A) HEK-293 cells were transiently transfected with the indicated constructs, and the interaction between DARPP-32 and ERBB3 or DARPP-32 and EGFR was examined by co-immunoprecipitation using specific antibodies. B) The protein interaction of endogenous DARPP-32, EGFR, and ERBB3 was evaluated by a three-way co-immunoprecipitation in MKN-45 cells. C) Immunofluorescence analysis using MKN-28 cells, following adenoviral infection with DARPP-32 (5 MOI), demonstrates co-localization of EGFR and DARPP-32 proteins on the cell membrane. D) Using immunoprecipitation of EGFR (left panel) or ERBB3 (right panel), the EGFR-ERBB3 interaction was examined in MKN-28 cells stably expressing DARPP-32 or empty vector. E) The same as in (D), using adenoviral infection of DARPP-32. F) The same as in (D), following lentiviral shRNA DARPP-32 knockdown in SNU-16 cells.