title: Parathyroid hormone synergizes with non-cyclic AMP pathways to activate the cyclic AMP response element.
abstract: Parathyroid hormone (PTH) activates multiple signaling pathways following binding to the PTH1 receptor in osteoblasts. Previous work revealed a discrepancy between cAMP stimulation and CRE reporter activation of truncated PTH peptides, suggesting that additional signaling pathways contribute to activation of the CRE. Using a CRE-Luciferase reporter containing multiple copies of the CRE stably transfected into the osteoblastic cell line Saos-2, we tested the ability of modulators of alternative pathways to activate the CRE or block the PTH-induced activation of the CRE. Activators of non-cyclic AMP pathways, that is, EGF (Akt, MAPK, JAK/STAT pathways); thapsigargin (intracellular calcium pathway); phorbol myristate acetate (protein kinase C, PKC pathway) induced minor increases in CRE-luciferase activity alone but induced dramatic synergistic effects in combination with PTH. The protein kinase A (PKA) inhibitor H-89 (10 microM) almost completely blocked PTH-induced activation of the CRE-reporter. Adenylate cyclase inhibitors SQ 22536 and DDA had profound and time-dependent biphasic effects on the CRE response. The MAPK inhibitor PD 98059 partially inhibited basal and PTH-induced CRE activity to the same degree, while the PKC inhibitor bisindolylmaleimide (BIS) had variable effects. The calmodulin kinase II inhibitor KN-93 had no significant effect on the response to PTH. We conclude that non-cAMP pathways (EGF pathway, calcium pathway, PKC pathway) converge on, and have synergistic effects on, the response of a CRE reporter to PTH.
authors.affiliation: Department of Osteoporosis & Frailty, Women's Health & Musculoskeletal Biology, Wyeth Research, Collegeville, Pennsylvania 19426, USA. murrilr@wyeth.com
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Murrills
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Andrews
authors.forename: Rachelle L
authors.initials: RL
authors.lastname: Samuel
authors.forename: Valerie E
authors.initials: VE
authors.lastname: Coleburn
authors.forename: Bheem M
authors.initials: BM
authors.lastname: Bhat
authors.forename: Ramesh A
authors.initials: RA
authors.lastname: Bhat
authors.forename: Frederick J
authors.initials: FJ
authors.lastname: Bex
authors.forename: Peter V N
authors.initials: PV
authors.lastname: Bodine
mesh_terms: D000249:Adenosine Monophosphate / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D045744:Cell Line, Tumor; D000242:Cyclic AMP / Q000378:metabolism*; D004815:Epidermal Growth Factor / Q000378:metabolism; D006801:Humans; D010281:Parathyroid Hormone / Q000494:pharmacology*; D011493:Protein Kinase C / Q000378:metabolism; D020218:Response Elements / Q000187:drug effects*; D015398:Signal Transduction
chemical_list: C470125:PTH protein, human; D010281:Parathyroid Hormone; D000249:Adenosine Monophosphate; D004815:Epidermal Growth Factor; D000242:Cyclic AMP; D011493:Protein Kinase C; D002118:Calcium