title: MAP-LC3, a promising autophagosomal marker, is processed during the differentiation and recovery of podocytes from PAN nephrosis.
abstract: Microtubule-associated protein 1 light chain 3 (LC3) is a unique modifier protein. LC3-I, the cytosolic form, is modified to LC3-II, the membrane-bound form, by a mechanism similar to ubiquitylation by E1- and E2-like enzymes, Apg7p and Apg3p, respectively. In the present study, we found that LC3-I is processed to LC3-II during the differentiation and recovery from puromycin aminonucleoside-induced nephrosis of podocytes. LC3 is especially expressed in the podocytes of rat kidney as the membrane-bound form LC3-II. Biochemical analysis using a conditionally immortalized mouse podocyte clone (MPC) revealed that LC3-I is processed to LC3-II during the differentiation of cells into mature podocytes and accumulates in the membrane-rich fraction of the cell lysate. LC3-II-localized vesicles, which differ from lysosomes and endosomes, in differentiated MPC cells are morphologically similar to autophagic vacuoles during starvation-induced autophagy. During starvation-induced autophagy, autophagosomes fuses with lysosome and LC3-II on autophagosomes is finally degraded by lysosomal proteases. However, in differentiated MPC cells, little LC3-II on the vesicles is degraded by lysosomal proteases, suggesting that little LC3-II-localized vesicles in differentiated MPC cells fuse with lysosome. Furthermore, the LC3-II level in differentiated MPC cells increases with recovery from damage caused by experimental puromycin aminonucleoside-induced nephrosis. These results suggest that LC3-II-localized vesicles play an important role in the physiological function of podocytes.
authors.affiliation: Division of Nephrology, Department of Internal Medicine, Juntendo University School of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo 113-8421, Japan.
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Asanuma
authors.forename: Isei
authors.initials: I
authors.lastname: Tanida
authors.forename: Isao
authors.initials: I
authors.lastname: Shirato
authors.forename: Takashi
authors.initials: T
authors.lastname: Ueno
authors.forename: Hisatsugu
authors.initials: H
authors.lastname: Takahara
authors.forename: Tomohito
authors.initials: T
authors.lastname: Nishitani
authors.forename: Eiki
authors.initials: E
authors.lastname: Kominami
authors.forename: Yasuhiko
authors.initials: Y
authors.lastname: Tomino
mesh_terms: D000818:Animals; D001343:Autophagy; D015415:Biomarkers / Q000032:analysis; D002454:Cell Differentiation; D002999:Clone Cells; D007668:Kidney / Q000166:cytology* / Q000378:metabolism / Q000648:ultrastructure; D051379:Mice; D008869:Microtubule-Associated Proteins / Q000032:analysis / Q000378:metabolism*; D008954:Models, Biological; D009401:Nephrosis / Q000139:chemically induced / Q000378:metabolism / Q000473:pathology; D010588:Phagosomes / Q000737:chemistry* / Q000648:ultrastructure; D011499:Protein Processing, Post-Translational; D011692:Puromycin Aminonucleoside; D051381:Rats; D014617:Vacuoles / Q000737:chemistry / Q000648:ultrastructure
chemical_list: D015415:Biomarkers; D008869:Microtubule-Associated Proteins; D011692:Puromycin Aminonucleoside