Fig. 1: PCV2 infection induces RBP4 expression via the MAPK–eIF4E axis.

Immunoblotting analysis of RBP4 protein levels and PCV2 capsid protein (Cap) expression in 3D4/21 cells and PK-15 cells infected with PCV2 (MOI = 0.2, the same dose below) at the indicated periods (a) or infected with PCV2 with increased dose for 36 h (b). Quantitative real-time PCR (qPCR) analysis of RBP4 mRNA expression in 3D4/21 cells and PK-15 cells infected with PCV2 at the indicated periods (c) or infected with PCV2 with increased dose for 36 h (d). e Immunoblotting analysis of RBP4 protein expression in 3D4/21 cells and PK-15 cells left untreated or infected with PCV2 for 36 h following treatment with cycloheximide (CHX, 50 μM) for the indicated periods. Densitometric quantitation of RBP4 was normalized relative to the levels at 0 h conditions. f Immunoblotting analysis of RBP4, phosphorylated (p-) and total p38, p-JNK and JNK, p-p65 and p65, and p-ERK1/2 and ERK1/2 in whole lysates of in 3D4/21 cells or PK-15 cells pretreated with DMSO or p38 inhibitor SB203580 (SB, 10 μM), JNK inhibitor SP600125 (SP, 10 μM), NF-κB inhibitor BAY11 (10 μM), or ERK inhibitor U0126 (10 μM) for 3 h followed by PCV2 infection for 36 h. g Immunoblotting analysis of RBP4, phosphorylated (p-) and total eIF4E, p-p38 and p38, and p-ERK1/2 and ERK1/2 in whole lysates of 3D4/21 cells and PK-15 cells left untreated or infected with PCV2 for the indicated periods. h Immunoblotting analysis of RBP4, p-eIF4E, and total eIF4E in whole-cell lysates of 3D4/21 cells and PK-15 cells left untreated or pretreated with DMSO, U0126 (10 μM), or SB (10 μM) for 3 h followed by PCV2 infection for the indicated periods. Data are representative of three independent experiments (a, b, e–h) or pooled from three independent experiments (c, d, mean ± SD).