Figure 6.

Association of AMAP1 and PRKD2 is required for the recycling back of β1 integrin. (A–D) MDA-MB-231 cells, treated with siRNAs specific to AMAP1 or PRKD2, were analyzed for the total cellular amounts (A), surface expression (B), activities of recycling back (C), and internalization (D) of β1 integrin. Percentages of β1 integrin molecules recycled back to the plasma membrane or internalized, as compared with those internalized or initially present at the plasma membrane, respectively, are shown. siRNA-treated cells were serum-starved for 2 h and processed for each assay as described in Materials and methods, and then treated (+) or left untreated (−) with 10 ng/ml EGF (C), or cultured in the absence of serum or EGF for the indicated times (D). An RNA duplex with an irrelevant sequence (Irr or Irrelevant) was used as a control. (E–I) MDA-MB-231 cells, treated with Rab5c siRNA (E–G) or overexpressing GST, GST-C1, or GST-C4 (H and I), were analyzed for their recycling-back (F and H) and internalization (G and I) of β1 integrin as above. Data are shown as mean ± SEM of triplicate experiments (error bars).