Parathyroid hormone synergizes with non-cyclic AMP pathways to activate the cyclic AMP response element.
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.
Murrills
Richard J
RJ
Department of Osteoporosis & Frailty, Women's Health & Musculoskeletal Biology, Wyeth Research, Collegeville, Pennsylvania 19426, USA. murrilr@wyeth.com
Andrews
Jennifer L
JL
Samuel
Rachelle L
RL
Coleburn
Valerie E
VE
Bhat
Bheem M
BM
Bhat
Ramesh A
RA
Bex
Frederick J
FJ
Bodine
Peter V N
PV
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
C470125:PTH protein, human; D010281:Parathyroid Hormone; D000249:Adenosine Monophosphate; D004815:Epidermal Growth Factor; D000242:Cyclic AMP; D011493:Protein Kinase C; D002118:Calcium