RESUMO
Burkitt lymphoma (BL) is an aggressive lymphoma type that is currently treated by intensive chemoimmunotherapy. Despite the favorable clinical outcome for most patients with BL, chemotherapy-related toxicity and disease relapse remain major clinical challenges, emphasizing the need for innovative therapies. Using genome-scale CRISPR-Cas9 screens, we identified B-cell receptor (BCR) signaling, specific transcriptional regulators, and one-carbon metabolism as vulnerabilities in BL. We focused on serine hydroxymethyltransferase 2 (SHMT2), a key enzyme in one-carbon metabolism. Inhibition of SHMT2 by either knockdown or pharmacological compounds induced anti-BL effects in vitro and in vivo. Mechanistically, SHMT2 inhibition led to a significant reduction of intracellular glycine and formate levels, which inhibited the mTOR pathway and thereby triggered autophagic degradation of the oncogenic transcription factor TCF3. Consequently, this led to a collapse of tonic BCR signaling, which is controlled by TCF3 and is essential for BL cell survival. In terms of clinical translation, we also identified drugs such as methotrexate that synergized with SHMT inhibitors. Overall, our study has uncovered the dependency landscape in BL, identified and validated SHMT2 as a drug target, and revealed a mechanistic link between SHMT2 and the transcriptional master regulator TCF3, opening up new perspectives for innovative therapies.
Assuntos
Fatores de Transcrição Hélice-Alça-Hélice Básicos/metabolismo , Linfoma de Burkitt/tratamento farmacológico , Linfoma de Burkitt/metabolismo , Glicina Hidroximetiltransferase/antagonistas & inibidores , Glicina Hidroximetiltransferase/metabolismo , Animais , Linfoma de Burkitt/genética , Linhagem Celular Tumoral , Sobrevivência Celular/efeitos dos fármacos , Descoberta de Drogas , Formiatos/metabolismo , Regulação Neoplásica da Expressão Gênica/efeitos dos fármacos , Técnicas de Silenciamento de Genes , Glicina/metabolismo , Glicina Hidroximetiltransferase/genética , Humanos , Camundongos , Terapia de Alvo Molecular , Proteólise/efeitos dos fármacosRESUMO
Despite progress in the treatment of acute lymphoblastic leukemia (ALL), T-cell ALL (T-ALL) has limited treatment options, particularly in the setting of relapsed/refractory disease. Using an unbiased genome-scale CRISPR-Cas9 screen we sought to identify pathway dependencies for T-ALL which could be harnessed for therapy development. Disruption of the one-carbon folate, purine and pyrimidine pathways scored as the top metabolic pathways required for T-ALL proliferation. We used a recently developed inhibitor of SHMT1 and SHMT2, RZ-2994, to characterize the effect of inhibiting these enzymes of the one-carbon folate pathway in T-ALL and found that T-ALL cell lines were differentially sensitive to RZ-2994, with the drug inducing a S/G2 cell cycle arrest. The effects of SHMT1/2 inhibition were rescued by formate supplementation. Loss of both SHMT1 and SHMT2 was necessary for impaired growth and cell cycle arrest, with suppression of both SHMT1 and SHMT2 inhibiting leukemia progression in vivo. RZ-2994 also decreased leukemia burden in vivo and remained effective in the setting of methotrexate resistance in vitro. This study highlights the significance of the one-carbon folate pathway in T-ALL and supports further development of SHMT inhibitors for treatment of T-ALL and other cancers.
Assuntos
Sistemas CRISPR-Cas , Resistencia a Medicamentos Antineoplásicos/efeitos dos fármacos , Inibidores Enzimáticos/farmacologia , Ácido Fólico/metabolismo , Glicina Hidroximetiltransferase/antagonistas & inibidores , Metotrexato/farmacologia , Leucemia-Linfoma Linfoblástico de Células T Precursoras/tratamento farmacológico , Animais , Antimetabólitos Antineoplásicos/farmacologia , Apoptose , Ciclo Celular , Proliferação de Células , Feminino , Humanos , Camundongos , Camundongos Endogâmicos NOD , Camundongos SCID , Leucemia-Linfoma Linfoblástico de Células T Precursoras/enzimologia , Leucemia-Linfoma Linfoblástico de Células T Precursoras/patologia , Prognóstico , Células Tumorais Cultivadas , Ensaios Antitumorais Modelo de XenoenxertoRESUMO
Mitochondrial serine hydroxymethyltransferase 2 (SHMT2) is an important drug target in the one-carbon metabolic pathway, since its activity is critical for purine and pyrimidine biosynthesis. Additionally, it plays a prominent role during metabolic reprogramming of cancer cells, and SHMT2 inhibitors have proven useful as anticancer drugs. Compared to drugs targeting one-carbon metabolic enzymes (mainly dihydrofolate reductase and thymidylate synthase) that have been used for clinical treatment of cancer, efficient SHMT2-specific inhibitors are lacking. Therefore, we established a direct system for virtual screening, protein expression, and identification of inhibitors targeting SHMT2. First, 27 compounds qualifying as potential SHMT2 inhibitors were selected for biological activity verification through virtual screening of the 210 thousand compounds registered in the Specs database. Second, these 27 hits were subjected to quick screening by an in vitro non-competitive kinetic assay of SHMT2 single-enzyme catalysis. This allowed us to identify three compounds featuring medium-strength and non-competitive inhibition of SHMT2: AM-807/42004511 (IC50 = 14.52 ± 4.1665 µM), AM-807/40675298 (IC50 = 12.74 ± 5.8991 µM), and AM-807/42004633 (IC50 = 9.43 ± 0.5646 µM). We describe a quick screening method for the identification of inhibitors targeting SHMT2, providing a basis for subsequent identification and screening of new inhibitors.
