MIR181A regulates starvation- and rapamycin-induced autophagy through targeting of ATG5

Abstract

Macroautophagy (autophagy herein) is a cellular catabolic mechanism activated in response to stress conditions including starvation, hypoxia and misfolded protein accumulation. Abnormalities in autophagy were associated with pathologies including cancer and neurodegenerative diseases. Hence, elucidation of the signaling pathways controlling autophagy is of utmost importance. Recently we and others described microRNAs (miRNAs) as novel and potent modulators of the autophagic activity. Here, we describe MIR181A (hsa-miR-181a-1) as a new autophagy-regulating miRNA. We showed that overexpression of MIR181A resulted in the attenuation of starvation- and rapamycin-induced autophagy in MCF-7, Huh-7 and K562 cells. Moreover, antagomir-mediated inactivation of endogenous miRNA activity stimulated autophagy. We identified ATG5 as an MIR181A target. Indeed, ATG5 cellular levels were decreased in cells upon MIR181A overexpression and increased following the introduction of antagomirs. More importantly, overexpression of ATG5 from a miRNA-insensitive cDNA construct rescued autophagic activity in the presence of MIR181A. We also showed that the ATG5 3′ UTR contained functional MIR181A responsive sequences sensitive to point mutations. Therefore, MIR181A is a novel and important regulator of autophagy and ATG5 is a rate-limiting miRNA target in this effect.

Keywords: :

• macroautophagy
• mammalian autophagy regulation
• microRNA
• hsa-miR-181a
• ATG5
• starvation
• rapamycin
• MTOR

Disclosure of Potential Conflicts of Interest

No potential conflicts of interest were disclosed.

Acknowledgments

pCI-hApg5 and GFP-LC3 plasmids were kindly provided by Noboru Mizushima and Tomatsu Yoshimori, respectively. We would also like to thank Carlos le Sage for technical assistance, and Gozuacik Lab members and Stuart James Lucas for fruitful discussions and critical reading of the manuscript. K562 cells were a kind gift of Ayhan Bilir. This work was supported by the Scientific and Technological Research Council of Turkey (TUBITAK) 1001 Grant and Sabanci University. D.G. is a recipient of EMBO Strategical Development and Installation Grant (EMBO-SDIG) and Turkish Academy of Sciences (TUBA) GEBIP Award. G.K. and K.A.T. are recipients of Yousef Jameel and TUBITAK-BIDEB Scholarships, respectively. The authors have no financial conflict of interests.

Supplemental Materials

Supplemental materials may be found here: www.landesbioscience.com/journals/autophagy/article/23117