A novel phospholipase C inhibitor and phorbol esters reveal selective regulation of thrombin- and parathyroid hormone-stimulated signaling pathways in rat osteosarcoma cells

M. Babich, G. E. Alford, R. A. Nissenson

Research output: Contribution to journalArticle

11 Scopus citations

Abstract

Previous studies have demonstrated that parathyroid hormone (PTH) and human α-thrombin mobilize intracellular calcium from distinct pools in UMR 106-H5 rat osteosarcoma cells. The present studies were designed to explore the molecular basis of this differential signaling. Maximally effective concentrations of both PTH (240 nM) and thrombin (10 U/ml) produced a rapid intracellular free calcium (Ca(i)++) transient (a 2- to 3-fold increase) that was inhibited by pretreatment with the phospholipase C inhibitor 1-[6- [[17β-3-methoxyestra-1,3,5(10)-trien-17-yl]amino]hexyl-1H-pyrrole-2,5-dion e (U73,122) in a dose-dependent manner (IC50 = 3 μM). Inhibition by U73,122 was not associated with a change in PTH-stimulated adenylate cyclase activity, whereas inositol phosphate accumulation, detected only in response to thrombin, was inhibited 23 to 45%. Prior exposure of cells for 5 min with the protein kinase C activators phorbol 12-myristate 13-acetate (8-80 nM) and phorbol 12,13-dibutyrate (80 nM) weakly inhibited (≤ 30%) the peak Ca(i)++ increase in response to thrombin but completely blocked the Ca(i)++ response to PTH. In contrast, 12-myristate 13-acetate produced a 1.55-fold increase in the maximal stimulatory effect of PTH on adenylate cyclase activity. These data suggest that activation of phospholipase C is a prerequisite for both PTH- and thrombin-stimulated increases in Ca(i)++ and that protein kinase C differentially regulates the ability of these agents to raise Ca(i)++. Collectively the results support the notion that the IP3/calcium mobilizing pathways utilized by PTH and thrombin are compartmentalized. Further, the finding that phorbol esters produce opposite effects on PTH-stimulated adenylate cyclase and Ca(i)++ suggests that protein kinase C can alter the cellular response to PTH by regulating the relative strength of signaling via these pathways.

Original languageEnglish (US)
Pages (from-to)172-177
Number of pages6
JournalJournal of Pharmacology and Experimental Therapeutics
Volume269
Issue number1
StatePublished - 1994
Externally publishedYes

ASJC Scopus subject areas

  • Pharmacology

Fingerprint Dive into the research topics of 'A novel phospholipase C inhibitor and phorbol esters reveal selective regulation of thrombin- and parathyroid hormone-stimulated signaling pathways in rat osteosarcoma cells'. Together they form a unique fingerprint.

  • Cite this