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Padeganeh A, Ghochani M, Brewer CJ, Hajianpour A, Becerra LJ, Ahmed SA, Moradian MM, Ramjit RT. 41. Clinical significance of comprehensive genetic workup prior to use of assisted reproductive technology: A case study. Cancer Genet 2021. [DOI: 10.1016/j.cancergen.2021.01.052] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Uchiyama S, Döhrmann S, Timmer AM, Dixit N, Ghochani M, Bhandari T, Timmer JC, Sprague K, Bubeck-Wardenburg J, Simon SI, Nizet V. Streptolysin O Rapidly Impairs Neutrophil Oxidative Burst and Antibacterial Responses to Group A Streptococcus. Front Immunol 2015; 6:581. [PMID: 26635795 PMCID: PMC4644796 DOI: 10.3389/fimmu.2015.00581] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2015] [Accepted: 10/30/2015] [Indexed: 12/11/2022] Open
Abstract
Group A Streptococcus (GAS) causes a wide range of human infections, ranging from simple pharyngitis to life-threatening necrotizing fasciitis and toxic shock syndrome. A globally disseminated clone of M1T1 GAS has been associated with an increase in severe, invasive GAS infections in recent decades. The secreted GAS pore-forming toxin streptolysin O (SLO), which induces eukaryotic cell lysis in a cholesterol-dependent manner, is highly upregulated in the GAS M1T1 clone during bloodstream dissemination. SLO is known to promote GAS resistance to phagocytic clearance by neutrophils, a critical first element of host defense against invasive bacterial infection. Here, we examine the role of SLO in modulating specific neutrophil functions during their early interaction with GAS. We find that SLO at subcytotoxic concentrations and early time points is necessary and sufficient to suppress neutrophil oxidative burst, in a manner reversed by free cholesterol and anti-SLO blocking antibodies. In addition, SLO at subcytotoxic concentrations blocked neutrophil degranulation, interleukin-8 secretion and responsiveness, and elaboration of DNA-based neutrophil extracellular traps, cumulatively supporting a key role for SLO in GAS resistance to immediate neutrophil killing. A non-toxic SLO derivate elicits protective immunity against lethal GAS challenge in a murine infection model. We conclude that SLO exerts a novel cytotoxic-independent function at early stages of invasive infections (<30 min), contributing to GAS escape from neutrophil clearance.
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Affiliation(s)
- Satoshi Uchiyama
- Department of Pediatrics, University of California San Diego , La Jolla, CA , USA
| | - Simon Döhrmann
- Department of Pediatrics, University of California San Diego , La Jolla, CA , USA
| | - Anjuli M Timmer
- Department of Pediatrics, University of California San Diego , La Jolla, CA , USA
| | - Neha Dixit
- Department of Biomedical Engineering, University of California Davis , Davis, CA , USA
| | - Mariam Ghochani
- Department of Biological Sciences, San Diego State University , San Diego, CA , USA
| | - Tamara Bhandari
- Department of Pediatrics, University of California San Diego , La Jolla, CA , USA
| | - John C Timmer
- Department of Pharmacology, University of California San Diego , La Jolla, CA , USA
| | - Kimberly Sprague
- Department of Pediatrics, University of California San Diego , La Jolla, CA , USA
| | | | - Scott I Simon
- Department of Biomedical Engineering, University of California Davis , Davis, CA , USA
| | - Victor Nizet
- Department of Pediatrics, University of California San Diego , La Jolla, CA , USA ; Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego , La Jolla, CA , USA
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Ghochani M, Nulton J, Salamon P, Frey T, Rabinovitch A, Baljon A. Tensile Forces Stabilize Observed Crista Structure in Mitochondria. Biophys J 2011. [DOI: 10.1016/j.bpj.2010.12.2961] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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Abstract
Autophagy is a highly regulated intracellular degradation process by which cells remove cytosolic long-lived proteins and damaged organelles. The mitochondrial permeability transition (MPT) results in mitochondrial depolarization and increased reactive oxygen species production, which can trigger autophagy. Therefore, we hypothesized that the MPT may have a role in signaling autophagy in cardiac cells. Mitochondrial membrane potential was lower in HL-1 cells subjected to starvation compared to cells maintained in full medium. Mitochondrial membrane potential was preserved in starved cells treated with cyclosporin A (CsA), suggesting the MPT pore is associated with starvation-induced depolarization. Starvation-induced autophagy in HL-1 cells, neonatal rat cardiomyocytes and adult mouse cardiomyocytes was inhibited by CsA. Starvation failed to induce autophagy in CypD-deficient murine cardiomyocytes, whereas in myocytes from mice overexpressing CypD the levels of autophagy were enhanced even under fed conditions. Collectively, these results demonstrate a role for CypD and the MPT in the initiation of autophagy. We also analyzed the role of the MPT in the degradation of mitochondria by biochemical analysis and electron microscopy. HL-1 cells subjected to starvation in the presence of CsA had higher levels of mitochondrial proteins (by Western blot), more mitochondria and less autophagosomes (by electron microscopy) than cells starved in the absence of CsA. Our results suggest a physiologic function for CypD and the MPT in the regulation of starvation-induced autophagy. Starvation-induced autophagy regulated by CypD and the MPT may represent a homeostatic mechanism for cellular and mitochondrial quality control.
