New Roles of Magnesium as a Regulatory Ion in Immune Responses and Cell Behavior

镁作为调节离子在免疫反应和细胞行为中的新作用

• 批准号: 10014219
• 负责人: michael j lenardo
• 金额: $ 81.89万
• 依托单位: NATIONAL INSTITUTE OF ALLERGY AND INFECTIOUS DISEASES
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10014219
• 关键词: Acute; Adenosine; Affect; Africa; Allergic; Antiviral Agents; Antiviral Response; Area; Autoimmune Process; B-Lymphocytes; Binding Sites; Blood specimen; Burkitt Lymphoma; CD28 gene; CD8-Positive T-Lymphocytes; Catalysis; Cell physiology; Cells; Cessation of life; Child; Chronic; Complex; Congenital disorders of glycosylation; Cyclosporine; Data; Defect; Diet; Dietary Practices; Dietary Supplementation; Disease; Divalent Cations; Double-Blind Method; Drops; Drug Targeting; Enzymes; Epithelial; Epstein-Barr Virus Infections; Equilibrium; Eukaryotic Cell; Exhibits; Experimental Animal Model; Gene Expression Profile; Genes; Genetic; Glycoproteins; Graft Rejection; Hodgkin Disease; Human; Human Herpesvirus 4; Hypomagnesemia; Immune; Immune response; Immunity; Immunologic Deficiency Syndromes; Immunosuppressive Agents; Impairment; In Vitro; Incidence; Incubated; Individual; Inhalation; Inositol; Interleukin-2; International; Ions; Lead; Light; Link; Liver; Lung; Lymphocyte; Lymphocyte Activation; Lymphoid; Lymphoma; Magnesium; Magnesium Deficiency; Maintenance; Malignant Neoplasms; Mammalian Cell; Mediator of activation protein; Metals; Methods; Mg supplementation; Modeling; Molecular; Mus; National Cancer Institute; Neoplasms; Nucleic Acids; Nutraceutical; Oral; Organism; PLC gamma1; Pathogenicity; Pathway interactions; Patients; Pharmacologic Substance; Phenotype; Phospholipids; Phosphotransferases; Physiological; Play; Predisposition; Primary Prevention; Production; Proteins; Regulation; Research Personnel; Risk; Role; Sampling; Second Messenger Systems; Secondary Prevention; Serum; Signal Transduction; Site; Stimulus; Stomach; Surface; Syndrome; T-Cell Activation; T-Lymphocyte; T-Lymphocyte and Natural Killer Cell; Testing; Time; United States; Virus Diseases; Work; body system; case control; cell behavior; cell growth regulation; congenital immunodeficiency; cytotoxic; deprivation; effective intervention; emt protein-tyrosine kinase; experience; glycosylation; human pathogen; immune function; improved; in vivo; influenzavirus; insight; interest; liver function; novel therapeutics; oral supplementation; placebo controlled study; premature; prevent; receptor; response; tripolyphosphate

The MAGT1 transporter is critically involved in the selective regulation of intracellular free Mg2+ levels in mammalian cells. The molecular functions of free Mg2+ in eukaryotic cells have not been fully established. We found that patients with genetic deficiencies in MAGT1 have high levels of Epstein-Barr virus (EBV) and a predisposition to lymphoma. In studying lymphocytes from these patients, we found that a deficiency of MAGT1 caused decreased basal intracellular free Mg2+ leading to defective expression of the natural killer activating receptor NKG2D in NK and CD8+ T cells. Without NKG2D, cytolytic responses against EBV are diminished, thereby revealing the first specific molecular function of intracellular basal free Mg2+ in eukaryotic cells. Intracellular free Mg2+, NKG2D expression and function can be rescued in vitro by incubating patient cells and elevated levels of Mg2+. Moreover, NKG2D expression and cytolytic function can be improved and EBV-infected cells reduced in vivo, in MAGT1-deficient patients by magnesium administration. Thus, our data indicate an important molecular function for free basal Mg2+ in immunity and demonstrate a requirement for NKG2D cytolytic function in an essential EBV antiviral response in humans. We are especially interested in pursuing additional questions related to the role of Mg2+ in the control of EBV. Despite being linked to both epithelial (nasopharyngeal and gastric) and lymphoid (Burkitt and Hodgkin lymphoma) malignancies, there are currently no known methods for primary or secondary prevention of chronic EBV infection or the associated malignancies. Our discovery that a genetic deficiency of a Mg2+ ion transporter