Molecular Physiology Lab

  • Research of adaptation to hypoxia at the cellular and organ-specific level
  • Mechanisms Up- and Downstream of Hypoxia-Inducible Factor in Acute Kidney Injury
  • Prevention of Cyclosporin-A mediated nephrotoxicity
  • Posttranscriptional control of the bHLH transcription factor hASH1/ Mash1
  • Cellular adaptation to hypoxia: Role of mRNA translation

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Main research topic of the Molecular Physiology Lab


Research topics focus on adaptation to hypoxia at the cellular and organ-specific level. Hypoxia per definition occurs when oxygen demand exceeds supply. Many physiological and pathophysiological conditions are attributed to the lack of oxygen, forcing cells to switch their energy metabolism and find a new balance between energy production and consumption. Understanding hypoxia tolerance is crucial e.g. in cancer treatment, while also being an attractive option to prevent hypoxia damage.

Research Projects

Mechanisms Up- and Downstream of Hypoxia-Inducible Factor in Acute Kidney Injury

(In collaboration with Prof. Dr. Christian Rosenberger. Part of the research unit "Hemodynamic Mechanisms of Acute Kidney Injury", funded by German Research Association FOR: 1368)

Renal hypoxia is widespread in acute kidney injury (AKI) of various etiologies. However, adaptation to hypoxia, conferred through the hypoxia-inducible factor (HIF), remains insufficient. HIF transcription factors are master regulators in the cellular adaptation to hypoxia. HIF target genes are involved in a complex regulatory network, e.g. adjusting energy metabolism to available oxygen levels, regulation of pH, inhibiting apoptosis, and activation of angiogenesis. So far, the cause for the relative lack of HIF activation in kidneys following AKI is unknown. Of note, limited renal HIF activation inversely correlates with tubular injury. The reasons for this phenomenon are likely complex, and may include mechanisms both up- and down-stream of HIF. At present, no specific therapy is available for AKI, and HIF-based interventions are among the most promising future prospects.

We recently reported that in Pax8-rt-TA based VHL knockout mice a profound and stable HIF activation in the entire nephron is inducible and protects from rhabdomyolysis induced kidney damage. Our data suggest an orchestrated metabolic shift towards increased glycolysis and glucose utilization by forced HIF activation. Evaluation of microarray data and subsequent gene ontology analysis revealed profound changes in gene expression by AKI per se, involving around 20% of the active genome. HIF activation in rhabdomyolysis-induced AKI creates a large and novel transcriptome, which is distinct from that observed in either AKI, or VHL knockout alone. We now seek for HIF mediated mechanisms of renal cell survival and factors mediating a limited HIF response to hypoxia in the kidney. We recently identified a micro-RNA that targets the Hif1a mRNA and is up-regulated in rhabdomyolysis mediated AKI. Currently, we are investigating the effect of in vivo micro-RNA inhibition on HIF activity and renal injury in AKI.

Prevention of Cyclosporin-A mediated nephrotoxicity

(In collaboration with Prof. Dr. Christian Rosenberger.)

The immunosuppressant Cyclosporin A (CsA) represents a standard of care in organ transplantation, as well as an important treatment option in a variety of autoimmune diseases. The immunosuppressive effect of CsA is mainly attributed to inhibition of calcineurin phosphatase activity, consequently favoring the inactive phosphorylated form of nuclear factor of activated T-cells (NFAT). However, renal toxicity is a serious adverse effect of CsA, but the underlying mechanism is insufficiently understood. Histological signs of renal CsA toxicity are all non-specific, and comprise arteriolar hyalinosis, isometric tubular vacuolization, tubular atrophy, striped tubular interstitial fibrosis and glomerular sclerosis. CsA acutely impairs renal haemodynamics, probably mediated by a combination of activated vasoconstrictors and inhibition of vasodilators. Finally, lowered perfusion causes local renal hypoxia leading to tubular interstitial fibrosis, the final stage of CsA-mediated renal dysfunction.

