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Sykes, David

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Sykes

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Sykes, David
Author's Publications: search.filters.isAuthorOfPublication.9c14340f-d772-4058-85dc-62126337147d

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    Fluorescent Tracking of Yeast Division Clarifies the Essential Role of Spleen Tyrosine Kinase in the Intracellular Control of Candida glabrata in Macrophages
    (Frontiers Media S.A., 2018) Dagher, Zeina; Xu, Shuying; Negoro, Paige E.; Khan, Nida S.; Feldman, Michael; Reedy, Jennifer; Tam, Jenny; Sykes, David; Mansour, Michael
    Macrophages play a critical role in the elimination of fungal pathogens. They are sensed via cell surface pattern-recognition receptors and are phagocytosed into newly formed organelles called phagosomes. Phagosomes mature through the recruitment of proteins and lysosomes, resulting in addition of proteolytic enzymes and acidification of the microenvironment. Our earlier studies demonstrated an essential role of Dectin-1-dependent activation of spleen tyrosine kinase (Syk) in the maturation of fungal containing phagosomes. The absence of Syk activity interrupted phago-lysosomal fusion resulting in arrest at an early phagosome stage. In this study, we sought to define the contribution of Syk to the control of phagocytosed live Candida glabrata in primary macrophages. To accurately measure intracellular yeast division, we designed a carboxyfluorescein succinimidyl ester (CFSE) yeast division assay in which bright fluorescent parent cells give rise to dim daughter cells. The CFSE-labeling of C. glabrata did not affect the growth rate of the yeast. Following incubation with macrophages, internalized CFSE-labeled C. glabrata were retrieved by cellular lysis, tagged using ConA-647, and the amount of residual CFSE fluorescence was assessed by flow cytometry. C. glabrata remained undivided (CFSE bright) for up to 18 h in co-culture with primary macrophages. Treatment of macrophages with R406, a specific Syk inhibitor, resulted in loss of intracellular control of C. glabrata with initiation of division within 4 h. Delayed Syk inhibition after 8 h was less effective indicating that Syk is critically required at early stages of macrophage–fungal interaction. In conclusion, we demonstrate a new method of tracking division of C. glabrata using CFSE labeling. Our results suggest that early Syk activation is essential for macrophage control of phagocytosed C. glabrata.
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    An unappreciated role for neutrophil-DC hybrids in immunity to invasive fungal infections
    (Public Library of Science, 2018) Fites, J. Scott; Gui, Michael; Kernien, John F.; Negoro, Paige; Dagher, Zeina; Sykes, David; Nett, Jeniel E.; Mansour, Michael; Klein, Bruce S.
    Neutrophils are classically defined as terminally differentiated, short-lived cells; however, neutrophils can be long-lived with phenotypic plasticity. During inflammation, a subset of neutrophils transdifferentiate into a population called neutrophil-DC hybrids (PMN-DCs) having properties of both neutrophils and dendritic cells. While these cells ubiquitously appear during inflammation, the role of PMN-DCs in disease remains poorly understood. We observed the differentiation of PMN-DCs in pre-clinical murine models of fungal infection: blastomycosis, aspergillosis and candidiasis. Using reporter strains of fungal viability, we found that PMN-DCs associate with fungal cells and kill them more efficiently than undifferentiated canonical neutrophils. During pulmonary blastomycosis, PMN-DCs comprised less than 1% of leukocytes yet contributed up to 15% of the fungal killing. PMN-DCs displayed higher expression of pattern recognition receptors, greater phagocytosis, and heightened production of reactive oxygen species compared to canonical neutrophils. PMN-DCs also displayed prominent NETosis. To further study PMN-DC function, we exploited a granulocyte/macrophage progenitor (GMP) cell line, generated PMN-DCs to over 90% purity, and used them for adoptive transfer and antigen presentation studies. Adoptively transferred PMN-DCs from the GMP line enhanced protection against systemic infection in vivo. PMN-DCs pulsed with antigen activated fungal calnexin-specific transgenic T cells in vitro and in vivo, promoting the production of interferon-γ and interleukin-17 in these CD4+ T cells. Through direct fungal killing and induction of adaptive immunity, PMN-DCs are potent effectors of antifungal immunity and thereby represent innovative cell therapeutic targets in treating life-threatening fungal infections.
