title: Regulation of PTH/PTH-related protein receptor expression by endogenous PTH-related protein in the rat osteosarcoma cell line ROS 17/2.8.
abstract: We have utilized clonal lines of the rat osteoblastic cell line ROS 17/2.8 stably transfected with full-length parathyroid hormone-related protein (PTHrP) cDNA in a sense or an antisense orientation to examine the effects of alteration in the production of endogenous PTHrP on expression of the PTH/PTHrP receptor. In the stably transfected clonal cell lines, changes in PTH/PTHrP receptor expression were evaluated by Northern blot analysis, whole-cell ligand binding of 125I-[Tyr36] PTHrP (1-36), and exogenous PTHrP (1-34)-stimulated cyclic adenosine monophosphate (cAMP) accumulation. Compared to control (vector-transfected) cells, PTHP-overproducing (sense-transfected) cells exhibited a marked decrease in the expression of PTH/PTHrP receptor mRNA and PTHrP ligand binding, as well as a corresponding decrease in the PTHrP (1-34)-stimulated cAMP response. By contrast, the antisense-transfected cells showed a marked increase in expression of PTH/PTHrP receptor mRNA and PTHrP (1-34) ligand binding, but a significant increase in the PTHrP (1-34)-stimulated cAMP response was not detected. Using antisense-transfected ROS cells, PTH/PTHrP receptor mRNA expression and 125I-[Tyr36] PTHrP (1-36) binding were downregulated by treatment for 24 h with exogenous PTHrP (1-36), forskolin, or dibutyryl cAMP. The findings extend those of earlier studies showing receptor downregulation by exogenous PTH by indicating that endogenous PTHrP, as well as circulating PTH, may help regulate receptor production; and suggesting that even very low concentrations of the peptide may influence receptor production.
authors.affiliation: Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, USA.
authors.forename: P
authors.initials: P
authors.lastname: Du
authors.forename: P K
authors.initials: PK
authors.lastname: Seitz
authors.forename: C W
authors.initials: CW
authors.lastname: Cooper
mesh_terms: D000818:Animals; D015152:Blotting, Northern; D003994:Bucladesine / Q000494:pharmacology; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects*; D006801:Humans; D010006:Osteoblasts / Q000378:metabolism; D012516:Osteosarcoma / Q000378:metabolism*; D044162:Parathyroid Hormone-Related Protein; D011506:Proteins / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*; D016372:RNA, Antisense / Q000032:analysis; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D018016:Receptors, Parathyroid Hormone / Q000235:genetics* / Q000378:metabolism; D014162:Transfection; D014407:Tumor Cells, Cultured
chemical_list: C470121:PTHLH protein, human; D044162:Parathyroid Hormone-Related Protein; D011506:Proteins; D016372:RNA, Antisense; D012333:RNA, Messenger; D018016:Receptors, Parathyroid Hormone; D005576:Colforsin; D003994:Bucladesine; D000242:Cyclic AMP