title: A naturally occurring isoform inhibits parathyroid hormone receptor trafficking and signaling.
abstract: Parathyroid hormone (PTH) regulates calcium homeostasis and bone remodeling through its cognitive receptor (PTHR). We describe here a PTHR isoform harboring an in-frame 42-bp deletion of exon 14 (Δe14-PTHR) that encodes transmembrane domain 7. Δe14-PTHR was detected in human kidney and buccal epithelial cells. We characterized its topology, cellular localization, and signaling, as well as its interactions with PTHR. The C-terminus of the Δe14-PTHR is extracellular, and cell surface expression is strikingly reduced compared with the PTHR. Δe14-PTHR displayed impaired trafficking and accumulated in endoplasmic reticulum. Signaling and activation of cAMP and ERK by Δe14-PTHR was decreased significantly compared with PTHR. Δe14-PTHR acts as a functional dominant-negative by suppressing the action of PTHR. Cells cotransfected with both receptors exhibit markedly reduced PTHR cell membrane expression, colocalization with Δe14-PTHR in endoplasmic reticulum, and diminished cAMP activation and ERK phosphorylation in response to challenge with PTH. Δe14-PTHR forms heterodimers with PTHR, which may account for cytoplasmic retention of PTHR in the presence of Δe14-PTHR. Analysis of the PTHR heteronuclear RNA suggests that base-pair complementarity in introns surrounding exon 14 causes exon skipping and accounts for generation of the Δe14-PTHR isoform. Thus Δe14-PTHR is a poorly functional receptor that acts as a dominant-negative of PTHR trafficking and signaling and may contribute to PTH resistance.
authors.affiliation: Laboratory for G Protein-Coupled Receptor Biology, Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA.
authors.forename: Verónica
authors.initials: V
authors.lastname: Alonso
authors.forename: Juan A
authors.initials: JA
authors.lastname: Ardura
authors.forename: Bin
authors.initials: B
authors.lastname: Wang
authors.forename: W Bruce
authors.initials: WB
authors.lastname: Sneddon
authors.forename: Peter A
authors.initials: PA
authors.lastname: Friedman
mesh_terms: D000242:Cyclic AMP / Q000494:pharmacology; D004705:Endocytosis / Q000187:drug effects; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D005091:Exons / Q000235:genetics; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects; D057809:HEK293 Cells; D006801:Humans; D010766:Phosphorylation / Q000187:drug effects; D011485:Protein Binding / Q000187:drug effects; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D021381:Protein Transport / Q000187:drug effects; D044168:Receptor, Parathyroid Hormone, Type 1 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017384:Sequence Deletion / Q000235:genetics; D015398:Signal Transduction / Q000187:drug effects
chemical_list: C473449:PTH1R protein, human; D020033:Protein Isoforms; D044168:Receptor, Parathyroid Hormone, Type 1; D000242:Cyclic AMP; D048049:Extracellular Signal-Regulated MAP Kinases