LC3-I conversion to LC3-II does not necessarily result in complete autophagy.
Autophagy was induced in human neuroblastoma SH-SY5Y cells by two different procedures: deprivation of fetal serum in culture medium, or treatment with dopamine. 3-methyladenine prevented autophagy in the two procedures. Although it is usually considered that the conversion of soluble LC3-I to lipid bound LC3-II is associated with the formation of autophagosomes, the inhibition of autophagy with 3-methyladenine prevented this transformation in serum-deprived but not in dopamine-treated cells. While the PI3K-mTOR pathway was inhibited by serum deprivation, dopamine increased the phosphorylation of Akt but inhibited mTOR activity in a similar way to rapamycin. Dopamine and rapamycin increased LC3-II levels by a mechanism not prevented by 3-methyladenine. The activation of LC3-I to LC3-II may then be necessary but not sufficient to trigger cell autophagy. Thus, the increase in LC3-II, as the main biochemical parameter for autophagy at present, should be considered with caution.
Giménez-Xavier
Pol
P
Unitat de Bioquímica, Departament de Ciències Fisiològiques II, Barcelona, Spain.
Francisco
Roser
R
Platini
Francesca
F
Pérez
Ricardo
R
Ambrosio
Santiago
S
D000225:Adenine / Q000031:analogs & derivatives / Q000494:pharmacology; D001343:Autophagy / Q000187:drug effects; D015153:Blotting, Western; D004298:Dopamine / Q000494:pharmacology; D006801:Humans; D008854:Microscopy, Electron; D008856:Microscopy, Fluorescence; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D009447:Neuroblastoma; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D011494:Protein Kinases / Q000378:metabolism; D044967:Serum; D020123:Sirolimus / Q000494:pharmacology; D058570:TOR Serine-Threonine Kinases; D014407:Tumor Cells, Cultured
D000225:Adenine; D004298:Dopamine; D008869:Microtubule-Associated Proteins; D019869:Phosphatidylinositol 3-Kinases; D011494:Protein Kinases; D020123:Sirolimus; D058570:TOR Serine-Threonine Kinases; C477012:MAP1LC3A protein, human; C025946:3-methyladenine; C546842:MTOR protein, human