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Subtypes of betaglycan and of type I and type II transforming growth factor‐β (TGF‐β) receptors with different affinities for TGF‐β1 and TGF‐β2 are exhibited by human placental trophoblast cells
Author(s) -
Mitchell E. Jane,
FitzGibbon Linda,
O'ConnorMcCourt Maureen D.
Publication year - 1992
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.1041500217
Subject(s) - transforming growth factor , trophoblast , receptor , biology , affinity labeling , cell culture , microbiology and biotechnology , placenta , biochemistry , fetus , genetics , pregnancy
Transforming growth factor‐β is likely to be an important factor controlling placental activities, including growth, differentiation, invasiveness, hormone production, and immunosuppression. We have used a chemical cross‐linking technique with either 125 I‐TGF‐β1 or 125 I‐TGF‐β2 and bis(sulfosuccinimidyl) suberate (BS 3 ) to characterize TGF‐β binding components on human placental cells in primary culture. Trophoblast‐enriched primary cultures exhibited a predominant affinity‐labelled complex characteristic of membrane‐anchored betaglycan (formerly termed the Type III TGF‐β receptor) and relatively low levels of the Type I and Type II TGF‐β receptor complexes. The results from affinity labelling saturation and competition experiments with TGF‐β1 and TGF‐β2 suggest the existence of two distinct subtypes of betaglycan: one subtype has a lower capacity and higher affinity, binds both TGF‐β1 and TGF‐β2, yet has a preferential affinity for TGF‐β2; the second subtype has a higher capacity and lower affinity and binds TGF‐β1 exclusively. In contrast, mesenchymal cell‐enriched placental primary cultures possessed only one subtype of the betaglycan component that binds the two TGF‐β isoforms with similar affinities and capacities as observed on most cell lines. These experiments demonstrate that the betaglycan component which exhibits a higher affinity for TGF‐β2 than for TGF‐β1, that we had observed previously on term placental membranes, is actually present on trophoblast cells. In addition to the two distinctive betaglycan subtypes, subtypes of the Type I and II TGF‐β receptors were detected on the trophoblast‐enriched cultures. In competition experiments, when 125 I‐TGF‐β1 was used as the radiotracer, the Type I and II TGF‐β receptors show a much higher affinity for TGF‐β1 than for TGF‐β2, as observed with other cell types. However, when 125 I‐TGF‐β2 was used, low abundance subtypes of both the Type I and II receptors that show similar affinities for TGF‐β1 and TGF‐β2 were also revealed.