Role of PI3K on the regulation of BMP2-induced beta-Catenin activation in human bone marrow stem cells.

Bone morphogenetic protein 2 (BMP2), a very potent bone-inducing agent, promotes the differentiation of bone marrow stem cells (BMSCs) to osteoblasts. However, the potency of BMP2 action is variable and its perturbed dynamic signaling pathways in human BMSCs has not been fully elucidated. In this study, we used a combination of stable isotope labeling by amino acids during cell culture (SILAC) and liquid-chromatography electrospray ionization mass spectrometry (LC-ESI-MS/MS) technology to reveal the BMP2 action in BMSC. In this quantitative proteomic analysis, 414 of 449 proteins were successfully quantified with 79.2% peptide quantification efficiency. Interestingly, beta-Catenin was identified in BMP2-stimulated heavy isotope-labeled cells, and further analysis confirmed that BMP2 increased beta-Catenin mRNA and protein levels. The increment effects of BMP2 on the beta-Catenin expression levels and its translocation to nucleus were diminished by blocking the PI3K signal pathway. In addition, BMP2-induced beta-Catenin activity and ALP activity were blocked by PI3K inhibition. Thus, our quantitative proteomics analysis and further biochemical investigations showed that BMP2 modulates beta-Catenin signaling via PI3K pathway and that this pathway plays roles in BMP2-induced osteoblast differentiation of hBMSCs.