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Shand EL, Sweeney K, Sundling KE, McClean MN, Brow DA. Live-cell analysis of IMPDH protein levels during yeast colony growth provides insights into the regulation of GTP synthesis. mBio 2024; 15:e0102124. [PMID: 38940616 PMCID: PMC11323793 DOI: 10.1128/mbio.01021-24] [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: 04/10/2024] [Accepted: 05/24/2024] [Indexed: 06/29/2024] Open
Abstract
The purine nucleotides ATP and GTP are made from the common precursor inosine monophosphate (IMP). Maintaining the correct balance of these nucleotides for optimal cell growth is controlled in part by the enzyme IMP dehydrogenase (IMPDH), which catalyzes the first dedicated step of GTP biosynthesis. The regulation of IMPDH mRNA and protein levels in the yeast S. cerevisiae grown in liquid culture has been studied in some detail, but regulation of IMPDH protein under conditions of cellular crowding on a solid substrate has not been examined. Here, we report real-time, live-cell analysis of the accumulation of the Imd2 isoform of IMPDH in yeast cells forming a monolayer colony in a microfluidic device over a 50-hour time course. We observe two distinct phases of increased Imd2 accumulation: a guanine-insensitive phase early in outgrowth and a guanine-sensitive phase later, when cells become crowded. We show that the IMPDH inhibitor mycophenolic acid enhances both phases of increase. Deletion of a transcription attenuator upstream of the mRNA start site that decreases Imd2 mRNA synthesis in the presence of high GTP increases the baseline level of Imd2 protein 10-fold and abolishes guanine-sensitive but not guanine-insensitive induction. Our results suggest that at least two mechanisms of yeast Imd2 regulation exist, the known GTP-dependent attenuation of RNA polymerase II elongation and a GTP concentration-independent pathway that may be controlled by cell growth state. Live-cell analysis of IMPDH protein levels in a growing yeast colony confirms a known mechanism of regulation and provides evidence for an additional mode of regulation. IMPORTANCE This study used live-cell microscopy to track changes in the level of a key enzyme in GTP nucleotide biosynthesis, inosine monophosphate dehydrogenase (IMPDH), during growth of a brewers yeast colony over 2 days in a microfluidic device. The results show that feedback regulation via transcription attenuation allows cells to adapt to nutrient limitation in the crowded environs of a yeast colony. They also identify a novel mode of regulation of IMPDH level that is not driven by guanine nucleotide availability.
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Affiliation(s)
- Erica L. Shand
- Department of Biomolecular Chemistry, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, USA
| | - Kieran Sweeney
- Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Kaitlin E. Sundling
- Department of Biomolecular Chemistry, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, USA
| | - Megan N. McClean
- Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, Wisconsin, USA
- University of Wisconsin Carbone Cancer Center, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, USA
| | - David A. Brow
- Department of Biomolecular Chemistry, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, USA
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2
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A Review of Emerging Goose Astrovirus Causing Gout. BIOMED RESEARCH INTERNATIONAL 2022; 2022:1635373. [PMID: 36072471 PMCID: PMC9441354 DOI: 10.1155/2022/1635373] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/16/2022] [Accepted: 08/11/2022] [Indexed: 11/21/2022]
Abstract
In recent years, an infection in geese caused by goose astrovirus (GAstV) has repeatedly occurred in coastal areas of China and rapidly spread to inland provinces. The infection is characterized by joint and visceral gout and is fatal. The disease has caused huge economic losses to China's goose industry. GAstV is a nonenveloped, single-stranded, positive-sense RNA virus. As it is a novel virus, there is no specific classification. Here, we review the current understanding of GAstV. The virus structure, isolation, diagnosis and detection, innate immune regulation, and transmission route are discussed. In addition, since GAstV can cause gout in goslings, the possible role of GAstV in gout formation and uric acid metabolism is discussed. We hope that this review will inform researchers to rapidly develop effective methods to prevent and treat this disease.
