C-terminal parathyroid hormone-related protein (PTHrP) (107-139) stimulates intracellular Ca(2+) through a receptor different from the type 1 PTH/PTHrP receptor in osteoblastic osteosarcoma UMR 106 cells
Authors: C Guill√©n
A Val√≠n
P Esbrit
Journal: Endocrinology (2001)
Discipline: BIOLOGY & BIOCHEMISTRY
Keywords: PTHrP (107-139); Ca(2+); osteoblastic osteosarcoma; UMR 106 cells; EC(50)
Affiliations: Bone and Mineral Metabolism Laboratory, Research Unit, FundacioÃÅn JimeÃÅnez DiÃÅaz, 28040 Madrid, Spain

Abstract:  Studies were undertaken to determine whether PTH-related protein (PTHrP) (107-139) mobilizes [Ca(2+)](i) in osteoblastic osteosarcoma UMR 106 cells. PTHrP (107-139), in a manner similar to PTHrP (107-111), induced a rapid [Ca(2+)](i) response in these cells that was dose dependent (EC(50) of approximately 0.1 pM) and more efficient than that of PTHrP (1-36) (EC(50) of approximately 1 nM). This effect of PTHrP (107-139) was abrogated by micromolar doses of verapamil or nifedipine. However, it was unaffected by 10 microM U73122 (a phospholipase C inhibitor), 100 microg/ml heparin (an inositol 1,4,5-trisphosphate receptor inhibitor), or 400 ng/ml pertussis toxin (a G(i) inhibitor), which inhibited the [Ca(2+)](i) response to PTHrP (1-36), or by either 25 nM bisindolylmaleimide I (BIM), a protein kinase (PK) C inhibitor, or 1 microM phorbol-12-myristate-13-acetate preincubation (22 h). PTHrP (107-139) and PTHrP (1-36), at 100 nM, desensitized the [Ca(2+)](i) response to a second challenge with the same peptide, but not with the other peptide in these cells. PTHrP (7-34), a type 1 PTH/PTHrP receptor (PTH1R) antagonist, decreased the effect of PTHrP (1-36) on [Ca(2+)](i). In contrast, PTHrP (107-111), but neither PTHrP (109-138) nor PTHrP (7-34), abolished this effect of PTHrP (107-139). Both PTHrP (107-139) and PTHrP (1-36), added together at submaximal doses, induced a higher [Ca(2+)](i) response. Moreover, PTHrP (107-139) increased the efficacy of PTHrP (1-36) on [Ca(2+)](i), but decreased its induced increase in PKA activity in these cells. Verapamil or nifedipine (at 50 microM) or 25 nM BIM, but not 25 microM adenosine 3',5'-cyclic monophosphorothioate, Rp-isomer, a PKA inhibitor, abolished the PTHrP (107-139)-induced increase in interleukin 6 messenger RNA (assessed by RT, followed by PCR) in UMR 106 cells. This peptide also increased c-fos messenger RNA in these cells; an effect inhibited by BIM, but unaffected by either verapamil or EGTA. These findings support the existence of high-affinity receptors for PTHrP (107-139), associated with an induced Ca(2+) influx, different from the PTH1R in UMR 106 cells. The present results suggest that PTHrP could affect bone turnover by interacting with the PTH1R and other yet unknown receptors in bone cells through complex mechanisms. 

Retracted: No

PubPeer comments:
 Figure 9: More similar than expected  , 
 Thanks to Strobilanthes involucrata for this comment. This is a paper published more than 20 years ago. I have to say that the laboratory is closed, because of the PI retired some years ago and we cannot access to the original images of the corresponding experiments. Furthermore, the laboratory was disassembled and does not exist at this moment. Best regards Carlos ,