyme IMPDH2 disrupt its allosteric regulation. J Biol Chem 2023; 299:105012. [PMID: 37414152 PMCID: PMC10407431 DOI: 10.1016/j.jbc.2023.105012] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2023] [Revised: 06/23/2023] [Accepted: 06/28/2023] [Indexed: 07/08/2023] Open
Abstract
Inosine 5' monophosphate dehydrogenase (IMPDH) is a critical regulatory enzyme in purine nucleotide biosynthesis that is inhibited by the downstream product GTP. Multiple point mutations in the human isoform IMPDH2 have recently been associated with dystonia and other neurodevelopmental disorders, but the effect of the mutations on enzyme function has not been described. Here, we report the identification of two additional missense variants in IMPDH2 from affected individuals and show that all of the disease-associated mutations disrupt GTP regulation. Cryo-EM structures of one IMPDH2 mutant suggest this regulatory defect arises from a shift in the conformational equilibrium toward a more active state. This structural and functional analysis provides insight into IMPDH2-associated disease mechanisms that point to potential therapeutic approaches and raises new questions about fundamental aspects of IMPDH regulation.
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Affiliation(s)
- Audrey G O'Neill
- Department of Biochemistry, University of Washington, Seattle, Washington, USA
| | - Anika L Burrell
- Department of Biochemistry, University of Washington, Seattle, Washington, USA
| | - Michael Zech
- Institute of Neurogenomics, Helmholtz Zentrum München, Munich, Germany; Institute of Human Genetics, School of Medicine, Technical University of Munich, Munich, Germany
| | - Orly Elpeleg
- Department of Genetics, Hadassah Medical Center, Jerusalem, Israel; Faculty of Medicine, Hebrew University of Jerusalem, Jerusalem, Israel
| | - Tamar Harel
- Department of Genetics, Hadassah Medical Center, Jerusalem, Israel; Faculty of Medicine, Hebrew University of Jerusalem, Jerusalem, Israel
| | - Simon Edvardson
- Alyn Hospital, Hebrew University School of Medicine, Jerusalem, Israel
| | - Hagar Mor-Shaked
- Department of Genetics, Hadassah Medical Center, Jerusalem, Israel; Faculty of Medicine, Hebrew University of Jerusalem, Jerusalem, Israel
| | - Alyssa L Rippert
- Division of Human Genetics, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA
| | - Tomoki Nomakuchi
- Division of Human Genetics, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA
| | - Kosuke Izumi
- Division of Human Genetics, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA
| | - Justin M Kollman
- Department of Biochemistry, University of Washington, Seattle, Washington, USA.
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2
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O'Neill AG, Burrell AL, Zech M, Elpeleg O, Harel T, Edvardson S, Shaked HM, Rippert AL, Nomakuchi T, Izumi K, Kollman JM. Point mutations in IMPDH2 which cause early-onset neurodevelopmental disorders disrupt enzyme regulation and filament structure. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.15.532669. [PMID: 36993700 PMCID: PMC10055058 DOI: 10.1101/2023.03.15.532669] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 04/29/2023]
Abstract
Inosine 5' monophosphate dehydrogenase (IMPDH) is a critical regulatory enzyme in purine nucleotide biosynthesis that is inhibited by the downstream product GTP. Multiple point mutations in the human isoform IMPDH2 have recently been associated with dystonia and other neurodevelopmental disorders, but the effect of the mutations on enzyme function has not been described. Here, we report identification of two additional affected individuals with missense variants in IMPDH2 and show that all of the disease-associated mutations disrupt GTP regulation. Cryo-EM structures of one IMPDH2 mutant suggest this regulatory defect arises from a shift in the conformational equilibrium toward a more active state. This structural and functional analysis provides insight into IMPDH2-associated disease mechanisms that point to potential therapeutic approaches and raises new questions about fundamental aspects of IMPDH regulation.