In contrast to the current view of CsA toxicity, our major finding is that CsA likely provokes episodic hypoxia. We demonstrated renal hypoxia 2 h after SC CsA injection, while 24 h later, values return within the range of controls. We concluded that chronic CsA administration (in clinical settings twice daily) translates into large daily fluctuations of pO2 in various kidney regions. Episodic periods of hypoxia and re-oxygenation as well as their possible implications on renal integrity and remodeling largely differs from conditions of permanent hypoxia. Thus, here we aim to investigate differences of episodic vs. permanent (either acute or chronic) hypoxia on cellular signaling and its participation in CsA mediated renal toxicity.

Posttranscriptional control of the bHLH transcription factor hASH1/ Mash1

The human achaete-scute homologue-1 (hASH1; ASCL1; Mash1) belongs to the bHLH (basic helix-loop-helix) family of transcription factors. Mash1/ hASH1 is expressed in both the central and the peripheral nervous system during development and promotes early neuronal differentiation as well as the specification of neuronal subtype identities. Furthermore, deregulation of Mash1/ hASH1 expression is correlated with a broad variety of tumors, including lung cancer, neuroendocrine tumors, foregut and midgut carcinoid tumors, pancreatic adenocarcinomas, islet cell tumors, gastrinomas, and parathyroid adenomas. Although the importance of Mash1/ hASH1 in neurogenesis and cancer has been well documented, the mechanism of its regulation and downstream targets are largely unknown. The aim of this project is the identification of trans-factors which modulate hASH1 gene expression at the level of posttranscriptional control. For instance, we identified hASH1 as a novel downstream target of FMRP (Fragile X-Mental Retardation Protein). FMRP was found to gate the translation of a large set of mRNAs in dendrites that are involved in synaptic plasticity. Dysfunction of the Fragile X-Mental Retardation-1 (FMR1) gene transcription is associated with neuronal disorders, such as the Fragile X-Syndrome (FXS) and the Fragile X-Associated Tremor/Ataxia Syndrome (FXTAS). Thus, improved translational efficiency of hASH1 mRNA by FMRP may represent an important regulatory switch in neuronal differentiation.

Currently we are investigating the role of oxygen in the alteration of hASH1 gene expression. Hypoxic suppression of hASH1 synthesis may participate in the hypoxia-induced dedifferentiation of tumor cells, especially of neuroblastoma cells. Although the initial cellular response to low oxygen concentrations is the suppression of energy consuming processes, including mRNA translation, our data suggest that inhibition of hASH1 in hypoxia is actively controlled by cis-regulatory elements, located in the hASH1 mRNA 3'UTR.

Cellular adaptation to hypoxia: Role of mRNA Translation

Under normal conditions oxidative phosphorylation constitutes the major source of the cellular energy intermediate adenosine triphosphate (ATP). High-rate energy production is a prerequisite for cells and tissues to achieve a high metabolic rate. Increased oxygen consumption or disturbance in oxygen supply result in decreased oxygen levels. Thus, hypoxia is a consequence of inadequate oxygen availability. As a consequence, multiple metabolic processes must be coordinated to achieve a net suppression that balances the rates of ATP production and ATP consumption at a new lower net rate of ATP turnover. The process of protein synthesis belongs to the most energy-consuming processes in the cell, accounting for 25-30% under resting conditions. Consequently, hypoxia causes metabolic rate depression and overall protein synthesis drops to ~10% compared to control level. Interestingly, it is well known that hundreds of hypoxia-sensitive genes are increasingly expressed, especially under prolonged hypoxic conditions. Thus, effective translation following oxygen deprivation seems to be possible. The aim of this project is to find out how specific mRNAs are selected to avoid the global suppression of mRNA translation.

Funding

  • Deutsche Forschungsgemeinschaft (DFG): FA 845/4 "Mechanisms Up- and Downstream of Hypoxia-Inducible Factor in Acute Kidney Injury", 2014-2017
  • Deutsche Forschungsgemeinschaft (DFG): FA 845/1 & FA 845/2 "Posttranskriptionelle Kontrolle des bHLH Transkriptionsfaktors Mash1", 2008-2014

