Figure 2.

Conditional deletion of clathrin inhibits BCR internalization. DKOS cells were grown with (+) or without (−) 0.5 μg/ml doxycycline for 96 h. (A) Ubiquitous clathrin heavy chain (CHC), clathrin heavy chain isoform CHC22, and actin expression were determined by immunoblotting with anti-clathrin heavy chain mAb (TD.1), anti-CHC22 rabbit antiserum, and anti-actin mAb (AC-40). CHC** designates that this blot was overexposed to show residual CHC expression. (B) Cells were treated with 10 μg/ml goat anti-chicken IgM or biotinylated transferrin for 30 min at 4°C, washed, and warmed to 37°C for the times indicated. To detect receptors remaining on the cell surface, cells were stained on ice with FITC-labeled anti-goat Ig or Rhodamine Red-labeled streptavidin and analyzed by flow cytometry. The percent uptake represents the percentage of cells that no longer stain for surface BCR or TfR relative to staining at 4°C.