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Affiliation(s)
- Audrey G O'Neill
- Department of Biochemistry, University of Washington, Seattle, WA, USA
| | - Anika L Burrell
- Department of Biochemistry, University of Washington, Seattle, WA, USA
| | - Michael Zech
- Institute of Neurogenomics, Helmholtz Zentrum München, 85764 Munich, Germany
- Institute of Human Genetics, School of Medicine, Technical University of Munich, 81675 Munich, Germany
| | - Orly Elpeleg
- Department of Genetics, Hadassah Medical Center, Jerusalem, Israel
- Faculty of Medicine, Hebrew University of Jerusalem, Jerusalem, Israel
| | - Tamar Harel
- Department of Genetics, Hadassah Medical Center, Jerusalem, Israel
- Faculty of Medicine, Hebrew University of Jerusalem, Jerusalem, Israel
| | - Simon Edvardson
- Alyn Hospital, Hebrew University School of Medicine, Jerusalem, Israel
| | - Hagar Mor Shaked
- Department of Genetics, Hadassah Medical Center, Jerusalem, Israel
- Faculty of Medicine, Hebrew University of Jerusalem, Jerusalem, Israel
| | - Alyssa L Rippert
- Division of Human Genetics, Children's Hospital of Philadelphia, Philadelphia, PA, USA
| | - Tomoki Nomakuchi
- Division of Human Genetics, Children's Hospital of Philadelphia, Philadelphia, PA, USA
| | - Kosuke Izumi
- Division of Human Genetics, Children's Hospital of Philadelphia, Philadelphia, PA, USA
| | - Justin M Kollman
- Department of Biochemistry, University of Washington, Seattle, WA, USA
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Gunda V, Pathania AS, Chava S, Prathipati P, Chaturvedi NK, Coulter DW, Pandey MK, Durden DL, Challagundla KB. Amino Acids Regulate Cisplatin Insensitivity in Neuroblastoma. Cancers (Basel) 2020; 12:cancers12092576. [PMID: 32927667 PMCID: PMC7563727 DOI: 10.3390/cancers12092576] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2020] [Revised: 09/08/2020] [Accepted: 09/08/2020] [Indexed: 02/07/2023] Open
Abstract
Simple Summary Neuroblastomas mostly show poor response to the Cisplatin therapy. Amino acids serve as building blocks for proteins, which are acquired either through diet or protein breakdown. Our study reveals high amino acid pools and dependence of Cisplatin-tolerant neuroblastomas cells on amino acids for their survival, especially, in drug treated conditions. Our study also demonstrates that response of neuroblastomas to Cisplatin can be improved by decreasing cellular amino acid levels either by reducing amino acid supplements or by applying autophagy inhibitor, Hydroxychloroquine. Thus, our findings establish that neuroblastomas can be sensitized to Cisplatin by targeting amino acid metabolism. Abstract Neuroblastoma are pediatric, extracranial malignancies showing alarming survival prognosis outcomes due to their resilience to current aggressive treatment regimens, including chemotherapies with cisplatin (CDDP) provided in the first line of therapy regimens. Metabolic deregulation supports tumor cell survival in drug-treated conditions. However, metabolic pathways underlying cisplatin-resistance are least studied in neuroblastoma. Our metabolomics analysis revealed that cisplatin-insensitive cells alter their metabolism; especially, the metabolism of amino acids was upregulated in cisplatin-insensitive cells compared to the cisplatin-sensitive neuroblastoma cell line. A significant increase in amino acid levels in cisplatin-insensitive cells led us to hypothesize that the mechanisms upregulating intracellular amino acid pools facilitate insensitivity in neuroblastoma. We hereby report that amino acid depletion reduces cell survival and cisplatin-insensitivity in neuroblastoma cells. Since cells regulate their amino acids levels through processes, such as autophagy, we evaluated the effects of hydroxychloroquine (HCQ), a terminal autophagy inhibitor, on the survival and amino acid metabolism of cisplatin-insensitive neuroblastoma cells. Our results demonstrate that combining HCQ with CDDP abrogated the amino acid metabolism in cisplatin-insensitive cells and sensitized neuroblastoma cells to sub-lethal doses of cisplatin. Our results suggest that targeting of amino acid replenishing mechanisms could be considered as a potential approach in developing combination therapies for treating neuroblastomas.
