Gonadotropin α subunit. Differential processing of free and combined forms in human trophoblast and transfected mouse cells

Christopher Corless, M. Bielinska, T. V. Ramabhadran, S. Daniels-McQueen, T. Otani, B. A. Reitz, D. C. Tiemeier, I. Boime

Research output: Contribution to journalArticle

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Abstract

The gonadotropins luteinizing hormone, follicle-stimulating hormone, and human chorionic gonadotropin are composed of two noncovalently linked subunits, α and β. The α subunit, identical in all three hormones, is produced in excess over the unique β subunits by pituitary and placenta, and is secreted as uncombined, or free subunit. Free α subunit from both tissues has a larger molecular weight than the dimer form. In bovine pituitary an extra O-linked oligosaccharide is added to free α subunit, and this modification has recently been detected at an analogous position (threonine 39) on human α subunit secreted by choriocarcinoma cells. To assess the contribution of N-linked and O-linked oligosaccharides to the heterogeneity of human free α subunit, we have compared free α with human chorionic gonadotropin α secreted by explants and cultured cytotrophoblasts of human first trimester placenta. We have also examined the free and combined forms of human α subunit expressed in transfected C-127 mouse mammary tumor cells. Processing of the α subunit in placental and C-127 cells was similar. Tryptic mapping of placental-derived and transfected α subunits indicated that O-glycosylation at threonine 39 was not a major modification. In the presence of the oligosaccharide processing inhibitor swainsonine the difference in size between the free and combined forms of α was eliminated in both placental and C-127 cells, indicating that the two forms of α differed in their N-linked oligosaccharides. Furthermore, the oligosaccharides of free α subunits from placental and transfected cells were resistant to endoglycosidase H, but the combined forms of α were partially sensitive to the enzyme. Thus, in human first trimester placenta and mouse C-127 cells, combination of α with human chorionic gonadotropin β alters the processing of N-linked oligosaccharides on α subunit.

Original languageEnglish (US)
Pages (from-to)14197-14203
Number of pages7
JournalJournal of Biological Chemistry
Volume262
Issue number29
StatePublished - 1987
Externally publishedYes

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Trophoblasts
Gonadotropins
Oligosaccharides
Chorionic Gonadotropin
Processing
Placenta
Threonine
First Pregnancy Trimester
Swainsonine
Glycosylation
Choriocarcinoma
Glycoside Hydrolases
Hormones
Follicle Stimulating Hormone
Luteinizing Hormone
Dimers
Tumors
Molecular Weight
Molecular weight
Cells

ASJC Scopus subject areas

  • Biochemistry

Cite this

Corless, C., Bielinska, M., Ramabhadran, T. V., Daniels-McQueen, S., Otani, T., Reitz, B. A., ... Boime, I. (1987). Gonadotropin α subunit. Differential processing of free and combined forms in human trophoblast and transfected mouse cells. Journal of Biological Chemistry, 262(29), 14197-14203.

Gonadotropin α subunit. Differential processing of free and combined forms in human trophoblast and transfected mouse cells. / Corless, Christopher; Bielinska, M.; Ramabhadran, T. V.; Daniels-McQueen, S.; Otani, T.; Reitz, B. A.; Tiemeier, D. C.; Boime, I.

In: Journal of Biological Chemistry, Vol. 262, No. 29, 1987, p. 14197-14203.

Research output: Contribution to journalArticle

Corless, C, Bielinska, M, Ramabhadran, TV, Daniels-McQueen, S, Otani, T, Reitz, BA, Tiemeier, DC & Boime, I 1987, 'Gonadotropin α subunit. Differential processing of free and combined forms in human trophoblast and transfected mouse cells', Journal of Biological Chemistry, vol. 262, no. 29, pp. 14197-14203.
Corless, Christopher ; Bielinska, M. ; Ramabhadran, T. V. ; Daniels-McQueen, S. ; Otani, T. ; Reitz, B. A. ; Tiemeier, D. C. ; Boime, I. / Gonadotropin α subunit. Differential processing of free and combined forms in human trophoblast and transfected mouse cells. In: Journal of Biological Chemistry. 1987 ; Vol. 262, No. 29. pp. 14197-14203.
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AU - Reitz, B. A.

AU - Tiemeier, D. C.

AU - Boime, I.

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