title: Disruption of parathyroid hormone and parathyroid hormone-related peptide receptor phosphorylation prolongs ERK1/2 MAPK activation and enhances c-fos expression.
abstract: Previous studies have demonstrated that parathyroid hormone (PTH) binding to the PTH/PTH-related peptide receptor (PPR) stimulates G protein coupling, receptor phosphorylation, β-arrestin translocation, and internalization of the ligand/receptor complex. The extracellular signal-regulated mitogen-activated protein kinases 1/2 (ERK1/2 MAPK) are downstream effectors of PPR. In the current study, we investigated the role of PPR phosphorylation in the PTH regulation of the ERK1/2 MAPK pathway. Short treatment with PTH (0-40 min) of LLCP-K(1) cells stably expressing a wild-type (WT) or a phosphorylation-deficient (PD) PPR (WT-PPR or PD-PPR cells, respectively) results in similar activation of ERK1/2. Interestingly, PTH stimulation of ERK1/2 in the WT-PPR cells then decreases as a result of longer PTH (60 min) treatment, and inhibition of ERK1/2 by PTH is observed at 90 min. Strikingly, the PD-PPR cells exhibit prolonged ERK1/2 activation up to 90 min of PTH treatment. An ERK1/2-dependent increase in c-fos expression is observed in the PD-PPR cells. Subsequently, c-fos expression in the WT-PPR and PD-PPR cells was markedly attenuated by a specific ERK1/2 pathway inhibitor. Further investigations revealed that PTH treatment causes a robust recruitment of a green fluorescent protein-tagged β-arrestin2 (β-arrestin2-GFP) in the WT-PPR cells. In contrast, β-arrestin2 recruitment was reduced in the PD-PPR cells. Importantly, expression of a receptor phosphorylation-independent β-arrestin2 (R169E) in the PD-PPR cells restored the biphasic effect of PTH on ERK1/2 as in the WT-PPR cells. The study reports a novel role for receptor phosphorylation and β-arrestin2 in the subsequent inhibition of the ERK1/2 pathway and in control of gene expression.
authors.affiliation: Center for Orthopaedic Research, Columbia University, 650 West 168th St., New York, NY 10032, USA. ht2323@columbia.edu
authors.forename: Hesham A
authors.initials: HA
authors.lastname: Tawfeek
authors.forename: Abdul B
authors.initials: AB
authors.lastname: Abou-Samra
mesh_terms: D000818:Animals; D019390:Arrestins / Q000378:metabolism; D015153:Blotting, Western; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D004789:Enzyme Activation; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D016762:Genes, fos / Q000235:genetics*; D049452:Green Fluorescent Proteins / Q000378:metabolism; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D007684:Kidney Tubules / Q000166:cytology / Q000378:metabolism; D020935:MAP Kinase Signaling System / Q000235:genetics; D018613:Microscopy, Confocal; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D010281:Parathyroid Hormone / Q000235:genetics / Q000502:physiology*; D044162:Parathyroid Hormone-Related Protein / Q000235:genetics / Q000502:physiology*; D010766:Phosphorylation; D013552:Swine; D000071557:beta-Arrestins
chemical_list: D019390:Arrestins; D010281:Parathyroid Hormone; D044162:Parathyroid Hormone-Related Protein; D000071557:beta-Arrestins; D049452:Green Fluorescent Proteins; D015544:Inositol 1,4,5-Trisphosphate; D048049:Extracellular Signal-Regulated MAP Kinases; D020928:Mitogen-Activated Protein Kinases