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Affiliation(s)
- Venugopal Gunda
- Department of Biochemistry and Molecular Biology & The Fred and Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE 68198, USA; (V.G.); (A.S.P.); (S.C.)
| | - Anup S. Pathania
- Department of Biochemistry and Molecular Biology & The Fred and Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE 68198, USA; (V.G.); (A.S.P.); (S.C.)
| | - Srinivas Chava
- Department of Biochemistry and Molecular Biology & The Fred and Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE 68198, USA; (V.G.); (A.S.P.); (S.C.)
| | - Philip Prathipati
- Laboratory of Bioinformatics, National Institutes of Biomedical Innovation, Health and Nutrition, 7-6-8 Saito-Asagi, Ibaraki City, Osaka 567-0085, Japan;
| | - Nagendra K. Chaturvedi
- Department of Pediatrics, Division of Hematology/Oncology, University of Nebraska Medical Center, Omaha, NE 68198, USA; (N.K.C.); (D.W.C.)
| | - Don W. Coulter
- Department of Pediatrics, Division of Hematology/Oncology, University of Nebraska Medical Center, Omaha, NE 68198, USA; (N.K.C.); (D.W.C.)
| | - Manoj K. Pandey
- Department of Biomedical Sciences, Cooper Medical School of Rowan University, 401 South Broadway, Camden, NJ 08103, USA;
| | - Donald L. Durden
- Division of Pediatric Hematology and Oncology, Department of Pediatrics, Moores Cancer Center, University of California, San Diego, 3855 Health Science Drive, MC-0815, La Jolla, CA 92093, USA;
- SignalRx Pharmaceuticals, Inc. 8330, Loveland Drive, Omaha, NE 68124, USA
| | - Kishore B. Challagundla
- Department of Biochemistry and Molecular Biology & The Fred and Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE 68198, USA; (V.G.); (A.S.P.); (S.C.)
- The Children’s Health Research Institute, University of Nebraska Medical Center, Omaha, NE 68198, USA
- Correspondence: ; Tel.: +1-402-559-9032
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4
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Fu R, Sutcliffe D, Zhao H, Huang X, Schretlen DJ, Benkovic S, Jinnah HA. Clinical severity in Lesch-Nyhan disease: the role of residual enzyme and compensatory pathways. Mol Genet Metab 2015; 114:55-61. [PMID: 25481104 PMCID: PMC4277921 DOI: 10.1016/j.ymgme.2014.11.001] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/02/2014] [Revised: 11/01/2014] [Accepted: 11/01/2014] [Indexed: 01/01/2023]
Abstract
Mutations in the HPRT1 gene, which encodes the purine salvage enzyme hypoxanthine-guanine phosphoribosyltransferase (HGprt), cause Lesch-Nyhan disease (LND) and more mildly affected Lesch-Nyhan variants. Prior studies have suggested a strong correlation between residual hypoxanthine recycling activity and disease severity. However, the relevance of guanine recycling and compensatory changes in the de novo synthesis of purines has received little attention. In the current studies, fibroblast cultures were established for 21 healthy controls and 36 patients with a broad spectrum of disease severity related to HGprt deficiency. We assessed hypoxanthine recycling, guanine recycling, steady-state purine pools, and de novo purine synthesis. There was a strong correlation between disease severity and either hypoxanthine or guanine recycling. Intracellular purines were normal in the HGprt-deficient fibroblasts, but purine wasting was evident as increased purine metabolites excreted from the cells. The normal intracellular purines in the HGprt-deficient fibroblasts were likely due in part to a compensatory increase in purine synthesis, as demonstrated by a significant increase in purinosomes. However, the increase in purine synthesis did not appear to correlate with disease severity. These results refine our understanding of the potential sources of phenotypic heterogeneity in LND and its variants.
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Affiliation(s)
- Rong Fu
- Department of Neurology, Emory University, Atlanta, GA, USA
| | - Diane Sutcliffe
- Department of Neurology, Emory University, Atlanta, GA, USA; Department of Human Genetics, Emory University, Atlanta, GA, USA; Department of Pediatrics, Emory University, Atlanta, GA, USA
| | - Hong Zhao
- Department of Chemistry, Pennsylvania State University, University Park, PA, USA
| | - Xinyi Huang
- Department of Chemistry, Pennsylvania State University, University Park, PA, USA
| | - David J Schretlen
- Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, MD, USA; Department of Radiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Steve Benkovic
- Department of Chemistry, Pennsylvania State University, University Park, PA, USA
| | - H A Jinnah
- Department of Neurology, Emory University, Atlanta, GA, USA; Department of Human Genetics, Emory University, Atlanta, GA, USA; Department of Pediatrics, Emory University, Atlanta, GA, USA.
