Figure 7.
Cullin‐3 (CUL3) and KCTD10 regulate cell proliferation in SKBR‐3 cells. A, SKBR‐3 cells were treated with indicated siRNA for CUL3, KCTD10, human epidermal growth factor receptor 2 (HER2) or Rac1 for 48 h. Trypsinized cells (total 0.5 × 105 cells) were then replated and treated with the same siRNA 24 h after replating in the presence of epidermal growth factor (EGF; 100 ng/mL). Cell number was counted every 24 h after replating. Data are mean ± SEM from three independent experiments. ***P < .001. B, Scheme of the present study. CUL3/KCTD10 E3 complex constitutively ubiquitinates RhoB leading to its degradation. Low level of RhoB enables activation of Rac1 by stimulation through the EGF/EGFR/HER2 signaling pathway in HER2‐positive breast cancer cells. In CUL3 or KCTD10 knockdown cells, accumulated RhoB impairs Rac1 trafficking from endosomes to the plasma membrane, resulting in the inhibition of Rac1‐dependent dorsal membrane ruffle formation and cell proliferation