WASH inhibits autophagy through suppression of Beclin 1 ubiquitination (2013)
Figure 7

WASH suppresses the ubiquitination of Beclin 1 to inactivate Vps34 activity. (A) WASH overexpression suppresses the ubiquitination of Beclin 1. HEK293T cells were transfected with the indicated vectors for 24 h followed by an Ni‐NTA‐based pull‐down assay and immunoblotted with anti‐poly‐ubiquitin (anti‐poly‐Ub) (left panel), and anti‐K63‐specific ubiquitin (anti‐K63‐Ub) (middle panel) antibodies. The same blot was stripped and probed with anti‐K48‐specific ubiquitin (anti‐K48‐Ub) antibody (right panel). (B) WASH overexpression hinders K63‐linked ubiquitination of Beclin 1. HeLa cells stably expressing vector or Flag–WASH were treated with CM or EBSS with or without BafA1 for 1 h and then stained with antibodies against endogenous Beclin 1 and K63‐linked polyubiquitin (K63‐Ub). The colocalization rate (Pearson's correlation coefficient) between Beclin 1 and K63‐Ub was calculated and shown in the right panel. (C) WASH overexpression inhibits LC3 lipidation. HeLa cells stably expressing vector or Flag–WASH were treated with CM or EBSS with or without BafA1 for 1 h and then stained with antibody against endogenous LC3. LC3 dots were calculated and shown in the right panel. (D) WASH deficiency increases K63‐linked ubiquitination of Beclin 1. WASH+/+ and WASH−/− MEFs were treated with EBSS at 37°C for 1 h and lysed for immunoprecipitation (IP) with anti‐Beclin 1 antibody and probed with antibody against K63‐linked poly‐ubiquitin. (E) WASH overexpression inhibits Vps34 activity. HeLa cells were transfected with the indicated vectors and subjected to immunoprecipitation with anti‐Beclin 1 antibody for Vps34 kinase activity assay. Immunoprecipitates were separated into two equal parts, one for kinase assay and the other for input detection. RLU, relative light unit. (F) Beclin 1 associates Ambra1 upon autophagy induction. HeLa cells treated with EBSS for 1 h were lysed for immunoprecipitation with anti‐Beclin 1 antibody. Immunoprecipitates were immunoblotted with the indicated antibodies. (G) Ambra1 knockdown declines Beclin 1 ubiquitination. HeLa cells with Ambra1 knockdown were treated with EBSS for 1 h, followed by immunoprecipitated with anti‐Beclin 1 antibody. Immunoprecipitates were dissociated with 1% SDS and re‐immunoprecipitated with anti‐Beclin 1 antibody, followed by immunoblotting with the indicated antibodies. (H) Ambra1 overexpression increases Beclin 1 ubiquitination. HeLa cells with Ambra1 overexpression were treated as above. (I) Ambra1 can directly ubiquitinate Beclin 1 by an in vitro ubiquitination assay. Recombinant Beclin 1 (rBeclin 1) and components of the ubiquitination system were expressed and purified as described in Materials and methods. The reaction started by mixing the indicated components in ubiquitination buffer at 37°C for 1 h and followed by immunoblotting. (J, K) WASH and Ambra1 competitively bind to Beclin 1. HeLa cells with vector or WASH overexpression were starved for 1 h and lysed for immunoprecipitation with anti‐Beclin 1 antibody (J). Recombinant Ambra1 and WASH proteins were incubated with GST–Beclin 1, followed by GST pull‐down assays (K). Scale bar, 10 μm. Data are shown as means±s.d. **P0.01 and ***P0.001. Data were repeated for at least three times with similar results.Source data for this figure is available on the online supplementary information page.