Loss of PGRMC1/2 by siRNA knockdown during progesterone treatment increased the levels of HEV-induced IFN-λ1 expression via ERK. (A) Experimental regimen. (B) Fold change in IFN-λ1 mRNA levels in various conditions tested. (C and D) Western blot analysis of phosphorylated ERK (pERK) and total ERK (tERK) levels during progesterone treatment. (C) PGRMC1/2 knockdown cells. (D) ERK inhibitor U0126 (U01) treated cells. (E) Fold change in IFN-λ1 mRNA levels in the presence or absence of ERK inhibitor U0126 (U01). The data represent an average ± SEM of 2 independent experiments; Student’s t test, N.S, nonsignificant; siCnt, scramble control siRNA transfected cells; siPGRMC1 + 2, PGRMC1/2 siRNA transfected cells; U01, 10 μM ERK inhibitor U0126; 80 nM PRO = 25 ng/ml progesterone final concentration.