title: Calpain mediates a von Hippel-Lindau protein-independent destruction of hypoxia-inducible factor-1alpha.
abstract: Hypoxia-inducible factor 1 (HIF-1) is controlled through stability regulation of its alpha subunit, which is expressed under hypoxia but degraded under normoxia. Degradation of HIF-1alpha requires association of the von Hippel Lindau protein (pVHL) to provoke ubiquitination followed by proteasomal digestion. Besides hypoxia, nitric oxide (NO) stabilizes HIF-1alpha under normoxia but destabilizes the protein under hypoxia. To understand the role of NO under hypoxia we made use of pVHL-deficient renal carcinoma cells (RCC4) that show a high steady state HIF-1alpha expression under normoxia. Exposing RCC4 cells to hypoxia in combination with the NO donor DETA-NO (2,2'-(hydroxynitrosohydrazono) bis-ethanimine), but not hypoxia or DETA-NO alone, decreased HIF-1alpha protein and attenuated HIF-1 transactivation. Mechanistically, we noticed a role of calpain because calpain inhibitors reversed HIF-1alpha degradation. Furthermore, chelating intracellular calcium attenuated HIF-1alpha destruction by hypoxia/DETA-NO, whereas a calcium increase was sufficient to lower the amount of HIF-1alpha even under normoxia. An active role of calpain in lowering HIF-1alpha amount was also evident in pVHL-containing human embryonic kidney cells when the calcium pump inhibitor thapsigargin reduced HIF-1alpha that was stabilized by the prolyl hydroxylase inhibitor dimethyloxalylglycine (DMOG). We conclude that calcium contributes to HIF-1alpha destruction involving the calpain system.
authors.affiliation: Institute of Biochemistry I, Faculty of Medicine, Johann Wolfgang Goethe-University Frankfurt, 60590 Frankfurt, Germany.
authors.forename: Jie
authors.initials: J
authors.lastname: Zhou
authors.forename: Roman
authors.initials: R
authors.lastname: Köhl
authors.forename: Barbara
authors.initials: B
authors.lastname: Herr
authors.forename: Ronald
authors.initials: R
authors.lastname: Frank
authors.forename: Bernhard
authors.initials: B
authors.lastname: Brüne
mesh_terms: D000595:Amino Acid Sequence; D000600:Amino Acids, Dicarboxylic / Q000494:pharmacology; D000693:Anaerobiosis; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000187:drug effects; D002154:Calpain / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002478:Cells, Cultured; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism*; D008969:Molecular Sequence Data; D009569:Nitric Oxide / Q000378:metabolism; D020030:Nitric Oxide Donors / Q000494:pharmacology; D014226:Triazenes / Q000494:pharmacology; D051794:Von Hippel-Lindau Tumor Suppressor Protein / Q000378:metabolism
chemical_list: C105351:1-hydroxy-2-oxo-3,3-bis(2-aminoethyl)-1-triazene; D000600:Amino Acids, Dicarboxylic; D002121:Calcium Channel Blockers; D015220:Calcium Channels; D015853:Cysteine Proteinase Inhibitors; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D020030:Nitric Oxide Donors; D014226:Triazenes; D009569:Nitric Oxide; D051794:Von Hippel-Lindau Tumor Suppressor Protein; D002154:Calpain; D002118:Calcium; C040947:oxalylglycine