ESCRT-III is required for scissioning new peroxisomes from the endoplasmic reticulum

Dynamic control of peroxisome proliferation is integral to the peroxisome's many functions. The endoplasmic reticulum (ER) serves as a source of preperoxisomal vesicles (PPVs) that mature into peroxisomes during de novo peroxisome biogenesis and support growth and division of existing peroxisomes. However, the mechanism of PPV formation and release from the ER remains poorly understood. In this study, we show that endosomal sorting complexes required for transport (ESC RT)-III are required to release PPVs budding from the ER into the cytosol. Absence of ESC RT-III proteins impedes de novo peroxisome formation and results in an aberrant peroxisome population in vivo. Using a cell-free PPV budding assay, we show that ESC RT-III proteins Vps20 and Snf7 are necessary to release PPVs from the ER. ESC RT-III is therefore a positive effector of membrane scission for vesicles budding both away from and toward the cytosol. These findings have important implications for the evolutionary timing of emergence of peroxisomes and the rest of the internal membrane architecture of the eukaryotic cell.