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Alpak I, Askin Uzel R, Sargin S, Yesil-Celiktas O. Supercritical CO2 extraction of an immunosuppressant produced by solid-state fermentation. J CO2 UTIL 2018. [DOI: 10.1016/j.jcou.2018.08.014] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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4
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Pan H, Hu Q, Wang J, Liu Z, Wu D, Lu W, Huang J. Myricetin is a novel inhibitor of human inosine 5'-monophosphate dehydrogenase with anti-leukemia activity. Biochem Biophys Res Commun 2016; 477:915-922. [PMID: 27378425 DOI: 10.1016/j.bbrc.2016.06.158] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2016] [Accepted: 06/30/2016] [Indexed: 01/14/2023]
Abstract
Human inosine 5'-monophosphate dehydrogenase (hIMPDH) is a rate-limiting enzyme in the de novo biosynthetic pathway of purine nucleotides, playing crucial roles in cellular proliferation, differentiation, and transformation. Dysregulation of hIMPDH expression and activity have been found in a variety of human cancers including leukemia. In this study, we found that myricetin, a naturally occurring phytochemical existed in berries, wine and tea, was a novel inhibitor of human type 1 and type 2 IMPDH (hIMPDH1/2) with IC50 values of 6.98 ± 0.22 μM and 4.10 ± 0.14 μM, respectively. Enzyme kinetic analysis using Lineweaver-Burk plot revealed that myricetin is a mix-type inhibitor for hIMPDH1/2. Differential scanning fluorimetry and molecular docking simulation data demonstrate that myricetin is capable of binding with hIMPDH1/2. Myricetin treatment exerts potent anti-proliferative and pro-apoptotic effects on K562 human leukemia cells in a dose-dependent manner. Importantly, cytotoxicity of myricetin on K562 cells were markedly attenuated by exogenous addition of guanosine, a salvage pathway of maintaining intracellular pool of guanine nucleotides. Taking together, these results indicate that natural product myricetin exhibits potent anti-leukemia activity by interfering with purine nucleotides biosynthetic pathway through the suppression of hIMPDH1/2 catalytic activity.
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Affiliation(s)
- Huiling Pan
- Shanghai Key Laboratory of New Drug Design, School of Pharmacy, East China University of Science and Technology, 130 Mei Long Road, Shanghai 200237, PR China
| | - Qian Hu
- Shanghai Key Laboratory of New Drug Design, School of Pharmacy, East China University of Science and Technology, 130 Mei Long Road, Shanghai 200237, PR China
| | - Jingyuan Wang
- Shanghai Key Laboratory of New Drug Design, School of Pharmacy, East China University of Science and Technology, 130 Mei Long Road, Shanghai 200237, PR China
| | - Zehui Liu
- Shanghai Key Laboratory of New Drug Design, School of Pharmacy, East China University of Science and Technology, 130 Mei Long Road, Shanghai 200237, PR China
| | - Dang Wu
- Shanghai Key Laboratory of New Drug Design, School of Pharmacy, East China University of Science and Technology, 130 Mei Long Road, Shanghai 200237, PR China
| | - Weiqiang Lu
- Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences and School of Life Sciences, East China Normal University, 500 Dongchuan Road, Shanghai 200241, PR China.
| | - Jin Huang
- Shanghai Key Laboratory of New Drug Design, School of Pharmacy, East China University of Science and Technology, 130 Mei Long Road, Shanghai 200237, PR China.
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5
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Rostirolla DC, Milech de Assunção T, Bizarro CV, Basso LA, Santos DS. Biochemical characterization of Mycobacterium tuberculosis IMP dehydrogenase: kinetic mechanism, metal activation and evidence of a cooperative system. RSC Adv 2014. [DOI: 10.1039/c4ra02142h] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Proposed kinetic mechanism forMtIMPDH in the presence of K+.
