Michael J Lenardo

National Institute of Allergy and Infectious Diseases, Maryland, United States

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Publications (233)2693.11 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Proteasomes and lysosomes constitute the major cellular systems that catabolize proteins to recycle free amino acids for energy and new protein synthesis. Tripeptidyl peptidase II (TPPII) is a large cytosolic proteolytic complex that functions in tandem with the proteasome-ubiquitin protein degradation pathway. We found that autosomal recessive TPP2 mutations cause recurrent infections, autoimmunity, and neurodevelopmental delay in humans. We show that a major function of TPPII in mammalian cells is to maintain amino acid levels and that TPPII-deficient cells compensate by increasing lysosome number and proteolytic activity. However, the overabundant lysosomes derange cellular metabolism by consuming the key glycolytic enzyme hexokinase-2 through chaperone-mediated autophagy. This reduces glycolysis and impairs the production of effector cytokines, including IFN-γ and IL-1β. Thus, TPPII controls the balance between intracellular amino acid availability, lysosome number, and glycolysis, which is vital for adaptive and innate immunity and neurodevelopmental health. Copyright © 2014 Elsevier Inc. All rights reserved.
    Cell. 12/2014; 159(7):1578-1590.
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    ABSTRACT: Class IA phosphatidylinositol 3-kinases (PI3K), which generate PIP3 as a signal for cell growth and proliferation, exist as an intracellular complex of a catalytic subunit bound to a regulatory subunit. We and others have previously reported that heterozygous mutations in PIK3CD encoding the p110δ catalytic PI3K subunit cause a unique disorder termed p110δ-activating mutations causing senescent T cells, lymphadenopathy, and immunodeficiency (PASLI) disease. We report four patients from three families with a similar disease who harbor a recently reported heterozygous splice site mutation in PIK3R1, which encodes the p85α, p55α, and p50α regulatory PI3K subunits. These patients suffer from recurrent sinopulmonary infections and lymphoproliferation, exhibit hyperactive PI3K signaling, and have prominent expansion and skewing of peripheral blood CD8(+) T cells toward terminally differentiated senescent effector cells with short telomeres. The PIK3R1 splice site mutation causes skipping of an exon, corresponding to loss of amino acid residues 434-475 in the inter-SH2 domain. The mutant p85α protein is expressed at low levels in patient cells and activates PI3K signaling when overexpressed in T cells from healthy subjects due to qualitative and quantitative binding changes in the p85α-p110δ complex and failure of the C-terminal region to properly inhibit p110δ catalytic activity.
    The Journal of experimental medicine. 12/2014;
  • Juha Grönholm, Michael J Lenardo
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    ABSTRACT: Type 1 diabetes is a progressive autoimmune disease with no curative treatment, making prevention critical. At the time of diagnosis, a majority of the insulin secreting β-cells has already been destroyed. Insulitis, lymphocytic infiltration to the pancreatic islets, is believed to begin months to years before the clinical symptoms of insulin deficiency appear. Insulitis should be treated as its own disease, for it is a known precursor to autoimmune diabetes. Because it is difficult to detect insulitic cellular infiltrates noninvasively, considerable interest has been focused on the levels of islet autoantibodies in blood as measurable diagnostic markers for islet autoimmunity. The traditional islet autoantibody detection assays have many limitations. New electrochemiluminescence-based autoantibody detection assays have the potential to overcome these challenges and they offer promising, cost-effective screening tools in identifying high-risk individuals for trials of preventive interventions. Here, we outline diagnostic and therapeutic strategies to overcome pancreatic β-cell destroying insulitis. Copyright © 2014. Published by Elsevier Inc.
    Clinical immunology (Orlando, Fla.). 12/2014;
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    ABSTRACT: To describe the role of the magnesium transporter 1 (MAGT1) in the pathogenesis of 'X-linked immunodeficiency with magnesium defect, Epstein-Barr virus (EBV) infection, and neoplasia' (XMEN) disease and its clinical implications.