Assuntos
Inibidores Enzimáticos/química , Glicina Hidroximetiltransferase/antagonistas & inibidores , Sítios de Ligação , Inibidores Enzimáticos/metabolismo , Glicina Hidroximetiltransferase/genética , Glicina Hidroximetiltransferase/metabolismo , Humanos , Concentração Inibidora 50 , Cinética , Ligantes , Mitocôndrias/metabolismo , Simulação de Acoplamento Molecular , Proteínas Recombinantes/biossíntese , Proteínas Recombinantes/química , Proteínas Recombinantes/isolamento & purificaçãoRESUMO
Folate metabolism enables cell growth by providing one-carbon (1C) units for nucleotide biosynthesis. The 1C units are carried by tetrahydrofolate, whose production by the enzyme dihydrofolate reductase is targeted by the important anticancer drug methotrexate. 1C units come largely from serine catabolism by the enzyme serine hydroxymethyltransferase (SHMT), whose mitochondrial isoform is strongly upregulated in cancer. Here we report the SHMT inhibitor SHIN2 and demonstrate its in vivo target engagement with 13C-serine tracing. As methotrexate is standard treatment for T-cell acute lymphoblastic leukemia (T-ALL), we explored the utility of SHIN2 in this disease. SHIN2 increases survival in NOTCH1-driven mouse primary T-ALL in vivo. Low dose methotrexate sensitizes Molt4 human T-ALL cells to SHIN2, and cells rendered methotrexate resistant in vitro show enhanced sensitivity to SHIN2. Finally, SHIN2 and methotrexate synergize in mouse primary T-ALL and in a human patient-derived xenograft in vivo, increasing survival. Thus, SHMT inhibition offers a complementary strategy in the treatment of T-ALL.
Assuntos
Sinergismo Farmacológico , Regulação Leucêmica da Expressão Gênica , Glicina Hidroximetiltransferase/antagonistas & inibidores , Metotrexato/farmacologia , Leucemia-Linfoma Linfoblástico de Células T Precursoras/terapia , Animais , Antimetabólitos Antineoplásicos/farmacologia , Apoptose , Proliferação de Células , Humanos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Leucemia-Linfoma Linfoblástico de Células T Precursoras/metabolismo , Leucemia-Linfoma Linfoblástico de Células T Precursoras/patologia , Células Tumorais Cultivadas , Ensaios Antitumorais Modelo de XenoenxertoRESUMO
Metabolic rewiring is a hallmark of cancer that supports tumor growth, survival, and chemotherapy resistance. Although normal cells often rely on extracellular serine and glycine supply, a significant subset of cancers becomes addicted to intracellular serine/glycine synthesis, offering an attractive drug target. Previously developed inhibitors of serine/glycine synthesis enzymes did not reach clinical trials due to unfavorable pharmacokinetic profiles, implying that further efforts to identify clinically applicable drugs targeting this pathway are required. In this study, we aimed to develop therapies that can rapidly enter the clinical practice by focusing on drug repurposing, as their safety and cost-effectiveness have been optimized before. Using a yeast model system, we repurposed two compounds, sertraline and thimerosal, for their selective toxicity against serine/glycine synthesis-addicted breast cancer and T-cell acute lymphoblastic leukemia cell lines. Isotope tracer metabolomics, computational docking, enzymatic assays, and drug-target interaction studies revealed that sertraline and thimerosal inhibit serine/glycine synthesis enzymes serine hydroxymethyltransferase and phosphoglycerate dehydrogenase, respectively. In addition, we demonstrated that sertraline's antiproliferative activity was further aggravated by mitochondrial inhibitors, such as the antimalarial artemether, by causing G1-S cell-cycle arrest. Most notably, this combination also resulted in serine-selective antitumor activity in breast cancer mouse xenografts. Collectively, this study provides molecular insights into the repurposed mode-of-action of the antidepressant sertraline and allows to delineate a hitherto unidentified group of cancers being particularly sensitive to treatment with sertraline. Furthermore, we highlight the simultaneous inhibition of serine/glycine synthesis and mitochondrial metabolism as a novel treatment strategy for serine/glycine synthesis-addicted cancers.