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Affiliation(s)
- Diana Carolina Rostirolla
- Centro de Pesquisas em Biologia Molecular e Funcional (CPBMF)
- Instituto Nacional de Ciência e Tecnologia em Tuberculose (INCT-TB)
- Pontifícia Universidade Católica do Rio Grande do Sul (PUCRS)
- Porto Alegre, Brazil
- Programa de Pós-Graduação em Medicina e Ciências da Saúde
| | | | - Cristiano Valim Bizarro
- Centro de Pesquisas em Biologia Molecular e Funcional (CPBMF)
- Instituto Nacional de Ciência e Tecnologia em Tuberculose (INCT-TB)
- Pontifícia Universidade Católica do Rio Grande do Sul (PUCRS)
- Porto Alegre, Brazil
| | - Luiz Augusto Basso
- Centro de Pesquisas em Biologia Molecular e Funcional (CPBMF)
- Instituto Nacional de Ciência e Tecnologia em Tuberculose (INCT-TB)
- Pontifícia Universidade Católica do Rio Grande do Sul (PUCRS)
- Porto Alegre, Brazil
- Programa de Pós-Graduação em Medicina e Ciências da Saúde
| | - Diogenes Santiago Santos
- Centro de Pesquisas em Biologia Molecular e Funcional (CPBMF)
- Instituto Nacional de Ciência e Tecnologia em Tuberculose (INCT-TB)
- Pontifícia Universidade Católica do Rio Grande do Sul (PUCRS)
- Porto Alegre, Brazil
- Programa de Pós-Graduação em Medicina e Ciências da Saúde
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6
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Bairagya HR, Mukhopadhyay BP, Bera AK. Conserved water mediated recognition and the dynamics of active site Cys 331 and Tyr 411 in hydrated structure of human IMPDH-II. J Mol Recognit 2010; 24:35-44. [DOI: 10.1002/jmr.1021] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Kagaya H, Miura M, Saito M, Habuchi T, Satoh S. Correlation of IMPDH1 gene polymorphisms with subclinical acute rejection and mycophenolic acid exposure parameters on day 28 after renal transplantation. Basic Clin Pharmacol Toxicol 2010; 107:631-6. [PMID: 20136638 DOI: 10.1111/j.1742-7843.2010.00542.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The risk of acute rejection in patients with higher exposure to mycophenolic acid (MPA), the active metabolite of mycophenolate mofetil (MMF), might be due to inosine 5'-monophosphate dehydrogenase (IMPDH) polymorphisms. The correlations with subclinical acute rejection, IMPDH1 polymorphisms and MPA exposure on day 28 post-transplantation were investigated in 82 Japanese recipients. Renal transplant recipients were given combination immunosuppressive therapy consisting of tacrolimus and 1.0, 1.5 or 2.0 g/day of MMF in equally divided doses every 12 hr at designated times. There were no significant differences in the incidence of subclinical acute rejection between IMPDH1 rs2278293 or rs2278294 polymorphisms (p = 0.243 and 0.735, respectively). However, in the high MPA night-time exposure range (AUC > 60 microg x h/ml and C(0 )> or = 1.9 microg/ml), there was a significant difference in the incidence of subclinical acute rejection between IMPDH1 rs2278293 A/A, A/G and G/G genotypes (each p = 0.019), but not the IMPDH1 rs2278294 genotype. In the higher daytime MPA exposure range, patients with the IMPDH1 rs2278293 G/G genotype also tended to develop subclinical acute rejection. In patients with the IMPDH rs2278293 A/A genotype, the risk of subclinical acute rejection episode tends to be low and the administration of MMF was effective. The risk of subclinical acute rejection for recipients who cannot adapt in therapeutic drug monitoring (TDM) of MPA seems to be influenced by IMPDH1 rs2278293 polymorphism. The prospective analysis of IMPDH1 rs2278293 polymorphism as well as monitoring of MPA plasma concentration after transplantation might help to improve MMF therapy.
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Affiliation(s)
- Hideaki Kagaya
- Department of Pharmacy, Akita University Hospital, Akita, Japan
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8
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Interpatient variability in IMPDH activity in MMF-treated renal transplant patients is correlated with IMPDH type II 3757T > C polymorphism. Pharmacogenet Genomics 2009; 19:626-34. [PMID: 19617864 DOI: 10.1097/fpc.0b013e32832f5f1b] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
OBJECTIVES The active metabolite of mycophenolate mofetil (MMF), mycophenolic acid, inhibits the activity of the target enzyme inosine monophosphate dehydrogenase (IMPDH). The aim of this study was to correlate eight different single nucleotide polymorphisms of the IMPDH type II gene to the activity of the IMPDH enzyme to explain between-patient differences in IMPDH activity. METHODS AND RESULTS In a prospective study, we measured IMPDH activity, mycophenolic acid plasma concentrations, and eight polymorphisms of IMPDH type II in de novo kidney transplant recipients, 6 days posttransplantation while on MMF treatment. Polymorphisms in the IMPDH type II gene were only observed for the IMPDH type II 3757T > C (rs11706052) single nucleotide polymorphism. Ten of 101 patients (10%) were heterozygous and two of 101 patients (2%) homozygous for IMPDH type II 3757T > C. The allele frequency was 6.9%. The IMPDH activity over 12 h (AUC(act)) was 49% higher for patients with an IMPDH type II 3757C variant [n = 12 vs. n = 68; 336 (95% confidence interval: 216-521) vs. 227 (95% confidence interval: 198-260) hmicromol/s/mol adenosine monophosphate; P = 0.04]. The IMPDH activity measured before transplantation (Act(pre-Tx)) was not significantly different between IMPDH type II 3757TT wild-type and variant carrier patients (P = 0.99). CONCLUSION We report that the IMPDH type II 3757T > C polymorphism is associated with an increased IMPDH activity in MMF-treated renal transplant patients. This polymorphism explains 8.0% of the interpatient variability in IMPDH activity.
