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To read the article visit the link below.

http://link.springer.com/article/10.1007%2Fs00125-014-3430-6

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Published in the journal “Diabetologia”


http://link.springer.com/article/10.1007%2Fs00125-014-3429-z


Obesity is a global epidemic resulting from increased energy intake, which alters energy homeostasis and results in an imbalance in fat storage and breakdown. G0/G1 switch gene 2 (G0s2) has been recently characterised in vitro as an inhibitor of adipose triglyceride lipase (ATGL), the rate limiting step in fat catabolism. In the current study we aim to functionally characterise G0s2 within the physiological context of a mouse model.  We generated a mouse model in which G0s2 was deleted. The homozygous G0s2 knockout (G0s2/) mice were studied over a period of 22 weeks. Metabolic variables were measured including body weight and body composition, food intake, glucose and insulin tolerance tests, energy metabolism and thermogenesis.  

 

We report that G0s2 inhibits ATGL and regulates lipolysis and energy metabolism in vivo. G0s2/mice are lean, resistant to weight gain induced by a high-fat diet and are glucose tolerant and insulin sensitive. The white adipose tissue of G0s2/mice has enhanced lipase activity and adipocytes showed enhanced stimulated lipolysis. Energy metabolism in the G0s2/mice is shifted towards enhanced lipid metabolism and increased thermogenesis. G0s2/mice showed enhanced cold tolerance and increased expression of thermoregulatory and oxidation genes within white adipose tissue, suggesting enhanced browningof the white adipose tissue.  Our data show that G0s2 is a physiological regulator of adiposity and energy metabolism and is a potential target in the treatment of obesity and insulin resistance.

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Published in the “Journal of Virology” and available online at:

http://jvi.asm.org/content/early/2014/09/04/JVI.00933-14.abstract

Abstract

Adenovirus type 5 E4orf4 is a multifunctional protein that regulates viral gene expression. The activities of E4orf4 are mainly mediated through binding to protein phosphatase 2A (PP2A). E4orf4 recruits target phosphoproteins into complexes with PP2A resulting in dephosphorylation of host factors, such as SR splicing factors. In the current study, we utilized immunoprecipitation followed by mass spectrometry to identify novel E4orf4 interacting proteins. In this manner we identified Nup205, a component of the nuclear pore complex (NPC) as an E4orf4 interacting partner. The Arginine Rich Motif (ARM) of E4orf4 was required for interaction with Nup205 and for nuclear localization of E4orf4. ARMs are commonly found on viral nuclear proteins and we observed that Nup205 interacts with three different nuclear viral proteins containing ARMs. E4orf4 formed a trimolecular complex containing both Nup205 and PP2A. Furthermore, Nup205 complexed with E4orf4 was hypophosphorylated suggesting the protein is specifically targeted for dephosphorylation. An adenovirus mutant that does not express E4orf4 (Orf4) displayed elevated early and reduced late gene expression relative to wild-type. We observed that knockdown of Nup205 resulted in the same phenotype as the Orf4 virus suggesting that the proteins function as a complex to regulate viral gene expression. Furthermore, knockdown of Nup205 resulted in a more than a four-fold reduction in the replication of wild-type adenovirus. Our data show for first time that Ad5 E4orf4 interacts with and modifies the NPC and that Nup205-E4orf4 binding is required for normal regulation of viral gene expression and viral replication.

Importance 

Nuclear pore complexes (NPCs) are highly regulated conduits in the nuclear membrane that control transport of macromolecules between the nucleus and cytoplasm. Viruses that replicate in the nucleus must negotiate the NPC during nuclear entry, and viral DNA, mRNA, and proteins must then be exported from the nucleus. Several types of viruses restructure the NPC to facilitate replication and the current study shows that adenovirus type 5 (Ad5) utilizes a novel mechanism to modify NPC function. We demonstrate that a subunit of the NPC, Nup205, is a phosphoprotein that is actively dephosphorylated by the Ad5 encoded protein E4orf4. Moreover, Nup205 is required by Ad5 to regulate viral gene expression and efficient viral replication. Nup205 is a non-structural subunit that is responsible for the gating functions of the NPC and this study suggests for the first time that the NPC is regulated by phosphorylation both during normal physiology and viral infection.

 

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Modulation of mitochondrial apoptosis in mitosis. (a) Central to mitochondrial apoptosis is the permeabilization of mitochondrial outer membrane by Bax and/or Bak multimers, leading to Cytochrome c release in the cytoplasm and subsequent activation of Caspase-9. This process is on one hand inhibited in mitosis by CDK1 (by direct phosphorylation of Caspase-2/8/9) and on the other hand promoted by inhibition of ‘Bax/Bak inhibitors’, that is, Bcl-2, Bcl-xL and Mcl-1. This latter phenomenon can occur either by direct inactivation of Bcl-2 and Bcl-xL by phosphorylation or by phosphorylation-dependent degradation of Mcl-1. Such degradation can have CDK1 and/or CKII/JNK/p38 as priming kinases and the APC/C-Cdc20 and/or SCF-FBW7 as phosphorylation-dependent Ubiquitin ligases, respectively. (b) Aurora A (and/or possibly Aurora B) kinase can reversibly phosphorylate Bim in mitosis and this modification is counteracted by the action of PP2A phosphatase. Phosphorylated Bim at Ser94/98 is selectively bound by SCF-βTrCP1, polyubiquitinated and degraded via the proteasome. Although the role of Bim in mitotic death remains to be fully understood, its regulation at the level of protein stability reveals how Aurora inhibitors might be used to promote cell death in mitosis.