Assuntos
Antidepressivos/farmacologia , Neoplasias da Mama/patologia , Reposicionamento de Medicamentos , Glicina Hidroximetiltransferase/antagonistas & inibidores , Glicina/biossíntese , Serina/sangue , Sertralina/farmacologia , Animais , Protocolos de Quimioterapia Combinada Antineoplásica/farmacologia , Protocolos de Quimioterapia Combinada Antineoplásica/uso terapêutico , Neoplasias da Mama/tratamento farmacológico , Linhagem Celular Tumoral , Proliferação de Células/efeitos dos fármacos , Feminino , Glicina Hidroximetiltransferase/metabolismo , Humanos , Camundongos Endogâmicos NOD , Camundongos SCID , Simulação de Acoplamento Molecular , Fosfoglicerato Desidrogenase/metabolismo , Timerosal/farmacologiaRESUMO
Folate-mediated one-carbon metabolism (FOCM) supports vital events for the growth and survival of proliferating cells. Nucleotide synthesis and DNA methylation are the biochemical bases of cancers that are highly dependent on FOCM. Recent studies revealed that FOCM is connected with redox homeostasis and epigenetics in cancer. Furthermore, folate-metabolizing enzymes, such as serine hydroxymethyltransferase 2 (SHMT2) and methylenetetrahydrofolate dehydrogenase 2 (MTHFD2), are associated with the development of cancers, including breast cancer, highlighting their potential application in tumor-targeted therapy. Therefore, targeting metabolizing enzymes, especially SHMT2 and MTHFD2, provides a novel strategy for cancer treatment. In this review, we outline current understanding of the functions of SHMT2 and MTHFD2, discussing their expression, potential functions, and regulatory mechanism in cancers. Furthermore, we discuss examples of inhibitors of SHMT2 and MTHFD2.
Assuntos
Terapia de Alvo Molecular , Neoplasias/tratamento farmacológico , Aminoidrolases/antagonistas & inibidores , Aminoidrolases/metabolismo , Animais , Carbono/metabolismo , Sobrevivência Celular/fisiologia , Metilação de DNA/genética , Ácido Fólico/metabolismo , Glicina Hidroximetiltransferase/antagonistas & inibidores , Glicina Hidroximetiltransferase/metabolismo , Humanos , Metilenotetra-Hidrofolato Desidrogenase (NADP)/antagonistas & inibidores , Metilenotetra-Hidrofolato Desidrogenase (NADP)/metabolismo , Enzimas Multifuncionais/antagonistas & inibidores , Enzimas Multifuncionais/metabolismo , Neoplasias/patologiaRESUMO
Serine hydroxymethyltransferase 2 (SHMT2) converts serine plus tetrahydrofolate (THF) into glycine plus methylene-THF and is upregulated at the protein level in lung and other cancers. In order to better understand the role of SHMT2 in cancer a model system of HeLa cells engineered for inducible over-expression or knock-down of SHMT2 was characterized for cell proliferation and changes in metabolites and proteome as a function of SHMT2. Ectopic over-expression of SHMT2 increased cell proliferation in vitro and tumor growth in vivo. Knockdown of SHMT2 expression in vitro caused a state of glycine auxotrophy and accumulation of phosphoribosylaminoimidazolecarboxamide (AICAR), an intermediate of folate/1-carbon-pathway-dependent de novo purine nucleotide synthesis. Decreased glycine in the HeLa cell-based xenograft tumors with knocked down SHMT2 was potentiated by administration of the anti-hyperglycinemia agent benzoate. However, tumor growth was not affected by SHMT2 knockdown with or without benzoate treatment. Benzoate inhibited cell proliferation in vitro, but this was independent of SHMT2 modulation. The abundance of proteins of mitochondrial respiration complexes 1 and 3 was inversely correlated with SHMT2 levels. Proximity biotinylation in vivo (BioID) identified 48 mostly mitochondrial proteins associated with SHMT2 including the mitochondrial enzymes Acyl-CoA thioesterase (ACOT2) and glutamate dehydrogenase (GLUD1) along with more than 20 proteins from mitochondrial respiration complexes 1 and 3. These data provide insights into possible mechanisms through which elevated SHMT2 in cancers may be linked to changes in metabolism and mitochondrial function.
Assuntos
Biomarcadores Tumorais/metabolismo , Regulação Neoplásica da Expressão Gênica , Glicina Hidroximetiltransferase/metabolismo , Neoplasias Pulmonares/patologia , Metaboloma , Proteoma/análise , Serina/metabolismo , Animais , Antifúngicos/farmacologia , Apoptose , Biomarcadores Tumorais/genética , Proliferação de Células , Glicina Hidroximetiltransferase/antagonistas & inibidores , Glicina Hidroximetiltransferase/genética , Células HeLa , Humanos , Neoplasias Pulmonares/tratamento farmacológico , Neoplasias Pulmonares/genética , Neoplasias Pulmonares/metabolismo , Camundongos , Camundongos Endogâmicos NOD , Camundongos SCID , Mitocôndrias/efeitos dos fármacos , Mitocôndrias/metabolismo , Mitocôndrias/patologia , Domínios e Motivos de Interação entre Proteínas , Benzoato de Sódio/farmacologia , Células Tumorais Cultivadas , Ensaios Antitumorais Modelo de XenoenxertoRESUMO
One-carbon (1C) metabolism encompasses folate-mediated 1C transfer reactions and related processes, including nucleotide and amino acid biosynthesis, antioxidant regeneration, and epigenetic regulation. 1C pathways are compartmentalized in the cytosol, mitochondria, and nucleus. 1C metabolism in the cytosol has been an important therapeutic target for cancer since the inception of modern chemotherapy, and "antifolates" targeting cytosolic 1C pathways continue to be a mainstay of the chemotherapy armamentarium for cancer. Recent insights into the complexities of 1C metabolism in cancer cells, including the critical role of the mitochondrial 1C pathway as a source of 1C units, glycine, reducing equivalents, and ATP, have spurred the discovery of novel compounds that target these reactions, with particular focus on 5,10-methylene tetrahydrofolate dehydrogenase 2 and serine hydroxymethyltransferase 2. In this review, we discuss key aspects of 1C metabolism, with emphasis on the importance of mitochondrial 1C metabolism to metabolic homeostasis, its relationship with the oncogenic phenotype, and its therapeutic potential for cancer.