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5
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Göttle M, Burhenne H, Sutcliffe D, Jinnah HA. Purine metabolism during neuronal differentiation: the relevance of purine synthesis and recycling. J Neurochem 2013; 127:805-18. [PMID: 23859490 DOI: 10.1111/jnc.12366] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2013] [Revised: 07/03/2013] [Accepted: 07/04/2013] [Indexed: 11/28/2022]
Abstract
Purines are a class of small organic molecules that are essential for all cells. They play critical roles in neuronal differentiation and function. Their importance is highlighted by several inherited disorders of purine metabolism, such as Lesch-Nyhan disease, which is caused by a deficiency of the purine salvage enzyme, hypoxanthine-guanine phosphoribosyltransferase (HGprt). Despite the known importance of purines in the nervous system, knowledge regarding their metabolism in neurons is limited. In the current studies, purine pools and their metabolism were examined in rat PC6-3 cells, a PC12 pheochromocytoma subclone that undergoes robust differentiation with nerve growth factor. The results were compared with five new independent PC6-3 subclones with defective purine recycling because of different mutations affecting HGprt enzyme activity. The results demonstrate an increase in most purines and in energy state following neuronal differentiation, as well as specific abnormalities when purine recycling is lost. The loss of HGprt-mediated purine recycling also is associated with significant loss of dopamine and related metabolites in the mutant PC6-3 lines, suggesting an important connection between purine and dopamine pathways. These results provide insights into how purine pools and metabolism change with neuronal differentiation, and how specific enzyme defects may cause neuronal dysfunction. Differentiation of dopaminergic PC6-3 cells is accompanied by increased purine pools and energy state. The lack of a functional purine recycling pathway causes purine limitation in both undifferentiated and differentiated cells, as well as profound loss of dopamine content. The results imply an unknown mechanism by which intracellular purine levels regulate dopamine levels.
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Affiliation(s)
- Martin Göttle
- Department of Neurology, Emory University, Atlanta, Georgia, USA
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6
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Allison AC, Hovi T, Watts RW, Webster AD. The role of de novo purine synthesis in lymphocyte transformation. CIBA FOUNDATION SYMPOSIUM 2008:207-24. [PMID: 415850 DOI: 10.1002/9780470720301.ch13] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Genetic defects in purine metabolism are associated with severe immunodeficiency. Adenosine deaminase deficiency impairs the function of both B- and T-lymphocytes whereas in purine nucleoside (inosine) phosphorylase deficiency there is more severe impairment of T-lymphocyte functions than of B-lymphocyte functions. The relative unimportance of the salvage pathway catalysed by hypoxanthine-guanine phosphoribosyltransferase is shown by the normal responses of T-lymphocytes from patients with the Lesch-Nyhan syndrome to antigenic and mitogenic stimulation. A mild deficiency of B-lymphocyte function is found in these patients. Agents inhibiting the de novo pathway of purine synthesis, including azaserine, 6-mercaptopurine and azathioprine in low doses, block the responses of normal human lymphocytes to mitogenic stimulation. These observations emphasize the importance of the de novo pathway of purine synthesis in lymphocyte responses to antigenic and mitogenic stimulation. There is considerable heterogeneity in the amount of labelled uridine incorporated into human and rat lymphocytes. This does not appear to reflect only a difference between T- and B-lymphocytes
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7
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Lewers JC, Ceballos-Picot I, Shirley TL, Mockel L, Egami K, Jinnah HA. Consequences of impaired purine recycling in dopaminergic neurons. Neuroscience 2008; 152:761-72. [PMID: 18313225 DOI: 10.1016/j.neuroscience.2007.10.065] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2007] [Revised: 10/04/2007] [Accepted: 01/16/2008] [Indexed: 10/22/2022]
Abstract
A unique sensitivity to specific biochemical processes is responsible for selective vulnerability of midbrain dopamine neurons in several diseases. Prior studies have shown these neurons are susceptible to energy failure and mitochondrial dysfunction, oxidative stress, and impaired disposal of misfolded proteins. These neurons also are especially vulnerable to the loss of purine recycling. In the brains of humans or mice with inherited defects of the purine recycling enzyme hypoxanthine-guanine phosphoribosyltransferase (HPRT), the most prominent defect is loss of basal ganglia dopamine. To investigate the nature of the relationship between HPRT deficiency and dopamine, the mouse MN9D dopaminergic neuronal cell line was used to prepare 10 sublines lacking HPRT. The mutant sublines grew more slowly than the parent line, but without morphological signs of impaired viability. As a group, the mutant sublines had significantly lower dopamine than the parent line. The loss of dopamine in the mutants did not reflect impaired energy status, as judged by ATP levels or vulnerability to inhibitors of energy production. Indeed, the mutant lines as a group appeared energetically more robust than the parent line. The loss of dopamine also was not accompanied by enhanced susceptibility to oxidative stress or proteasome inhibitors. Instead, the loss of dopamine reflected only one aspect of a broad change in the molecular phenotype of the cells affecting mRNAs encoding tyrosine hydroxylase, the dopamine transporter, the vesicular monoamine transporter, monoamine oxidase B, catechol-O-methyltransferase, and GTP-cyclohydrolase. These changes were selective for the dopamine phenotype, since multiple control mRNAs were normal. These studies suggest purine recycling is an intrinsic metabolic process of particular importance to the molecular phenotype of dopaminergic neurons independent of previously established mechanisms involving energy failure, oxidative stress, or proteasome dysfunction.