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    Amino acid–insensitive mTORC1 regulation enables nutritional stress resilience in hematopoietic stem cells
    (American Society for Clinical Investigation, 2017) Kalaitzidis, Demetrios; Lee, Dongjun; Efeyan, Alejo; Kfoury, Youmna; Nayyar, Naema; Sykes, David; Mercier, Francois; Papazian, Ani; Baryawno, Ninib; Victora, Gabriel D.; Neuberg, Donna; Sabatini, David; Scadden, David
    The mTOR pathway is a critical determinant of cell persistence and growth wherein mTOR complex 1 (mTORC1) mediates a balance between growth factor stimuli and nutrient availability. Amino acids or glucose facilitates mTORC1 activation by inducing RagA GTPase recruitment of mTORC1 to the lysosomal outer surface, enabling activation of mTOR by the Ras homolog Rheb. Thereby, RagA alters mTORC1-driven growth in times of nutrient abundance or scarcity. Here, we have evaluated differential nutrient-sensing dependence through RagA and mTORC1 in hematopoietic progenitors, which dynamically drive mature cell production, and hematopoietic stem cells (HSC), which provide a quiescent cellular reserve.In nutrient-abundant conditions, RagA-deficient HSC were functionally unimpaired and upregulated mTORC1 via nutrientinsensitive mechanisms. RagA was also dispensable for HSC function under nutritional stress conditions. Similarly, hyperactivation of RagA did not affect HSC function. In contrast, RagA deficiency markedly altered progenitor population function and mature cell output. Therefore, RagA is a molecular mechanism that distinguishes the functional attributes of reactive progenitors from a reserve stem cell pool. The indifference of HSC to nutrient sensing through RagA contributes to their molecular resilience to nutritional stress, a characteristic that is relevant to organismal viability in evolution and in modern HSC transplantation approaches.
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    Non-genotoxic conditioning for hematopoietic stem cell transplantation using a hematopoietic-cell-specific internalizing immunotoxin
    (Springer Nature, 2016) Palchaudhuri, Rahul; Saez, Borja; Hoggatt, Jonathan; Schajnovitz, Amir; Sykes, David; Tate, Tiffany A; Czechowicz, Agnieszka; Kfoury, Youmna; Ruchika, FNU; Rossi, Derrick; Verdine, Gregory; Mansour, Michael; Scadden, David
    Hematopoietic stem cell transplantation (HSCT) offers curative therapy for patients with hemoglobinopathies, congenital immunodeficiencies, and other conditions, possibly including AIDS. Autologous HSCT using genetically corrected cells would avoid the risk of graft-versus-host disease (GVHD), but the genotoxicity of conditioning remains a substantial barrier to the development of this approach. Here we report an internalizing immunotoxin targeting the hematopoietic-cell-restricted CD45 receptor that effectively conditions immunocompetent mice. A single dose of the immunotoxin, CD45–saporin (SAP), enabled efficient (>90%) engraftment of donor cells and full correction of a sickle-cell anemia model. In contrast to irradiation, CD45–SAP completely avoided neutropenia and anemia, spared bone marrow and thymic niches, enabling rapid recovery of T and B cells, preserved anti-fungal immunity, and had minimal overall toxicity. This non-genotoxic conditioning method may provide an attractive alternative to current conditioning regimens for HSCT in the treatment of non-malignant blood diseases.
