Decreased STAT3 in human idiopathic fetal growth restriction contributes to trophoblast dysfunction
REPRODUCTION
Authors: Borg, A. J.; Yong, H. E. J.; Lappas, M.; Degrelle, S. A.; Keogh, R. J.; Da Silva-Costa, F.; Fournier, T.; Abumaree, M.; Keelan, J. A.; Kalionis, B.; Murthi, P.
Abstract
Abnormal trophoblast function is associated with fetal growth restriction (FGR). The JAK-STAT pathway is one of the principal signalling mechanisms by which cytokines and growth factors modulate cell proliferation, differentiation, cell migration and apoptosis. The expression of placental JAK-STAT genes in human idiopathic FGR is unknown. In this study, we propose the hypothesis that JAK-STAT pathway genes are differentially expressed in idiopathic FGR-affected pregnancies and contribute to abnormal feto-placental growth by modulating the expression of the amino acid transporter SNAT2, differentiation marker CGB/human chorionic gonadotrophin beta-subunit (beta-hCG) and apoptosis markers caspases 3 and 8, and TP53. Expression profiling of FGR-affected placentae revealed that mRNA levels of STAT3, STAT2 and STAT5B decreased by 69, 52 and 50%, respectively, compared with gestational-age-matched controls. Further validation by real-time PCR and immunoblotting confirmed significantly lower STAT3 mRNA and STAT3 protein (total and phosphorylated) levels in FGR placentae. STAT3 protein was localised to the syncytiotrophoblast (ST) in both FGR and control placentae. ST differentiation was modelled by in vitro differentiation of primary villous trophoblast cells from first-trimester and term placentae, and by treating choriocarcinoma-derived BeWo cells with forskolin in cell culture. Differentiation in these models was associated with increased STAT3 mRNA and protein levels. In BeWo cells treated with siRNA targeting STAT3, the mRNA and protein levels of CGB/beta-hCG, caspases 3 and 8, and TP53 were significantly increased, while that of SNAT2 was significantly decreased compared with the negative control siRNA. In conclusion, we report that decreased STAT3 expression in placentae may contribute to abnormal trophoblast function in idiopathic FGR-affected pregnancies.
Crystal structure of the carbon monoxide complex of human cytoglobin
PROTEINS-STRUCTURE FUNCTION AND BIOINFORMATICS
Authors: Makino, Masatomo; Sawai, Hitomi; Shiro, Yoshitsugu; Sugimoto, Hiroshi
Abstract
Cytoglobin (Cgb) is a vertebrate heme-containing globin-protein expressed in a broad range of mammalian tissues. Unlike myoglobin, Cgb displays a hexa-coordinated (bis-hystidyl) heme iron atom, having the heme distal His81(E7) residue as the endogenous sixth ligand. In the present study, we crystallized human Cgb in the presence of a reductant Na2S2O4 under a carbon monoxide (CO) atmosphere, and determined the crystal structure at 2.6 angstrom resolution. The CO ligand occupies the sixth axial position of the heme ferrous iron. Eventually, the imidazole group of His81(E7) is expelled from the sixth position and swings out of the distal heme pocket. The flipping motion of the His81 imidazole group accompanies structural readjustments of some residues (Gln62, Phe63, Gln72, and Ser75) in both the CD-corner and D-helix regions of Cgb. On the other hand, no significant structural changes were observed in other Cgb regions, for example, on the proximal side. These structural alterations that occurred as a result of exogenous ligand (CO) binding are clearly different from those observed in other vertebrate hexa-coordinated globins (mouse neuroglobin, Drosophila melanogaster hemoglobin) and penta-coordinated sperm whale myoglobin. The present study provides the structural basis for further discussion of the unique ligand-binding properties of Cgb.