Publications (8) View all
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Article: The Mycobacterium tuberculosis SecA2 system subverts phagosome maturation to promote growth in macrophages.
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ABSTRACT: The ability of Mycobacterium tuberculosis to grow in macrophages is critical to the virulence of this important pathogen. One way M. tuberculosis is thought to maintain a hospitable niche in macrophages is by arresting the normal process of phagosomes maturing into acidified phagolysosomes. The process of phagosome maturation arrest by M. tuberculosis is not fully understood, and there has remained a need to firmly establish a requirement for phagosome maturation arrest for M. tuberculosis growth in macrophages. Other intracellular pathogens that control the phagosomal environment use specialized protein export systems to deliver effectors of phagosome trafficking to the host cell. In M. tuberculosis, the accessory SecA2 system is a specialized protein export system that is required for intracellular growth in macrophages. In studying the importance of the SecA2 system in macrophages, we discovered that SecA2 is required for phagosome maturation arrest. Shortly after infection, phagosomes containing a ΔsecA2 mutant of M. tuberculosis were more acidified and showed greater association with markers of late endosomes than phagosomes containing wild-type M. tuberculosis. We further showed that inhibitors of phagosome acidification rescued the intracellular growth defect of the ΔsecA2 mutant, which demonstrated that the phagosome maturation arrest defect of the ΔsecA2 mutant is responsible for the intracellular growth defect. This study demonstrates the importance of phagosome maturation arrest for M. tuberculosis growth in macrophages, and it suggests there are effectors of phagosome maturation that are exported into the host environment by the accessory SecA2 system.Infection and immunity 01/2012; 80(3):996-1006. · 4.21 Impact Factor -
Article: HLA-A2-matched peripheral blood mononuclear cells from type 1 diabetic patients, but not nondiabetic donors, transfer insulitis to NOD-scid/γc(null)/HLA-A2 transgenic mice concurrent with the expansion of islet-specific CD8+ T cells.
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ABSTRACT: Type 1 diabetes is an autoimmune disease characterized by the destruction of insulin-producing β-cells. NOD mice provide a useful tool for understanding disease pathogenesis and progression. Although much has been learned from studies with NOD mice, increased understanding of human type 1 diabetes can be gained by evaluating the pathogenic potential of human diabetogenic effector cells in vivo. Therefore, our objective in this study was to develop a small-animal model using human effector cells to study type 1 diabetes. We adoptively transferred HLA-A2-matched peripheral blood mononuclear cells (PBMCs) from type 1 diabetic patients and nondiabetic control subjects into transgenic NOD-scid/γc(null)/HLA-A*0201 (NOD-scid/γc(null)/A2) mice. At various times after adoptive transfer, we determined the ability of these mice to support the survival and proliferation of the human lymphoid cells. Human lymphocytes were isolated and assessed from the blood, spleen, pancreatic lymph node and islets of NOD-scid/γc(null)/A2 mice after transfer. Human T and B cells proliferate and survive for at least 6 weeks and were recovered from the blood, spleen, draining pancreatic lymph node, and most importantly, islets of NOD-scid/γc(null)/A2 mice. Lymphocytes from type 1 diabetic patients preferentially infiltrate the islets of NOD-scid/γc(null)/A2 mice. In contrast, PBMCs from nondiabetic HLA-A2-matched donors showed significantly less islet infiltration. Moreover, in mice that received PBMCs from type 1 diabetic patients, we identified epitope-specific CD8(+) T cells among the islet infiltrates. We show that insulitis is transferred to NOD-scid/γc(null)/A2 mice that received HLA-A2-matched PBMCs from type 1 diabetic patients. In addition, many of the infiltrating CD8(+) T cells are epitope-specific and produce interferon-γ after in vitro peptide stimulation. This indicates that NOD-scid/γc(null)/A2 mice transferred with HLA-A2-matched PBMCs from type 1 diabetic patients may serve as a useful tool for studying epitope-specific T-cell-mediated responses in patients with type 1 diabetes.Diabetes 06/2011; 60(6):1726-33. · 8.29 Impact Factor -
Article: Toxin-coupled MHC class I tetramers can specifically ablate autoreactive CD8+ T cells and delay diabetes in nonobese diabetic mice.
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ABSTRACT: There is compelling evidence that self-reactive CD8(+) T cells are a major factor in development and progression of type 1 diabetes in animals and humans. Hence, great effort has been expended to define the specificity of autoimmune CD8(+) T cells and to alter their responses. Much work has focused on tolerization of T cells using proteins or peptides. A weakness in this approach is that residual autoreactive T cells may be activated and exacerbate disease. In this report, we use a novel approach, toxin-coupled MHC class I tetramers. Used for some time to identify Ag-specific cells, in this study, we use that same property to delete the Ag-specific cells. We show that saporin-coupled tetramers can delete islet-specific glucose-6-phosphatase catalytic subunit-related protein (IGRP)-reactive T cells in vitro and in vivo. Sequence analysis of TCRbeta-chains of IGRP(+) cells reveals the repertoire complexity in the islets is markedly decreased as NOD mice age and significantly altered in toxic tetramer-treated NOD mice. Further tetramer(+) T cells in the islets are almost completely deleted, and, surprisingly, loss of tetramer(+) T cells in the islets is long lasting. Finally, we show deletion at 8 wk of age of IGRP(+) CD8(+) T cells, but not dystophia myotonica kinase- or insulin B-reactive cells, significantly delays diabetes in NOD mice.The Journal of Immunology 03/2010; 184(8):4196-204. · 5.79 Impact Factor -
Article: The role of phospholamban in the regulation of calcium transport by cardiac sarcoplasmic reticulum
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ABSTRACT: The calcium transport mechanism of cardiac sarcoplasmic reticulum (SR) is regulated by a phosphoregulatory mechanism involving the phosphorylation-dephosphorylation of an integral membrane component, termed phospholamban. Phospholamban, a 27,000 Da proteolipid, contains phosphorylation sites for three independent protein kinases: 1) cAMP-dependent, 2) Ca2+-calmodulin-dependent, and 3) Ca2+-phospholipid-dependent. Phosphorylation of phospholamban by any one of these kinases is associated with stimulation of the calcium transport rates in isolated SR vesicles. Dephosphorylation of phosphorylated phospholamban results in the reversal of the stimulatory effects produced by the protein kinases. Studies conducted on perfused hearts have shown that during exposure to beta-adrenergic agents, a good correlation exists between the in situ phosphorylation of phospholamban and the relaxation of the left ventricle. Phosphorylation of phospholamban in situ is also associated with stimulation of calcium transport rates by cardiac SR, similar to in vitro findings. Removal of beta-adrenergic agents results in the reversal of the inotropic response and this is associated with dephosphorylation of phospholamban. These findings indicate that a phospho-regulatory mechanism involving phospholamban may provide at least one of the controls for regulation of the contractile properties of the myocardium.Molecular and Cellular Biochemistry 01/1990; 99(2):83-88. · 2.06 Impact Factor -
Article: The molecular neurobiology of the acetylcholine receptor.
Annual Review of Neuroscience 02/1986; 9:383-413. · 25.74 Impact Factor
