The GTPase RAB20 is a HIF target with mitochondrial localization mediating apoptosis in hypoxia

AbstractHypoxia is a common pathogenic stress, which requires adaptive activation of the Hypoxia-inducible transcription factor (HIF). In concert transcriptional HIF targets enhance oxygen availability and simultaneously reduce oxygen demand, enabling survival in a hypoxic microenvironment. Here, we describe the characterization of a new HIF-1 target gene, Rab20, which is a member of the Rab family of small GTP-binding proteins, regulating intracellular trafficking and vesicle formation. Rab20 is directly regulated by HIF-1, resulting in rapid upregulation of Rab20 mRNA as well as protein under hypoxia. Furthermore, exogenous as well as endogenous Rab20 protein colocalizes with mitochondria. Knockdown studies reveal that Rab20 is involved in hypoxia induced apoptosis. Since mitochondria play a key role in the control of cell death, we suggest that regulating mitochondrial homeostasis in hypoxia is a key function of Rab20. Furthermore, our study implicates that cellular transport pathways play a role in oxygen homeostasis. Hypoxia-induced Rab20 may influence tissue homeostasis and repair during and after hypoxic stress

Renal tubular HIF-2α expression requires VHL inactivation and causes fibrosis and cysts.

The Hypoxia-inducible transcription Factor (HIF) represents an important adaptive mechanism under hypoxia, whereas sustained activation may also have deleterious effects. HIF activity is determined by the oxygen regulated α-subunits HIF-1α or HIF-2α. Both are regulated by oxygen dependent degradation, which is controlled by the tumor suppressor "von Hippel-Lindau" (VHL), the gatekeeper of renal tubular growth control. HIF appears to play a particular role for the kidney, where renal EPO production, organ preservation from ischemia-reperfusion injury and renal tumorigenesis are prominent examples. Whereas HIF-1α is inducible in physiological renal mouse, rat and human tubular epithelia, HIF-2α is never detected in these cells, in any species. In contrast, distinct early lesions of biallelic VHL inactivation in kidneys of the hereditary VHL syndrome show strong HIF-2α expression. Furthermore, knockout of VHL in the mouse tubular apparatus enables HIF-2α expression. Continuous transgenic expression of HIF-2α by the Ksp-Cadherin promotor leads to renal fibrosis and insufficiency, next to multiple renal cysts. In conclusion, VHL appears to specifically repress HIF-2α in renal epithelia. Unphysiological expression of HIF-2α in tubular epithelia has deleterious effects. Our data are compatible with dedifferentiation of renal epithelial cells by sustained HIF-2α expression. However, HIF-2α overexpression alone is insufficient to induce tumors. Thus, our data bear implications for renal tumorigenesis, epithelial differentiation and renal repair mechanisms

Die Rolle von HIF bei zellulären Transformationsprozessen: I. HIF-2 alpha im renalen Tubulus – ein transgenes Mausmodel II. Identifizierung und Charakterisierung von Lysyloxidasen als tumorfördernde HIF-Zielgene

This thesis presents new insights into the important role of HIF expression during development and progression of tumours. The transgenic mouse model with specific overexpression of HIF-2 alpha in renal epithelial cells indicates the critical role of HIF-2 alpha for renal degeneration, which may finally result in carcinogenesis. Furthermore, the knowledge about the influence of HIF and its target gene activation on cellular transformation is extended, confirming a suggested pathway from hypoxia to E-cadherin repression beeing a lysyl oxidase-depedent mechanism, possibly influencing the process of EMT during tumour evolution.Diese Arbeit zeigt neue Erkenntnisse über den Einfluß der HIF-Expression während der Tumorentstehung und –progression. Das transgene Mausmodel mit spezifischer HIF-2 alpha-Expression in renalen Tubulusepithelzellen zeigt die bedeutende Rolle von HIF-2 für degenerative Prozesse in der Niere, welche zur renalen Karzinogenese führen könnten. Desweiteren konnte der Einfluß von HIF und der Aktivierung seiner Zielgene für die zelluläre Transformation weiter charakterisiert werden. Die vermutete Lysyloxidsase-Abhängigkeit der Hypoxie-induzierten E-cadherin-Repression konnte bestätigt werden und gibt neue Hinweise auf den bedeutenden Einfluß von Hypoxie/HIF auf den Prozess der EMT während der Tumorevolution