caused a selective immunodeficiency that led to uncontrolled EBV infection and an extremely high rate of EBV+ lymphoma in affected children and that dietary supplementation with Mg2+ (a widely available and inexpensive nutraceutical) could correct the immune defect by increasing a specific antiviral receptor called NKG2D which markedly decreased or eliminated EBV offered a new hypothesis about chronic EBV in Africa. We are collaborating with Sam Mbulaiteye, a National Cancer Institute investigator, who studies EBV/lymphoma risk in Africa. We have carried out a preliminary study of previously collected case-control blood samples from Africa and showed that there was a statistically significant deficiency of serum Mg2+ in Burkitt lymphoma (BL) patients with high EBV. This preliminary study could not answer whether intracellular Mg2+ and NKG2D expression were deficient in these patients which requires flow cytometric analysis on site in Africa or whether these could be restored by adding more Mg2+ to the cells. However, these results held promise that endemic EBV and the consequent lymphomas could be prevented by simple dietary supplementation with Mg2+. We now show that either chronic or acute deprivation of Mg2+ decreases the setpoint of intracellular Mg2+ and blocks TCR signal propagation at the level of IL-2 inducible T-cell kinase (ITK). Although the role of a second Mg2+ binding site for enzymes has been debated for years, our study of ITK strongly supports the model of two metal catalysis for kinases and shows, for the first time, how this could exert a positive regulatory effect on the physiological activity of a cell, specifically in response to an antigenic stimulus. Severe deprivation of Mg2+ may begin to impair T cell function as well lead to multiple roadblocks to full T cell activation. We observed that a reduction in dietary Mg2+ can lead to hypomagnesemia and reduced cellular Mg2+. The large amount of bound Mg2+ in lymphocytes does not buffer the external drop. This has the consequence of impairing T cell activation and compromising the immune response in the lung against inhaled influenza virus infection. Taken together, our work demonstrates how lymphocyte responses are modulated at the molecular level by Mg2+ and shows that a Mg2+ sufficient diet, which may not be achieved by currently dietary practices in the United States, is crucial for optimal immune function against a common human pathogen. Our studies also shed new light on the biomedical importance and functional association of MAGT1 with the canonical subunits of the cellular glycosylation machinery. We additionally showed that XMEN disease has certain selective features of congenital disorders of glycosylation. Our current observations raise the possibility that MAGT1 plays a unique dual role in glycosylation and ion regulation, which together may contribute to the specific phenotype observed in XMEN syndrome. Particularly, underglycosylation of CD28 in MAGT1-deficient cells defect could be the cause for much of the gene expression pattern and the functional T cell defect that we see in XMEN patient samples. The abundance of MAGT1 in immune cells and in the liver may help to rationalize why XMEN patients have functional defects in both immune cell and liver function. The fact that NKG2D demonstrates a glycosyltransfer defect likely from the loss of MAGT1 in the oligosaccharyltransferase complex and is dependent on normal physiological concentrations of Mg2+ for its stability, may explain why this protein was so dramatically perturbed in XMEN. NKG2D is particularly suited to curbing EBV infection, which thereby links both a glycosylation defect and Mg2+ deficiency to the XMEN patients' conspicuous susceptibility to chronic active EBV infection. This connection is particularly important because EBV infection often leads to lymphoma which can cause the premature death of XMEN patients. Our studies clearly show that Mg2+ deprivation lowers the glycosylation level of a specific subset of N-glycoproteins and reduces the killing function of cytotoxic immune cells. It remains unknown what step Mg2+ is required for in the expression or maintenance of these molecules.