Assuntos
Antineoplásicos/farmacologia , Metabolismo Energético/efeitos dos fármacos , Redes e Vias Metabólicas/efeitos dos fármacos , Mitocôndrias/efeitos dos fármacos , Mitocôndrias/metabolismo , Terapia de Alvo Molecular , Neoplasias/metabolismo , Aminoidrolases/antagonistas & inibidores , Animais , Antineoplásicos/química , Antineoplásicos/uso terapêutico , Biomarcadores , Carbono/metabolismo , Regulação Enzimológica da Expressão Gênica/efeitos dos fármacos , Regulação Neoplásica da Expressão Gênica/efeitos dos fármacos , Glicina Hidroximetiltransferase/antagonistas & inibidores , Humanos , Metilenotetra-Hidrofolato Desidrogenase (NADP)/antagonistas & inibidores , Terapia de Alvo Molecular/métodos , Enzimas Multifuncionais/antagonistas & inibidores , Neoplasias/tratamento farmacológico , Neoplasias/etiologia , Neoplasias/patologia , Serina/biossínteseRESUMO
Folate-dependent one-carbon (C1) metabolism is compartmentalized in the mitochondria and cytosol and is a source of critical metabolites for proliferating tumors. Mitochondrial C1 metabolism including serine hydroxymethyltransferase 2 (SHMT2) generates glycine for de novo purine nucleotide and glutathione biosynthesis and is an important source of NADPH, ATP, and formate, which affords C1 units as 10-formyl-tetrahydrofolate and 5,10-methylene-tetrahydrofolate for nucleotide biosynthesis in the cytosol. We previously discovered novel first-in-class multitargeted pyrrolo[3,2-d]pyrimidine inhibitors of SHMT2 and de novo purine biosynthesis at glycinamide ribonucleotide formyltransferase and 5-aminoimidazole-4-carboxamide ribonucleotide formyltransferase with potent in vitro and in vivo antitumor efficacy toward pancreatic adenocarcinoma cells. In this report, we extend our findings to an expanded panel of pancreatic cancer models. We used our lead analog AGF347 [(4-(4-(2-amino-4-oxo-3,4-dihydro-5H-pyrrolo[3,2-d]pyrimidin-5-yl)butyl)-2-fluorobenzoyl)-l-glutamic acid] to characterize pharmacodynamic determinants of antitumor efficacy for this series and demonstrated plasma membrane transport into the cytosol, uptake from cytosol into mitochondria, and metabolism to AGF347 polyglutamates in both cytosol and mitochondria. Antitumor effects of AGF347 downstream of SHMT2 and purine biosynthesis included suppression of mammalian target of rapamycin signaling, and glutathione depletion with increased levels of reactive oxygen species. Our results provide important insights into the cellular pharmacology of novel pyrrolo[3,2-d]pyrimidine inhibitors as antitumor compounds and establish AGF347 as a unique agent for potential clinical application for pancreatic cancer, as well as other malignancies. SIGNIFICANCE STATEMENT: This study establishes the antitumor efficacies of novel inhibitors of serine hydroxymethyltransferase 2 and of cytosolic targets toward a panel of clinically relevant pancreatic cancer cells and demonstrates the important roles of plasma membrane transport, mitochondrial accumulation, and metabolism to polyglutamates of the lead compound AGF347 to drug activity. We also establish that loss of serine catabolism and purine biosynthesis resulting from AGF347 treatment impacts mammalian target of rapamycin signaling, glutathione pools, and reactive oxygen species, contributing to antitumor efficacy.
