AJP - Endocrinology and Metabolism, Vol 262, Issue 6 E863-E868, Copyright © 1992 by American Physiological Society
Insulin-like growth factor I-dependent tyrosine kinase activity in stromal cells of human endometrium in vitro
H. Von Eye Corleta, T. Strowitzki, M. Kellerer and H. U. Haring
Institut fur Diabetesforschung, Munich, Federal Republic of Germany.
The study was undertaken to identify and characterize insulin-like growth
factor I (IGF-I) receptors in human endometrial stromal cells in culture
and to examine whether these receptors are modulated by estradiol (E2)
and/or progesterone (P). We found that partially purified plasma membrane
proteins from these cells contain specific high-affinity binding sites for
IGF-I (10 fmol/micrograms protein). Chemical cross-linking with
125I-labeled IGF-I and autophosphorylation with [32P]ATP-labeled proteins
of relative molecular weight 135,000 and 95,000 correspond to the known Mr
values of the alpha- and the beta-subunits of IGF-I receptors. Receptor
autophosphorylation and phosphorylation of the substrate poly(Glu,Na4Tyr1)
was stimulated in vitro by IGF-I (half-maximally at 1 nM, maximally at 100
nM). After stimulation of intact cells with IGF-I (5 nM) and subsequent
partial purification of receptors in the presence of phosphatase
inhibitors, a 2.5- to 3.6-fold stimulation of the kinase activity toward
poly(Glu,Na4Tyr1) was found. Preincubation of the cells for 16 h with E2,
P, and E2 + P did not modify the IGF-I binding characteristics nor the
effect of IGF-I (5 nM) on tyrosine kinase stimulation in intact cells. This
suggests that, in isolated humans, endometrial cell modulation of IGF-I
receptor function by estrogen and P does not occur.
