TOR and heat shock response pathways regulate peroxisome biogenesis during proteotoxic stress

ABSTRACT Peroxisomes are versatile organelles mediating energy homeostasis and redox balance. While peroxisome dysfunction is linked to numerous diseases, the molecular mechanisms and signaling pathways regulating peroxisomes during cellular stress remain elusive. Using yeast, we show that perturbations disrupting protein homeostasis including loss of ER or cytosolic chaperone function, impairments in ER protein translocation, blocking ER N-glycosylation, or reductive stress, cause peroxisome proliferation. This proliferation is driven by increased de novo biogenesis from the ER as well as increased fission of pre-existing peroxisomes, rather than impaired pexophagy. Notably, peroxisome biogenesis is essential for cellular recovery from proteotoxic stress. Through comprehensive testing of major signaling pathways, we determine this response to be mediated by activation of the heat shock response and inhibition of Target of Rapamycin (TOR) signaling. Finally, the effects of proteotoxic stress and TOR inhibition on peroxisomes are also captured in human fibroblasts. Overall, our findings reveal a critical and conserved role of peroxisomes in cellular response to proteotoxic stress. Competing Interest Statement The authors have declared no competing interest. Abbreviations - CSM - Complete Supplement Mixture - ER - endoplasmic reticulum - DIC - Differential Interference Contrast - GET - Guided entry of tail-anchored proteins - GFP - Green Fluorescent Protein - GSH - glutathione (reduced) - GSSG - oxidized glutathione - HSE - Heat Shock Response Element - K. phaffii - Komagataella phaffii - PMP - Peroxisomal membrane protein - PO - peroxisome - PTS - peroxisomal targeting signal - S. cerevisiae - Saccharomyces cerevisiae - SD - synthetic defined - STE - steryl esters - TAG - triacylglycerol - TRX - thioredoxin - ts - temperature sensitive - YE - Yeast extract - YNB - Yeast nitrogen base - UPR - Unfolded Protein Response - UPRE - Unfolded Protein Response Element - WT - Wild type (n)/ wild-type (adj.)