Inhibiting Ribosomal RNA Synthesis in C. elegans Protects Against Reductive Stress During de novo Fatty Acid...

Area of Science:

• Biochemistry
• Molecular Biology
• Genetics

Background:

• Reductive stress, an imbalance in cellular redox state due to accumulated reducing equivalents like NADH and NADPH, is increasingly linked to metabolic diseases.
• The nematode Caenorhabditis elegans serves as a model organism to study complex biological processes.
• FASN-1 deficiency and biguanide treatment can induce a severe condition known as reductive-death.

Purpose of the Study:

• To investigate the mechanisms underlying catastrophic reductive-death induced by combined biguanide treatment and fasn-1 deficiency in C. elegans.
• To identify genetic factors that confer protection against biguanide-induced reductive stress.
• To explore potential therapeutic strategies for diseases associated with reductive stress.

Main Methods:

• Utilized Caenorhabditis elegans as a model organism.
• Induced reductive stress through combined biguanide treatment and fasn-1 deficiency.
• Employed RNA interference (RNAi) to knock down specific genes, including crn-3, involved in RNA processing and rRNA synthesis.
• Observed hypodermal stress response gene activation and nucleolar morphology changes.
• Investigated downstream nuclear RNAi pathways.

Main Results:

• Combined biguanide treatment and fasn-1 deficiency led to catastrophic reductive-death, associated with stress response activation and nucleolar alterations.
• Loss-of-function or RNAi-mediated knockdown of the catalytic RNA exosome subunit crn-3 significantly protected against reductive death.
• Knockdown of other genes involved in ribosomal RNA (rRNA) synthesis also conferred protection.
• Impaired rRNA biogenesis was postulated to enhance tolerance to accumulated reducing equivalents (NADPH, NADH) and potentially modulate GSH levels.
• A downstream nuclear RNAi pathway, activated by phenformin in a fasn-1 dependent manner, was identified and found to be activated upon disruption of rRNA processing.

Conclusions:

• Impaired rRNA biogenesis is a key factor in conferring tolerance to reductive stress.
• Disruption of rRNA processing represents a novel protective mechanism against reductive death.
• This study identifies a potential therapeutic avenue for ameliorating pathological states of reductive stress in diseases like cancer, cardiac disease, and diabetes.