Knockdown of CD81 increases the levels of TfR2, TfR2CD/TfR1-f, and TfR2ΔCD.
A, knockdown of CD81 increases the levels of TfR2 but not TfR1. Hep3B-TfR2 cells were transfected with control siRNA (lane C and column C) or siRNA against CD81 (siRNA CD81) for 48 h. The blot was probed with anti-TfR2, anti-TfR1, and anti-actin antibodies. The protein levels of TfR2 and TfR1 were normalized to that of actin. CD81 mRNA was normalized to GAPDH mRNA. The changes in TfR2 and TfR1 and CD81/GAPDH mRNA in response to knockdown of CD81 were normalized to control siRNA-treated cells. The graphs represent the average data of 20 experiments. B, knockdown of CD81 increases the protein level of the TfR2CD/TfR1-f chimera. Hep3B-TfR2CD/TfR1-f cells were transfected as described in A. The blot of the cell lysates was probed with anti-Flag and anti-actin antibodies. The levels of TfR2CD/TfR1-f and CD81 mRNA were analyzed as described in A. The graphs show the average data from nine experiments. C, knockdown of CD81 increases the levels of TfR2ΔCD but not TfR1. Hep3B-TfR2ΔCD cells were treated and analyzed as described in A. The graphs show the average data from seven experiments.