Fig. 10.

Working model for MIEL1 functions at peroxisomes. MIEL1 is necessary for oleosin (green hairpins) ubiquitination and timely degradation during lipid mobilization. Oleosin ubiquitination allows extraction by PUX10 and CDC48A (20, 21) and proteasomal degradation. MIEL1 localizes at peroxisomes, perhaps via interaction with an organelle surface protein, such as the ubiquitin-conjugating enzyme PEX4. PEX4 (blue) and other peroxins (numbered shapes) function in the import of lumenal cargo proteins with PTS1 or PTS2 signals via the PEX7 and PEX7 cycling receptors. MIEL1 may also target proteins on the peroxisome that modulate peroxisome dynamics, such as the formation of ILVs, which are implicated in fatty acid β-oxidation and protein sorting (39). SDP1 is a peroxisome-associated TAG lipase (34, 35), and PXA1 transports fatty acids into the organelle for β-oxidation (36, 37).