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Bugger H.,Program in Molecular Medicine | Bugger H.,Albert Ludwigs University of Freiburg | Schwarzer M.,University of Leipzig | Chen D.,Utah State University | And 9 more authors.
Cardiovascular Research | Year: 2010

Aims Impairment in mitochondrial energetics is a common observation in animal models of heart failure, the underlying mechanisms of which remain incompletely understood. It was our objective to investigate whether changes in mitochondrial protein levels may explain impairment in mitochondrial oxidative capacity in pressure overload-induced heart failure. Methods and resultsTwenty weeks following aortic constriction, Sprague-Dawley rats developed contractile dysfunction with clinical signs of heart failure. Comparative mitochondrial proteomics using label-free proteome expression analysis (LC-MS/MS) revealed decreased mitochondrial abundance of fatty acid oxidation proteins (six of 11 proteins detected), increased levels of pyruvate dehydrogenase subunits, and upregulation of two tricarboxylic acid cycle proteins. Regulation of mitochondrial electron transport chain subunits was variable, with downregulation of 53 of proteins and upregulation of 25 of proteins. Mitochondrial state 3 respiration was markedly decreased independent of the substrate used (palmitoyl-carnitine -65, pyruvate -75, glutamate -75, dinitrophenol -82; all P < 0.05), associated with impaired mitochondrial cristae morphology in failing hearts. Perfusion of isolated working failing hearts showed markedly reduced oleate (-68; P < 0.05) and glucose oxidation (-64; P < 0.05). Conclusion Pressure overload-induced heart failure is characterized by a substantial defect in cardiac oxidative capacity, at least in part due to a mitochondrial defect downstream of substrate-specific pathways. Numerous changes in mitochondrial protein levels have been detected, and the contribution of these to oxidative defects and impaired cardiac energetics in failing hearts is discussed.


Davey J.R.,Garvan Institute of Medical Research | Davey J.R.,University of New South Wales | Humphrey S.J.,Garvan Institute of Medical Research | Humphrey S.J.,University of New South Wales | And 7 more authors.
Traffic | Year: 2012

Insulin stimulates glucose transport in adipocytes by triggering translocation of GLUT4 glucose transporters to the plasma membrane (PM) and several Rabs including Rab10 have been implicated in this process. To delineate the molecular regulation of this pathway, we conducted a TBC/RabGAP overexpression screen in adipocytes. This identified TBC1D13 as a potent inhibitor of insulin-stimulated GLUT4 translocation without affecting other trafficking pathways. To determine the potential Rab substrate for TBC1D13 we conducted a yeast two-hybrid screen and found that the GTP bound forms of Rabs 1 and 10 specifically interacted with TBC1D13 but not with eight other TBC proteins. Surprisingly, a comprehensive in vitro screen for TBC1D13 GAP activity revealed Rab35 but not Rab10 as a specific substrate. TBC1D13 also displayed in vivo GAP activity towards Rab35. Overexpression of constitutively active Rab35 but not constitutively active Rab10 reversed the block in insulin-stimulated GLUT4 translocation observed with TBC1D13 overexpression. These studies implicate an important role for Rab35 in insulin-stimulated GLUT4 translocation in adipocytes. © 2012 John Wiley & Sons A/S.


Chou Y.-T.,National Tsing Hua University | Lee C.-C.,Academia Sinica, Taiwan | Hsiao S.-H.,Program in Molecular Medicine | Lin S.-E.,Taipei Medical University Hospital | And 13 more authors.
Stem Cells | Year: 2013

Tumor cells have long been observed to share several biological characteristics with normal stem/progenitor cells; however, the oncogenic mechanisms underlying the lung stem/progenitor cell signaling remain elusive. Here, we report that SOX2, a self-renewal factor in lung stem/progenitor cells, is highly expressed in a subclass of lung cancer cells, the proliferation, survival, and chemoresistance of which are dependent on SOX2 signaling. Overexpression of SOX2 promotes oncogenic phenotypes in lung cancer cells; knockdown of SOX2 attenuated cell proliferation. We observed that SOX2 increased the expression of epidermal growth factor receptor (EGFR), and EGFR activation further upregulated SOX2 levels, forming a positive feedback loop. SOX2 expression promoted chemoresistance, and silencing of SOX2 perturbed mitochondrial function, causing marked apoptosis and autophagy. SOX2 induced BCL2L1, the ectopic expression of which rescued the effects of SOX2 silencing on apoptosis, autophagy, and mitochondrial function. SOX2 promoted tumor formation, along with increased cell proliferation in a xenograft mouse model. SOX2 expression is associated with poor prognosis in lung cancer patients; moreover, SOX2, EGFR, and BCL2L1 expression levels were significantly correlated in lung tumors. Our findings support the emerging role of SOX2 in cell proliferation and survival by eliciting oncogenic EGFR and BCL2L1 signaling with potential applications as a prognosis marker and a therapeutic target in lung cancer. © AlphaMed Press.


