Upregulated pexophagy limits the capacity of selective autophagy
Selective autophagy is an essential mechanism to maintain organelle integrity and cellular homeostasis through the constant recycling of damaged or superfluous components. While distinct selective autophagy pathways mediate the degradation of diverse cellular substrates including organelles and pathogens, whether these distinct pathways can influence one another remains unknown. We address this question here using pexophagy, the autophagic degradation of peroxisomes, as a model. We demonstrate in cells that upregulated pexophagy exhausts selective autophagy and limits the degradation of both mitochondria and protein aggregates. We confirmed this finding in the pexophagy-mediated form of Zellweger Spectrum Disorder, a rare disease characterized by peroxisome dysfunction. Further, we extend the generalizability of limited selective autophagy by determining that increased aggrephagy reduces pexophagy using a model of Huntingtons Disease. Our findings suggest that the degradative capacity of selective autophagy can become limited by an increased substrate load.