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Affiliation(s)
- J C Lewers
- Department of Neurology, Meyer Room 6-181, 600 North Wolfe Street, Johns Hopkins University, Baltimore, MD 21287, USA
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8
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Shirley TL, Lewers JC, Egami K, Majumdar A, Kelly M, Ceballos-Picot I, Seidman MM, Jinnah HA. A human neuronal tissue culture model for Lesch-Nyhan disease. J Neurochem 2007; 101:841-53. [PMID: 17448149 DOI: 10.1111/j.1471-4159.2007.04472.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Mutations in the gene encoding the purine salvage enzyme, hypoxanthine-guanine phosphoribosyltransferase (HPRT) cause Lesch-Nyhan disease, a neurodevelopmental disorder characterized by cognitive, neurological, and behavioral abnormalities. Despite detailed knowledge of the enzyme's function, the key pathophysiological changes that accompany loss of purine recycling are unclear. To facilitate delineating the consequences of HPRT deficiency, four independent HPRT-deficient sublines of the human dopaminergic neuroblastoma, SK-N-BE(2) M17, were isolated by targeted mutagenesis with triple helix-forming oligonucleotides. As a group, these HPRT-deficient cells showed several significant abnormalities: (i) impaired purine recycling with accumulation of hypoxanthine, guanine, and xanthine, (ii) reduced guanylate energy charge and GTP:GDP ratio, but normal adenylate energy charge and no changes in any adenine nucleotide ratios, (iii) increased levels of UTP and NADP+, (iv) reduced DOPA decarboxylase, but normal monoamines, and (v) reduction in cell soma size. These cells combine the analytical power of multiple lines and a human, neuronal origin to provide an important tool to investigate the pathophysiology of HPRT deficiency.
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Affiliation(s)
- Thomas L Shirley
- Department of Neurology, Johns Hopkins University, Baltimore, Maryland, USA, and Department of Biology, Necker-Enfants Malades Hospital, Paris, France
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9
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Becker MA, Raivio KO, Seegmiller JE. Synthesis of phosphoribosylpyrophosphate in mammalian cells. ADVANCES IN ENZYMOLOGY AND RELATED AREAS OF MOLECULAR BIOLOGY 2006; 49:281-306. [PMID: 95664 DOI: 10.1002/9780470122945.ch7] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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10
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Skaper SD, Seegmiller JE. INCREASED CONCENTRATIONS OF GLYCINE IN HYPOXANTHINE-GUANINE PHOSPHORIBOSYLTRANSFERASE-DEFICIENT MOUSE NEUROBLASTOMA CELLS1. J Neurochem 2006. [DOI: 10.1111/j.1471-4159.1976.tb04437.x-i1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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11
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Pinto CS, Jinnah HA, Shirley TL, Nyhan WL, Seifert R. Altered membrane NTPase activity in Lesch-Nyhan disease fibroblasts: comparison with HPRT knockout mice and HPRT-deficient cell lines. J Neurochem 2005; 93:1579-86. [PMID: 15935074 DOI: 10.1111/j.1471-4159.2005.03151.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Lesch-Nyhan disease (LND) is a rare disorder caused by a defect of an enzyme in the purine salvage pathway, hypoxanthine phosphoribosyl transferase (HPRT). It is still unknown how the metabolic defect translates into the complex neuropsychiatric phenotype characterized by self-injurious behavior, dystonia and mental retardation. There are abnormalities in purine and pyrimidine nucleotide content in HPRT-deficient cells. We hypothesized that altered nucleotide concentrations in HPRT deficiency change G-protein-mediated signal transduction. Therefore, our original study aim was to examine the high-affinity GTPase activity of G-proteins in membranes from primary human skin and immortalized mouse skin fibroblasts, rat