Unbalanced lipolysis results in lipotoxicity and mitochondrial damage in peroxisome-deficient Pex19 mutants

Area of Science:

• Cell Biology
• Genetics
• Biochemistry

Background:

• Inherited peroxisomal biogenesis disorders (PBDs) result from mutations in Pex genes, leading to absent functional peroxisomes and complex pathologies.
• PBDs involve accumulation of metabolic byproducts like very-long-chain fatty acids (VLCFAs) and detrimental mitochondrial abnormalities, with underlying mechanisms often unclear.

Purpose of the Study:

• To investigate the mechanisms behind mitochondrial damage in PBDs using a Pex19 Drosophila mutant model.
• To elucidate the role of lipotoxicity and specific signaling pathways in PBD pathogenesis.

Main Methods:

• Generation and analysis of Pex19 Drosophila mutants exhibiting PBD hallmarks.
• Investigation of hepatocyte nuclear factor 4 (Hnf4) signaling, lipolysis, and mitochondrial beta-oxidation pathways.
• Analysis of Pex19-deficient patient skin fibroblast lines.

Main Results:

• Pex19 Drosophila mutants displayed absent peroxisomes, reduced viability, neurodegeneration, mitochondrial abnormalities, and VLCFA accumulation.
• A model was established where hyperactive Hnf4 signaling induces lipotoxicity and free fatty acid accumulation, causing mitochondrial damage.
• Increased acid lipase expression and free fatty acid accumulation were observed in both fly mutants and patient-derived cells.

Conclusions:

• Hepatocyte nuclear factor 4 (Hnf4)-induced lipotoxicity is a key mechanism driving mitochondrial damage in Pex19-deficient peroxisomal biogenesis disorders.
• The findings highlight conserved pathways in PBDs, offering insights into disease mechanisms and potential therapeutic targets.