β-Actin is a downstream effector of the PI3K/AKT signaling pathway in myeloma cells.

Interleukin 6 is the in vivo growth factor of myeloma cells. In response to IL-6 stimulation, the PI3K/AKT signaling pathway is activated in these cells. With comparative proteomic approaches, this study reveals many putative downstream effectors of the PI3K/AKT pathway. Mass spectrometry analysis of excised protein spots from 2-dimensional gel allowed the identification of proteins such as β-Actin, cyclophilin A, E3 SUMO-protein ligase PIAS-NY protein, HSP 27, PML, and transforming growth factor β-2. Among these putative effectors, β-Actin was chosen for further characterization. Phosphorylation of β-Actin by AKT upon IL-6 stimulation was confirmed by western blotting using a phospho-AKT substrate antibody. Interestingly, IL-6 significantly increased cell migration (P < 0.05) and the content of filamentous actin (P < 0.05). Therefore, IL-6 stimulation could have effects on the migration of myeloma cells, and the phosphorylation of β-Actin is probably involved in the process.