Kuştepe

Taha Toros Arşivi, Dosya Adı: İstanbul Genel Dokümanları. Not: Gazetenin "İstanbul" köşesinde yayımlanmıştır.İstanbul Kalkınma Ajansı (TR10/14/YEN/0033) İstanbul Development Agency (TR10/14/YEN/0033

Identification of a nuclear export signal in the catalytic subunit of AMP-activated protein kinase

AMP-activated protein kinase (AMPK) is an energy sensor that regulates both cellular and organismal energy levels through phosphorylation, leading to the activation or inhibition of target proteins. AMPK functions as a heterotrimeric complex consisting of a catalytic α subunit and regulatory β and γ subunits. Until recently, research on AMPK was based on cell culture studies and the use of non-specific drugs. Since there are multiple isoforms of each subunit of AMPK, it was difficult to characterize AMPK’s role due to genetic redundancy. In our lab, we identified the first null mutation of the AMPK α subunit in the fruit fly, Drosophila Melanogaster. Studying AMPK in fruit flies is somewhat ideal since all of its subunit functions and domains are conserved from flies to human and also since there are only one gene for each subunit of AMPK, overcoming the redundancy effect. During my graduate study, we have characterized AMPK regulation in three distinct aspects. First, we identified AMPK’s role in cell polarity and cell division. We demonstrated loss of AMPK activity causes loss of epithelial cell polarity and over proliferation under energetic stress. Second, we characterized AMPK’s role at the whole organism level. Reduced AMPK causes hypersensitivity to starvation conditions and this causes a shortened life span and higher locomoter activity under energetic stress. In addition, loss of AMPK function causes inability to process and store lipids efficiently. Third, we identified a highlyconserved nuclear export sequence (NES) at the very C-terminal end of AMPKα. We showed that the loss of this sequence leads to increased nuclear localization. A transgenic fly expressing a truncated copy of AMPKα does not rescue the lethality or neuronal phenotype of AMPKα null mutant flies. A truncated copy also shows a reduced phosphorylation rate -- proposing AMPK’s phosphorylation and activation takes place in the cytoplasm

LKB1 and AMPK maintain epithelial cell polarity under energetic stress

LKB1 is mutated in both familial and spontaneous tumors, and acts as a master kinase that activates the PAR-1 polarity kinase and the adenosine 5′monophosphate–activated kinase (AMPK). This has led to the hypothesis that LKB1 acts as a tumor suppressor because it is required to maintain cell polarity and growth control through PAR-1 and AMPK, respectively. However, the genetic analysis of LKB1–AMPK signaling in vertebrates has been complicated by the existence of multiple redundant AMPK subunits. We describe the identification of mutations in the single Drosophila melanogaster AMPK catalytic subunit AMPKα. Surprisingly, ampkα mutant epithelial cells lose their polarity and overproliferate under energetic stress. LKB1 is required in vivo for AMPK activation, and lkb1 mutations cause similar energetic stress–dependent phenotypes to ampkα mutations. Furthermore, lkb1 phenotypes are rescued by a phosphomimetic version of AMPKα. Thus, LKB1 signals through AMPK to coordinate epithelial polarity and proliferation with cellular energy status, and this might underlie the tumor suppressor function of LKB1

Surgical Removal of an Extrauterine Device Migrating to Appendix

Intrauterine devices (IUDs) remain highly effective reversible family planning methods in developing countries. We aimed to report one of the complications of extrauterine and intrauterine devices. A 44-year-old woman was admitted to our hospital with mislocated intrauterine device and abnormal uterine bleeding. Extrauterine IUD device was proven by ultrasound and X-ray. She had normal blood test count with a negative pregnancy test. There are several cases of complications with intrauterine devices, but this is the first case report about an extrauterine IUD embedded by inflame enlarged appendix presenting with abnormal uterine bleeding. Although intrauterine devices are a common safe method for contraception, there is no risk-free insertion even with advanced ultrasounds. A regular self-examination should be taught to the patients and ultrasonography should be performed in the follow-up of the patients especially for inserted devices during lactation period. Extrauterine IUDs can be successfully removed by laparotomy

