Oncotarget

Research Papers:

Beclin-1-independent autophagy positively regulates internal ribosomal entry site-dependent translation of hypoxia-inducible factor 1α under nutrient deprivation

Ching-An Wu, Duen-Yi Huang and Wan-Wan Lin _

PDF  |  HTML  |  Order a Reprint

Oncotarget. 2014; 5:7525-7539. https://doi.org/10.18632/oncotarget.2265

Metrics: PDF 1575 views  |   HTML 1476 views  |   ?  


Abstract

Ching-An Wu1, Duen-Yi Huang1 and Wan-Wan Lin1,2

1 Department of Pharmacology, College of Medicine, National Taiwan University, Taipei, Taiwan

2 Graduate Institute of Medical Sciences, Taipei Medical University, Taipei, Taiwan

Correspondence:

Wan-Wan Lin, email:

Keywords: nutrient deprivation, Beclin-1-independent autophagy, HIF-1α, IRES, hypoxia, ATG5-independent autophagy

Received: April 28, 2014 Accepted: July 26, 2014 Published: July 26, 2014

Abstract

Hypoxia has been shown to induce hypoxia-inducible factor-1alpha (HIF-1α) expression to support many cellular changes required for tumor growth and metastasis. In addition to hypoxia, nutrient deprivation is another stress condition widely existing in solid tumors due to the poor blood supply. Our data showed that nutrient deprivation induces a significant HIF-1α protein expression and potentiates the HIF-1α responses of hypoxia and CoCl2. This effect is not because of enhancement of HIF-1α stability or transcription. Rather we found it is through the cap-independent but internal ribosome entry site (IRES)-dependent translation. Notably inhibition of autophagy by si-ATG5, 3-methyladenine and chloroquine, but not si-Beclin-1, significantly reverses nutrient deprivation-induced HIF-1α responses. Furthermore, it is interesting to note the contribution of IRES activation for hypoxia-induced HIF-1α expression, however, different from nutrient starvation, si-Beclin 1 but not si-ATG5 can inhibit hypoxia-induced HIF-1α IRES activation and protein expression. Taken together, we for the first time highlight a link from alternative autophagy to cap-independent protein translation of HIF-1α under two unique stress conditions. We demonstrate Beclin 1-independent autophagy is involved to positively regulate nutrient deprivation induced-HIF-1α IRES activity and protein expression, while ATG5-independent autophagy is involved in the HIF-1 IRES activation caused by hypoxia.


Creative Commons License All site content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 License.
PII: 2265