Fbxo21, but not Fbxo45, regulates the turnover of endogenous NMNAT2 protein in neurons. (A and B) Representative phase contrast images (A) and quantification (B) of the time course of injury-induced axon degeneration of the DRG neurons infected with indicated shRNAs. The equal lentivirus loads of shRNAs were used in all groups by adding supplemental amount of scrambled shRNA(sh-Ctrl). % of deg. axons, the percentage of degenerated axons. (C and D) The qPCR analysis examining the KD efficiency of sh-Fbxo21 (C) and sh-Fbxo45 (D) in the DRG neurons in A. All mRNA levels are normalized to Gapdh and shown as average percentage to that of the sh-Ctrl group (set to 100%). (E–H) Representative western blot images (E and G) and quantifications (F and H) of NMNAT2 protein levels in the neurites only (E and F) or soma and neurites samples (G and H) of mouse DRG neurons at the different time points after axotomy (E and F) or the CHX treatment (G and H). All NMNAT2 levels are normalized to Tuj1, and the relative NMNAT2 level of each group at 0 h is set to 100%. Mean ± SEM. N = 9 DRG cultures per group from pooled results of three independent repeats in B, n = 3 in C and D, n = 3 in (F and H). Student’s t test (C and D) and two-way ANOVA (B, F, and H); *P < 0.05, **P < 0.01, and ***P < 0.001; ns, not significant. Scale bar: 50 µm. Source data are available for this figure: SourceData F4.