Browsing by Author "Dubois, Laura G"

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    Characterization of the ubiquitin-modified proteome regulated by transient forebrain ischemia.
    (Journal of cerebral blood flow and metabolism : official journal of the International Society of Cerebral Blood Flow and Metabolism, 2014-03) Iwabuchi, Masahiro; Sheng, Huaxin; Thompson, J Will; Wang, Liangli; Dubois, Laura G; Gooden, David; Moseley, Marthur; Paschen, Wulf; Yang, Wei
    Ubiquitylation is a posttranslational protein modification that modulates various cellular processes of key significance, including protein degradation and DNA damage repair. In animals subjected to transient cerebral ischemia, ubiquitin-conjugated proteins accumulate in Triton-insoluble aggregates. Although this process is widely considered to modulate the fate of postischemic neurons, few attempts have been made to characterize the ubiquitin-modified proteome in these aggregates. We performed proteomics analyses to identify ubiquitylated proteins in postischemic aggregates. Mice were subjected to 10 minutes of forebrain ischemia and 4 hours of reperfusion. The hippocampi were dissected, aggregates were isolated, and trypsin-digested after spiking with GG-BSA as internal standard. K-ɛ-GG-containing peptides were immunoprecipitated and analyzed by label-free quantitative liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis. We identified 1,664 peptides to 520 proteins containing at least one K-ɛ-GG. Sixty-six proteins were highly ubiquitylated, with 10 or more K-ɛ-GG peptides. Based on selection criteria of greater than fivefold increase and P<0.001, 763 peptides to 272 proteins were highly enriched in postischemic aggregates. These included proteins involved in important neuronal functions and signaling pathways that are impaired after ischemia. Results of this study could serve as an important platform to uncover the mechanisms linking insoluble ubiquitin aggregates to the functions of postischemic neurons.
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    Chlamydia trachomatis Infection Leads to Defined Alterations to the Lipid Droplet Proteome in Epithelial Cells.
    (PLoS One, 2015) Saka, Hector Alex; Thompson, J Will; Chen, Yi-Shan; Dubois, Laura G; Haas, Joel T; Moseley, Arthur; Valdivia, Raphael H
    The obligate intracellular bacterium Chlamydia trachomatis is a major human pathogen and a main cause of genital and ocular diseases. During its intracellular cycle, C. trachomatis replicates inside a membrane-bound vacuole termed an "inclusion". Acquisition of lipids (and other nutrients) from the host cell is a critical step in chlamydial replication. Lipid droplets (LD) are ubiquitous, ER-derived neutral lipid-rich storage organelles surrounded by a phospholipids monolayer and associated proteins. Previous studies have shown that LDs accumulate at the periphery of, and eventually translocate into, the chlamydial inclusion. These observations point out to Chlamydia-mediated manipulation of LDs in infected cells, which may impact the function and thereby the protein composition of these organelles. By means of a label-free quantitative mass spectrometry approach we found that the LD proteome is modified in the context of C. trachomatis infection. We determined that LDs isolated from C. trachomatis-infected cells were enriched in proteins related to lipid metabolism, biosynthesis and LD-specific functions. Interestingly, consistent with the observation that LDs intimately associate with the inclusion, a subset of inclusion membrane proteins co-purified with LD protein extracts. Finally, genetic ablation of LDs negatively affected generation of C. trachomatis infectious progeny, consistent with a role for LD biogenesis in optimal chlamydial growth.
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    Erratum: Neuroprotective pentapeptide CN-105 improves functional and histological outcomes in a murine model of intracerebral hemorrhage.
    (Sci Rep, 2017-01-05) Lei, Beilei; James, Michael L; Liu, Ji; Zhou, Guanen; Venkatraman, Talaignair N; Lascola, Christopher D; Acheson, Shawn K; Dubois, Laura G; Laskowitz, Daniel T; Wang, Haichen
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    Microgravity induces proteomics changes involved in endoplasmic reticulum stress and mitochondrial protection.
    (Scientific reports, 2016-09-27) Feger, Bryan J; Thompson, J Will; Dubois, Laura G; Kommaddi, Reddy P; Foster, Matthew W; Mishra, Rajashree; Shenoy, Sudha K; Shibata, Yoichiro; Kidane, Yared H; Moseley, M Arthur; Carnell, Lisa S; Bowles, Dawn E
    On Earth, biological systems have evolved in response to environmental stressors, interactions dictated by physical forces that include gravity. The absence of gravity is an extreme stressor and the impact of its absence on biological systems is ill-defined. Astronauts who have spent extended time under conditions of minimal gravity (microgravity) experience an array of biological alterations, including perturbations in cardiovascular function. We hypothesized that physiological perturbations in cardiac function in microgravity may be a consequence of alterations in molecular and organellar dynamics within the cellular milieu of cardiomyocytes. We used a combination of mass spectrometry-based approaches to compare the relative abundance and turnover rates of 848 and 196 proteins, respectively, in rat neonatal cardiomyocytes exposed to simulated microgravity or normal gravity. Gene functional enrichment analysis of these data suggested that the protein content and function of the mitochondria, ribosomes, and endoplasmic reticulum were differentially modulated in microgravity. We confirmed experimentally that in microgravity protein synthesis was decreased while apoptosis, cell viability, and protein degradation were largely unaffected. These data support our conclusion that in microgravity cardiomyocytes attempt to maintain mitochondrial homeostasis at the expense of protein synthesis. The overall response to this stress may culminate in cardiac muscle atrophy.
