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

Peroxisomes are versatile organelles mediating energy homeostasis and redox balance. While peroxisome dysfunction is linked to numerous diseases, the mechanisms regulating peroxisome dynamics during cellular stress remain elusive. Using yeast, we show that proteotoxic stress, including loss of endoplasmic reticulum (ER) or cytosolic chaperone function, impaired ER protein translocation, disrupted N-linked glycosylation, or reductive stress, triggers peroxisome proliferation. This occurs through increased de novo biogenesis from the ER, as well as growth and division, rather than impaired pexophagy. 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. Notably, the effects of proteotoxic stress and TOR inhibition on peroxisomes are also observed in human fibroblasts. Our findings reveal a critical and conserved role of peroxisomes in cellular response to proteotoxic stress.