    Current opinion in pediatrics. 10/2014;
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    ABSTRACT: Cytotoxic T lymphocyte antigen-4 (CTLA-4, CD152, OMIM: 123890) is an inhibitory receptor found on immune cells. The consequences of mutations in CTLA4 in humans are unknown. We identified germline heterozygous mutations in CTLA4 in subjects from four unrelated families suffering from severe immune dysregulation. While Ctla4 heterozygous mice have no obvious phenotype, human CTLA4 haploinsufficiency caused dysregulation of FoxP3(+) regulatory T (Treg) cells, hyperactivation of effector T cells and lymphocytic infiltration of target organs. Patients also exhibited progressive loss of circulating B cells, associated with an increase of predominantly autoreactive CD21(lo) B cells and accumulation of B cells in non-lymphoid organs. Inherited human CTLA-4 haploinsufficiency demonstrates a critical quantitative role for CTLA-4 in governing T and B lymphocyte homeostasis.
    Science (New York, N.Y.). 09/2014;
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    European journal of human genetics: EJHG 09/2014; · 3.56 Impact Factor
  • Benjamin Chaigne-Delalande, Michael J Lenardo
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    ABSTRACT: Divalent cations of two alkaline earth metals Ca(2+) and Mg(2+) and the transition metal Zn(2+) play vital roles in the immune system, and several immune disorders are associated with disturbances of their function. Until recently only Ca(2+) was considered to serve as a second messenger. However, signaling roles for Mg(2+) and Zn(2+) have been recently described, leading to a reevaluation of their role as potential second messengers. We review here the roles of these cations as second messengers in light of recent advances in Ca(2+), Mg(2+), and Zn(2+) signaling in the immune system. Developing a better understanding of these signaling cations may lead to new therapeutic strategies for immune disorders.
    Trends in immunology. 06/2014;
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    ABSTRACT: Epstein Barr virus (EBV) is an oncogenic gammaherpesvirus that infects and persists in 95% of adults worldwide and has the potential to cause fatal disease, especially lymphoma, in immunocompromised hosts. Primary immunodeficiencies (PIDs) that predispose to EBV-associated malignancies have provided novel insights into the molecular mechanisms of immune defense against EBV. We have recently characterized a novel PID now named "X-linked immunodeficiency with magnesium defect, Epstein-Barr virus (EBV) infection, and neoplasia" (XMEN) disease characterized by loss-of-function mutations in the gene encoding magnesium transporter 1 (MAGT1), chronic high level EBV with increased EBV-infected B cells, and heightened susceptibility to EBV-associated lymphomas. The genetic etiology of XMEN disease has revealed an unexpected quantitative role for intracellular free magnesium in immune functions and led to novel diagnostic and therapeutic strategies. Here, we review the clinical presentation, genetic mutation spectrum, molecular mechanisms of pathogenesis, and diagnostic and therapeutic considerations for this previously unrecognized disease.
    Blood 02/2014; · 9.78 Impact Factor
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    ABSTRACT: The Autoimmune Lymphoproliferative Syndrome (ALPS) presents in childhood with nonmalignant lymphadenopathy and splenomegaly associated with a characteristic expansion of mature CD4 and CD8 negative or "double negative" TCRαβ(+) T (DNT) lymphocytes. Patients often present with chronic multilineage cytopenias due to autoimmune peripheral destruction and/or splenic sequestration of blood cells and have an increased risk of B cell lymphoma. Deleterious heterozygous mutations in the FAS gene are the most common cause of this condition, termed ALPS-FAS. We report the natural history and pathophysiology of 150 ALPS-FAS patients and 63 healthy mutation-positive relatives evaluated in our institution over the last two decades. Our principal findings are that FAS mutations have a clinical penetrance of less than 60%, elevated serum vitamin B12 is a reliable and accurate biomarker of ALPS-FAS, and the major causes of morbidity and mortality in these patients are the overwhelming post-splenectomy sepsis (OPSI) and development of lymphoma. With longer follow up, we observed a significantly greater relative risk of lymphoma than previously reported. Avoiding splenectomy while controlling hypersplenism by using corticosteroid-sparing treatments improves the outcome in ALPS-FAS patients. This trial has been registered at www.clinicaltrials.gov (identifier: NCT00001350).