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    Endogenous transmembrane protein UT2 inhibits pSTAT3 and suppresses hematological malignancy
    (American Society for Clinical Investigation, 2016) Lee, Dongjun; Wang, Ying-Hua; Kalaitzidis, Demetrios; Ramachandran, Janani; Eda, Homare; Sykes, David; Raje, Noopur; Scadden, David
    Regulation of STAT3 activation is critical for normal and malignant hematopoietic cell proliferation. Here, we have reported that the endogenous transmembrane protein upstream-of-mTORC2 (UT2) negatively regulates activation of STAT3. Specifically, we determined that UT2 interacts directly with GP130 and inhibits phosphorylation of STAT3 on tyrosine 705 (STAT3Y705). This reduces cytokine signaling including IL6 that is implicated in multiple myeloma and other hematopoietic malignancies. Modulation of UT2 resulted in inverse effects on animal survival in myeloma models. Samples from multiple myeloma patients also revealed a decreased copy number of UT2 and decreased expression of UT2 in genomic and transcriptomic analyses, respectively. Together, these studies identify a transmembrane protein that functions to negatively regulate cytokine signaling through GP130 and pSTAT3Y705 and is molecularly and mechanistically distinct from the suppressors of cytokine signaling (SOCS) family of genes. Moreover, this work provides evidence that perturbations of this activation-dampening molecule participate in hematologic malignancies and may serve as a key determinant of multiple myeloma pathophysiology. UT2 is a negative regulator shared across STAT3 and mTORC2 signaling cascades, functioning as a tumor suppressor in hematologic malignancies driven by those pathways.
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    RECQL5 Suppresses Oncogenic JAK2-Induced Replication Stress and Genomic Instability
    (Elsevier BV, 2015) Chen, Edwin; Ahn, Jong Sook; Sykes, David; Breyfogle, Lawrence J.; Godfrey, Anna L.; Nangalia, Jyoti; Ko, Amy; DeAngelo, Daniel; Green, Alexander; Mullally, Ann
    JAK2V617F is the most common oncogenic lesion in patients with myeloproliferative neoplasms (MPNs). Despite the ability of JAK2V617F to instigate DNA damage in vitro, MPNs are nevertheless characterized by genomic stability. In this study, we address this paradox by identifying the DNA helicase RECQL5 as a suppressor of genomic instability in MPNs. We report increased RECQL5 expression in JAK2V617F-expressing cells and demonstrate that RECQL5 is required to counteract JAK2V617F-induced replication stress. Moreover, RECQL5 depletion sensitizes JAK2V617F mutant cells to hydroxyurea (HU), a pharmacological inducer of replication stress and the most common treatment for MPNs. Using single-fiber chromosome combing, we show that RECQL5 depletion in JAK2V617F mutant cells impairs replication dynamics following HU treatment, resulting in increased double-stranded breaks and apoptosis. Cumulatively, these findings identify RECQL5 as a critical regulator of genome stability in MPNs and demonstrate that replication stress-associated cytotoxicity can be amplified specifically in JAK2V617F mutant cells through RECQL5-targeted synthetic lethality.
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    Control of signaling-mediated clearance of apoptotic cells by the tumor suppressor p53
    (American Association for the Advancement of Science (AAAS), 2015) Yoon, K. W.; Byun, S.; Kwon, Eunjeong; Hwang, So-Young; Chu, Kiki; Hiraki, Masatsugu; Jo, Seung-Hee; Weins, Astrid; Hakroush, Samy; Cebulla, Angelika; Sykes, David; Greka, Anna; Mundel, Peter; Fisher, David; Mandinova, Anna; Lee, Sam
    The inefficient clearance of dying cells can lead to abnormal immune responses, such as unresolved inflammation and autoimmune conditions. We show that tumor suppressor p53 controls signaling-mediated phagocytosis of apoptotic cells through its target, Death Domain1α (DD1α), which suggests that p53 promotes both the proapoptotic pathway and postapoptotic events. DD1α appears to function as an engulfment ligand or receptor that engages in homophilic intermolecular interaction at intercellular junctions of apoptotic cells and macrophages, unlike other typical scavenger receptors that recognize phosphatidylserine on the surface of dead cells. DD1α-deficient mice showed in vivo defects in clearing dying cells, which led to multiple organ damage indicative of immune dysfunction. p53-induced expression of DD1α thus prevents persistence of cell corpses and ensures efficient generation of precise immune responses.
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    Neuregulin1-β Decreases IL-1β -Induced Neutrophil Adhesion to Human Brain Microvascular Endothelial Cells
    (Springer Nature, 2014) Wu, Limin; Walas, Samantha; Leung, Wendy; Sykes, David; Wu, Jiang; Lo, Eng; Lok, Josephine M.