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    Neuroprotective pentapeptide CN-105 improves functional and histological outcomes in a murine model of intracerebral hemorrhage.
    (Sci Rep, 2016-10-07) Lei, Beilei; James, Michael L; Liu, Ji; Zhou, Guanen; Venkatraman, Talaignair N; Lascola, Christopher D; Acheson, Shawn K; Dubois, Laura G; Laskowitz, Daniel T; Wang, Haichen
    Presently, no pharmacological treatments have been demonstrated to improve long-term functional outcomes following intracerebral hemorrhage (ICH). Clinical evidence associates apolipoprotein E (apoE) genotype with ICH incidence and outcome. While apoE modifies neuroinflammatory responses through its adaptive role in glial downregulation, intact apoE holoprotein is too large to cross the blood-brain barrier (BBB). Therefore, we developed a 5-amino acid peptide - CN-105 - that mimics the polar face of the apoE helical domain involved in receptor interactions. In the current study, we investigated the therapeutic potential of CN-105 in a mouse model of ICH. Three doses of CN-105 (0.05 mg/kg) was administered by tail vein injection within 24 hours after ICH induction. Functional assessment showed durable improvement in vestibulomotor performance after CN-105 treatment, as quantified by increased Rotarod latencies on Days 1-5 post-ICH, and long-term improvement in neurocognitive performance, as quantified by reduced Morris water maze latencies on Days 29-32 post-ICH. Further, brain water content was significantly reduced, neuroinflammation was decreased and hippocampal CA3 neuronal survival was increased, although hemorrhage volume was not affected by CN-105. We concluded, therefore, that pentapeptide CN-105 improved short- and long-term neurobehavioral outcomes in a murine model of ICH, suggesting therapeutic potential for patients with acute ICH.
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    Proteomic analysis of ERK1/2-mediated human sickle red blood cell membrane protein phosphorylation.
    (Clin Proteomics, 2013-01-03) Soderblom, Erik J; Thompson, J Will; Schwartz, Evan A; Chiou, Edward; Dubois, Laura G; Moseley, M Arthur; Zennadi, Rahima
    UNLABELLED: BACKGROUND: In sickle cell disease (SCD), the mitogen-activated protein kinase (MAPK) ERK1/2 is constitutively active and can be inducible by agonist-stimulation only in sickle but not in normal human red blood cells (RBCs). ERK1/2 is involved in activation of ICAM-4-mediated sickle RBC adhesion to the endothelium. However, other effects of the ERK1/2 activation in sickle RBCs leading to the complex SCD pathophysiology, such as alteration of RBC hemorheology are unknown. RESULTS: To further characterize global ERK1/2-induced changes in membrane protein phosphorylation within human RBCs, a label-free quantitative phosphoproteomic analysis was applied to sickle and normal RBC membrane ghosts pre-treated with U0126, a specific inhibitor of MEK1/2, the upstream kinase of ERK1/2, in the presence or absence of recombinant active ERK2. Across eight unique treatment groups, 375 phosphopeptides from 155 phosphoproteins were quantified with an average technical coefficient of variation in peak intensity of 19.8%. Sickle RBC treatment with U0126 decreased thirty-six phosphopeptides from twenty-one phosphoproteins involved in regulation of not only RBC shape, flexibility, cell morphology maintenance and adhesion, but also glucose and glutamate transport, cAMP production, degradation of misfolded proteins and receptor ubiquitination. Glycophorin A was the most affected protein in sickle RBCs by this ERK1/2 pathway, which contained 12 unique phosphorylated peptides, suggesting that in addition to its effect on sickle RBC adhesion, increased glycophorin A phosphorylation via the ERK1/2 pathway may also affect glycophorin A interactions with band 3, which could result in decreases in both anion transport by band 3 and band 3 trafficking. The abundance of twelve of the thirty-six phosphopeptides were subsequently increased in normal RBCs co-incubated with recombinant ERK2 and therefore represent specific MEK1/2 phospho-inhibitory targets mediated via ERK2. CONCLUSIONS: These findings expand upon the current model for the involvement of ERK1/2 signaling in RBCs. These findings also identify additional protein targets of this pathway other than the RBC adhesion molecule ICAM-4 and enhance the understanding of the mechanism of small molecule inhibitors of MEK/1/2/ERK1/2, which could be effective in ameliorating RBC hemorheology and adhesion, the hallmarks of SCD.