Comparative analysis of methods for strategic security research planning

Within the FP7-supported project “Evaluation of critical and emerging technologies for the elaboration of a security research agenda” (ETCETERA, Oct. 2011 to Nov. 2013), technologies that are critical for security functions in Europe were checked for dependencies on extra-European sources. Furthermore, technologies that are now just emerging and will reach maturity in 10 to 15 years were assessed concerning their relevance for European security. In order to achieve these goals, a plethora of methods was employed, including desktop research, scientometrics (e.g., bibliometrics and patentometrics), a Weighted-Bit Assessment Method to aggregate expert opinion, an adapted TEPID-OIL filtering methodology (ITIPOLITRE), parallel workshops applying the World Café method, a dedicated Security Emerging Technology Assessment Game(SETAG) and a complex scenario process. Some of these methods have been specifically developed for the ETCTERA project and/or applied in the context of security research planning for the first time. A comparative analysis of the methods applied was performed, and recommendations for their employment in security research planning were made. This will facilitate better choices concerning methodology in future planning efforts

Recommendations for an emerging security technology research agenda (ESTRA): Deliverable D6.1

ETCETERA: EvaluaTion of Critical and Emerging security Technologies for the Elaboration of a strategic Research Agend

Scenario-oriented assessment of hazardous biological agents

The aim of this study is to elaborate a system that will enable easy, yet sound, communication between persons of different background on the topic of dangers and risks associated with the liberation of potentially hazardous biological agents. This system could then be used to assist planning procedures involving people with different professional backgrounds, e.g. for identifying, discussing and assessing possible gaps in security concepts and associated research needs. As a first step the feasibility of such a system assisting biological hazard assessment is tested, including the analysis of possible limitations

Deletion of the oxygen-dependent degradation domain results in impaired transcriptional activity of hypoxia-inducible factors

Hypoxia-inducible factors (HIF1α/HIF2α) are key transcription factors that promote angiogenesis. The overexpression of degradation-resistant HIF mutants is considered a promising pro-angiogenic therapeutic tool. We compared the transcriptional activity of HIF1α/HIF2α mutants that obtained their resistance to oxygen-dependent degradation either by deletion of their entire oxygen-dependent degradation (ODD) domain or by replacement of prolyl residues that are crucial for oxygen-dependent degradation. Although all HIF mutants translocated into the nucleus, HIF1α and HIF2α mutants inclosing the point mutations were significantly more effective in trans-activating the target gene VEGF and in inducing tube formation of endothelial cells than mutants lacking the complete ODD domain

Expression of HIF-1α and HIF-2α in the human kidney.

<p>HIF-1α and HIF-2α expression was analyzed by immunohistochemistry in human kidneys. After carbon monoxide (CO) intoxication HIF-1α accumulation was detected in tubular epithelial cells (A) and HIF-2α was detected in interstitial cells and in the glomeruli, indicated by arrows (B). In kidneys of RCC patients HIF-1α and HIF-2α were detected in the tumor tissue as well as in the adjacent kidney (C and D). In the latter HIF-1α was found in tubular epithelial cells (E) and HIF-2α restricted to interstitial cells (F).</p

HIF-1α and HIF-2α expression in mouse kidney.

<p>The physiological expression pattern of HIF-1α and HIF-2α was analyzed by immunohistochemistry on kidney sections of normoxic and hypoxic (6 h, 7% O₂) mice. HIF-1α expression was detected in the nuclei of renal tubular epithelial cells after hypoxic stimulation, whereas HIF-2α accumulated in interstitial and glomerular cells.</p