Differential regulation by AMP and ADP of AMPK complexes containing different γ subunit isoforms

The γ subunits of heterotrimeric AMPK complexes contain the binding sites for the regulatory adenine nucleotides AMP, ADP and ATP. We addressed whether complexes containing different γ isoforms display different responses to adenine nucleotides by generating cells stably expressing FLAG-tagged versions of the γ 1, γ 2 or γ 3 isoform. When assayed at a physiological ATP concentration (5 mM), γ 1- and γ 2-containing complexes were allosterically activated almost 10-fold by AMP, with EC50 values one to two orders of magnitude lower than the ATP concentration. By contrast, γ 3 complexes were barely activated by AMP under these conditions, although we did observe some activation at lower ATP concentrations. Despite this, all three complexes were activated, due to increased Thr172 phosphorylation, when cells were incubated with mitochondrial inhibitors that increase cellular AMP. With γ 1 complexes, activation and Thr172 phosphorylation induced by the upstream kinase LKB1 [liver kinase B1; but not calmodulin-dependent kinase kinase (CaMKKβ)] in cell-free assays was markedly promoted by AMP and, to a smaller extent and less potently, by ADP. However, effects of AMP or ADP on activation and phosphorylation of the γ 2 and γ 3 complexes were small or insignificant. Binding of AMP or ADP protected all three γ subunit complexes against inactivation by Thr172 dephosphorylation; with γ 2 complexes, ADP had similar potency to AMP, but with γ 1 and γ 3 complexes, ADP was less potent than AMP. Thus, AMPK complexes containing different γ subunit isoforms respond differently to changes in AMP, ADP or ATP. These differences may tune the responses of the isoforms to fit their differing physiological roles

AMP-activated protein kinase:a cellular energy sensor that comes in twelve flavours

The AMP‐activated protein kinase (AMPK) is a sensor of cellular energy status that is expressed in essentially all eukaryotic cells, suggesting that it arose during early eukaryotic evolution. It occurs universally as heterotrimeric complexes containing catalytic α subunits and regulatory β and γ subunits. Although Drosophila melanogaster contains single genes encoding each subunit, in mammals, each subunit exists as multiple isoforms encoded by distinct genes, giving rise to up to 12 heterotrimeric combinations. The multiple isoforms of each subunit are 2R‐ohnologues generated by the two rounds of whole genome duplication that occurred at the evolutionary origin of the vertebrates. Although the differential roles of these isoform combinations remain only partly understood, there are indications that they may have different subcellular locations, different inputs and outputs, and different functions. The multiple isoforms are of particular interest with respect to the roles of AMPK in cancer because the genes encoding some isoforms, such as PRKAA1 and PRKAB2 (encoding α1 and β2), are quite frequently amplified in tumour cells, whereas the genes encoding others, such as PRKAA2 (encoding α2), tend to be mutated, which, in some but not all cases, may result in a loss of function. Thus, although AMPK acts downstream of the tumour suppressor liver kinase B1, and some of its isoform combinations may act as tumour suppressors that restrain the growth and proliferation of tumour cells, other isoform combinations may paradoxically act as oncogenes, perhaps by aiding the survival of tumour cells undergoing environmental stresses such as hypoxia or nutrient deprivation

Demographic and microbial characteristics of extrapulmonary tuberculosis cases diagnosed in Malatya, Turkey, 2001-2007