Collaboration

  • Dr. M. Hultsröm, Department of Renal Physiology, Uppsala University, Sweden
  • Dr. A. Henrion-Caude, Institut National de la Santé et de la Recherche Médicale (INSERM), Université Paris Descartes, France
  • Prof. Dr. Antje Ostareck-Lederer & Prof. Dr. Dirk Ostareck, Klinik für Operative Intensivmedizin und Intermediate Care, Uniklinik RWTH Aachen
  • Prof. Jochen C. Meier, Zoological Institute, Division of Cell Physiology, TU Braunschweig
  • Prof. Dr. med. Ralf Mrowka, Experimentelle Nephrologie, Universitätsklinikum Jena
  • Prof. Dr. Christian Rosenberger, Institute für Nephrologie, CharitéUniversitätsmedizin Berlin
  • Prof. S. Bachmann, Dr. A. Paliege, Institut für Vegetative Anatomie, CharitéUniversitätsmedizin Berlin
  • Prof. H. Kühn, Dr. C. Ufer, Institut für Biochemie, CharitéUniversitätsmedizin Berlin

Publications (since 2006)

Editorial:

Fähling M: Regulating Gene Expression at the Post-Transcriptional Level: Spotlight on RNA-Binding Proteins. Current Protein and Peptide Science 13(4): 281-283, 2012

Reviews:

Fähling M, Seeliger E, Patzak A, Persson PB: Understanding and preventing contrast-induced acute kidney injury. Nat Rev Nephrol. 13(3): 169-180, 2017

Rosenberger C, Fähling M: Selective endothelin inhibition in diabetic nephropathy: Is it the Icing on the Cake? Acta Physiologica 212: 1-4, 2014

Fähling M, Persson PB: Oxygen Sensing, Uptake, Delivery, Consumption and Related Disorders. Acta Physiol (Oxf.) 205:191-193, 2012

Gorospe M, Tominaga K, Wu X, Fähling M, Ivan M: Post-transcriptional control of the hypoxic response by RNA-binding proteins and microRNAs. Front Mol Neurosci. 4, Article 7:1-14, 2011

Fähling M: Surviving hypoxia by modulation of mRNA translation rate. J Cell Mol Med. 13(9A):2770-2779, 2009

Fähling M: Cellular oxygen sensing, signalling and how to survive translational arrest in hypoxia. Acta Physiol (Oxf.). 195(2):205-230, 2009

Original Article:

Seibert FS, Rosenberger C, Mathia S, Arndt R, Arns W, Andrea H, Pagonas N, Bauer F, Zidek W, Westhoff TH: Urinary calprotectin differentiates between prerenal and intrinsic acute renal allograft failure. Transplantation 101(2): 387-394, 2017

Fähling M, Mathia S, Scheidl J, Abramovitch R, Milman Z, Paliege A, Peters H, Persson PB, Heyman SN, Rosenberger C: Cyclosporine a induces renal episodic hypoxia. Acta Physiol (Oxf). 219(3): 625-639, 2017

Kasim M, Heß V, Scholz H, Persson PB, Fähling M: Achaete-Scute homolog 1 expression controls cellular differentiation of neuroblastoma. Front Mol Neurosci. 9: 156, 2016

Staudacher JJ, Naarmann-de Vries IS, Ujvari SJ, Klinger B, Kasim M, Benko E, Ostareck-Lederer A, Ostareck DH, Bondke Persson A, Lorenzen S, Meier JC, Blüthgen N, Persson PB, Henrion-Caude A, Mrowka R, Fähling M: Hypoxia-induced gene expression results from selective mRNA partitioning to the endoplasmic reticulum. Nucleic Acids Research 43: 3219-3236, 2015

Kaufmann J, Martinka P, Moede O, Sendeski M, Steege A, Fähling M, Hultström M, Gaestel M, Moraes-Silva IC, Nikitina T, Liu ZZ, Zavaritskaya O, Patzak A: Noradrenaline enhances angiotensin II responses via p38 MAPK activation after hypoxia/re-oxygenation in renal interlobar arteries. Acta Physiologica 213: 920-932, 2015

Kasim M, Benko E, Winkelmann A, Mrowka R, Staudacher JJ, Persson PB, Scholz H, Meier JC, Fähling M: Shutdown of Achaete-scute Homolog-1 Expression by Heterogeneous Nuclear Ribonucleoprotein (hnRNP)-A2/B1 in Hypoxia. Journal of Biologica Chemistry 289: 26973-26988, 2014

Förstera B, a Dzaye OD, Winkelmann A, Semtner M, Benedetti B, Markovic DS, Synowitz M, Wend P, Fähling M, Junier MP, Glass R, Kettenmann H, Meier JC: Intracellular glycine receptor function facilitates glioma formation in vivo. Journal of Cell Sciences 127: 3687-3698, 2014