Assuntos
Antineoplásicos/farmacologia , Citosol/efeitos dos fármacos , Glicina Hidroximetiltransferase/antagonistas & inibidores , Mitocôndrias/efeitos dos fármacos , Pirimidinas/farmacologia , Pirróis/farmacologia , Antineoplásicos/química , Antineoplásicos/uso terapêutico , Linhagem Celular Tumoral , Membrana Celular/efeitos dos fármacos , Membrana Celular/metabolismo , Citosol/metabolismo , Ensaios de Seleção de Medicamentos Antitumorais , Técnicas de Inativação de Genes , Glutationa/biossíntese , Glicina Hidroximetiltransferase/genética , Glicina Hidroximetiltransferase/metabolismo , Humanos , Leucovorina/análogos & derivados , Leucovorina/metabolismo , Mitocôndrias/metabolismo , Neoplasias Pancreáticas/tratamento farmacológico , Neoplasias Pancreáticas/patologia , Nucleotídeos de Purina/biossíntese , Pirimidinas/química , Pirimidinas/uso terapêutico , Pirróis/química , Pirróis/uso terapêutico , Espécies Reativas de Oxigênio/metabolismo , Serina/metabolismo , Tetra-Hidrofolatos/metabolismoRESUMO
Mitochondrial serine hydroxymethyl transferase isoform 2 (SHMT2) has attracted increasing attention as a pivotal catalyzing regulator of the serine/glycine pathway in the one-carbon metabolism of cancer cells. However, few inhibitors that target this potential anticancer target have been discovered. Quantitative characterization of the interactions between SHMT2 and its known inhibitors should benefit future discovery of novel inhibitors. In this study, we employed a recently developed alanine-scanning-interaction-entropy method to quantitatively calculate the residue-specific binding free energy of 28 different SHMT2 inhibitors that originate from the same skeleton. Major contributing residues from SHMT2 and chemical groups from the inhibitors were identified, and the binding energy of each residue was quantitatively determined, revealing essential features of the protein-inhibitor interaction. The most important contributing residue is Y105 of the B chain followed by L166 of the A chain. The calculated protein-ligand binding free energies are in good agreement with the experimental results and showed better correlation and smaller errors compared with those obtained using the conventional MM/GBSA with the normal mode method. These results may aid the rational design of more effective SHMT2 inhibitors.
Assuntos
Inibidores Enzimáticos/metabolismo , Inibidores Enzimáticos/farmacologia , Glicina Hidroximetiltransferase/antagonistas & inibidores , Glicina Hidroximetiltransferase/metabolismo , Simulação de Dinâmica Molecular , Mutagênese Sítio-Dirigida , Alanina , Glicina Hidroximetiltransferase/química , Glicina Hidroximetiltransferase/genética , Ligação Proteica , Conformação Proteica , TermodinâmicaRESUMO
Serine hydroxymethyltransferase (SHMT) is the major source of 1-carbon units required for nucleotide synthesis. Humans have cytosolic (SHMT1) and mitochondrial (SHMT2) isoforms, which are upregulated in numerous cancers, making the enzyme an attractive drug target. Here, we show that the antifolates lometrexol and pemetrexed are inhibitors of SHMT2 and solve the first SHMT2-antifolate structures. The antifolates display large differences in their hydrogen bond networks despite their similarity. Lometrexol was found to be the best hSHMT1/2 inhibitor from a panel antifolates. Comparison of apo hSHMT1 with antifolate bound hSHMT2 indicates a highly conserved active site architecture. This structural information offers insights as to how these compounds could be improved to produce more potent and specific inhibitors of this emerging anti-cancer drug target.
Assuntos
Inibidores Enzimáticos/química , Inibidores Enzimáticos/farmacologia , Antagonistas do Ácido Fólico/química , Antagonistas do Ácido Fólico/farmacologia , Glicina Hidroximetiltransferase/antagonistas & inibidores , Inibidores Enzimáticos/metabolismo , Antagonistas do Ácido Fólico/metabolismo , Glicina Hidroximetiltransferase/química , Glicina Hidroximetiltransferase/metabolismo , Humanos , Simulação de Acoplamento Molecular , Conformação ProteicaRESUMO
Serine hydroxymethyltransferase (SHMT) catalyzes the reversible conversion of l-serine and tetrahydrofolate into glycine and 5,10-methylenetetrahydrofolate. This enzyme, which plays a pivotal role in one-carbon metabolism, is involved in cancer metabolic reprogramming and is a recognized target of chemotherapy intervention. In humans, two isoforms of the enzyme exist, which are commonly termed cytosolic SHMT1 and mitochondrial SHMT2. Considerable attention has been paid to the structural, mechanistic, and metabolic features of these isozymes. On the other hand, a detailed comparison of their catalytic and regulatory properties is missing, although this aspect seems to be considerably important, considering that SHMT1 and SHMT2 reside in different cellular compartments, where they play distinct roles in folate metabolism. Here we performed a full kinetic characterization of the serine hydroxymethyltransferase reaction catalyzed by SHMT1 and SHMT2, with a focus on pH dependence and substrate inhibition. Our investigation, which allowed the determination of all kinetic parameters of serine hydroxymethyltransferase forward and backward reactions, uncovered a previously unobserved substrate inhibition by l-serine and highlighted several interesting differences between SHMT1 and SHMT2. In particular, SHMT2 maintains a pronounced tetrahydrofolate substrate inhibition even at the alkaline pH characteristic of the mitochondrial matrix, whereas with SHMT1 this is almost abolished. At this pH, SHMT2 also shows a catalytic efficiency that is much higher than that of SHMT1. These observations suggest that such different properties represent an adaptation of the isoforms to the respective cellular environments and that substrate inhibition may be a form of regulation.