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9
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Wang J, Yang JW, Zeevi A, Webber SA, Girnita DM, Selby R, Fu J, Shah T, Pravica V, Hutchinson IV, Burckart GJ. IMPDH1 gene polymorphisms and association with acute rejection in renal transplant patients. Clin Pharmacol Ther 2007; 83:711-7. [PMID: 17851563 DOI: 10.1038/sj.clpt.6100347] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Inosine 5'-monophosphate dehydrogenase 1 (IMPDH1) catalyzes the rate-limiting step of the de novo pathway for purine synthesis and is a major target of the immunosuppressive drug mycophenolic acid (MPA). Few variants of the IMPDH1 gene have been reported. The objective of this study was to identify and characterize IMPDH1 variants to determine whether genetic variation contributes to differences in MPA response and toxicity in transplant patients. Seventeen genetic variants were identified in the IMPDH1 gene with allele frequencies ranging from 0.2 to 42.7%. In this study, 191 kidney transplant patients who received mycophenolate mofetil were genotyped for IMPDH1. Two single-nucleotide polymorphisms, rs2278293 and rs2278294, were significantly associated with the incidence of biopsy-proven acute rejection in the first year post-transplantation. Future studies of the multifactorial nature of acute rejection must consider IMPDH1 polymorphisms in MPA-treated patients.
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Affiliation(s)
- J Wang
- Department of Pharmacy, University of Southern California, Los Angeles, California, USA
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10
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Karaer S, Sarikaya AT, Arda N, Temizkan G. The 3' terminal sequence of the inosine monophosphate dehydrogenase gene encodes an active domain in the yeast Schizosaccharomyces pombe. Genet Mol Biol 2006. [DOI: 10.1590/s1415-47572006000300026] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Affiliation(s)
| | | | - Nazli Arda
- Istanbul University, Turkey; Istanbul University, Turkey
| | - Güler Temizkan
- Istanbul University, Turkey; Istanbul University, Turkey
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11
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MacPhee IAM, Fredericks S, Holt DW. Does pharmacogenetics have the potential to allow the individualisation of immunosuppressive drug dosing in organ transplantation? Expert Opin Pharmacother 2005; 6:2593-605. [PMID: 16316299 DOI: 10.1517/14656566.6.15.2593] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
The immunosuppressive drugs used in organ transplantation have a narrow therapeutic index, with rejection occurring as a consequence of underdosing and infection, malignancy and a number of drug-specific side effects with excessive dosing. Significant heterogeneity in the dose of drug required to achieve therapeutic blood concentrations adds to the complexity of the problem, which has been partly resolved by therapeutic drug monitoring. Single nucleotide polymorphisms have been identified in genes encoding metabolic enzymes, drug efflux pumps and drug targets for most of the drugs in widespread use. A pharmacogenetic approach to immunosuppressive drug prescribing remains to be tested. Based on current evidence, the most promising strategy would be use of the cytochrome P450 3A5 expressor genotype to guide initial dosing with tacrolimus.
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Affiliation(s)
- Iain A M MacPhee
- Cellular and Molecular Medicine, Renal Medicine, St. George's Hospital, University of London, Cranmer Terrace, London, SW17 0RE, UK.