    Blood 01/2014; · 9.78 Impact Factor
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    ABSTRACT: Mitophagy is a specialized form of autophagy that selectively disposes of dysfunctional mitochondria. Delineating the molecular regulation of mitophagy is of great importance because defects in this process lead to a variety of mitochondrial diseases. Here we report that mice deficient for the mitochondrial protein, phosphoglycerate mutase family member 5 (PGAM5), displayed a Parkinson's-like movement phenotype. We determined biochemically that PGAM5 is required for the stabilization of the mitophagy-inducing protein PINK1 on damaged mitochondria. Loss of PGAM5 disables PINK1-mediated mitophagy in vitro and leads to dopaminergic neurodegeneration and mild dopamine loss in vivo. Our data indicate that PGAM5 is a regulator of mitophagy essential for mitochondrial turnover and serves a cytoprotective function in dopaminergic neurons in vivo. Moreover, PGAM5 may provide a molecular link to study mitochondrial homeostasis and the pathogenesis of a movement disorder similar to Parkinson's disease.
    Nature Communications 01/2014; 5:4930. · 10.74 Impact Factor
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    ABSTRACT: The p110δ subunit of phosphatidylinositol-3-OH kinase (PI(3)K) is selectively expressed in leukocytes and is critical for lymphocyte biology. Here we report fourteen patients from seven families who were heterozygous for three different germline, gain-of-function mutations in PIK3CD (which encodes p110δ). These patients presented with sinopulmonary infections, lymphadenopathy, nodular lymphoid hyperplasia and viremia due to cytomegalovirus (CMV) and/or Epstein-Barr virus (EBV). Strikingly, they had a substantial deficiency in naive T cells but an over-representation of senescent effector T cells. In vitro, T cells from patients exhibited increased phosphorylation of the kinase Akt and hyperactivation of the metabolic checkpoint kinase mTOR, enhanced glucose uptake and terminal effector differentiation. Notably, treatment with rapamycin to inhibit mTOR activity in vivo partially restored the abundance of naive T cells, largely 'rescued' the in vitro T cell defects and improved the clinical course.
    Nature Immunology 10/2013; · 26.20 Impact Factor
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    ABSTRACT: The magnesium transporter 1 (MAGT1) is a critical regulator of basal intracellular free magnesium (Mg(2+)) concentrations. Individuals with genetic deficiencies in MAGT1 have high levels of Epstein-Barr virus (EBV) and a predisposition to lymphoma. We show that decreased intracellular free Mg(2+) causes defective expression of the natural killer activating receptor NKG2D in natural killer (NK) and CD8(+) T cells and impairs cytolytic responses against EBV. Notably, magnesium supplementation in MAGT1-deficient patients restores intracellular free Mg(2+) and NKG2D while concurrently reducing EBV-infected cells in vivo, demonstrating a link between NKG2D cytolytic activity and EBV antiviral immunity in humans. Moreover, these findings reveal a specific molecular function of free basal intracellular Mg(2+) in eukaryotic cells.
    Science 07/2013; 341(6142):186-191. · 31.20 Impact Factor
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    ABSTRACT: Nuclear factor-κB (NF-κB) controls genes involved in normal lymphocyte functions, but constitutive NF-κB activation is often associated with B cell malignancy. Using high-throughput whole transcriptome sequencing, we investigated a unique family with hereditary polyclonal B cell lymphocytosis. We found a novel germline heterozygous missense mutation (E127G) in affected patients in the gene encoding CARD11, a scaffolding protein required for antigen receptor (AgR)-induced NF-κB activation in both B and T lymphocytes. We subsequently identified a second germline mutation (G116S) in an unrelated, phenotypically similar patient, confirming mutations in CARD11 drive disease. Like somatic, gain-of-function CARD11 mutations described in B cell lymphoma, these germline CARD11 mutants spontaneously aggregate and drive constitutive NF-κB activation. However, these CARD11 mutants rendered patient T cells less responsive to AgR-induced activation. By reexamining this rare genetic disorder first reported four decades ago, our findings provide new insight into why activating CARD11 mutations may induce B cell expansion and preferentially predispose to B cell malignancy without dramatically perturbing T cell homeostasis.
