ORAI2 promotes BMP9-induced osteogenic differentiation via the MAPK/ERK1/2 and PI3K/AKT pathways in MEFs

Bone morphogenetic protein (BMP)9 is crucial for osteogenic differentiation. Our RNA-sequencing results revealed that calcium release-activated calcium modulator 2 (ORAI2) was upregulated in mesenchymal stem cells (MSCs) in which osteogenic differentiation was induced by BMP9. ORAI2 is a subunit of store-operated Ca2+ (SOC) channels, which is associated with the second messenger Ca2+. In this study, we found that ORAI2 was downregulated in the bone tissue of ovariectomy (OVX) rats. Subsequently, we examined the impact of ORAI2 on BMP9-induced MSC osteogenic differentiation. Exogenous ORAI2 expression promoted osteogenic differentiation in vitro and bone repair in vivo, whereas silencing ORAI2 inhibited them. Similar results were also revealed using the SOC entry inhibitor SKF96365. Mechanistically, Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis revealed that the effects of ORAI2 may involve the PI3K/AKT signaling pathway. Consistent with the KEGG analysis results, western blotting results further revealed that exogenous expression of ORAI2 increased the levels of phosphorylated-Akt in cells undergoing BMP9-induced osteogenic differentiation, whereas silencing of ORAI2 reduced them. Furthermore, mass spectrometry results suggested that ORAI2 may bind to IQGAP1, which was confirmed by co-immunoprecipitation and western blotting; notably, ORAI2 could interact with IQGAP1 and then facilitate mitogen-activated protein kinase/ERK1/2 signaling. Our results demonstrated that ORAI2 may promote osteogenic differentiation and play an important role in osteogenesis.