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12
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Cattaneo D, Tankiewicz A, Merlini S, Perico N, Remuzzi G. Pharmacogenetics and pharmacogenomics of immunosuppressive agents: perspective for individualized therapy. Per Med 2004; 1:53-62. [DOI: 10.1517/17410541.1.1.53] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Immunosuppressive therapy has markedly improved over the past years with the advent of highly potent and rationally targeted immunosuppressive agents. Since these drugs are characterized by a narrow therapeutic index, major efforts have been carried out to define therapeutic windows based on the blood levels of each immunosuppressant, and relating those concentrations to clinical events. Although pharmacokinetic-based approaches are currently used as useful tools to guide drug dosing, they present several limitations. Pharmacogenomics – a science that studies the inherited basis of differences between individual responses to drugs in order to identify the best dose and therapy for each patient – might represent a complementary support. Preliminary studies that have focused on polymorphisms of genes encoding enzymes involved in drug metabolism, drug distribution, and pharmacological target, have shown promising results. Indeed, pharmacogenomics holds promise for improvement in the ability to individualize pharmacological therapy based on the patient’s genetic profile.
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Affiliation(s)
- Dario Cattaneo
- Mario Negri Institute, Department of Medicine and Transplantation Ospedali Riuniti di Bergamo, Mario Negri Institute for Pharmacological Research, Via Gavazzeni 11- 24125 Bergamo, Italy.
| | - Anna Tankiewicz
- Medical University of Bialystok, Department of Pharmacodynamics, Medical University of Bialystok, Poland
| | - Simona Merlini
- Mario Negri Institute, Department of Medicine and Transplantation Ospedali Riuniti di Bergamo, Mario Negri Institute for Pharmacological Research, Via Gavazzeni 11- 24125 Bergamo, Italy
| | - Norberto Perico
- Mario Negri Institute, Department of Medicine and Transplantation Ospedali Riuniti di Bergamo, Mario Negri Institute for Pharmacological Research, Via Gavazzeni 11- 24125 Bergamo, Italy
| | - Giuseppe Remuzzi
- Mario Negri Institute, Department of Medicine and Transplantation Ospedali Riuniti di Bergamo, Mario Negri Institute for Pharmacological Research, Via Gavazzeni 11- 24125 Bergamo, Italy
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13
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McPhillips CC, Hyle JW, Reines D. Detection of the mycophenolate-inhibited form of IMP dehydrogenase in vivo. Proc Natl Acad Sci U S A 2004; 101:12171-6. [PMID: 15292516 PMCID: PMC514452 DOI: 10.1073/pnas.0403341101] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
IMP dehydrogenase (IMPDH) is the rate-limiting enzyme for de novo GMP synthesis. Its activity is correlated with cell growth, and it is the target of a number of proven and experimental drug therapies including mycophenolic acid (MPA). MPA inhibits the enzyme by trapping a covalent nucleotide-enzyme intermediate. Saccharomyces cerevisiae has four IMPDH genes called IMD1-IMD4. IMD2 is transcriptionally regulated and is the only one that enables yeast to grow in the presence of MPA. We show here that de novo synthesis of the IMD2-encoded protein is strongly induced upon MPA treatment. We also monitor the in vivo formation of a covalent nucleotide-enzyme intermediate for Imd2, Imd3, and Imd4 that accumulates in the presence of MPA. Complete formation of the Imd2 intermediate requires drug concentrations manyfold higher than that required to quantitatively trap the Imd3- or Imd4-nucleotide adducts. Purification of the tagged IMD gene products reveals that the family of polypeptides coassemble to form heteromeric IMPDH complexes, suggesting that they form mixed tetramers. These data demonstrate that S. cerevisiae harbor multiple IMPDH enzymes with varying drug sensitivities and offer an assay to monitor the inhibition of IMPDH in living cells. They also suggest that mixed inhibition profiles may result from heteromeric complexes in cell types that contain multiple IMPDH gene products. The mobility shift assay could serve as a tool for the detection of drug-inactivated IMPDH in the cells of patients receiving MPA therapy.