    Journal of Experimental Medicine 11/2012; · 13.21 Impact Factor
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    ABSTRACT: Deleterious mutations in genes involved in the Fas apoptosis pathway lead to Autoimmune Lymphoproliferative Syndrome (ALPS). Demonstration of an apoptosis defect is critical for the diagnosis and study of ALPS. The traditional in vitro apoptosis assay, however, requires a week of experimental procedures. Here, we show that defects in Fas-induced apoptosis in PBMCs can be evaluated directly ex vivo using multicolor flow cytometry to analyze the apoptosis of effector memory T cells, a Fas-sensitive subset of PBMCs. This method allowed us to sensitively quantify defective apoptosis in ALPS patients within a few hours. Some ALPS patients (ALPS-sFAS) without germline mutations have somatic mutations in Fas specifically in double-negative αβ T cells (DNTs), an unusual lymphocyte population that is characteristically expanded in ALPS. Since DNTs have been notoriously difficult to culture, defective apoptosis has not been previously demonstrated for ALPS-sFAS patients. Using our novel ex vivo apoptosis assay, we measured Fas-induced apoptosis of DNTs for the first time and found that ALPS-sFAS patients had significant apoptosis defects in these cells compared to healthy controls. Hence, this rapid apoptosis assay can expedite the diagnosis of new ALPS patients, including those with somatic mutations, and facilitate clinical and molecular investigation of these diseases.
    Journal of Clinical Immunology 10/2012; · 3.38 Impact Factor
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    ABSTRACT: IL-15 is an important IL-2-related cytokine whose role in Th17 cell biology has not been fully elucidated. In this study, we show that exogenous IL-15 decreased IL-17A production in Th17 cultures. Neutralization of IL-15 using an Ab led to increases in IL-17A production in Th17 cultures. Both Il15(-/-) and Il15r(-/-) T cell cultures displayed higher frequency of IL-17A producers and higher amounts of IL-17A in the supernatants compared with those of wild-type (WT) cells in vitro. IL-15 down-modulated IL-17A production independently of retinoic acid-related orphan receptor-γt, Foxp3, and IFN-γ expression. Both Th17 cells and APCs produced IL-15, which induced binding of STAT5, an apparent repressor to the Il17 locus in CD4 T cells. Also, in a model of myelin oligodendrocyte glycoprotein-induced experimental autoimmune encephalomyelitis (EAE), Il15(-/-) mice displayed exacerbated inflammation-correlating with increased IL-17A production by their CD4(+) T cells-compared with WT controls. Exogenous IL-15 administration and IL-17A neutralization reduced the severity of EAE in Il15(-/-) mice. Taken together, these data indicate that IL-15 has a negative regulatory role in fine-tuning of IL-17A production and Th17-mediated inflammation.
    The Journal of Immunology 09/2012; 189(9):4237-46. · 5.52 Impact Factor
  • Pushpa Pandiyan, Michael Lenardo
    The Journal of Immunology 06/2012; 188(11):5203-4; author reply 5204-5. · 5.52 Impact Factor
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    Zhihua Liu, Michael J Lenardo
    Cell Research 03/2012; 22(7):1092-4. · 10.53 Impact Factor
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    ABSTRACT: The detection of insulin autoantibodies (IAA) aids in the prediction of autoimmune diabetes development. However, the long-standing, gold standard 125I-insulin radiobinding assay (RBA) has low reproducibility between laboratories, long sample processing times and requires the use of newly synthesized radiolabeled insulin for each set of assays. Therefore, a rapid, non-radioactive, and reproducible assay is highly desirable. We have developed electrochemiluminescence (ECL)-based assays that fulfill these criteria in the measurement of IAA and anti-insulin antibodies (IA) in non-obese diabetic (NOD) mice and in type 1 diabetic individuals, respectively. Using the murine IAA ECL assay, we examined the correlation between IAA, histopathological insulitis, and blood glucose in a cohort of female NOD mice from 4 up to 36 weeks of age. We developed a human IA ECL assay that we compared to conventional RBA and validated using samples from 34 diabetic and 59 non-diabetic individuals in three independent laboratories. Our ECL assays were rapid and sensitive with a broad dynamic range and low background. In the NOD mouse model, IAA levels measured by ECL were positively correlated with insulitis severity, and the values measured at 8-10 weeks of age were predictive of diabetes onset. Using human serum and plasma samples, our IA ECL assay yielded reproducible and accurate results with an average sensitivity of 84% at 95% specificity with no statistically significant difference between laboratories. These novel, non-radioactive ECL-based assays should facilitate reliable and fast detection of antibodies to insulin and its precursors sera and plasma in a standardized manner between laboratories in both research and clinical settings. Our next step is to evaluate the human IA assay in the detection of IAA in prediabetic subjects or those at risk of type 1 diabetes and to develop similar assays for other autoantibodies that together are predictive for the diagnosis of this common disorder, in order to improve prediction and facilitate future therapeutic trials.