    Neuroinflammation contributes to the pathophysiology of diverse diseases including stroke, traumatic brain injury, Alzheimer's Disease, Parkinson's Disease, and multiple sclerosis, resulting in neurodegeneration and loss of neurological function. The response of the microvascular endothelium often contributes to neuroinflammation. One such response is the up-regulation of endothelial adhesion molecules which facilitate neutrophil adhesion to the endothelium and their migration from blood to tissue. Neuregulin-1 (NRG1) is an endogenous growth factor which has been reported to have anti-inflammatory effects in experimental stroke models. We hypothesized that NRG1 would decrease the endothelial response to inflammation, and result in a decrease in neutrophil adhesion to endothelial cells. We tested this hypothesis in an in-vitro model of cytokine-induced endothelial injury, in which human brain microvascular endothelial cells (BMECs) were treated with IL-1β, along with co-incubation with vehicle or NRG1-β. Outcome measures included protein levels of endothelial ICAM-1, VCAM-1, and E-selectin; as well as the number of neutrophils that adhere to the endothelial monolayer. Our data show that NRG1-β decreased the levels of VCAM-1, E-selectin, and neutrophil adhesion to brain microvascular endothelial cells activated by IL1-β. These findings open new possibilities for investigating NRG1 in neuroprotective strategies in brain injury.
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    Niche-Based Screening in Multiple Myeloma Identifies a Kinesin-5 Inhibitor with Improved Selectivity over Hematopoietic Progenitors
    (Elsevier BV, 2015) Chattopadhyay, Shrikanta; Stewart, Alison L.; Mukherjee, Siddhartha; Huang, Cherrie; Hartwell, Kimberly A.; Miller, Peter; Subramanian, Radhika; Carmody, Leigh C.; Yusuf, Rushdia; Sykes, David; Paulk, Joshiawa; Vetere, Amedeo; Vallet, Sonia; Santo, Loredana; Cirstea, Diana D.; Hideshima, Teru; Dan?ík, Vlado; Majireck, Max M.; Hussain, Mahmud M.; Singh, Shambhavi; Quiroz, Ryan; Iaconelli, Jonathan; Karmacharya, Rakesh; Tolliday, Nicola J.; Clemons, Paul A.; Moore, Malcolm A.S.; Stern, Andrew M.; Shamji, Alykhan; Ebert, Benjamin; Golub, Todd; Raje, Noopur; Scadden, David; Schreiber, Stuart
    Novel therapeutic approaches are urgently required for multiple myeloma (MM). We used a phenotypic screening approach using co-cultures of MM cells with bone marrow stromal cells to identify compounds that overcome stromal resistance. One such compound, BRD9876, displayed selectivity over normal hematopoietic progenitors and was discovered to be an unusual ATP non-competitive kinesin-5 (Eg5) inhibitor. A novel mutation caused resistance, suggesting a binding site distinct from known Eg5 inhibitors, and BRD9876 inhibited only microtubule-bound Eg5. Eg5 phosphorylation, which increases microtubule binding, uniquely enhanced BRD9876 activity. MM cells have greater phosphorylated Eg5 than hematopoietic cells, consistent with increased vulnerability specifically to BRD9876’s mode of action. Thus, differences in Eg5-microtubule binding between malignant and normal blood cells may be exploited to treat multiple myeloma. Additional steps are required for further therapeutic development, but our results indicate that unbiased chemical biology approaches can identify therapeutic strategies unanticipated by prior knowledge of protein targets.
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    Case report: a 37-year-old male with telangiectasias, polycythemia vera, perinephric fluid collections, and intrapulmonary shunting
    (Springer Nature, 2014) Khan, Javed; Sykes, David
    The TEMPI syndrome was recently described in 2011, and is characterized by the constellation of five hallmarks: Telangiectasias, Erythrocytosis and elevated Erythropoietin, Monoclonal gammopathy, Perinephric fluids collections, and Intrapulmonary shunting. The underlying pathophysiology is unknown, though it has been postulated that the monoclonal gammopathy may play a causal role.