Posttranscriptional Regulation of Human Leukocyte Antigen G During Human Extravillous Cytotrophoblast Differentiation
Human maternal tolerance to a semiallogenic fetus may be maintained, in part, by the unusual expression pattern of antigen-presenting molecules in placental trophoblast cells. Extravillous cytotrophoblast (EVC) cells, which invade the maternal decidua, express high levels of human leukocyte antigen...
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Veröffentlicht in: | Biology of reproduction 2000-06, Vol.62 (6), p.1543-1550 |
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Zusammenfassung: | Human maternal tolerance to a semiallogenic fetus may be maintained, in part, by the unusual expression pattern of antigen-presenting
molecules in placental trophoblast cells. Extravillous cytotrophoblast (EVC) cells, which invade the maternal decidua, express
high levels of human leukocyte antigen G (HLA-G), a nonclassical, major histocompatibility complex (MHC) class I molecule.
HLA-G transcripts have been detected in tumors and other tissues, yet protein accumulation is rare. We show that, within EVC
cells themselves, the mRNA is more broadly expressed than the protein. Specifically, accumulation of HLA-G protein was markedly
delayed during EVC cell differentiation. To elucidate this mechanism, we performed a comprehensive analysis comparing the
expression of HLA-G and proteins essential for MHC class I expression at the cell surface. The transporter for antigen processing
proteins TAP1 and TAP2, as well as tapasin and β 2 -microglobulin, appeared to be coordinately expressed throughout EVC cell columns. Strikingly, they all accumulated well in
advance of the HLA-G protein but concurrently with its mRNA. A similar delay in the accumulation of the HLA-G protein was
observed in vitro, using cultures of chorionic villi. We conclude that posttranscriptional regulation of HLA-G is fundamental
to EVC cell development and is achieved independently of the peptide loading system. This represents a novel mechanism of
MHC class I regulation. |
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ISSN: | 0006-3363 1529-7268 |
DOI: | 10.1095/biolreprod62.6.1543 |