micropexophagy

Micropexophagy is a form of selective autophagy in which peroxisomes are degraded inside the vacuole by direct enclosure of the organelles through invagination of the vacuolar membrane, rather than being sequestered first by a double-membrane autophagosome. It is one of two major pexophagy pathways described in certain yeasts, the other being macropexophagy, where cytosolic autophagosomes carry peroxisomes to the vacuole for degradation.

In micropexophagy, the vacuolar membrane wraps around and engulfs adjacent peroxisomes, leading to their breakdown within the vacuolar lumen. This contrasts with macropexophagy, in which autophagosomes form a vesicular compartment that contains peroxisomes before fusing with the vacuole. The process is part of the broader autophagy-related pathways that regulate organelle turnover in response to cellular conditions.

Organisms in which micropexophagy has been described include certain methylotrophic yeasts, notably Pichia pastoris (Komagataella phaffii) and related species. In Saccharomyces cerevisiae, pexophagy more commonly proceeds via macropexophagy, though the full spectrum of pexophagic responses can vary among species and conditions.

Triggers for micropexophagy generally involve nutrient limitation or shifts in carbon source that favor remodeling of the peroxisome population. The process helps the cell adapt to changing metabolic needs by selectively degrading surplus or dysfunctional peroxisomes. Molecularly, micropexophagy relies on autophagy-related genes, with the precise requirements and vacuolar remodeling steps differing from those in macropexophagy across species.