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

ABSTRACT: 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.

ORGANISM(S): Mus musculus

PROVIDER: GSE253866 | GEO | 2024/08/31

REPOSITORIES: GEO

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Project description:Osteoporosis is characterized by bone loss, reduced bone strength, and increased fracture risk. Studies have shown that epigenetic mechanisms play a role during bone formation and bone-related disorders, including osteoporosis. However, the contribution of bivalent domains, which are chromatin regions that are co-occupied by the gene activating Histone 3 lysine 4 trimethylation (H3K4me3) and the gene suppressive Histone 3 lysine 27 trimethylation (H3K27me3) marks, has not been elucidated during osteogenesis. Previous work demonstrated that the enhancer of zeste homolog 2 (Ezh2), a histone 3 lysine 27 (H3K27) methyltransferase, suppressed differentiation of osteogenic progenitor cells and that a small molecule inhibitor of Ezh2 (GSK126) enhanced osteogenic commitment of osteoblast progenitors in vitro and bone formation in vivo. Tazemetostat (or EPZ6438) is an Ezh2 inhibitor (iEzh2) that is FDA approved for the treatment of epithelioid sarcoma and might be repurposed to mitigate bone loss. The present study aimed to elucidate mechanisms by which Tazemetostat-mediated H3K27me3 reduction regulates bivalent domain associated enhancers critical for bone formation. Tazemetostat enhanced the expression of bone-related genes (e.g., Runx2-p57, Bglap, Ibsp) as measured by qPCR analysis and stimulated extracellular matrix deposition as revealed by alizarin red staining of cell cultures. Western blotting analysis revealed that Tazemetostat reduced H3K27me3 levels and concomitantly enhanced H3K27Ac, as well as increased protein levels of the osteoblastic master regulator Runx2. Integrative analysis of RNA-seq and ChIP-seq datasets revealed that upregulation of group of genes that are associated with bivalent domains. Importantly, gene ontology analysis showed that genes associated with Wnt, Pth and Hh signaling pathways are enriched within these up-regulated genes. Follow-up mechanistic-based studies revealed that the pro-osteogenic effects induced by Ezh2 inhibition are attenuated by inhibition of Hh signaling and enhanced by disruption of Wnt signaling. Our data demonstrate that the genes controlled by bivalent domains are associated with key osteogenic signaling pathways and are induced upon Ezh2 inhibition and subsequent H3K27me3 reduction. Our data also demonstrate that iEzh2-induced osteogenic differentiation is modulated by Wnt and Hh signaling pathways.

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

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