Disease‐associated mutation in PTH reveals molecular mechanisms in endosomal GPCR signaling

Abstract

Parathyroid hormone (PTH) and its related peptide (PTHrP) activate PTH receptor (PTHR) signaling, but only PTH sustains GS–mediated cAMP production after PTHR internalization into early endosomes. The physiological relevance of this unexpected behavior for PTHR is unclear. Here we present evidence that endosomal PTHR signaling through cAMP also has disease relevance. We demonstrated that R25C mutation recently identified in PTH as a new cause of hypocalcemia in humans affects receptor binding at endosomal pH resulting in rapid ligand dissociation and recycling of PTHR preventing sustained endosomal cAMP signaling. Using hydrogen–deuterium exchange coupled with mass spectrometry (HDXMS) to map structural changes of PTHR upon PTH binding, we identified acidic clusters in the receptor's first extracellular loop as key determinants for Arg25 binding and endosomal cAMP signaling. Determination of the dynamic of protein‐protein interaction using FRET approaches revealed that PTH R25C has a lower potency to form and stabilize the functional complex between β‐Arrestin, Gβγ and PTHR required for endosomal cAMP generation. Overall, these new findings indicate that PTH‐induced endosomal cAMP signaling is likely a primary signaling component regulating calcium homeostasis.Support or Funding InformationNIH R01‐DK102495 and R01‐DK087688 National Research Foundation of Korea NRF‐2013R1A1A1A05005629This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.