B103 neuroblastoma cells and mouse Neuro-2a neuroblastoma cells. Unexpectedly, in membranes from human fibroblasts, B103- and Neuro-2a cells, V(max) of low-affinity nucleoside 5'-triphosphatase (NTPase) activities was decreased up to 7-fold in HPRT deficiency. In contrast, in membranes from mouse fibroblasts, HPRT deficiency increased NTPase activity up to 4-fold. The various systems analyzed differed from each other in terms of K(m) values for NTPs, absolute V(max) values and K(i) values for nucleoside 5'-[beta,gamma-imido]triphosphates. Our data show that altered membrane NTPase activity is a biochemical hallmark of HPRT deficiency, but species and cell-type differences have to be considered. Thus, future studies on biochemical changes in LND should be conducted in parallel in several HPRT-deficient systems.
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Affiliation(s)
- Cibele S Pinto
- Department of Pharmacology and Toxicology, University of Kansas, Lawrence, Kansas, USA
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12
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Crawford CR, Bryant RE. Isolation of a Chinese hamster cell mutant with low intracellular phosphoribosylpyrophosphate concentration. Mol Cell Biol 2003; 2:1619-27. [PMID: 14582202 PMCID: PMC369969 DOI: 10.1128/mcb.2.12.1619-1627.1982] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A tritium-adenine suicide procedure was used to select for mutants with reduced uptake of adenine from a population of Chinese hamster V79 cells mutagenized with ethyl methane sulfonate. In one of the mutant lines isolated, designated KC62, the uptake of adenine, hypoxanthine, and guanine was reduced by approximately 70%. The specific activities, Km values, and Vmax values of adenine phosphoribosyltransferase and of hypoxanthine phosphoribosyltransferase were the same in extracts from KC62 and from the parental cell line. Metabolic fate studies of incorporated [3H]adenine and 3[H]hypoxanthine revealed a metabolic block at the level of phosphoribosylation. Determination of phosphoribosylpyrophosphate pool size showed that the mutant contained only 25% of the phosphoribosylpyrophosphate found in the parent. Its reduced availability in KC62 appears to result in a decreased ability to salvage adenine, hypoxanthine, and guaninine via phosphoribosylation. Phosphoribosylpyrophosphate synthetase from KC62 was shown to have an increased sensitivity to inhibition by a variety of nucleotides.
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Affiliation(s)
- C R Crawford
- Department of Biochemistry, University of Tennessee, Knoxville, Tennessee 37996, USA
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13
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Connolly GP. Hypoxanthine-guanine phosphoribosyltransferase-deficiency produces aberrant neurite outgrowth of rodent neuroblastoma used to model the neurological disorder Lesch Nyhan syndrome. Neurosci Lett 2001; 314:61-4. [PMID: 11698147 DOI: 10.1016/s0304-3940(01)02290-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Lesch Nyhan syndrome (LNS) manifests in bizarre and horrific neurological symptoms, the primary cause being a deficiency of the purine salvage enzyme, hypoxanthine-guanine phosphoribosyltransferase (HGPRT). How and why this enzyme deficiency leads to abnormal brain development is unknown. To investigate this phenomenon the present study was designed to examine if the growth of two HGPRT-deficient neuroblastomas, mouse N2aTG and rat B103-4C was different with respect to their corresponding control cell lines, N2a and B103. Data is provided showing that compared to control cell lines, HGPRT-deficient cells proliferated less and exhibited greater morphological complexity. If these abnormalities occur during neurogenesis of human HGPRT-deficient brain neurones, they could profoundly influence central nervous system development and thus, may form the aetiological basis for the symptoms of LNS.
