title: Inactivation of tristetraprolin in chronic hypoxia provokes the expression of cathepsin B.
abstract: Macrophages play important roles in many diseases and are frequently found in hypoxic areas. A chronic hypoxic microenvironment alters global cellular protein expression, but molecular details remain poorly understood. Although hypoxia-inducible factor (HIF) is an established transcription factor allowing adaption to acute hypoxia, responses to chronic hypoxia are more complex. Based on a two-dimensional differential gel electrophoresis (2D-DIGE) approach, we aimed to identify proteins that are exclusively expressed under chronic but not acute hypoxia (1% O2). One of the identified proteins was cathepsin B (CTSB), and a knockdown of either HIF-1α or -2α in primary human macrophages pointed to an HIF-2α dependency. Although chromatin immunoprecipitation (ChIP) experiments confirmed HIF-2 binding to a CTSB enhancer in acute hypoxia, an increase of CTSB mRNA was evident only under chronic hypoxia. Along those lines, CTSB mRNA stability increased at 48 h but not at 8 h of hypoxia. However, RNA stability at 8 h of hypoxia was enhanced by a knockdown of tristetraprolin (TTP). Inactivation of TTP under prolonged hypoxia was facilitated by c-Jun N-terminal kinase (JNK), and inhibition of this kinase lowered CTSB mRNA levels and stability. We postulate a TTP-dependent mechanism to explain delayed expression of CTSB under chronic hypoxia.
authors.affiliation: Institute of Biochemistry I/ZAFES, Goethe University Frankfurt, Frankfurt, Germany.
authors.forename: Dominik C
authors.initials: DC
authors.lastname: Fuhrmann
authors.affiliation: Institute of Biochemistry I/ZAFES, Goethe University Frankfurt, Frankfurt, Germany.
authors.forename: Michaela
authors.initials: M
authors.lastname: Tausendschön
authors.affiliation: Functional Proteomics, SFB 815 Core Unit, Goethe University Frankfurt, Frankfurt, Germany.
authors.forename: Ilka
authors.initials: I
authors.lastname: Wittig
authors.affiliation: Functional Proteomics, SFB 815 Core Unit, Goethe University Frankfurt, Frankfurt, Germany.
authors.forename: Mirco
authors.initials: M
authors.lastname: Steger
authors.affiliation: Institute of Biochemistry I/ZAFES, Goethe University Frankfurt, Frankfurt, Germany.
authors.forename: Martina G
authors.initials: MG
authors.lastname: Ding
authors.affiliation: Institute of Biochemistry I/ZAFES, Goethe University Frankfurt, Frankfurt, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Schmid
authors.affiliation: Institute of Biochemistry I/ZAFES, Goethe University Frankfurt, Frankfurt, Germany.
authors.forename: Nathalie
authors.identifier: http://orcid.org/0000-0002-0822-2180
authors.initials: N
authors.lastname: Dehne
authors.affiliation: Institute of Biochemistry I/ZAFES, Goethe University Frankfurt, Frankfurt, Germany b.bruene@biochem.uni-frankfurt.de.
authors.forename: Bernhard
authors.initials: B
authors.lastname: Brüne
mesh_terms: D002401:Cathepsin B / Q000276:immunology / Q000378:metabolism*; D015687:Cell Hypoxia / Q000235:genetics*; D002460:Cell Line; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000276:immunology / Q000378:metabolism; D048031:JNK Mitogen-Activated Protein Kinases / Q000276:immunology / Q000378:metabolism; D008264:Macrophages / Q000276:immunology / Q000378:metabolism*; D020871:RNA Stability / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics / Q000276:immunology; D051816:Tristetraprolin / Q000276:immunology / Q000378:metabolism*
chemical_list: D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D012333:RNA, Messenger; D051816:Tristetraprolin; D048031:JNK Mitogen-Activated Protein Kinases; D002401:Cathepsin B