Dataset Information

N- and O-glycosylation patterns and functional testing of CGB7 versus CGB3/5/8 variants of the human chorionic gonadotropin (hCG) beta subunit.

ABSTRACT: The classical function of human chorionic gonadotropin (hCG) is its role in supporting pregnancy. hCG is a dimer consisting of two highly glycosylated subunits, alpha (CGA) and beta (CGB). The beta-hCG protein is encoded by CGB3, CGB5, CGB7 and CGB8 genes. CGB3, 5 and 8 code for an identical protein, CGB3/5/8, whereas CGB7 differs in three amino acids from CGB3/5/8. We had observed earlier that CGB7 and CGB3/5/8 display very distinct tissue expression patterns and that the tumor suppressor and transcription factor p53 can activate expression of CGB7 but not of CGB3/5/8 genes. Here, we investigate the glycan structures and possible functional differences of the two CGB variants. To this end, we established a system to produce and isolate recombinant CGA, CGB7 and CGB3/5/8 proteins. We found that N- and O-glycosylation patterns of CGB7 and CGB3/5/8 are quite similar. Functional assays were performed by testing activation of the ERK1/2 pathway and demonstrated that CGB7 and CGB5/5/8 appear to be functionally redundant isoforms, although a slight difference in the kinetics of ERK1/2 pathway activation was observed. This is the first time that biological activity of CGB7 is shown. In summary, the results lead to the hypothesis that CGB7 and CGB3/5/8 do not hold significant functional differences but that timing and cell type of their expression is the key for understanding their divergent evolution.

SUBMITTER: Biskup K

PROVIDER: S-EPMC7501100 | biostudies-literature | 2020 Oct

REPOSITORIES: biostudies-literature

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N- and O-glycosylation patterns and functional testing of CGB7 versus CGB3/5/8 variants of the human chorionic gonadotropin (hCG) beta subunit.

Biskup Karina K Blanchard Véronique V Castillo-Binder Paola P Alexander Henry H Engeland Kurt K Schug Sindy S

Glycoconjugate journal 20200807 5

The classical function of human chorionic gonadotropin (hCG) is its role in supporting pregnancy. hCG is a dimer consisting of two highly glycosylated subunits, alpha (CGA) and beta (CGB). The beta-hCG protein is encoded by CGB3, CGB5, CGB7 and CGB8 genes. CGB3, 5 and 8 code for an identical protein, CGB3/5/8, whereas CGB7 differs in three amino acids from CGB3/5/8. We had observed earlier that CGB7 and CGB3/5/8 display very distinct tissue expression patterns and that the tumor suppressor and t ...[more]

PMID: 32767150

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Project description:During histiotrophic nutrition of the embryo, maternal platelets may be the first circulating maternal cells that find their way into the placental intervillous space through narrow intertrophoblastic gaps within the plugs of spiral arteries. Activation of platelets at the maternal-fetal interface can influence trophoblast behavior and has been implicated in serious pregnancy pathologies. Here, we show that platelet-derived factors impaired expression and secretion of the human chorionic gonadotropin beta-subunit (?hCG) in human first trimester placental explants and the trophoblast cell line BeWo. Impaired ?hCG synthesis was not the consequence of hampered morphological differentiation, as assessed by analysis of differentiation-associated genes and electron microscopy. Platelet-derived factors did not affect intracellular cAMP levels and phosphorylation of CREB, but activated Smad3 and its downstream-target plasminogen activator inhibitor (PAI)-1 in forskolin-induced BeWo cell differentiation. While TGF-? type I receptor inhibitor SB431542 did not restore impaired ?hCG production in response to platelet-derived factors, Smad3 inhibitor SIS3 interfered with CREB activation, suggesting an interaction of cAMP/CREB and Smad3 signaling. Sequestration of transcription co-activators CBP/p300, known to bind both CREB and Smad3, may limit ?hCG production, since CBP/p300 inhibitor C646 significantly restricted its forskolin-induced upregulation. In conclusion, our study suggests that degranulation of maternal platelets at the early maternal-fetal interface can impair placental ?hCG production, without substantially affecting morphological and biochemical differentiation of villous trophoblasts. KEY MESSAGES: Maternal platelets can be detected on the surface of the placental villi and in intercellular gaps of trophoblast cell columns from gestational week 5 onwards. Platelet-derived factors impair hCG synthesis in human first trimester placenta. Platelet-derived factors activate Smad3 in trophoblasts. Smad3 inhibitor SIS3 interferes with forskolin-induced CREB signaling. Sequestration of CBP/p300 by activated Smad3 may limit placental hCG production.

Dataset Information

N- and O-glycosylation patterns and functional testing of CGB7 versus CGB3/5/8 variants of the human chorionic gonadotropin (hCG) beta subunit.

Publications

N- and O-glycosylation patterns and functional testing of CGB7 versus CGB3/5/8 variants of the human chorionic gonadotropin (hCG) beta subunit.

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