Lysosomal colocalization of BCR-ABL and p62/SQSTM1. (A) K562 cells were incubated in the presence of As₂O₃ for the indicated times. Cells were lysed and lysates were immunoprecipitated (IP) with an anti-p62/SQSTM1 antibody or control normal mouse IgG (mIgG), as indicated. EL indicates an empty lane. Immunoprecipitated proteins were resolved by SDS-PAGE and immunoblotted with anti-ABL or anti-p62/SQSTM1 antibodies, as indicate. (B) K562 cells were treated with As₂O₃ (2μM) for 24 hours. Before collection, cells were stained with quenched probe DQ-BSA (red), and after collection stained with either anti-ABL (blue) or anti-p62/SQSTM1 (green) and signals were detected by confocal microscopy. Merged panels indicate overlapping images of the 3 fluorescing signals, and arrows show the colocalization of p62/SQSTM1, BCR-ABL and lysosomal probe DQ-BSA. (C) As₂O₃–dependent colocalization of BCR-ABL with p62/SQSTM1, detected by electron microscopy. K562 cells were treated for 16 hours with AS₂O₃ (2μM) and were subsequently processed as described in “Electron microscopy.” Red arrows indicate BCR-ABL (15 nm gold-conjugate) and yellow arrows indicate p62 (6 nm gold-conjugate).