Biochemical and morphological characterization of parathyroid hormone receptor binding to the rat osteosarcoma cell line UMR-106.
We have used both biochemical and morphological techniques to characterize PTH receptors on the clonal osteosarcoma cell line UMR-106, a widely used model of the osteoblast phenotype. 125I-labeled rat (r) PTH-(1-34) bound to a single class of specific saturable receptors on both whole cells and membranes prepared from UMR-106 cells in a time- and temperature-dependent manner. A decrease in PTH receptor affinity seen in the presence of guanine nucleotides demonstrated that PTH receptors on the UMR-106 cells are coupled to guanyl nucleotide-binding proteins. Although PTH is a potent stimulator of adenylate cyclase in the UMR-106 cells, comparison of PTH-stimulated adenylate cyclase and PTH binding curves indicated the presence of receptors that are not linked to the adenylate cyclase system. Our studies also demonstrated that 125I-labeled rPTH-(1-34) bound to UMR-106 cells is rapidly internalized at 22 C, whereas PTH bound at 4 C remains intact and on the cell surface. Internalization of 125I-labeled rPTH-(1-34) was associated with degradation and release of the hormone at 22 C. Three morphologically distinct cell types were identified in subconfluent cultures of UMR-106 cells. Autoradiographic analysis of 125I-labeled rPTH-(1-34) binding demonstrated differential PTH receptor expression in these cell types. The most abundant PTH binding was observed over a cell type with long cytoplasmic extensions. This cell was reminiscent of the predominant PTH target cell previously identified in the rat metaphysis in vivo, suggesting that the UMR-106 cell line may represent neoplastic transformation of the PTH target cell.
Mitchell
J
J
Department of Physiology, McGill University, Montreal, Quebec, Canada.
Rouleau
M F
MF
Goltzman
D
D
D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D003593:Cytoplasm / Q000648:ultrastructure; D004789:Enzyme Activation; D019204:GTP-Binding Proteins / Q000378:metabolism; D006165:Guanylyl Imidodiphosphate / Q000494:pharmacology; D012516:Osteosarcoma / Q000378:metabolism* / Q000648:ultrastructure; D010281:Parathyroid Hormone / Q000378:metabolism; D010446:Peptide Fragments / Q000378:metabolism; D051381:Rats; D011956:Receptors, Cell Surface / Q000378:metabolism*; D018016:Receptors, Parathyroid Hormone; D019379:Teriparatide; D014407:Tumor Cells, Cultured
D010281:Parathyroid Hormone; D010446:Peptide Fragments; D011956:Receptors, Cell Surface; D018016:Receptors, Parathyroid Hormone; D019379:Teriparatide; D006165:Guanylyl Imidodiphosphate; D019204:GTP-Binding Proteins; D000262:Adenylyl Cyclases