Schlüsselwörter
(Englisch)
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Oxygen sensing; hypoxia; HIF
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Forschungsprogramme
(Englisch)
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COST-Action TD0901 - Hypoxia sensing, signaling and adaptation
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Kurzbeschreibung
(Englisch)
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A crucial step in the adaptation of mammalian cells to oxygen deficiency is the transcriptional activation of hy-poxia-inducible genes. Heterodimeric hypoxia-inducible transcription factors (HIFs) are master regulators for the up-regulation of these genes under physiological as well as pathophysiological conditions, such as tumor development and metastasis, cardiovascular diseases and inflammation. HIF subunits are O2-dependently hydroxylated at conserved prolyl residues by recently discovered prolyl-4-hydroxylase domain proteins (PHDs). Therefore, PHDs function as molecular oxygen sensors by determining the protein stability of HIF subunits. Importantly, non-HIF proteins have been reported to represent PHD hydroxylation substrates, indicating that O2-dependent prolyl hydroxylation might be a more common post-translational modification than previously thought. In addition, hydroxylation-independent functions have been re-ported for PHDs. We recently discovered that ZBTB3, a putative transcription factor with a BTB domain, is a novel PHD2 interactor (unpublished data). BTB domain proteins have been shown to act in a wide range of critical cellular processes including apoptosis, development, oncogenesis and transcription. Up to date no functional data on ZBTB3 are available. The aim of this project is to study the functional consequences of the ZBTB3-PHD interaction, to elucidate the role of ZBTB3 in PHD/HIF-mediated signaling in hypoxia and to determine the physiological function of ZBTB3.
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Partner und Internationale Organisationen
(Englisch)
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BE, CH, CZ, DE, DK, EL, ES, FI, FR, HR, IE, IL, IT, LT, LV, NL, PL, RO, RS, SK, TR, UK
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Abstract
(Englisch)
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An essential step in the cellular adaptation to oxygen deficiency is the transcriptional activation of hypoxiainducible genes. Heterodimeric hypoxia-inducible transcription factors (HIFs), composed of an oxygen-sensitive alpha-subunit and a constitutive beta-subunit, are master regulators for the up-regulation of these genes under physiological as well as pathophysiological conditions, such as tumor development and metastasis, cardiovascular diseases and inflammation. HIFalpha subunits are oxygen-dependently hydroxylated at conserved prolyl residues by recently discovered prolyl-4-hydroxylase domain proteins (PHDs). Therefore, PHDs function as molecular oxygen sensors by determining the protein stability of HIFalpha subunits. A first part of this study focused on erythrocytosis-associated PHD2 mutations. Five PHD2-variants, four of which were novel, were identified in patients with congenital erythrocytosis. These PHD2-variants were functionally analyzed and compared with the PHD2 mutant previously identified in a patient with polycythemia and paraganglioma. The capacity of PHD2 to regulate activity, stability and hydroxylation of HIFalpha was assessed using hypoxia-inducible reporter gene, one-hybrid and in vitro hydroxylation assays, respectively. This functional comparative study shows that two categories of PHD2 mutants could be distinguished: one category with a weak deficiency in HIFalpha regulation and a second one with a deleterious effect; the mutant implicated in tumor occurrence belongs to the second category. As observed with germline VHL mutations, there are functional differences between the PHD2 mutants regarding HIF regulation. Therefore, the PHD2 mutation carriers need careful medical follow-up, since some mutations must be considered as potential candidates for tumor predisposition. The second part of this study analyzed the hypoxic regulation of a transmembrane adaptor protein. Hypoxic regulation could be demonstrated in several cell lines on both mRNA and protein level as well as in vivo. Additionally, RNAi, ChIP and reporter gene assays confirmed a HIF-dependent mechanism. Furthermore, we found evidence for the importance of this adaptor protein in chronic kidney disease.
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Datenbankreferenzen
(Englisch)
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Swiss Database: COST-DB of the State Secretariat for Education and Research Hallwylstrasse 4 CH-3003 Berne, Switzerland Tel. +41 31 322 74 82 Swiss Project-Number: C10.0106
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