FIGURE 6.

Role of RACK1 in the regulation of HIF-1α by ErbB4. A, MCF-7 cells were transfected with a plasmid encoding HIF-1〈 and with a nonspecific control siRNA (−) or with two different RACK1-targeted siRNAs (#1 and #2). The cells were stimulated with or without NRG-1 for 18 h, and analyzed by Western blotting. B, proximity ligation assay of endogenous proteins in MCF-7 cells treated for 24 h with CoCl₂ and for 4 h with or without NRG-1. Analysis was carried out using antibodies against RACK1 and HIF-1α. Proximity of the epitopes is indicated by red fluorescent signals. Nuclei were stained with DAPI (blue). C, quantification of the proximity ligation assay data (n = 40 for -NRG-1; n = 35 for +NRG-1). Columns represent the mean number of signals per cell ± S.E.