Assuntos
Glicina Hidroximetiltransferase/metabolismo , Citosol/enzimologia , Glicina/metabolismo , Glicina Hidroximetiltransferase/antagonistas & inibidores , Glicina Hidroximetiltransferase/química , Humanos , Concentração de Íons de Hidrogênio , Isoenzimas/antagonistas & inibidores , Isoenzimas/química , Isoenzimas/metabolismo , Cinética , Mitocôndrias/enzimologia , Modelos Biológicos , Serina/metabolismo , Especificidade por Substrato , Tetra-Hidrofolatos/metabolismoRESUMO
Serine hydroxymethyltransferase (SHMT) is a pivotal enzyme in one-carbon metabolism that catalyses the reversible conversion of serine and tetrahydrofolate into glycine and methylenetetrahydrofolate. It exists in cytosolic (SHMT1) and mitochondrial (SHMT2) isoforms. Research on one-carbon metabolism in cancer cell lines has shown that SHMT1 preferentially catalyses serine synthesis, whereas in mitochondria SHMT2 is involved in serine breakdown. Recent research has focused on the identification of inhibitors that bind at the folate pocket. We have previously found that a representative derivative of the pyrazolopyran scaffold, namely 2.12, inhibits both SHMT isoforms, with a preference for SHMT1, causing apoptosis in lung cancer cell lines. Here we show that the affinity of 2.12 for SHMT depends on the identity of the amino acid substrate bound to the enzyme. The dissociation constant of 2.12 is 50-fold lower when it binds to SHMT1 enzyme-serine complex, as compared to the enzyme-glycine complex. Evidence is presented for a similar behaviour of compound 2.12 in the cellular environment. These findings suggest that the presence and identity of the amino acid substrate should be considered when designing SHMT inhibitors. Moreover, our data provide the proof-of-concept that SHMT inhibitors selectively targeting the directionality of one-carbon metabolism flux could be designed.
Assuntos
Inibidores Enzimáticos/farmacologia , Glicina Hidroximetiltransferase/antagonistas & inibidores , Glicina Hidroximetiltransferase/química , Glicina/química , Piranos/farmacologia , Pirazóis/farmacologia , Serina/química , Apoptose/efeitos dos fármacos , Linhagem Celular Tumoral , Inibidores Enzimáticos/metabolismo , Humanos , Ligação de Hidrogênio , Neoplasias Pulmonares/patologia , Piranos/química , Pirazóis/química , Espectrometria de Fluorescência , Especificidade por SubstratoRESUMO
Upon glucose restriction, eukaryotic cells upregulate oxidative metabolism to maintain homeostasis. Using genetic screens, we find that the mitochondrial serine hydroxymethyltransferase (SHMT2) is required for robust mitochondrial oxygen consumption and low glucose proliferation. SHMT2 catalyzes the first step in mitochondrial one-carbon metabolism, which, particularly in proliferating cells, produces tetrahydrofolate (THF)-conjugated one-carbon units used in cytoplasmic reactions despite the presence of a parallel cytoplasmic pathway. Impairing cytoplasmic one-carbon metabolism or blocking efflux of one-carbon units from mitochondria does not phenocopy SHMT2 loss, indicating that a mitochondrial THF cofactor is responsible for the observed phenotype. The enzyme MTFMT utilizes one such cofactor, 10-formyl THF, producing formylmethionyl-tRNAs, specialized initiator tRNAs necessary for proper translation of mitochondrially encoded proteins. Accordingly, SHMT2 null cells specifically fail to maintain formylmethionyl-tRNA pools and mitochondrially encoded proteins, phenotypes similar to those observed in MTFMT-deficient patients. These findings provide a rationale for maintaining a compartmentalized one-carbon pathway in mitochondria.
Assuntos
Neoplasias da Mama/genética , Neoplasias da Mama/patologia , Glicina Hidroximetiltransferase/metabolismo , Mitocôndrias/genética , Iniciação Traducional da Cadeia Peptídica , RNA de Transferência de Metionina/química , Serina/química , Animais , Apoptose , Neoplasias da Mama/metabolismo , Sistemas CRISPR-Cas , Proliferação de Células , Citosol/metabolismo , Feminino , Glicina Hidroximetiltransferase/antagonistas & inibidores , Glicina Hidroximetiltransferase/genética , Humanos , Camundongos , Camundongos Endogâmicos NOD , Camundongos SCID , Mitocôndrias/efeitos dos fármacos , Mitocôndrias/metabolismo , Processamento de Proteína Pós-Traducional , RNA de Transferência de Metionina/genética , RNA de Transferência de Metionina/metabolismo , Serina/genética , Serina/metabolismo , Tetra-Hidrofolatos/farmacologia , Células Tumorais Cultivadas , Ensaios Antitumorais Modelo de XenoenxertoRESUMO
The mitochondrial serine hydroxymethyltransferase SHMT2, which catalyzes the rate-limiting step in serine catabolism, drives cancer cell proliferation, but how this role is regulated is undefined. Here, we report that the sirtuin SIRT5 desuccinylates SHMT2 to increase its activity and drive serine catabolism in tumor cells. SIRT5 interaction directly mediated desuccinylation of lysine 280 on SHMT2, which was crucial for activating its enzymatic activity. Conversely, hypersuccinylation of SHMT2 at lysine 280 was sufficient to inhibit its enzymatic activity and downregulate tumor cell growth in vitro and in vivo Notably, SIRT5 inactivation led to SHMT2 enzymatic downregulation and to abrogated cell growth under metabolic stress. Our results reveal that SHMT2 desuccinylation is a pivotal signal in cancer cells to adapt serine metabolic processes for rapid growth, and they highlight SIRT5 as a candidate target for suppressing serine catabolism as a strategy to block tumor growth.Significance: These findings reveal a novel mechanism for controlling cancer cell proliferation by blocking serine catabolism, as a general strategy to impede tumor growth. Cancer Res; 78(2); 372-86. ©2017 AACR.