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Affiliation(s)
- G P Connolly
- Purine NeuroScience Laboratory, Chemical Pathology, Guy's King's and St. Thomas' Medical School, Kings College London, Guy's Hospital, London SE1 9RT, UK.
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14
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Smith DW, Friedmann T. Characterization of the dopamine defect in primary cultures of dopaminergic neurons from hypoxanthine phosphoribosyltransferase knockout mice. Mol Ther 2000; 1:486-91. [PMID: 10933970 DOI: 10.1006/mthe.2000.0057] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Lesch-Nyhan disease (LND) is an X-linked metabolic disorder caused by lack of activity of the purine salvage enzyme hypoxanthine phosphoribosyltransferase (HPRT) and characterized by hyperuricemia and debilitating neurological manifestations. The mechanisms underlying the neuropathology are not well understood and the principal neurochemical lesion characterized to date is a deficiency of the dopamine system in the basal ganglia. To facilitate the study of mechanism(s) by which HPRT deficiency causes the dopamine defect, we have compared the survival and dopamine phenotype of primary cultures of dopamine neurons derived from HPRT-deficient mice with the dopaminergic neurons from wild-type mice. The survival of dopaminergic neurons from both sources was promoted to an equal extent by glial cell line-derived neurotrophic factor (GDNF), a potent survival factor for dopamine neurons in vitro. Although the survival of the HPRT-deficient neurons was indistinguishable from that of cells derived from wild-type counterparts, the HPRT-deficient cells demonstrated a persistent deficiency of dopamine content and dopamine uptake with increasing neuritic differentiation, indicating that GDNF does not restore the normal phenotype in HPRT-deficient dopamine neurons despite its well-known protective and regenerative properties in several neurodegeneration models. Nevertheless, the demonstration that GDNF trophic support promotes the survival of these dopaminergic neurons will facilitate gaining a better understanding of the neuropathological mechanisms of LND by allowing a more extensive analysis of the cells central to the Lesch-Nyhan phenotype, the dopaminergic neurons of the basal ganglia.
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Affiliation(s)
- D W Smith
- Center for Molecular Genetics, Room 122, Department of Pediatrics, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0634, USA.
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15
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Connolly GP, Duley JA. Uridine and its nucleotides: biological actions, therapeutic potentials. Trends Pharmacol Sci 1999; 20:218-25. [PMID: 10354618 DOI: 10.1016/s0165-6147(99)01298-5] [Citation(s) in RCA: 130] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
There are many disorders of pyrimidine metabolism and those that involve an alteration in uridine metabolism have neurological and systemic effects, which provide insights into the biological activity of uridine and its analogues. Studies of the metabolism and actions of pyrimidines have uncovered a wealth of information on how these endogenous metabolites modulate cell physiology. In this article, the roles for the pyrimidine nucleoside uridine and its nucleotide derivatives in the regulation of a number of biological systems are examined and benefits of further studies are outlined. An understanding of how uridine and its nucleotides modulate such vastly complicated biological systems should ultimately lead to the development of new ways for modulating human physiology in both normal and diseased states. Likely targets for therapy include the respiratory, circulatory, reproductive, and nervous systems, and the treatment of cancer and HIV infection.
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Affiliation(s)
- G P Connolly
- Purine Neuroscience Laboratory, Department of Chemical Pathology, Guy's King's, Thomas' Medical, Dental and Biomedical Sciences, 5th Floor Guy's Tower, Guy's Hospital, Weston Street, London, UK SE1 9RT
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Archer S, Juranka PF, Ho JH, Chan VL. An analysis of multiple mechanisms of adenosine toxicity in baby hamster kidney cells. J Cell Physiol 1985; 124:226-32. [PMID: 3900094 DOI: 10.1002/jcp.1041240209] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Analysis of the response of baby hamster kidney cells to adenosine in the presence of the adenosine deaminase inhibitor erythro-9-(2-hydroxy-3-nonyl) adenine has revealed two distinct mechanisms of toxicity. The first is apparent at low concentrations of adenosine (less than 5 microM) and is dependent upon the presence of a functional adenosine kinase. The initial toxicity is abolished by uridine, is unrelated to the inhibition of ribonucleotide reductase, and is accompanied by a decrease in the size of the pyrimidine nucleotide pool. Toxicity at higher concentrations of adenosine is adenosine kinase independent and is potentiated by homocysteine thiolactone. An elevation in the intracellular level of S-adenosylhomocysteine, which was observed following treatment with higher concentrations of adenosine (greater than 10 microM), is believed to mediate toxicity at these levels. Interestingly, BHK cells were resistant to intermediate levels of adenosine. The mechanism of resistance is currently unknown, but appears unrelated to a lack of inhibition of adenosine deaminase. It is proposed that substrate inhibition of adenosine kinase may be a determinant of this property.
