Developmental Changes in the Glycosylation of Glycoprotein Hormone Free α Subunit during Pregnancy*
- Martin Nemansky‡§,
- N. Rao Thotakura‡¶,
- Curtis D. Lyons‡,
- Song Ye‖,
- Bruce B. Reinhold‖,
- Vernon N. Reinhold‖ and
- Diana L. Blithe‡**
- From the ‡Unit of Glycobiology, Developmental Endocrinology Branch, NICHD, National Institutes of Health, Bethesda, Maryland 20892 and the ‖Department of Microbiology and Immunology/Mass Spectrometry Resource, Boston University Medical Center, Boston, Massachusetts 02118
Abstract
Glycoprotein hormone α subunit, in its free form (free α), is a major placental product. Its glycosylation was found to change dramatically during the advancement of pregnancy. In this study, we have analyzed these glycosylation changes in five normal pregnancies. Binding to Lens culinaris lectin increased dramatically in all subjects between weeks 14 and 17 from the last menstrual period, indicating more core fucosylation as well as possible changes in branching of glycans. Studies using Datura stramonium agglutinin confirmed that the type of triantennary branching changed in this period of pregnancy. The precise structural nature of these changes was determined by high-pH anion-exchange chromatography and electrospray ionization mass spectrometry. Amounts of core fucosylation and of triantennary glycans increased substantially from early to late second trimester, and a shift was observed from 1→4/1→3- toward predominantly 1→6/1→6-branched triantennary structures. The glycosylation changes occurred in all five individuals at the same time period in gestation, suggesting developmental regulation ofN-acetylglucosaminyltransferases IV and V and α6-fucosyltransferase during normal pregnancy. These enzymatic activities also appear to be affected in malignant transformation of the trophoblast. Our findings have important implications for the proposed use of specific forms of glycosylation as markers for cancer, as the relative amounts of these glycans in normal pregnancy will be determined by gestational age.
Footnotes
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↵* The mass spectral studies carried out at the Boston University Mass Spectrometry Resource were supported by National Institutes of Health Grants NCRR 5P41RR10888 (to C. E. Costello, Principal Investigator) and RO1 GM54045 (to V. N. R., Principal Investigator).The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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↵§ Present address: Pharma Bio-Research Laboratories B. V., Westerbrink 3, 9405BJ Assen, The Netherlands.
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↵¶ Present address: Human Genome Sciences, Inc., Rockville, MD 20850.
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↵** To whom correspondence should be addressed: Contraception and Reproductive Health Branch, NICHD, National Institutes of Health, Bldg. 61E, Rm. 8B13, Bethesda, MD 20892. Tel.: 301-496-1661; Fax: 301-480-1972; E-mail: BlitheD{at}exchange.nih.gov.
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↵1 The abbreviations used are: hCG, human chorionic gonadotropin; BSA, bovine serum albumin; LcH, Lens culinaris lectin; DSA, Datura stramonium agglutinin; RIA, radioimmunoassay; HPAEC-PAD, high-pH anion-exchange chromatography with pulsed amperometric detection; ESI-MS, electrospray ionization mass spectrometry; LMP, last menstrual period; ODM, oxidation-deuterioreduction and methylation; Fuc, l-fucose. All sugars were of the d-configuration unless noted otherwise.
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- Received December 9, 1997.
- Revision received March 3, 1998.
- The American Society for Biochemistry and Molecular Biology, Inc.
