Figure 6: Δ133p53α is colocalized with p62/SQSTM1 and LC3B.

(a) Δ133p53α is colocalized with p62/SQSTM1 upon autophagy induction. MRC-5 fibroblasts expressing FLAG-Δ133p53α (wild-type) were cultured under amino-acid- and serum-starved conditions for 4 h, and co-immunostained with anti-FLAG antibody (Δ133p53α, green) and anti-p62/SQSTM1 antibody (red). Two representative sets of images, including nuclear staining with 4′,6-diamidino-2-phenylindole (DAPI) and merged images, are shown. Scale bars, 10 μm. (b) Knockdown of p62/SQSTM1 stabilizes endogenous Δ133p53α. MRC-5 fibroblasts at late passage (PDLs 51) were transfected with p62/SQSTM1 siRNA (p62) or control siRNA (C) for 3 days, and examined in immunoblots for Δ133p53α and p62/SQSTM1 expression. The relative expression levels of Δ133p53α (normalized with β-actin) are shown. (c) Δ133p53α is colocalized with LC3B upon autophagy induction. MRC-5 fibroblasts with FLAG-Δ133p53α under starved conditions (as in a) were co-immunostained with anti-FLAG antibody (Δ133p53α, green) and anti-LC3B antibody (red). Two representative sets of images, including DAPI and merged images, are shown. Scale bars, 10 μm. (d) Quantitative analysis of Δ133p53α-LC3B colocalization. The number of colocalized signals out of total number of Δ133p53α signals or out of total number of LC3B signals was counted in 26 cells. Data (percent colocalization) are mean±s.d. Almost all Δ133p53α signals were colocalized with LC3B, while ~80% of LC3B signals were colocalized with Δ133p53α.