(B) epicardial cells were infected with adenovirus co-expressing GFP and either FL, CYTO, or 3 receptor and incubated with 5000 pM BMP2. with the scaffolding protein GIPC (GAIP-interacting protein, C terminus) did not rescue. Knockdown of GIPC in or Topiroxostat (FYX 051) cells rescued with TGFR3 decreased BMP2-stimulated invasion confirming a requirement for TGFR3/GIPC interaction. Our results reveal the relative roles of TGFR3-dependent and TGFR3-independent signaling in the actions of BMP2 on epicardial cell behavior and demonstrate the critical role of TGFR3 in mediating BMP2-stimulated invasion. in mice causes embryonic lethality due to failed coronary vessel development [18] associated with dysregulated epicardial cell invasion [19]. TGFR3 binds multiple members of the TGF family. In addition to binding TGF1 and TGF3, TGFR3 is required for the high affinity binding of TGF2 [20]. TGFR3 has also been identified as the inhibin receptor [21] and binds BMP2 [22]. Studies of epicardial cells have shown that TGF stimulates the loss of epithelial cell character and smooth muscle differentiation [23]. Although loss of epithelial character and smooth muscle differentiation does not require TGFR3, TGF-mediated epicardial cell invasion was shown to be dependent on specific cytoplasmic residues of TGFR3 and the interaction of these residues with the scaffolding protein GIPC [19]. TGF-stimulated epicardial cell invasion also requires TGFR3 to access the Par6/Smurf1/RhoA pathway which is necessary for cell invasion [24]. The role of TGFR3 in BMP2 signaling is less well described. BMP2 binds TGFR3 and is required for endothelial cell transformation [22]. In endothelial cells, both TGF and BMP2 share a common, TGFR3-dependent pathway to signal transformation that includes activation of the Par6/Smurf1/RhoA pathway [25, 26] and a requirement for specific cytoplasmic residues of TGFR3 and the interaction of these residues with the scaffolding protein GIPC [27]. In epicardial cells, BMP2 is known to induce invasion that is dependent on the Par6/Smurf1/RhoA Topiroxostat (FYX 051) pathway [24]. Here we show that TGFR3 is required for BMP2-stimulated epicardial cell invasion although TGFR3 is not required Topiroxostat (FYX 051) for BMP2-stimulated loss of epithelial character as measured by the AKAP12 redistribution of ZO1. BMP2-stimulated invasion was shown to require specific cytoplasmic residues in TGFR3 that are known to interact with the scaffolding protein GIPC. Deletion of these residues, or the targeting of GIPC, demonstrated a requirement for each in BMP2-stimulated invasion. These data suggest that loss of BMP2 responsiveness, as well as the previously recognized loss of TGF responsiveness, may underlie the epicardial defects associated with failed coronary vessel development in mice [18]. 2.0 Methods 2.1 Immortalized Epicardial Explant Culture Immortalized epicardial cell lines from and mice were generated as described previously [23]. To sustain the cells immortalized state, they were grown at 33C in immorto media: 10% fetal bovine serum (FBS), 100U/ml Penicillin/Streptomycin (P/S), 1X Insulin-Transferrin-Selenium (ITS; 1 g/ml insulin, 5.510?4 g/ml transferrin, 0.677 g/ml selenium), and 10U/ml interferon (INF). For growth factor addition, cells were transferred to standard DMEM media (5% FBS and 100U/ml P/S) and cultured at 37C for 24 hours prior to growth factor addition. Growth factors (TGF1, TGF2, or BMP2) or small molecule inhibitors were added to the cell medium and assayed after 24, 48, or 72 hours. Multiple immortalized epicardial cell lines (E11.5) were generated from and littermate pairs and used in experiments. 2.2 Growth Factors and Inhibitors Reagents were obtained from the following sources: TGF1, TGF2, and BMP2 were purchased from R&D Systems; SB431542, from Sigma-Aldrich. DMH1 was a generous gift from Dr. Charles Hong. 2.3 Immunohistochemistry and epicardial cells (E11.5) were plated in 4-well collagen coated chamber slides Topiroxostat (FYX 051) (BD Biosciences) at a density of 50,000 cells per well. Cells for ZO-1 staining were fixed in 70% methanol for 10 min at room temperature, then blocked with 2% bovine serum albumin in PBS for 1 hr and incubated with diluted primary antibody (ZO-1, 2 g/ml) overnight.
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