Nrdp1 accelerates ubiquitin-mediated degradation of USP8 and decreases its interaction with HIF-1α. (A) The lysates from Ad-GFP/Ad- Nrdp1 adenovirus PC12 cells were immune-precipitated with anti-USP8 antibody and analyzed by immunoblotted with anti-ubiquitin antibody to detect ubiquitylated forms of USP8 in vitro. (B) The interactions of USP8 with HIF-1α were detected with co-immunoprecipitation in PC12 cells under OGD treatment or (C) after transfected Ad-si-control/Ad-si-Nrdp1/Ad-Nrdp1 adenovirus. PC12 cells lysates were immune-precipitated with anti-USP8 antibody or control IgG, and the immune-precipitates were subjected to sodium dodecylsulfate-polyacrylamide gel electrophoresis and immunoblotted with anti-USP8 and anti-HIF-1α antibody.