Gille C, Fähling M, Weyand B, Wieland T, Gille A: Alignment-Annotator web server: rendering and annotating sequence alignments. Nucleic Acids Research, 42: (Web server issue) W3-W6, 2014 (doi: 10.1093/nar/gku400)

Potthoff SA, Fähling M, Clasen T, Mende S, Ishak B, Suvorava T, Stamer S, Thieme M, Sivritas SH, Kojda G, Patzak A, Rump LC, Stegbauer J: Angiotensin-(1-7) modulates renal vascular resistance through inhibition of p38 mitogen-activated protein kinase in apolipoprotein E-deficient mice. Hypertension 63: 265-272, 2014

Fähling M, Mathia S, Paliege A, Koesters R, Mrowka R, Peters H, Persson PB, Neumayer HH, Bachmann S, Rosenberger C: Tubular von Hippel-Lindau knockout protects against rhabdomyolysis-induced AKI. Journal of the American Society of Nephrology 24:1806-1819, 2013

Fähling M, Persson AB, Klinger B, Benko E, Steege A, Kasim M, Patzak A, Persson PB, Wolf G, Blüthgen N, Mrowka R: Multi-level regulation of HIF-1 signaling by TTP. Mol Biol Cell 23(20):4129-4141, 2012

Cartault F, Munier P, Benke E, Desguerre I, Hanein S, Boddaert N, Bandiera S, Vellayoudom J, Krejbich-Trotot P, Bintner M, Hoarau JJ, Girard M, Génin E, de Lonlay P, Fourmaintraux A, Naville M, Rodriguez D, Feingold J, Renouil M, Munnich A, Westhof E, Fähling M, Lyonnet S, Henrion-Caude A: Mutation in a primate-conserved retrotransposon reveals a noncoding RNA as a mediator of infantile encephalopathy. PNAS 109 (13): 4980-4985, 2012

Benko E, Winkelmann A, Meier JC, Persson PB, Scholz H, and Fähling M: Phorbol-ester mediated suppression of hASH1 synthesis: Multiple ways to keep the level down. Front Mol Neurosci. 4, Article 1:1-11, 2011

Schildroth J, Rettig-Zimmermann J, Kalk P, Steege A, Fähling M, Sendeski M, Paliege A, Lai EY, Bachmann S, Persson PB, Hocher B, Patzak A: Endothelin type A and B receptors in the control of afferent and efferent arterioles in mice. Nephrol Dial Transplant. 26:779-789, 2011

Perlewitz A, Nafz B, Skalweit A, Fähling M, Persson PB, Thiele BJ: Aldosterone and vasopressin affect alpha- and gamma-ENaC mRNA translation. Nucleic Acids Res. 38(17):5746-60, 2010

Kielbasa SA, Blüthgen N, Fähling M, Mrowka R: Targetfinder.org: A resource for systematic discovery of transcription factor target genes. Nucleic Acids Res. 38 Suppl:W233-8, 2010

Westphal K, Stangl V, Fähling M, Dreger H, Weller A, Baumann G, Stangl K, Meiners S: Human-specific Induction of Glutathione Peroxidase-3 by Proteasome Inhibition in Cardiovascular Cells. Free Radic Biol Med. 47(11):1652-60, 2009

Eichler SA, Förstera B, Smolinsky B, Jüttner R, Lehmann TN, Fähling M, Schwarz G, Legendre P, Meier JC: Splice-specific roles of glycine receptor a3 in the hippocampus. Eur J Neurosci. 30(6):1077-91, 2009

Lai EY, Fähling M, Ma Z, Källskog Ö, Persson PB, Patzak A, Persson AE, Hultström M: Norepinephrine increases calcium sensitivity of mouse afferent arteriole, thereby enhancing angiotensin II-mediated vasoconstriction. Kidney Int. 76(9):953-9, 2009

Fähling M, Mrowka R, Steege A, Kirschner KM, Benko E, Förstera B, Persson PB, Thiele BJ, Meier JC, Scholz H: Translational regulation of the human Achaete-Scute Homologue-1 (hASH1) by Fragile X Mental Retardation Protein (FMRP). J Biol Chem. 284(7):4255-66, 2009

