Histone deacetylase 6 deacetylates and ubiquitinates ATG3 to regulate autophagy.

ATG3 (autophagy-related gene 3), an E2 like enzyme, plays a vital role in autophagy by regulating the lipidation modification of LC3 (microtubule-associated protein 1A/1B-light chain 3). Although the level of ATG3 can be reduced by the ubiquitin-proteasome pathway, the detailed mechanisms of this regulation remain elusive. Histone deacetylase 6 (HDAC6) is involved in multiple cellular activities by regulating acetylation of its substrates such as α-tubulin and cortactin. Here, we revealed a novel function of HDAC6 in autophagy regulation by mediating the post-translational modifications of ATG3. We found that HDAC6 interacts with ATG3 and deacetylates ATG3. In addition, HDAC6 acts its ubiquitin E3 ligase activity and ubiquitinates ATG3 at lysine 272, leading to ATG3 degradation. Intriguingly, lysine 272 of ATG3 is targeted for deacetylation as well as ubiquitination by HDAC6. Further study showed that HDAC6 participates in autophagy by mediating ATG3 degradation. Taken together, our findings uncover a novel role of HDAC6 in autophagy regulation by mediating the protein modification and degradation of ATG3.