<p>Abstract</p> <p>Background</p> <p>Extrapulmonary tuberculosis (EPTB) has an increasing rate in Turkey. The reason remains largely unknown. A better understanding of the demographic and microbial characteristics of EPTB in the Turkish population would extend the knowledgebase of EPTB and allow us to develop better strategies to control tuberculosis (TB).</p> <p><b>Methods</b></p> <p>We retrospectively evaluated clinical and laboratory data of 397 bacteriologically-confirmed TB cases diagnosed during an eight year-period using by chi-square analysis and multivariate logistic regression model.</p> <p>Results</p> <p>Of the 397 study patients, 103 (25.9%) had EPTB and 294 (74.1%) had pulmonary tuberculosis (PTB). The most commonly seen two types of EPTB were genitourinary TB (27.2%) and meningeal TB (19.4%). TB in bone/joints, pleural cavity, lymph nodes, skin, and peritoneal cavity occurred at a frequency ranging from 9.7% to 10.7%. The age distribution was significantly different (P < 0.01) between PTB and EPTB, with patients older than 45 years tending to have an increased risk of EPTB. Furthermore, the distribution of different types of EPTB differed significantly among age groups (P = 0.03). Meningeal and bone and/or joint TB were more commonly observed among the male patients, while lymphatic, genitourinary, and peritoneal TB cases were more frequently seen among females. Unique strain infection was statistically significantly associated with EPTB (OR: 2.82, 95% CI [1.59, 5.00])</p> <p>Conclusions</p> <p>EPTB accounted for a significant proportion of TB cases in Malatya, Turkey between 2001 and 2007. The current study has provided an insight into the dynamics of EPTB in Malatya, Turkey. However, the risk factors for having EPTB in Malatya, Turkey remain to be assessed in future studies using population-based or randomly selected sample.</p

Tilly's Technical Accounts and Standard Stories Explored in Financial Markets:The Case of the Istanbul Stock Exchange

In this article, I follow the lead opened up by Tilly (1999, 2002) who was interested in people's storytelling. I do so by looking at sense-making and the legitimacy narratives of market actors in the Istanbul Stock Exchange. Tilly (2006, 2008) himself walked the narrative path and investigated Why and how people give reasons and how people attribute Credit and Blame to other's actions. These books provide insights into people's storytelling in the everyday situations of the home, courtrooms, hospitals, and so on. Nevertheless, Tilly's faith in the prevalence of technical accounts as modes of explanation in intra and inter organisational settings, and superior stories as mode of communication between expert givers and non-specialized receivers, seems to ignore informational uncertainties, intra and inter organisational hierarchies and conflicts pertinent to organisations. It is these factors that push standard stories (Tilly, 1999) into the forefront at the expense of technical stories within the story exchanges of market actors. I demonstrate this by presenting a sample of story exchanges from the Istanbul Stock Exchange under situations of informational uncertainties and organisational conflicts

Altered Metabolism and Persistent Starvation Behaviors Caused by Reduced AMPK Function in Drosophila

Organisms must utilize multiple mechanisms to maintain energetic homeostasis in the face of limited nutrient availability. One mechanism involves activation of the heterotrimeric AMP-activated protein kinase (AMPK), a cell-autonomous sensor to energetic changes regulated by ATP to AMP ratios. We examined the phenotypic consequences of reduced AMPK function, both through RNAi knockdown of the gamma subunit (AMPKγ) and through expression of a dominant negative alpha (AMPKα) variant in Drosophila melanogaster. Reduced AMPK signaling leads to hypersensitivity to starvation conditions as measured by lifespan and locomotor activity. Locomotor levels in flies with reduced AMPK function were lower during unstressed conditions, but starvation-induced hyperactivity, an adaptive response to encourage foraging, was significantly higher than in wild type. Unexpectedly, total dietary intake was greater in animals with reduced AMPK function yet total triglyceride levels were lower. AMPK mutant animals displayed starvation-like lipid accumulation patterns in metabolically key liver-like cells, oenocytes, even under fed conditions, consistent with a persistent starved state. Measurements of O2 consumption reveal that metabolic rates are greater in animals with reduced AMPK function. Lastly, rapamycin treatment tempers the starvation sensitivity and lethality associated with reduced AMPK function. Collectively, these results are consistent with models that AMPK shifts energy usage away from expenditures into a conservation mode during nutrient-limited conditions at a cellular level. The highly conserved AMPK subunits throughout the Metazoa, suggest such findings may provide significant insight for pharmaceutical strategies to manipulate AMPK function in humans