AIM: Hypoxia-inducible gene expression is an important physiological adaptive mechanism in response to a decreased oxygen supply. We have recently described an oxygen- and prolyl-4-hydroxylase (PHD)3-dependent stabilization of the activating transcription factor 4 (ATF-4). The aim of the present study was to examine if the normoxic destabilization of ATF-4 is regulated by oxygen-dependent proteasomal degradation. METHODS: We determined poly-ubiquitination of ATF-4 in normoxia compared to hypoxia by immunoprecipitation and immunoblots. Furthermore, we analysed the expression of the ATF-4 target gene GADD153 as a function of oxygen concentration. RESULTS: ATF-4 protein levels were not detectable in normoxia. Normoxic degradation correlated with an oxygen-dependent poly-ubiquitination of ATF-4, which was hindered by hypoxic incubation of the cells. As a result of hypoxia, GADD153 was expressed. The hypoxic GADD153 expression was attenuated or increased by transfecting the cells with ATF-4 siRNA or PHD3 siRNA respectively. CONCLUSION: Our results demonstrate the involvement of oxygen-dependent proteasomal degradation of ATF-4 in the hypoxia-induced expression of GADD153. Taken together, hypoxia/PHD3-regulated stabilization of ATF-4 by hindering oxygen-dependent degradation may play a critical role in linking cell fate decisions to oxygen availability.
AIM: Hypoxia-inducible gene expression is an important physiological adaptive mechanism in response to a decreased oxygen supply. We have recently described an oxygen- and prolyl-4-hydroxylase (PHD)3-dependent stabilization of the activating transcription factor 4 (ATF-4). The aim of the present study was to examine if the normoxic destabilization of ATF-4 is regulated by oxygen-dependent proteasomal degradation. METHODS: We determined poly-ubiquitination of ATF-4 in normoxia compared to hypoxia by immunoprecipitation and immunoblots. Furthermore, we analysed the expression of the ATF-4 target gene GADD153 as a function of oxygen concentration. RESULTS:ATF-4 protein levels were not detectable in normoxia. Normoxic degradation correlated with an oxygen-dependent poly-ubiquitination of ATF-4, which was hindered by hypoxic incubation of the cells. As a result of hypoxia, GADD153 was expressed. The hypoxicGADD153 expression was attenuated or increased by transfecting the cells with ATF-4 siRNA or PHD3 siRNA respectively. CONCLUSION: Our results demonstrate the involvement of oxygen-dependent proteasomal degradation of ATF-4 in the hypoxia-induced expression of GADD153. Taken together, hypoxia/PHD3-regulated stabilization of ATF-4 by hindering oxygen-dependent degradation may play a critical role in linking cell fate decisions to oxygen availability.
Authors: Carsten C Scholz; Javier Rodriguez; Christina Pickel; Stephen Burr; Jacqueline-Alba Fabrizio; Karen A Nolan; Patrick Spielmann; Miguel A S Cavadas; Bianca Crifo; Doug N Halligan; James A Nathan; Daniel J Peet; Roland H Wenger; Alex Von Kriegsheim; Eoin P Cummins; Cormac T Taylor Journal: PLoS Biol Date: 2016-01-11 Impact factor: 8.029
Authors: Andrey A Poloznikov; Stepan A Nersisyan; Dmitry M Hushpulian; Eliot H Kazakov; Alexander G Tonevitsky; Sergey V Kazakov; Valery I Vechorko; Sergey V Nikulin; Julia A Makarova; Irina G Gazaryan Journal: Front Pharmacol Date: 2021-01-29 Impact factor: 5.810