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Affiliation(s)
- Raquel S. Carreira
- BioScience Center, San Diego State University, 5500 Campanile Drive, San Diego, CA 92182-4650, USA
| | - Youngil Lee
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, 9500 Gilman Drive #0748, La Jolla, CA 92093-0748, USA
| | - Mariam Ghochani
- BioScience Center, San Diego State University, 5500 Campanile Drive, San Diego, CA 92182-4650, USA
- Departments of Physics and Biology, San Diego State University, 5500 Campanile Drive, San Diego, CA 92182-4650, USA
| | - Åsa B. Gustafsson
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, 9500 Gilman Drive #0748, La Jolla, CA 92093-0748, USA
| | - Roberta A. Gottlieb
- BioScience Center, San Diego State University, 5500 Campanile Drive, San Diego, CA 92182-4650, USA
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Ghochani M, Rabinovitch A, Frey T, Nulton J, Salamon P, Baljon AR. Investigation of Mitochondrial Crista Membrane Morphologies in Terms of Minimizing the Free Energy of the Configuration. Biophys J 2010. [DOI: 10.1016/j.bpj.2009.12.3675] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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Köckritz-Blickwede MV, Chow O, Ghochani M, Nizet V. Visualization and Functional Evaluation of Phagocyte Extracellular Traps. Immunology of Infection 2010. [DOI: 10.1016/s0580-9517(10)37007-3] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
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Abstract
Mitochondrial fusion requires the coordinated fusion of the outer and inner membranes. Three large GTPases--OPA1 and the mitofusins Mfn1 and Mfn2--are essential for the fusion of mammalian mitochondria. OPA1 is mutated in dominant optic atrophy, a neurodegenerative disease of the optic nerve. In yeast, the OPA1 ortholog Mgm1 is required for inner membrane fusion in vitro; nevertheless, yeast lacking Mgm1 show neither outer nor inner membrane fusion in vivo, because of the tight coupling between these two processes. We find that outer membrane fusion can be readily visualized in OPA1-null mouse cells in vivo, but these events do not progress to inner membrane fusion. Similar defects are found in cells lacking prohibitins, which are required for proper OPA1 processing. In contrast, double Mfn-null cells show neither outer nor inner membrane fusion. Mitochondria in OPA1-null cells often contain multiple matrix compartments bounded together by a single outer membrane, consistent with uncoupling of outer versus inner membrane fusion. In addition, unlike mitofusins and yeast Mgm1, OPA1 is not required on adjacent mitochondria to mediate membrane fusion. These results indicate that mammalian mitofusins and OPA1 mediate distinct sequential fusion steps that are readily uncoupled, in contrast to the situation in yeast.
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Affiliation(s)
- Zhiyin Song
- Howard Hughes Medical Institute and Division of Biology, California Institute of Technology, Pasadena, CA 91125, USA
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Timmer AM, Timmer JC, Pence MA, Hsu LC, Ghochani M, Frey TG, Karin M, Salvesen GS, Nizet V. Streptolysin O promotes group A Streptococcus immune evasion by accelerated macrophage apoptosis. J Biol Chem 2008; 284:862-71. [PMID: 19001420 DOI: 10.1074/jbc.m804632200] [Citation(s) in RCA: 130] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Group A Streptococcus (GAS) is a leading human bacterial pathogen capable of producing invasive infections even in previously healthy individuals. As frontline components of host innate defense, macrophages play a key role in control and clearance of GAS infections. We find GAS induces rapid, dose-dependent apoptosis of primary and cultured macrophages and neutrophils. The cell death pathway involves apoptotic caspases, is partly dependent on caspase-1, and requires GAS internalization by the phagocyte. Analysis of GAS virulence factor mutants, heterologous expression, and purified toxin studies identified the pore-forming cytolysin streptolysin O (SLO) as necessary and sufficient for the apoptosis-inducing phenotype. SLO-deficient GAS mutants induced less macrophage apoptosis in vitro and in vivo, allowed macrophage cytokine secretion, and were less virulent in a murine systemic infection model. Ultrastructural evidence of mitochondrial membrane remodeling, coupled with loss of mitochondrial depolarization and cytochrome c release, suggests a direct attack of the toxin initiates the intrinsic apoptosis pathway. A general caspase inhibitor blocked SLO-induced apoptosis and enhanced macrophage killing of GAS. We conclude that accelerated, caspase-dependent macrophage apoptosis induced by the pore-forming cytolysin SLO contributes to GAS immune evasion and virulence.
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Affiliation(s)
- Anjuli M Timmer
- Department of Pediatrics, Biomedical Sciences Graduate Program, Laboratory of Signal Transduction, University of California, San Diego, La Jolla, California 92093, USA
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