Ding W.,Program in Molecular Medicine | Smulan L.J.,Program in Molecular Medicine | Hou N.S.,University of British Columbia | Taubert S.,University of British Columbia | And 2 more authors.
Cell Metabolism | Year: 2015

s-adenosylmethionine (SAM) is the sole methyl donor modifying histones, nucleic acids, and phospholipids. Its fluctuation affects hepatic phosphatidylcholine (PC) synthesis or may be linked to variations in DNA or histone methylation. Physiologically, low SAM is associated with lipid accumulation, tissue injury, and immune responses in fatty liver disease. However, molecular connections among SAM limitation, methyltransferases, and disease-associated phenotypes are unclear. We find that low SAM can activate or attenuate Caenorhabditis elegans immune responses. Immune pathways are stimulated downstream of PC production on a non-pathogenic diet. In contrast, distinct SAM-dependent mechanisms limit survival on pathogenic Pseudomonas aeruginosa. C. elegans undertakes a broad transcriptional response to pathogens and we find that low SAM restricts H3K4me3 at Pseudomonas-responsive promoters, limiting their expression. Furthermore, this response depends on the H3K4 methyltransferase set-16/MLL. Thus, our studies provide molecular links between SAM and innate immune functions and suggest that SAM depletion may limit stress-induced gene expression. © 2015 Elsevier Inc.


PubMed | Program in Molecular Medicine, University of British Columbia and Washington State University
Type: Journal Article | Journal: Cell metabolism | Year: 2015

s-adenosylmethionine (SAM) is the sole methyl donor modifying histones, nucleic acids, and phospholipids. Its fluctuation affects hepatic phosphatidylcholine (PC) synthesis or may be linked to variations in DNA or histone methylation. Physiologically, low SAM is associated with lipid accumulation, tissue injury, and immune responses in fatty liver disease. However, molecular connections among SAM limitation, methyltransferases, and disease-associated phenotypes are unclear. We find that low SAM can activate or attenuate Caenorhabditis elegans immune responses. Immune pathways are stimulated downstream of PC production on a non-pathogenic diet. In contrast, distinct SAM-dependent mechanisms limit survival on pathogenic Pseudomonas aeruginosa. C. elegans undertakes a broad transcriptional response to pathogens and we find that low SAM restricts H3K4me3 at Pseudomonas-responsive promoters, limiting their expression. Furthermore, this response depends on the H3K4 methyltransferase set-16/MLL. Thus, our studies provide molecular links between SAM and innate immune functions and suggest that SAM depletion may limit stress-induced gene expression.


Smulan L.J.,Program in Molecular Medicine | Ding W.,Program in Molecular Medicine | Freinkman E.,Whitehead Institute For Biomedical Research | Gujja S.,Program in Molecular Medicine | And 2 more authors.
Cell Reports | Year: 2016

Lipogenesis requires coordinated expression of genes for fatty acid, phospholipid, and triglyceride synthesis. Transcription factors, such as SREBP-1 (Sterol regulatory element binding protein), may be activated in response to feedback mechanisms linking gene activation to levels of metabolites in the pathways. SREBPs can be regulated in response to membrane cholesterol and we also found that low levels of phosphatidylcholine (a methylated phospholipid) led to SBP-1/SREBP-1 maturation in C. elegans or mammalian models. To identify additional regulatory components, we performed a targeted RNAi screen in C. elegans, finding that both lpin-1/Lipin 1 (which converts phosphatidic acid to diacylglycerol) and arf-1.2/ARF1 (a GTPase regulating Golgi function) were important for low-PC activation of SBP-1/SREBP-1. Mechanistically linking the major hits of our screen, we find that limiting PC synthesis or LPIN1 knockdown in mammalian cells reduces the levels of active GTP-bound ARF1. Thus, changes in distinct lipid ratios may converge on ARF1 to increase SBP-1/SREBP-1 activity. © 2016 The Authors


PubMed | Program in Molecular Medicine
Type: | Journal: BMC immunology | Year: 2015

Sepsis is a dynamic infectious disease syndrome characterized by dysregulated inflammatory responses.Despite decades of research, improvements in the treatment of sepsis have been modest. These limited advances are likely due, in part, to multiple factors, including substantial heterogeneity in septic syndromes, significant knowledge gaps in our understanding of how immune cells function in sepsis, and limitations in animal models that accurately recapitulate the human septic milieu. The goal of this brief review is to describe current challenges in understanding immune cell functions during sepsis. We also provide a framework to guide scientists and clinicians in research and patient care as they strive to better understand dysregulated cell responses during sepsis.Additional, well-designed translational studies in sepsis are critical for enhancing our understanding of the role of immune cells in sepsis.


