ATG7 is dispensable for LC3–PE conjugation in thioglycolate-elicited mouse peritoneal macrophages

Abstract

Thioglycolate-elicited macrophages exhibit abundant conjugation of LC3 with PE (LC3-II). Among other autophagy-related (ATG) proteins, it is proposed that, like in yeast, both ATG5 and ATG7 are essential for LC3 conjugation. Using <i>atg5</i>-deficient (<i>^-/-</i>) and <i>atg7^-/-</i>macrophages, we provide evidence that loss of ATG5 but not of ATG7 resulted in LC3-II depletion. Accumulation of LC3-II in elicited <i>atg7^-/-</i> macrophages in response to bafilomycin A₁ validated these data. Furthermore, complete loss of ATG3 in <i>atg7</i>^-/- macrophages demonstrated that ATG7 and ATG3 are dispensable for LC3-PE conjugation. In contrast to thioglycolate-elicited macrophages, naïve peritoneal and bone marrow-derived <i>atg7^-/-</i> macrophages exhibited no LC3-II, even under inflammatory stimuli <i>in vitro</i>. Hence, the macrophage metabolic status dictates the level of LC3-PE conjugation with a supportive but nonessential role of ATG7, disclosing the eukaryotic exception from the LC3 lipidation model based on yeast data. <b>Abbreviations</b>: ATG: autophagy-related; BM: bone marrow; MAP1LC3/LC3: microtubule-associated protein 1 light chain 3; PE: phosphatidylethanolamine.