Demonstration of a Relaxin Receptor and Relaxin-Stimulated Tyrosine Phosphorylation in Human Lower Uterine Segment Fibroblasts1
To elucidate the mechanism of relaxin action, we studied the binding characteristics of human relaxin and its effects on intracellular concentrations of cAMP and tyrosine phosphorylation of cellular proteins in a model system of human cervix, human lower uterine segment fibroblasts. Human relaxin la...
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Published in | Endocrinology (Philadelphia) Vol. 139; no. 3; pp. 1208 - 1212 |
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Main Authors | , , , , |
Format | Journal Article |
Language | English |
Published |
Endocrine Society
01.03.1998
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Online Access | Get full text |
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Summary: | To elucidate the mechanism of relaxin action, we studied the binding
characteristics of human relaxin and its effects on intracellular
concentrations of cAMP and tyrosine phosphorylation of cellular
proteins in a model system of human cervix, human lower uterine segment
fibroblasts. Human relaxin labeled with 125I bound
specifically to a single class of high-affinity relaxin binding sites,
distinct from insulin receptors, with a mean (±sem)
dissociation constant (Kd) of 4.36 ± 1.7 ×
10−9 m and a mean of 3220 ± 557 binding
sites per cell in human lower uterine segment fibroblasts. Relaxin, in
quantities that were shown previously to stimulate intracellular levels
of cAMP in other cell types, had no effect on intracellular levels of
cAMP in human lower uterine segment fibroblasts even in the presence of
the phosphodiesterase inhibitor 3-isobutyl-1-methyl-xanthine (IBMX).
Incubation of the cells with relaxin caused a significant increase in
tyrosine phosphorylation of a protein with an apparent Mr
of approximately 220 kDa in these cells. In concert with results
of recent studies that demonstrated that the Mr of the
relaxin receptor is approximately 220 kDa, our data suggest that the
phosphorylated protein is likely to be the relaxin receptor. |
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ISSN: | 0013-7227 1945-7170 |
DOI: | 10.1210/endo.139.3.5772 |