Lüdemann L, Nafz B, Elsner F, Grosse-Siestrup C, Meissler M, Kaufels N, Rehbein H, Persson PB, Michaely HJ, Lengsfeld P, Voth M, Gutberlet M: Absolute quantification of regional renal blood flow in swine by dynamic contrast-enhanced magnetic resonance imaging using a blood pool contrast agent. Invest Radiol. 44(3):125-34, 2009

Ufer C, Wang CC, Fähling M, Schiebel H, Thiele BJ, Billett EE, Kuhn HH, Borchert A: Translational regulation of glutathione peroxidase 4 expression through guanine-rich sequence binding factor 1 is essential for embryonic brain development. Genes  Dev. 22(13):1838-50, 2008

Steege A, Fähling M, Paliege A, Bondke A, Kaps C, Kirschner KM, Martinka P, Patzak A, Scholz H, Persson PB, Thiele BJ, Mrowka R: Wilms' tumor protein WT1(-KTS) modulates renin gene transcription. Kidney Int. 74(4):458-66, 2008

Mrowka R, Blüthgen N, Fähling M: Seed based systematic discovery of specific transcription factor target genes. FEBS J. 275(12):3178-92, 2008

Martinka P, Lai EY, Fähling M, Jankowski V, Jankowski J, Schubert R, Gaestel M, Persson AE, Persson PB, Patzak A: Adenosine increases calcium sensitivity via receptor-independent activation of p38 MAPK/MK2 pathway in isolated mesenteric arteries. Acta Physiol (Oxf.). 193(1):37-46, 2008

Patzak A, Steege A, Lai EY, Brinkmann JO, Kupsch E, Spielmann N, Gericke A, Skalweit A, Stegbauer J, Persson PB, Seeliger E: Angiotensin II response in afferent arterioles of mice lacking either the endothelial or neuronal isoform of nitric oxide synthase. Am J Physiol Regul Integr Comp Physiol. 294(2):R429-37, 2008

Patzak A, Lai EY, Fähling M, Sendeski M, Martinka P, Persson PB, Persson AE: Adenosine enhances long-term the contractile response to angiotensin II in afferent arterioles. Am J Physiol Regul Integr Comp Physiol. 293(6):R2232-42, 2007

Mrowka R, Steege A, Kaps C, Herzel H, Thiele BJ, Persson PB, Blüthgen N: Dissecting the action of an evolutionary conserved non-coding region on renin promoter activity. Nucleic Acids Res. 35(15):5120-9, 2007

Schmidt I, Fähling M,  Nafz B, Skalweit A, Thiele BJ: Induction of translationally controlled tumour protein (TCTP) by transcriptional and posttranscriptional mechanisms. FEBS J. 274(20):5416-24, 2007

Lai EY, Martinka P, Fähling M, Mrowka R, Steege A, Gericke A, Sendeski M, Persson PB, Persson AE, Patzak A: Adenosine Restores Angiotensin II-Induced Contractions by Receptor-Independent Enhancement of Calcium Sensitivity in Renal Arterioles. Circulation Res. 99:1117-1124, 2006

Fähling M, Mrowka R, Steege A, Nebrich G, Perlewitz A, Persson PB, Thiele BJ: Translational Control of Collagen Prolyl 4-Hydroxylase alpha (I) Gene Expression under Hypoxia. J Biol Chem. 281(36):26089-10, 2006

Andree H, Thiele H, Fähling M, Schmidt I, Thiele BJ: Expression of the human TPT1 gene coding for translationally controlled tumor protein (TCTP) is regulated by CREB transcription factors. Gene. 380(2):95-103, 2006

Fähling M, Mrowka R, Steege A, Martinka P, Persson PB, Thiele BJ: Heterogeneous Nuclear Ribonucleoprotein-A2/B1 Modulate Collagen Prolyl 4-Hydroxylase alpha (I) mRNA Stability. J Biol Chem. 281(14):9279-86, 2006

Theilig F, Debiec H, Nafz B, Ronco P, Nüsing R, Seyberth HW, Pavenstädt H, Bouby N, Bachmann S: Renal cortical regulation of COX-1 and functionally related products in early renovascular hypertension (rat). Am J Physiol Renal Physiol. 291(5):F987-94, 2006