SYK is an HSP90 client protein. (A) BCR cell surface expression in DG75 and Daudi cells treated for 24 and 48 hours with either DMSO or AT13387 and STA-9090, measured by flow cytometry. Unstained cells were used as controls (gray lines). (B) Anti-LYN immunoblot of CCL from DG75 cells transduced with doxycycline-inducible constructs encoding GFP together with control shRNAs or shRNAs targeting LYN. GFP and actin served as induction and loading controls, respectively. (C) Fraction of mCherry-positive transduced cells relative to mCherry-negative untransduced cells at the indicated time points. Error bars are mean ± SD, n = 3. (D) Cell viability normalized to DMSO controls in 5 BL cell lines treated with the indicated concentrations of AT13387, STA-9090, or the SYK inhibitor PRT062607. (E-F) Coimmunoprecipitation of HSP90 and SYK. CCL from DG75 and Daudi cells were subjected to immunoprecipitation using anti-HSP90 antibodies (IP: HSP90) (E) or anti-SYK antibodies (IP: SYK) (F) or isotype-matched control antibodies (IgG) and blotted for HSP90, SYK, and AKT. CCLs are shown as input controls.