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Chen J, Jones M. Effect of 5-phosphoribosyl-a-pyrophosphate on de novo pyrimidine biosynthesis in cultured Ehrlich ascites cells made permeable with dextran sulfate 500. J Biol Chem 1979. [DOI: 10.1016/s0021-9258(17)30128-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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18
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May SR, Hashmi S, Miller OJ, Krooth RS. Increased intracellular phosphoribosylpyrophosphate and accelerated orotic acid decarboxylation in a mouse cell line resistant to purine and pyrimidine ribonucleosides. SOMATIC CELL GENETICS 1977; 3:263-80. [PMID: 415375 DOI: 10.1007/bf01538745] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
A line of mouse fibroblasts (A9AU-1), originally selected for growth in the presence of 6-azauridine, has been found to be resistant to cytotoxic concentrations of adenosine, guanosine, and thymidine. A9AU-1 cells convert orotic acid to uridine 5'-monophosphate at twice the rate of the A9P line from which the A9AU-1 clone was selected. The resistant cells also excrete purines, synthesized de novo, into the medium at an increased velocity. The average intracellular 5-phosphoribosyl-1-pyrophosphate (PRPP) concentration of the resistant line is 45% higher than that of the parental line. The elevated PRPP concentration is likely to be responsible for both the apparent acceleration of pyrimidine synthesis and the increased excretion of purines into the growth medium; it might also account, by one of the several possible mechanisms, for the resistance of the cells to cytotoxic concentrations of the various nucleosides.
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Martin DW, Maler BA. Phosphoribosylpyrophosphate synthetase is elevated in fibroblasts from patients with the Lesch-Nyhan syndrome. Science 1976; 193:408-11. [PMID: 180603 DOI: 10.1126/science.180603] [Citation(s) in RCA: 32] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
In subconfluent cultures of fibroblasts from patients with complete or partial deficiencies of hypoxanthine-guanine phosphoribosyltransferase, phosphoribosylpyrophosphate synthetase activity is elevated. The abnormally high catalytic activity of the synthetase appears to account for the overproduction of purines by the cultured mutant cells and presumably for that by the patients.
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Breakefield XO, Castiglione CM, Edelstein SB. Monoamine oxidase activity decreased in cells lacking hypoxanthine phosphoribosyltransferase activity. Science 1976; 192:1018-20. [PMID: 1273584 DOI: 10.1126/science.1273584] [Citation(s) in RCA: 53] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The Lesch-Nyhan syndrome in humans is characterized by lack of hypoxanthine phosphoribosyltransferase activity and neurologic abnormalities that suggest changes in catecholamine metabolism. Monoamine oxidase, which degrades biogenic amines, has decreased activity in noradrenergic murine neuroblastoma cell lines lacking hypoxanthine phosphoribosyltransferase activity and in skin fibroblasts from patients with the Lesch-Nyhan syndrome.
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Skaper SD, Seegmiller JE. Increased concentrations of glycine in hypoxanthine-guanine phosphoribosyltransferase-deficient mouse neuroblastoma cells. J Neurochem 1976; 26:689-94. [PMID: 965960 DOI: 10.1111/j.1471-4159.1976.tb04438.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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Seegmiller JE. Inherited deficiency of hypoxanthine-guanine phosphoribosyltransferase in X-linked uric aciduria (the Lesch-Nyhan syndrome and its variants). ADVANCES IN HUMAN GENETICS 1976; 6:75-163. [PMID: 779428 DOI: 10.1007/978-1-4615-8264-9_2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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23
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Human phosphoribosylpyrophosphate synthetase. Comparison of purified normal and mutant enzymes. J Biol Chem 1975. [DOI: 10.1016/s0021-9258(19)41005-3] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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