The antibody addition also reduced DNA synthesis by a fifth upon coculturing MB-1 cells with MS-5 cells (Figure?2C). with MB-1 cells. GST-pulldown and luciferase reporter assays showed that uncarboxylated MGP interacted with BMP-4 and that Astragaloside III anti-MGP antibody abolished this interaction. LDN-193189, a selective BMP signaling inhibitor, inhibited growth and cobblestone formation of MB-1 cells. The addition of warfarin, a selective inhibitor of vitamin K-dependent Glu -carboxylation, did not affect MB-1 cell growth, suggesting that uncarboxylated MGP has a biological effect in niche. These results indicate that Astragaloside III MGP may maintain normal and malignant hematopoietic progenitor cells, possibly by modulating BMP signals independently of Glu -carboxylation. Aberrant MGP by leukemic cells and selective induction of BMP-4 relative to BMP-2 in stromal cells might specify malignant niche. [10, 11, 12]. An 85-residue 10-kDa protein, matrix Gla protein (MGP), which was originally identified as a -carboxyglutamic acid (Gla)-containing protein that was associated with the bovine bone matrix [13, 14], is now highlighted in a context of molecular taxonomy of BM stroma, as it is abundantly expressed specifically in a subset of bone marrow (BM) leptin-receptor-positive mesenchymal stem/stromal cells, major components of the BM hematopoietic microenvironment, and their descendent osteolineage cells [15, 16]. MGP reportedly interacts with BMP-4 and BMP-2 and modulates the BMP-SMAD signals [17, 18]. The promoter has putative binding sites for vitamin D and retinoic acid receptors [14], and vitamin D enhances MGP expression in bone cells [19], indicating as a putative MED1-targeted gene. MGP is known as a functional inhibitor of calcification: MGP-deficient mice die of arterial ectopic calcification associated with activated BMP signals and subsequent rupture [20, 21]; and patients with Keutel syndrome, whose MGP is nonfunctional, suffer from diffuse cartilage calcification and mid-facial dysmorphism [22]. The Astragaloside III inhibition of ossification appears to depend on the Glu -carboxylation of MGP, as uncarboxylated MGP is associated with arterial stiffness in humans [23]. Apart from the role for MGP in inhibiting calcification, however, biological action of MGP expressed abundantly in BM stromal cells has been veiled. Recently, MGP has been identified as a metastasis-related poor-prognostic factor for osteosarcoma, and notably, its prometastatic activity is independent of Glu -carboxylation [24], indicating that uncarboxylated Rabbit Polyclonal to NBPF1/9/10/12/14/15/16/20 MGP is functional in a setting other than ossification. In this study, we looked at MGP whose expression was profoundly attenuated in proteinCprotein interaction analysis, immobilized GST or GST-mMGP (10 g) and recombinant mBMP-4 or mBMP-2 (Wako) (50 ng) were incubated in BC150 buffer with 0.1% NP-40 and 1 mM -mercaptoethanol at 4 C for 1 h. The beads were then washed extensively with the binding buffer. Bound proteins were eluted in 0.3% sarkosyl and detected through western blotting. 2.7. Mammalian two-hybrid assay The cDNA encoding mMGP (20C104) was fused to GAL4 and subcloned into pCDM8 (Invitrogen) to generate pGal4-mMGP. The cDNAs encoding secreted forms of mBMP-4 and mBMP-2 (mBMP-4 (293C408) and mBMP-2 (281C394)), were fused to the VP16 activation domain and subcloned into pcDNA3.1neo (Thermo Fisher) to create pVP16-mBMP-4 and pVP16-mBMP-2. For mammalian two-hybrid assays, cells (2 104) in 24-well Astragaloside III plates were transfected with pGal4-mMGP (10 ng) and either pVP16-mBMP-4 or pVP16-mBMP-2 (150 ng), together with 5 GAL4-LUC (100 ng) and the control luciferase vector (5 ng) using Lipofectamine 2000 (Thermo Fisher). 2.8. Statistical analyses Results (N = 4, if unspecified otherwise) were shown as means SD, and analyzed using Student’s is reduced in MED1-deficient stromal cells [10], and that a subset of BM stromal cells highly expresses MGP [15, 16], we hypothesized that MGP may be a novel niche factor for hematopoiesis. To explore the aptness of this hypothesis, we analyzed the effect of downregulation of MGP produced by BM stromal cells in hematopoietic coculture. Repeated endeavors of CRISPR-Cas9-mediated inactivation in MS-5 stromal cells resulted in failure, after screening clones.