GCK kinase activity is required for MM cell growth. (A) GCK consists of 820 amino acid residues. The kinase domain (in orange) is located at its N terminus. Lysine 45 is critical for GCK kinase activity. Lysine 45 was replaced by alanine for kinase dead mutation. (B-F) MM.1S cells were transduced with EV (PCDH-EV), shRNA-resistant GCK-M5 (PCDH-GCK(M5)-myc), or shRNA-resistant GCK and GCK kinase dead mutation K45A-M5 (PCDH-GCK-K45A(M5)-myc). GFP sorted cells were cultured in the presence of Dox and analyzed for (B) GCK expression by western blot, (C) proliferation by MTS assay, and (D) for GCK and c-MYC expression by western blot. Selected cells from panel D were cultured in the presence of Dox and analyzed for (E) cell proliferation by MTS assay (F) apoptosis by Annexin V and 7-AAD staining.