The full editorial, published in Cell Death and Differentiation, can be found here: 

http://www.nature.com/cdd/journal/v20/n12/full/cdd2013140a.html

Published in the journal “Cell Death and Differentiation” and available online at:

http://www.nature.com/cdd/journal/vaop/ncurrent/full/cdd201393a.html
 
Abstract 
 
Bcl-2-interacting mediator of cell death (Bim) is a pro-apoptotic B-cell lymphoma 2 family member implicated in numerous apoptotic stimuli. In particular, Bim is required for cell death mediated by antimitotic agents, however, mitotic regulation of Bim remains poorly understood. Here, we show that the major splice variant of Bim, BimEL, is regulated during mitosis by the Aurora A kinase and protein phosphatase 2A (PP2A). We observed that BimEL is phosphorylated by Aurora A early in mitosis and reversed by PP2A after mitotic exit. Aurora A phosphorylation stimulated binding of BimEL to the F-box protein beta-transducin repeat containing E3 ubiquitin protein ligase and promoted ubiquitination and degradation of BimEL. These findings describe a novel mechanism by which the oncogenic kinase Aurora A promotes cell survival during mitosis by downregulating proapoptotic signals. Notably, we observed that knockdown of Bim significantly increased resistance of cells to the Aurora A inhibitor MLN8054. Inhibitors of Aurora A are currently under investigation as cancer chemotherapeutics and our findings suggest that efficacy of this class of drugs may function in part by enhancing apoptotic activity of BimEL.

Published in the journal “Cancer Research” and available online today at:

http://cancerres.aacrjournals.org/content/early/2012/01/14/0008-5472.CAN-11-2348.full.pdf+html

Abstract

Several types of collagen contain cryptic antiangiogenic non-collagenous domains that are released upon proteolysis of extracellular matrix (ECM). Among those is Arresten, a collagen-derived antiangiogenic factor (CDAF) that is processed from alpha 1 collagen 4. However, the conditions under which Arresten is released from collagen 4 in vivo or whether the protein functions in tumor suppressor pathways remain unknown. Here we show that p53 induces the expression of 1 collagen 4 and release of Arresten containing fragments from the ECM. Comparison of the transcriptional activation of COL4A1 with other CDAF containing genes revealed that COL4A1 is a major antiangiogenic gene induced by p53 in human adenocarinoma cells. p53 directly activated transcription of the COL4A1 gene by binding to an enhancer region 26kbp downstream of its 3 prime end. p53 also stabilized the expression of full length 1 collagen 4 by upregulation of alpha (II) prolyl-hydroxylase and increased the release of Arresten in the ECM through an MMP-dependent mechanism. The resulting upregulation of alpha 1 collagen 4 and production of Arresten by the tumor cells significantly inhibited angiogenesis and limited tumor growth in vivo. Furthermore, we demonstrate that immunostaining of Arresten correlated with p53 status in human prostate cancer specimens. Our findings therefore link the production of Arresten to the p53 tumor suppressor pathway and demonstrate a novel mechanism through which p53 can inhibit angiogenesis.

Below is a figure from the paper showing a Tumour Microarray linking status of p53 in human prostate cancers to expression of the anti-angiogenic factor Arresten.

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Published in the Journal of Virology and available online here.

Abstract

The chicken anemia virus (CAV) protein Apoptin is a small 13.6 kDa protein that has the intriguing activity of inducing G2/M arrest and apoptosis specifically in cancer cells by a mechanism that is independent of p53.  The activity of Apoptin is regulated at the level of localization. Whereas Apoptin is cytoplasmic in primary cells and does not affect cell growth, it localizes to the nucleus in transformed cells where it induces apoptosis. The properties of cancer cells that are responsible for activating the pro-apoptotic activities of Apoptin remain unclear. In the current study we show that DNA damage response (DDR) signaling is required to induce Apoptin nuclear localization in primary cells. Induction of DNA damage in combination with Apoptin expression was able to induce apoptosis in primary cells. Conversely, chemical or RNAi inhibition of DDR signaling by ATM and DNA-PK was sufficient to cause Apoptin to localize in the cytoplasm of transformed cells. Interestingly, nuclear localization of Apoptin in primary cells was able to inhibit the formation of DNA damage foci containing 53BP1. Apoptin has been shown to bind and inhibit the anaphase promoting complex/cyclosome (APC/C). We observe that Apoptin is able to inhibit formation of DNA damage foci by targeting the APC/C associated factor MDC1 for degradation. We suggest that these results may point to a novel mechanism of DDR inhibition during viral infection.

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Immunohistochemistry of the Apoptin protein in primary cells.