MAGT1转运蛋白与哺乳动物细胞中细胞内游离MG2+水平的选择性调节有关。真核细胞中游离MG2+的分子功能尚未完全确定。我们发现，MAGT1中遗传缺陷的患者具有高水平的爱泼斯坦 - 巴尔病毒（EBV）和淋巴瘤易感性。在研究这些患者的淋巴细胞时，我们发现MAGT1的缺乏导致基础内游离MG2+降低，导致NK和CD8+ T细胞中天然杀伤受体NKG2D的表达有缺陷。没有NKG2D，针对EBV的细胞溶解反应会减少，从而揭示了真核细胞中细胞内基基基基Mg2+的第一个特异性分子功能。细胞内游离MG2+，NKG2D表达和功能可以通过孵育患者细胞和Mg2+水平升高来挽救。此外，可以通过镁给药，可以改善NKG2D表达和细胞溶解功能，并通过镁给予EBV感染的细胞在体内减少体内。因此，我们的数据表明免疫中游离基础MG2+的重要分子功能，并证明了人类必需的EBV抗病毒反应中NKG2D细胞溶解功能的要求。 我们特别有兴趣提出与MG2+在控制EBV中的作用有关的其他问题。尽管与上皮（鼻咽和胃）以及淋巴样（伯基特和霍奇金淋巴瘤）恶性肿瘤有联系，但目前尚无针对初级或二级预防慢性EBV感染或相关恶性肿瘤的预防方法的已知方法。 Our discovery that a genetic deficiency of a Mg2+ ion transporter caused a selective immunodeficiency that led to uncontrolled EBV infection and an extremely high rate of EBV+ lymphoma in affected children and that dietary supplementation with Mg2+ (a widely available and inexpensive nutraceutical) could correct the immune defect by increasing a specific antiviral receptor called NKG2D which markedly decreased or eliminated EBV提出了关于非洲慢性EBV的新假设。我们正在与国家癌症研究所研究员Sam Mbulaiteye合作，该研究人员研究非洲的EBV/淋巴瘤风险。我们已经对非洲的病例对照血液样本进行了初步研究，并表明Burkitt淋巴瘤（BL）EBV患者的血清MG2+具有统计学意义。这项初步研究无法回答细胞内MG2+和NKG2D表达是否缺乏这些患者，需要对非洲现场进行流式细胞术分析，或者是否可以通过向细胞添加更多的MG2+来恢复这些表达。但是，这些结果认为，通过简单的饮食补充MG2+可以预防流行EBV和随之而来的淋巴瘤。 现在，我们表明，Mg2+的慢性或急性剥夺会降低细胞内MG2+的设定点，并阻止IL-2诱导型T细胞激酶（ITK）水平下TCR信号传播。尽管多年来已经讨论了第二个MG2+结合位点在酶中的争论，但我们对ITK的研究强烈支持激酶的两种金属催化的模型，并首次表明，这如何对细胞的生理活性产生积极的调节作用，这是针对抗原性刺激的反应。 MG2+的严重剥夺可能会开始损害T细胞功能，还会导致多个障碍引起全T细胞的激活。我们观察到饮食中的MG2+降低会导致低磁性血症和细胞MG2+降低。淋巴细胞中的大量结合Mg2+不会缓冲外部滴。这是由于损害T细胞激活并损害了肺部对吸入流感病毒感染的免疫反应的结果。综上所述，我们的工作证明了如何通过MG2+在分子水平调节淋巴细胞反应，并表明MG2+足够的饮食（当前在美国目前的饮食实践可能无法实现）对于针对常见人类病原体的最佳免疫功能至关重要。 我们的研究还展示了MAGT1与细胞糖基化机制的典型亚基的生物医学重要性和功能关联的新启示。我们还表明，Xmen疾病具有某些选择性的先天性糖基化疾病。我们目前的观察结果提出了MAGT1在糖基化和离子调节中起独特的双重作用的可能性，这可能会导致在Xmen综合征中观察到的特定表型。特别是，在缺陷型细胞缺陷中，CD28的糖基化良好可能是我们在XMEN患者样品中看到的许多基因表达模式和功能性T细胞缺陷的原因。免疫细胞和肝脏中MAGT1的丰度可能有助于合理化为什么XMEN患者在免疫细胞和肝功能中均具有功能缺陷。 NKG2D证明了寡糖基质转移酶复合酶的MAGT1可能出现的糖基转移缺陷，并且取决于其稳定性的正常生理浓度，因此可能解释了为什么这种蛋白在Xmen中如此剧烈地受到影响。 NKG2D特别适合抑制EBV感染，从而将糖基化缺陷和MG2+缺乏症与XMEN患者对慢性活动EBV感染的明显敏感性联系起来。这种联系尤其重要，因为EBV感染通常会导致淋巴瘤，这会导致XMEN患者过早死亡。我们的研究清楚地表明，MG2+剥夺降低了N-糖蛋白特定子集的糖基化水平，并降低了细胞毒性免疫细胞的杀伤功能。在这些分子的表达或维持中，需要哪个步骤MG2+。