Direct evidence that lactogenic hormones induce homodimerization of membrane-anchored prolactin receptor in intact Nb2-11C rat lymphoma cells.
The ability of full-size prolactin receptor (PRLR) from Nb2 rat lymphoma cell line to undergo lactogenic hormone-induced dimerization in intact cells or in a partially purified microsomal fraction was tested. The stoichiometry of ovine placental lactogen (oPL) binding to PRLR was documented by SDS-PAGE of the covalently cross-linked complexes between [125I]oPL and intact Nb2-11C cells. The molecular masses of the specific bands were 82 and 141 kDa, corresponding to PRLR:oPL and (PRLR)2:oPL complexes. These results provide direct evidence for the occurrence of hormone-induced receptor dimerization in intact cells. Gel-filtration studies revealed that under non-denaturing conditions, the purified receptor forms high-molecular-mass aggregates (190 and 540 kDa) composed of receptor dimers and oligomers. Since this aggregation was not dependent on the presence of lactogenic hormone, it is possible that the receptor in the intact cells may already exist as a noncovalent dimer or oligomer and that hormone-induced dimerization stabilizes the complex or changes its conformation.
Sakal
E
E
Institute of Biochemistry, Food Science and Nutrition, Faculty of Agriculture, The Hebrew University of Jerusalem, Rehovot, Israel.
Elberg
G
G
Gertler
A
A
D000345:Affinity Labels; D000818:Animals; D002462:Cell Membrane; D002850:Chromatography, Gel; D003432:Cross-Linking Reagents / Q000378:metabolism / Q000494:pharmacology; D019281:Dimerization; D006133:Growth Substances / Q000494:pharmacology; D006801:Humans; D008223:Lymphoma; D010928:Placental Lactogen / Q000378:metabolism / Q000494:pharmacology*; D011487:Protein Conformation; D051381:Rats; D011981:Receptors, Prolactin / Q000737:chemistry / Q000187:drug effects* / Q000378:metabolism; D012756:Sheep; D014407:Tumor Cells, Cultured
D000345:Affinity Labels; D003432:Cross-Linking Reagents; D006133:Growth Substances; D011981:Receptors, Prolactin; D010928:Placental Lactogen