RESUMO
Protein arginine methyltransferase 7 (PRMT7) catalyzes the introduction of monomethylation marks at the arginine residues of substrate proteins. PRMT7 plays important roles in the regulation of gene expression, splicing, DNA damage, paternal imprinting, cancer and metastasis. However, little is known about the interaction partners of PRMT7. To address this, we performed yeast two-hybrid screening of PRMT7 and identified argininosuccinate synthetase (ASS1) as a potential interaction partner of PRMT7. We confirmed that PRMT7 directly interacts with ASS1 using pull-down studies. ASS1 catalyzes the rate-limiting step of arginine synthesis in urea cycle and citrulline-nitric oxide cycle. We mapped the interface of PRMT7-ASS1 complex through computational approaches and validated the predicted interface in vivo by site-directed mutagenesis. Evolutionary analysis revealed that the ASS1 residues important for PRMT7-ASS1 interaction have co-evolved with PRMT7. We showed that ASS1 mutations linked to type I citrullinemia disrupt the ASS1-PRMT7 interaction, which might explain the molecular pathogenesis of the disease.
Assuntos
Argininossuccinato Sintase/genética , Argininossuccinato Sintase/metabolismo , Proteína-Arginina N-Metiltransferases/metabolismo , Centrifugação , Citrulinemia/fisiopatologia , Análise Mutacional de DNA , Humanos , Simulação de Dinâmica Molecular , Mutagênese Sítio-Dirigida , Ligação Proteica , Mapeamento de Interação de Proteínas , Técnicas do Sistema de Duplo-HíbridoAssuntos
Proteínas de Ligação ao Cálcio/deficiência , Transportadores de Ânions Orgânicos/deficiência , Ácido Aspártico/metabolismo , Cálcio/metabolismo , Proteínas de Ligação ao Cálcio/fisiologia , Colestase Intra-Hepática/etiologia , Mapeamento Cromossômico/métodos , Citrulinemia/classificação , Citrulinemia/genética , Citrulinemia/fisiopatologia , Frequência do Gene , Homozigoto , Humanos , Recém-Nascido , Maleatos/metabolismo , Proteínas de Membrana Transportadoras/genética , Mitocôndrias/metabolismo , Proteínas de Transporte da Membrana Mitocondrial , Proteínas Mitocondriais/genética , Mutação , NAD/metabolismo , Transportadores de Ânions Orgânicos/fisiologiaRESUMO
UNLABELLED: Adult-onset type 2 citrullinaemia (CTLN2) is caused by a deficiency of the citrin protein encoded by the SLC25A13 gene. Citrin, an aspartate glutamate carrier in mitochondria, is an essential component of the malate-aspartate NADH shuttle. Recently, citrin deficiency has been reported to manifest as neonatal intrahepatic cholestasis. We report here five cases with neonatal intrahepatic cholestasis caused by citrin deficiency. Genetic diagnosis revealed compound heterozygotes of 851del4/IVS11 + 1G-->A in two patients, IVS11 + 1G-->A/E601X, and IVS11 + 1G-->A/unknown in each one patient and homozygote for S225X in one patient. All cases revealed high levels of alpha-fetoprotein, which are not observed in CTLN2 patients. The condition was self-limiting and spontaneously disappeared after 5-7 months of age in four patients. However, one patient developed hepatic dysfunction from the age of 6 months and required a living-related liver transplantation at the age of 10 months. The patient showed complete recovery after transplantation, and now at the age of 3 years, shows normal growth and mental development. CONCLUSION: we report the first case of neonatal intrahepatic cholestasis caused by citrin deficiency with severe hepatic dysfunction requiring a living-related liver transplantation. Patients with this disorder should be followed up carefully, even during infancy.
Assuntos
Proteínas de Ligação ao Cálcio/deficiência , Colestase Intra-Hepática/etiologia , Colestase Intra-Hepática/cirurgia , Citrulinemia/fisiopatologia , Transplante de Fígado , Transportadores de Ânions Orgânicos/deficiência , Colestase Intra-Hepática/congênito , Feminino , Humanos , Lactente , Recém-Nascido , Doadores Vivos , Masculino , Proteínas de Membrana Transportadoras/genética , Proteínas de Transporte da Membrana Mitocondrial , Proteínas Mitocondriais/genética , Mutação , Remissão EspontâneaRESUMO
Type II citrullinaemia (CTLN2) is an adult- or late childhood-onset liver disease characterized by a liver-specific defect in argininosuccinate synthetase protein. The enzyme abnormality is caused by deficiency of the protein citrin, which is encoded by the SLC25A 13 gene. Until now, however, few cases with SLC25A13 mutations have been reported in children with liver disease. We describe an infant who presented with neonatal hepatitis in association with hypergalactosaemia detected by neonatal mass screening. DNA analysis of SLC25A13 revealed that the patient was homozygous for a IVS11+1G>A mutation. This case suggests that SLC25A13 mutant should be suspected in neonatal patients with hypergalactosaemia of unknown cause.
Assuntos
Citrulinemia/genética , Galactosemias/genética , Proteínas de Membrana Transportadoras/genética , Proteínas Mitocondriais/genética , Citrulinemia/sangue , Citrulinemia/complicações , Citrulinemia/fisiopatologia , Feminino , Galactose/sangue , Galactosemias/sangue , Galactosemias/complicações , Humanos , Recém-Nascido , Programas de Rastreamento , Proteínas de Transporte da Membrana MitocondrialRESUMO
We describe a 64-year-old man with 'citrullinemia type II' whose serum citrulline levels fluctuated between normal and abnormally high during episodic manifesting periods. Elevations of the serum threonine/serine ratio and pancreatic secretory trypsin inhibitor level are very useful diagnostic markers. Our patient's cerebrospinal fluid citrulline level was also elevated, and T1-weighted magnetic resonance images revealed high-intensity signals at the bilateral internal capsule and the cerebral peduncles. Single-photon emission computed tomography of his brain showed reduced bilateral temporal lobar blood flow. Even if the serum citrulline level is within the normal range, citrullinemia should be considered in adult patients without primary liver dysfunction who show episodic consciousness disturbance, psychotic symptoms or both.