Assuntos
Biomarcadores Tumorais/metabolismo , Proliferação de Células , Neoplasias do Colo/patologia , Glicina Hidroximetiltransferase/metabolismo , Processamento de Proteína Pós-Traducional , Sirtuínas/metabolismo , Succinatos/metabolismo , Animais , Apoptose , Biomarcadores Tumorais/genética , Sistemas CRISPR-Cas , Neoplasias do Colo/genética , Neoplasias do Colo/metabolismo , Regulação Neoplásica da Expressão Gênica , Glicina Hidroximetiltransferase/antagonistas & inibidores , Glicina Hidroximetiltransferase/genética , Humanos , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Nus , Serina/metabolismo , Sirtuínas/genética , Succinatos/química , Células Tumorais Cultivadas , Ensaios Antitumorais Modelo de XenoenxertoRESUMO
The enzyme serine hydroxymethyltransferse (SHMT) converts serine into glycine and a tetrahydrofolate-bound one-carbon unit. Folate one-carbon units support purine and thymidine synthesis, and thus cell growth. Mammals have both cytosolic SHMT1 and mitochondrial SHMT2, with the mitochondrial isozyme strongly up-regulated in cancer. Here we show genetically that dual SHMT1/2 knockout blocks HCT-116 colon cancer tumor xenograft formation. Building from a pyrazolopyran scaffold that inhibits plant SHMT, we identify small-molecule dual inhibitors of human SHMT1/2 (biochemical IC50 â¼ 10 nM). Metabolomics and isotope tracer studies demonstrate effective cellular target engagement. A cancer cell-line screen revealed that B-cell lines are particularly sensitive to SHMT inhibition. The one-carbon donor formate generally rescues cells from SHMT inhibition, but paradoxically increases the inhibitor's cytotoxicity in diffuse large B-cell lymphoma (DLBCL). We show that this effect is rooted in defective glycine uptake in DLBCL cell lines, rendering them uniquely dependent upon SHMT enzymatic activity to meet glycine demand. Thus, defective glycine import is a targetable metabolic deficiency of DLBCL.
Assuntos
Inibidores Enzimáticos/síntese química , Inibidores Enzimáticos/farmacologia , Glicina Hidroximetiltransferase/antagonistas & inibidores , Glicina/metabolismo , Linfoma Difuso de Grandes Células B/tratamento farmacológico , Linfoma Difuso de Grandes Células B/metabolismo , Animais , Sítios de Ligação , Linhagem Celular Tumoral , Inibidores Enzimáticos/química , Feminino , Deleção de Genes , Regulação Neoplásica da Expressão Gênica , Humanos , Camundongos , Camundongos Nus , Modelos Moleculares , Estrutura Molecular , Neoplasias Experimentais/metabolismo , Conformação ProteicaRESUMO
Serine hydroxymethyltransferase (SHMT), an essential enzyme for cell growth and development, catalyzes the transfer of -CH2OH from l-serine to tetrahydrofolate (THF) to form glycine and 5,10-methylenetetrahydrofolate (MTHF) which is used for nucleotide synthesis. Insights into the ligand binding and inhibition properties of human cytosolic SHMT (hcSHMT) and Plasmodium SHMT (PvSHMT) are crucial for designing specific drugs against malaria and cancer. The results presented here revealed strong and pH-dependent THF inhibition of hcSHMT. In contrast, in PvSHMT, THF inhibition and the influence of pH were not as pronounced. Ligand binding experiments performed at various pH values indicated that the hcSHMT:Gly complex binds THF more tightly at lower pH conditions, while the binding affinity of the PvSHMT:Gly complex for THF is not pH-dependent. Pre-steady state kinetic (rapid-quench) analysis of hcSHMT showed burst kinetics, indicating that glycine formation occurs fastest in the first turnover relative to the subsequent turnovers i.e. glycine release is the rate-limiting step in the hcSHMT reaction. All data suggest that excess THF likely binds E:Gly binary complex and forms the E:Gly:THF dead-end complex before glycine is released. A unique flap motif found in the structure of hcSHMT may be the key structural feature that imparts these described characteristics of hcSHMT.