    Journal of Translational Medicine 11/2011; 9:203. · 3.46 Impact Factor
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    ABSTRACT: Leucine-rich repeat kinase 2 (LRRK2) has been identified by genome-wide association studies as being encoded by a major susceptibility gene for Crohn's disease. Here we found that LRRK2 deficiency conferred enhanced susceptibility to experimental colitis in mice. Mechanistic studies showed that LRRK2 was a potent negative regulator of the transcription factor NFAT and was a component of a complex that included the large noncoding RNA NRON (an NFAT repressor). Furthermore, the risk-associated allele encoding LRRK2 Met2397 identified by a genome-wide association study for Crohn's disease resulted in less LRRK2 protein post-translationally. Severe colitis in LRRK2-deficient mice was associated with enhanced nuclear localization of NFAT1. Thus, our study defines a new step in the control of NFAT activation that involves an immunoregulatory function of LRRK2 and has important implications for inflammatory bowel disease.
    Nature Immunology 11/2011; 12(11):1063-70. · 26.20 Impact Factor
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    ABSTRACT: Although Mg(2+) has a well-recognized role as an essential cofactor for all ATP-binding enzymes, its role as a signaling ion, like Ca(2+), has been controversial. A requirement for Mg(2+)for optimal T lymphocyte stimulation was demonstrated more than 30 years ago, but the mechanism of its synergistic effect with Ca(2+)in T cell activation remains elusive. Here, we summarize our recent discovery of a signaling role for Mg(2+)in the T cell antigen receptor (TCR) signaling pathway from the study of a novel primary immunodeficiency, now named X-linked immunodeficiency with Mg(2+)defect, EBV infection and neoplasia (XMEN). XMEN patients were found to have a deficiency in magnesium transporter 1 (MAGT1), an Mg(2+)-specific transporter, which leads to the absence of a TCR-stimulated Mg(2+)flux and an attenuation of T cell activation. We further showed that this Mg(2+)flux is required proximally for the temporal orchestration of phospholipase C-γ1 (PLCγ1) activation. Thus, our study not only provides a second messenger role for Mg(2+)to explain its synergism with calcium in T cell signaling, it also identifies a potential extracellular therapeutic target for T cell-specific immunomodulation.
    Magnesium research: official organ of the International Society for the Development of Research on Magnesium 09/2011; 24(3):S109-14. · 1.38 Impact Factor

Publication Stats

22k Citations
2,693.11 Total Impact Points

Institutions

  • 1991–2014
    • National Institute of Allergy and Infectious Diseases
      • Laboratory of Immunoregulation
      Maryland, United States
    • National Cancer Institute (USA)
      • Metabolism Branch
      Maryland, United States
  • 2012
    • Northeast Institute of Geography and Agroecology
      • Institute of Biophysics
      Beijing, Beijing Shi, China
  • 1993–2012
    • National Institutes of Health
      • • Section of Inflammation Immunobiology
      • • Laboratory of Immunology
      • • Section on Cellular and Developmental Biology
      • • Department of Laboratory Medicine
      • • Branch of Neuroimmunology and Virology
      Maryland, United States
  • 2011
    • Tsinghua University
      • School of Life Sciences
      Beijing, Beijing Shi, China
  • 2010
    • University of Pennsylvania
      Philadelphia, Pennsylvania, United States
  • 2006–2009
    • Oxford University Hospitals NHS Trust
      Oxford, England, United Kingdom
  • 2005
    • National Institute of Allergy and Infectious Disease
      Maryland, United States
  • 2001
    • University of California, San Francisco
      • Division of Hospital Medicine
      San Francisco, CA, United States
  • 1998–1999
    • National Human Genome Research Institute
      Maryland, United States
    • Texas Tech University Health Sciences Center
      • Department of Pediatrics
      Lubbock, TX, United States
    • Massachusetts Institute of Technology
      • Department of Biology
      Cambridge, MA, United States
  • 1996
    • University of Toronto
      • Department of Immunology
      Toronto, Ontario, Canada
  • 1988–1990
    • Whitehead Institute for Biomedical Research
      Cambridge, Massachusetts, United States