PEX2 is the E3 ubiquitin ligase required for pexophagy during starvation.
Peroxisomes are metabolic organelles necessary for anabolic and catabolic lipid reactions whose numbers are highly dynamic based on the metabolic need of the cells. One mechanism to regulate peroxisome numbers is through an autophagic process called pexophagy. In mammalian cells, ubiquitination of peroxisomal membrane proteins signals pexophagy; however, the E3 ligase responsible for mediating ubiquitination is not known. Here, we report that the peroxisomal E3 ubiquitin ligase peroxin 2 (PEX2) is the causative agent for mammalian pexophagy. Expression of PEX2 leads to gross ubiquitination of peroxisomes and degradation of peroxisomes in an NBR1-dependent autophagic process. We identify PEX5 and PMP70 as substrates of PEX2 that are ubiquitinated during amino acid starvation. We also find that PEX2 expression is up-regulated during both amino acid starvation and rapamycin treatment, suggesting that the mTORC1 pathway regulates pexophagy by regulating PEX2 expression levels. Finally, we validate our findings in vivo using an animal model.
Cell Biology Department, The Hospital for Sick Children, Toronto, ON M5G 1X8, Canada Biochemistry Department, University of Toronto, Toronto, ON M5S 1A8, Canada.
Graeme
G
Sargent
Department of Pediatrics, Center for Liver, Digestive and Metabolic Diseases, University of Groningen, University Medical Center Groningen, 9700 AD Groningen, Netherlands.
Tim
T
van Zutphen
Biochemistry Department, University of Toronto, Toronto, ON M5S 1A8, Canada.
Tatiana
T
Shatseva
Physiology and Experimental Medicine Program, Research Institute, The Hospital for Sick Children, Toronto, ON M5G 1X8, Canada.
Ling
L
Zhang
Physiology and Experimental Medicine Program, Research Institute, The Hospital for Sick Children, Toronto, ON M5G 1X8, Canada.
Valeria
V
Di Giovanni
Department of Paediatric Laboratory Medicine, The Hospital for Sick Children, Toronto, ON M5G 1X8, Canada Physiology and Experimental Medicine Program, Research Institute, The Hospital for Sick Children, Toronto, ON M5G 1X8, Canada Division of Gastroenterology, Hepatology and Nutrition, The Hospital for Sick Children, Toronto, ON M5G 1X8, Canada Centre for Global Child Health, The Hospital for Sick Children, Toronto, ON M5G 1X8, Canada pkim@sickkids.ca robert.bandsma@sickkids.ca.
Robert
R
Bandsma
Cell Biology Department, The Hospital for Sick Children, Toronto, ON M5G 1X8, Canada Biochemistry Department, University of Toronto, Toronto, ON M5S 1A8, Canada.
Peter Kijun
0000-0001-6626-0575
PK
Kim
D018528:ATP-Binding Cassette Transporters / Q000378:metabolism; D000596:Amino Acids / Q000172:deficiency; D000818:Animals; D001343:Autophagy / Q000187:drug effects; D004195:Disease Models, Animal; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D008297:Male; D000076222:Mechanistic Target of Rapamycin Complex 1; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008810:Mice, Inbred C57BL; D046912:Multiprotein Complexes / Q000378:metabolism; D000074428:Peroxisomal Biogenesis Factor 2; D000074435:Peroxisome-Targeting Signal 1 Receptor; D020675:Peroxisomes / Q000187:drug effects / Q000201:enzymology* / Q000473:pathology; D011502:Protein-Energy Malnutrition / Q000201:enzymology* / Q000235:genetics / Q000473:pathology; D011506:Proteins / Q000378:metabolism; D059748:Proteolysis; D034622:RNA Interference; D051381:Rats; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D015398:Signal Transduction; D020123:Sirolimus / Q000494:pharmacology; D058570:TOR Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D013997:Time Factors; D014162:Transfection; D054875:Ubiquitination
C063305:ABCD3 protein, human; D018528:ATP-Binding Cassette Transporters; C489271:Abcd3 protein, mouse; D000596:Amino Acids; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D046912:Multiprotein Complexes; C549756:NBR1 protein, human; C000614230:PEX2 protein, human; C000614231:PEX2 protein, mouse; C000614264:PEX5 protein, human; D000074435:Peroxisome-Targeting Signal 1 Receptor; C000614232:Pex2 protein, rat; C000614265:Pex5 protein, mouse; D011506:Proteins; D018160:Receptors, Cytoplasmic and Nuclear; D000074428:Peroxisomal Biogenesis Factor 2; C546842:MTOR protein, human; D000076222:Mechanistic Target of Rapamycin Complex 1; D058570:TOR Serine-Threonine Kinases; D020123:Sirolimus