PubMed | Program in Molecular Medicine, University of Utah, Intermountain Medical Center and Program in Molecular Medicine.
Type: Journal Article | Journal: The journals of gerontology. Series A, Biological sciences and medical sciences | Year: 2015

Aging-related changes in platelet and monocyte interactions may contribute to adverse outcomes in sepsis but remain relatively unexamined. We hypothesized that differential platelet-monocyte aggregate (PMA) formation in older septic patients alters inflammatory responses and mortality.We prospectively studied 113 septic adults admitted to the intensive care unit with severe sepsis or septic shock. Patients were dichotomized a priori into one of two groups: older (age 65 years, n = 28) and younger (age < 65 years, n = 85). PMA levels were measured in whole blood via flow cytometry within 24 hours of admission. Plasma levels of IL-6 and IL-8, proinflammatory cytokines produced by monocytes upon PMA formation, were determined by commercial assays. Patients were followed for the primary outcome of 28-day, all-cause mortality.Elevated PMA levels were associated with an increased risk of mortality in older septic patients (hazard ratio for mortality 5.64, 95% confidence interval 0.64-49.61). This association remained after adjusting for potential confounding variables in multivariate regression. Receiver operating curve analyses demonstrated that PMA levels greater than or equal to 8.43% best predicted 28-day mortality in older septic patients (area under the receiver operating curve 0.82). Plasma IL-6 and IL-8 levels were also significantly higher in older nonsurvivors. In younger patients, neither PMA levels nor plasma monokines were significantly associated with mortality.Increased PMA formation, and associated proinflammatory monokine synthesis, predicts mortality in older septic patients. Although larger studies are needed, our findings suggest that heightened PMA formation in older septic patients may contribute to injurious inflammatory responses and an increased risk of mortality.


PubMed | Program in Molecular Medicine and Whitehead Institute For Biomedical Research
Type: Journal Article | Journal: Cell reports | Year: 2016

Lipogenesis requires coordinated expression of genes for fatty acid, phospholipid, and triglyceride synthesis. Transcription factors, such as SREBP-1 (Sterol regulatory element binding protein), may be activated in response to feedback mechanisms linking gene activation to levels of metabolites in the pathways. SREBPs can be regulated in response tomembrane cholesterol and we also found that low levels of phosphatidylcholine (a methylated phospholipid) led to SBP-1/SREBP-1 maturation in C.elegans or mammalian models. To identify additional regulatory components, we performed a targeted RNAi screen in C.elegans, finding that both lpin-1/Lipin 1 (which converts phosphatidic acid to diacylglycerol) and arf-1.2/ARF1 (a GTPase regulating Golgi function) were important for low-PC activation of SBP-1/SREBP-1. Mechanistically linking the major hits of our screen, we find that limiting PCsynthesis or LPIN1 knockdown in mammalian cells reduces the levels of active GTP-bound ARF1. Thus, changes in distinct lipid ratios may converge on ARF1 to increase SBP-1/SREBP-1 activity.


PubMed | Program in Molecular Medicine, Pfizer, University of Massachusetts Medical School and Cardiovascular and Metabolic Research Unit
Type: | Journal: Nature communications | Year: 2015

Signalling pathways that control endothelial cell (EC) permeability, leukocyte adhesion and inflammation are pivotal for atherosclerosis initiation and progression. Here we demonstrate that the Sterile-20-like mitogen-activated protein kinase kinase kinase kinase 4 (MAP4K4), which has been implicated in inflammation, is abundantly expressed in ECs and in atherosclerotic plaques from mice and humans. On the basis of endothelial-specific MAP4K4 gene silencing and gene ablation experiments in Apoe(-/-) mice, we show that MAP4K4 in ECs markedly promotes Western diet-induced aortic macrophage accumulation and atherosclerotic plaque development. Treatment of Apoe(-/-) and Ldlr(-/-) mice with a selective small-molecule MAP4K4 inhibitor also markedly reduces atherosclerotic lesion area. MAP4K4 silencing in cultured ECs attenuates cell surface adhesion molecule expression while reducing nuclear localization and activity of NFB, which is critical for promoting EC activation and atherosclerosis. Taken together, these results reveal that MAP4K4 is a key signalling node that promotes immune cell recruitment in atherosclerosis.

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