Phosphatidylinositol 4‐phosphate on Rab7‐positive autophagosomes revealed by the freeze‐fracture replica labeling
| Autor: | Kenji Tanabe, Akikazu Fujita, Hiroki Hayashi, Emi Fujii, Kanna Tomioku, Akane Yoshida, Yuna Kurokawa |
|---|---|
| Rok vydání: | 2018 |
| Předmět: |
Autophagosome
Phosphatidylinositol 4-phosphate Endosome GABARAP Autophagosome maturation Biology Phosphatidylinositols Biochemistry 03 medical and health sciences chemistry.chemical_compound symbols.namesake 0302 clinical medicine Structural Biology Cell Line Tumor Genetics Freeze Fracturing Humans Phosphatidylinositol Molecular Biology Adaptor Proteins Signal Transducing 030304 developmental biology 0303 health sciences Autophagy Autophagosomes rab7 GTP-Binding Proteins Intracellular Membranes Cell Biology Golgi apparatus Cell biology chemistry rab GTP-Binding Proteins symbols Apoptosis Regulatory Proteins Microtubule-Associated Proteins 030217 neurology & neurosurgery |
| Zdroj: | Traffic. 20:82-95 |
| ISSN: | 1600-0854 1398-9219 |
| Popis: | Phosphatidylinositol 4-phophate (PtdIns(4)P) is an essential signaling molecule in the Golgi body, endosomal system, and plasma membrane and functions in the regulation of membrane trafficking, cytoskeletal organization, lipid metabolism and signal transduction pathways, all mediated by direct interaction with PtdIns(4)P-binding proteins. PtdIns(4)P was recently reported to have functional roles in autophagosome biogenesis. LC3 and GABARAP subfamilies and a small GTP-binding protein, Rab7, are localized on autophagosomal membranes and participate at each stage of autophagosome formation and maturation. To better understand autophagosome biogenesis, it is essential to determine the localization of PtdIns(4)P and to examine its relationship with LC3 and GABARAP subfamilies and Rab7. To analyze PtdIns(4)P distribution, we used an electron microscopy technique that labels PtdIns(4)P on the freeze-fracture replica of intracellular biological membranes, which minimizes the possibility of artificial perturbation because molecules in the membrane are physically immobilized in situ. Using this technique, we found that PtdIns(4)P is localized on the cytoplasmic, but not the luminal (exoplasmic), leaflet of the inner and outer membranes of autophagosomes. Double labeling revealed that PtdIns(4)P mostly colocalizes with Rab7, but not with LC3B, GABARAP, GABARAPL1 and GABARAPL2. Rab7 plays essential roles in autophagosome maturation and in autophagosome-lysosome fusion events. We suggest that PtdIns(4)P is localized to the cytoplasmic leaflet of the autophagosome at later stages, which may illuminate the importance of PtdIns(4)P at the later stages of autophagosome formation. |
| Databáze: | OpenAIRE |
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