Fig. 4: RBP4 promotes autophagic degradation of PCV2 ORF1.

a Immunoblotting analysis of Myc-tagged protein expression of PCV2 ORF1 (left), ORF2 (middle), or ORF3 (right) in whole-cell lysates of WT and RBP4-KO 3D4/21 cells transfected with the expression plasmids for the indicated periods, respectively. b Immunoblotting analysis of PCV2 ORF1 protein levels in whole-cell lysates of WT and RBP4-KO 3D4/21 cells transfected with PCV2 ORF1 expression plasmid for 24 h following treatment with CHX alone (left) (50 μM), CHX together with MG-132 (middle) (30 μM), or CHX together with CQ (right) (20 μM) for the indicated times. Densitometric quantitation of PCV2 ORF1 was normalized relative to the levels of 0 h conditions (b, lower). c Immunoblotting analysis of PCV2 ORF1 protein expression in whole-cell lysates of RBP4-KO 3D4/21 cells transfected with the PCV2 ORF1 expression plasmid for 24 h and then left untreated or stimulated with rpRBP4 protein (30 μg/mL) for 1 h following treatment with CHX alone, CHX together with MG132, or CHX together with CQ for the indicated times. Densitometric quantitation of PCV2 ORF1 was normalized relative to the levels at 0 h conditions (c, lower). Immunoblotting analysis of PCV2 ORF1 protein expression in 3D4/21 cells transfected with PCV2 ORF1 expression plasmid for 6 h following treatment with CQ (20 μM) (d) or rapamycin (1 μM) (e) for the indicated periods. f Immunoblotting analysis of LC3 expression in RBP4-KO 3D4/21 cells stimulated with rpRBP4 with increased dose for 6 h (upper) or stimulated with rpRBP4 protein (30 μg/mL) for indicated periods (lower). Data are representative of three (a, d, e) or two (b, c, f) independent experiments.