Assuntos
Inibidores Enzimáticos/química , Glicina Hidroximetiltransferase/antagonistas & inibidores , Glicina Hidroximetiltransferase/química , Plasmodium falciparum/enzimologia , Plasmodium vivax/enzimologia , Proteínas de Protozoários/antagonistas & inibidores , Proteínas de Protozoários/química , Motivos de Aminoácidos , Humanos , Concentração de Íons de Hidrogênio , Especificidade da EspécieRESUMO
Target-based approaches toward new antimalarial treatments are highly valuable to prevent resistance development. We report several series of pyrazolopyran-based inhibitors targeting the enzyme serine hydroxymethyltransferase (SHMT), designed to improve microsomal metabolic stability and to identify suitable candidates for in vivo efficacy evaluation. The best ligands inhibited Plasmodium falciparum (Pf) and Arabidopsis thaliana (At) SHMT in target assays and PfNF54 strains in cell-based assays with values in the low nanomolar range (3.2-55 nM). A set of carboxylate derivatives demonstrated markedly improved in vitro metabolic stability (t1/2 > 2 h). A selected ligand showed significant in vivo efficacy with 73% of parasitemia reduction in a mouse model. Five new cocrystal structures with PvSHMT were solved at 2.3-2.6 Å resolution, revealing a unique water-mediated interaction with Tyr63 at the end of the para-aminobenzoate channel. They also displayed the high degree of conformational flexibility of the Cys364-loop lining this channel.
Assuntos
Antimaláricos/farmacologia , Inibidores Enzimáticos/química , Inibidores Enzimáticos/farmacologia , Glicina Hidroximetiltransferase/antagonistas & inibidores , Animais , Antimaláricos/química , Proteínas de Arabidopsis/antagonistas & inibidores , Técnicas de Química Sintética , Cristalografia por Raios X , Cisteína/química , Estabilidade de Medicamentos , Inibidores Enzimáticos/metabolismo , Glicina Hidroximetiltransferase/metabolismo , Meia-Vida , Ligantes , Malária Falciparum/tratamento farmacológico , Camundongos SCID , Plasmodium falciparum/efeitos dos fármacos , Plasmodium falciparum/enzimologia , Plasmodium falciparum/patogenicidade , Plasmodium vivax/enzimologia , Conformação Proteica , Ratos , Relação Estrutura-Atividade , Tiofenos/síntese química , Tiofenos/farmacologiaRESUMO
The cytosolic and mitochondrial isoforms of serine hydroxymethyltransferase (SHMT1 and SHMT2, respectively) are well-recognized targets of cancer research, since their activity is critical for purine and pyrimidine biosynthesis and because of their prominent role in the metabolic reprogramming of cancer cells. Here we show that 3-bromopyruvate (3BP), a potent novel anti-tumour agent believed to function primarily by blocking energy metabolism, differentially inactivates human SHMT1 and SHMT2. SHMT1 is completely inhibited by 3BP, whereas SHMT2 retains a significant fraction of activity. Site directed mutagenesis experiments on SHMT1 demonstrate that selective inhibition relies on the presence of a cysteine residue at the active site of SHMT1 (Cys204) that is absent in SHMT2. Our results show that 3BP binds to SHMT1 active site, forming an enzyme-3BP complex, before reacting with Cys204. The physiological substrate l-serine is still able to bind at the active site of the inhibited enzyme, although catalysis does not occur. Modelling studies suggest that alkylation of Cys204 prevents a productive binding of l-serine, hampering interaction between substrate and Arg402. Conversely, the partial inactivation of SHMT2 takes place without the formation of a 3BP-enzyme complex. The introduction of a cysteine residue in the active site of SHMT2 by site directed mutagenesis (A206C mutation), at a location corresponding to that of Cys204 in SHMT1, yields an enzyme that forms a 3BP-enzyme complex and is completely inactivated. This work sets the basis for the development of selective SHMT1 inhibitors that target Cys204, starting from the structure and reactivity of 3BP.
Assuntos
Antineoplásicos/química , Cisteína/química , Glicina Hidroximetiltransferase/química , Piruvatos/química , Serina/química , Sequência de Aminoácidos , Domínio Catalítico , Clonagem Molecular , Cisteína/metabolismo , Citosol/química , Citosol/enzimologia , Ensaios Enzimáticos , Escherichia coli/genética , Escherichia coli/metabolismo , Expressão Gênica , Glicina Hidroximetiltransferase/antagonistas & inibidores , Glicina Hidroximetiltransferase/genética , Glicina Hidroximetiltransferase/metabolismo , Humanos , Cinética , Mitocôndrias/química , Mitocôndrias/enzimologia , Simulação de Acoplamento Molecular , Mutagênese Sítio-Dirigida , Ligação Proteica , Domínios Proteicos , Estrutura Secundária de Proteína , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Serina/metabolismo , Relação Estrutura-AtividadeRESUMO
Several of the enzymes related to the folate cycle are well-known for their role as clinically validated antimalarial targets. Nevertheless for serine hydroxymethyltransferase (SHMT), one of the key enzymes of this cycle, efficient inhibitors have not been described so far. On the basis of plant SHMT inhibitors from an herbicide optimization program, highly potent inhibitors of Plasmodium falciparum (Pf) and Plasmodium vivax (Pv) SHMT with a pyrazolopyran core structure were identified. Cocrystal structures of potent inhibitors with PvSHMT were solved at 2.6 Å resolution. These ligands showed activity (IC50/EC50 values) in the nanomolar range against purified PfSHMT, blood-stage Pf, and liver-stage P. berghei (Pb) cells and a high selectivity when assayed against mammalian cell lines. Pharmacokinetic limitations are the most plausible explanation for lack of significant activity of the inhibitors in the in vivo Pb mouse malaria model.