Insulin-like growth factor I-dependent tyrosine kinase activity in stromal cells of human endometrium in vitro.
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.
Von Eye Corleta
H
H
Institut für Diabetesforschung, Munich, Federal Republic of Germany.
Strowitzki
T
T
Kellerer
M
M
Häring
H U
HU
D000328:Adult; D002478:Cells, Cultured; D004717:Endometrium / Q000166:cytology / Q000201:enzymology / Q000378:metabolism*; D004958:Estradiol / Q000494:pharmacology; D005260:Female; D006801:Humans; D007328:Insulin / Q000031:analogs & derivatives / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000378:metabolism / Q000494:pharmacology*; D007457:Iodine Radioisotopes; D007700:Kinetics; D046911:Macromolecular Substances; D010766:Phosphorylation; D011374:Progesterone / Q000494:pharmacology; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000302:isolation & purification / Q000378:metabolism*; D017451:Receptors, Somatomedin; D013002:Somatomedins / Q000378:metabolism*
D007328:Insulin; D007457:Iodine Radioisotopes; D046911:Macromolecular Substances; D011956:Receptors, Cell Surface; D017451:Receptors, Somatomedin; D013002:Somatomedins; C008147:insulin, iodo-; D011374:Progesterone; D004958:Estradiol; D007334:Insulin-Like Growth Factor I; D011505:Protein-Tyrosine Kinases