NOXA upregulation by the prohibitin-binding compound fluorizoline is transcriptionally regulated by integrated stress...

Area of Science:

• Molecular Biology
• Cancer Research
• Cellular Stress Response

Background:

• Fluorizoline is a novel synthetic molecule targeting prohibitins (PHBs) to induce apoptosis.
• It demonstrates efficacy in various tumor cell lines and primary leukemia cells.
• Its mechanism involves p53-independent apoptosis induction.

Purpose of the Study:

• To elucidate the mechanism by which fluorizoline induces apoptosis.
• To investigate the role of the integrated stress response (ISR) and NOXA in fluorizoline's action.
• To identify transcription factors regulating NOXA induction by fluorizoline.

Main Methods:

• Utilized tumor cell lines (HeLa, HAP1) and primary leukemia cells.
• Assessed apoptosis induction, protein levels of BCL-2 family members, and caspase activation.
• Analyzed integrated stress response (ISR) activation, including eIF2α phosphorylation and ATF3, ATF4, CHOP induction.
• Employed CRISPR technology to knock out ATF3 and ATF4 for functional studies.
• Investigated NOXA promoter binding by transcription factors.

Main Results:

• Fluorizoline induces NOXA without altering anti-apoptotic BCL-2 family members.
• It synergizes with ABT-737 to enhance apoptosis.
• Fluorizoline triggers ISR activation, characterized by eIF2α phosphorylation and ATF3/ATF4/CHOP induction.
• PHB downregulation mimics fluorizoline's effects on ISR and apoptosis.
• ATF3 and ATF4 were identified as key transcription factors mediating NOXA induction and apoptosis.

Conclusions:

• Fluorizoline-induced apoptosis is mediated by ISR activation.
• ATF3 and ATF4 are crucial transcription factors that induce NOXA expression, leading to apoptosis.
• Fluorizoline offers a promising therapeutic strategy by targeting PHBs and leveraging the ISR pathway.