Increased receptor stimulation elicits differential calcium-sensing receptor T888 dephosphorylation

WD McCormick, R Atkinson-Dell, K Campion, H-C Mun, AD Conigrave, DT Ward

    Research output: Contribution to journalArticlepeer-review

    Abstract

    The calcium-sensing receptor (CaR) elicits oscillatory Ca(2+)(i) mobilization associated with dynamic, inhibitory protein kinase C-mediated phosphorylation of CaR(T888). While modest CaR stimulation elicits Ca(2+)(i) oscillations, greater stimulation either increases oscillation frequency or elicits sustained responses by an unknown mechanism. Here, moderate CaR stimulation (2.5 mm Ca(2+)(o), 10 min) increased CaR(T888) phosphorylation (160-kDa mature receptor) 5-fold in CaR stably transfected HEK-293 cells, whereas 3-5 mm Ca(2+)(o) treatments were without apparent effect. Treatment with 2 mm Ca(2+)(o) caused sustained CaR(T888) phosphorylation (> or = 20 min) and oscillatory Ca(2+)(i) mobilization. However, 5 mm Ca(2+)(o) increased CaR(T888) phosphorylation only briefly while eliciting sustained Ca(2+)(i) mobilization, suggesting that greater CaR activation induces rapid CaR(T888) dephosphorylation, thus permitting sustained Ca(2+)(i) responses. Indeed, 5 mm Ca(2+)(o) stimulated protein phosphatase 2A activity and induced CaR(T888) dephosphorylation following acute phorbol ester pretreatment, the latter effect being mimicked by CaR-positive allosteric modulators (NPS-R467 and l-Phe). Finally, the phosphatase inhibitor calyculin-A reversed CaR-induced inhibition of parathyroid hormone secretion from bovine parathyroid slices and normal human parathyroid cells, demonstrating the physiological importance of phosphorylation status on parathyroid function. Therefore, high Ca(2+)(o)-stimulated protein kinase C acts in concert with high Ca(2+)(o)-induced phosphatase activity to generate and maintain CaR-induced Ca(2+)(i) oscillations via the dynamic phosphorylation and dephosphorylation of CaR(T888).
    Original languageEnglish
    Article numberjbc.M109.071084
    Pages (from-to)14170-14177
    Number of pages7
    JournalJournal of Biological Chemistry
    Volume285
    Issue number19
    DOIs
    Publication statusPublished - 7 May 2010

    Keywords

    • Calcium/Intracellular Release
    • G Proteins/Coupled Receptors (GPCR)
    • Receptors/Phosphatases
    • Signal Transduction/Calcium
    • Signal Transduction/Phorbol Esters
    • Signal Transduction/Phosphoprotein Phosphatases
    • Signal Transduction/Phosphoprotein Phosphatases/PP1/PP2A

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