Hypoxia-induced MIR155 is a potent autophagy inducer by targeting multiple players in the MTOR pathway

Area of Science:

• Molecular Biology
• Cellular Biology
• Oncology

Background:

• Autophagy is a cellular process activated by hypoxia, crucial for cellular homeostasis.
• Dysfunctional autophagy is linked to various diseases, notably cancer.
• Hypoxia triggers the upregulation of specific microRNAs (miRNAs).

Purpose of the Study:

• To investigate the role of hypoxia-induced microRNAs in autophagy.
• To identify specific miRNAs involved in hypoxia-mediated autophagy.
• To elucidate the mechanism by which MIR155 regulates autophagy and cancer cell behavior.

Main Methods:

• Investigated MIR155 expression under hypoxic conditions.
• Assessed autophagy levels upon MIR155 manipulation (enforced expression and knockdown).
• Utilized luciferase reporter assays to confirm MIR155 binding to 3' UTRs of target genes in the MTOR pathway.
• Analyzed cell proliferation and cell cycle progression.

Main Results:

• Hypoxia-induced MIR155 was identified as a potent inducer of autophagy.
• Enforced MIR155 expression enhanced autophagy in nasopharyngeal and cervical cancer cells.
• Knockdown of MIR155 inhibited hypoxia-induced autophagy.
• MIR155 directly targets RHEB, RICTOR, and RPS6KB2 within the MTOR signaling pathway.
• MIR155-mediated MTOR pathway downregulation reduced cell proliferation and induced G1/S cell cycle arrest.

Conclusions:

• MIR155 is a key regulator of autophagy, acting through the MTOR signaling pathway.
• MIR155's role in modulating autophagy and cell cycle provides insights into cancer development.
• This study reveals a novel mechanism for MIR155 in cellular response to hypoxia.