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Affiliation(s)
- Christine C McPhillips
- Department of Biochemistry, Emory University School of Medicine, Rollins Research Center, 1510 Clifton Road, Atlanta, GA 30322, USA
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14
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Cattaneo D, Perico N, Remuzzi G. From pharmacokinetics to pharmacogenomics: a new approach to tailor immunosuppressive therapy. Am J Transplant 2004; 4:299-310. [PMID: 14961981 DOI: 10.1111/j.1600-6143.2004.00312.x] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
One of the main tasks in the management of organ transplantation is the optimization of immunosuppressive therapy, in order to provide therapeutic efficacy limiting drug-related toxicity. In the past years major efforts have been carried out to define therapeutic windows based on blood/plasma levels of each immunosuppressant relating those concentrations to drug dosing and clinical events. Although this traditional approach is able to identify environmental and nongenetic factors that can influence drug exposure during the course of treatment, it presents limitations. Therefore, complementary strategies are advocated. The advent of the genomic era gives birth to pharmacogenomics, a science that studies how the genome as a whole, including single genes as well as gene-to-gene interactions, may affect the action of a drug. This science is of particular importance for drugs characterized by a narrow therapeutic index, such as the immunosuppressants. Preliminary studies focused on polymorphisms of genes encoding for enzymes actively involved in drug metabolism, drug transport and pharmacological target. Pharmacogenomics holds promise for improvement in the ability to individualize immunosuppressive therapy based on the patient's genetic profile, and can be viewed as a support to traditional therapeutic drug monitoring. However, the clinical applicability of this approach is still to be proven.
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Affiliation(s)
- Dario Cattaneo
- Department of Medicine and Transplantation, Ospedali Riuniti di Bergamo-Mario Negri Institute for Pharmacological Research, Bergamo, Italy.
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15
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Gu JJ, Tolin AK, Jain J, Huang H, Santiago L, Mitchell BS. Targeted disruption of the inosine 5'-monophosphate dehydrogenase type I gene in mice. Mol Cell Biol 2003; 23:6702-12. [PMID: 12944494 PMCID: PMC193693 DOI: 10.1128/mcb.23.18.6702-6712.2003] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Inosine 5'-monophosphate dehydrogenase (IMPDH) is the critical, rate-limiting enzyme in the de novo biosynthesis pathway for guanine nucleotides. Two separate isoenzymes, designated IMPDH types I and II, contribute to IMPDH activity. An additional pathway salvages guanine through the activity of hypoxanthine-guanine phosphoribosyltransferase (HPRT) to supply the cell with guanine nucleotides. In order to better understand the relative contributions of IMPDH types I and II and HPRT to normal biological function, a mouse deficient in IMPDH type I was generated by standard gene-targeting techniques and bred to mice deficient in HPRT or heterozygous for IMPDH type II. T-cell activation in response to anti-CD3 plus anti-CD28 antibodies was significantly impaired in both single- and double-knockout mice, whereas a more general inhibition of proliferation in response to other T- and B-cell mitogens was observed only in mice deficient in both enzymes. In addition, IMPDH type I(-/-) HPRT(-/0) splenocytes showed reduced interleukin-4 production and impaired cytolytic activity after antibody activation, indicating an important role for guanine salvage in supplementing the de novo synthesis of guanine nucleotides. We conclude that both IMPDH and HPRT activities contribute to normal T-lymphocyte activation and function.
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Affiliation(s)
- Jing Jin Gu
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27599, USA
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16
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Gan L, Seyedsayamdost MR, Shuto S, Matsuda A, Petsko GA, Hedstrom L. The immunosuppressive agent mizoribine monophosphate forms a transition state analogue complex with inosine monophosphate dehydrogenase. Biochemistry 2003; 42:857-63. [PMID: 12549902 DOI: 10.1021/bi0271401] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Mizoribine monophosphate (MZP) is the active metabolite of the immunosuppressive agent mizoribine and a potent inhibitor of IMP dehydrogenase (IMPDH). This enzyme catalyzes the oxidation of IMP to XMP with the concomitant reduction of NAD via a covalent intermediate at Cys319 (E-XMP). Surprisingly, mutational analysis indicates that MZP is a transition state analogue although its structure does not resemble that of the expected transition state. Here we report the X-ray crystal structure of the E.MZP complex at 2.0 A resolution that reveals a transition state-like structure and solves the mechanistic puzzle of the IMPDH reaction. The protein assumes a new conformation where a flap folds into the NAD site and MZP, Cys319, and a water molecule are arranged in a geometry resembling the transition state. The water appears to be activated by interactions with a conserved Arg418-Tyr419 dyad. Mutagenesis experiments confirm that this new closed conformation is required for the hydrolysis of E-XMP, but not for the reduction of NAD. The closed conformation provides a structural explanation for the differences in drug selectivity and catalytic efficiency of IMPDH isozymes.
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Affiliation(s)
- Lu Gan
- Department of Biochemistry and Chemistry and the Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, Massachusetts 02454, USA
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