Dataset Information

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 (?e14-PTHR) that encodes transmembrane domain 7. ?e14-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 ?e14-PTHR is extracellular, and cell surface expression is strikingly reduced compared with the PTHR. ?e14-PTHR displayed impaired trafficking and accumulated in endoplasmic reticulum. Signaling and activation of cAMP and ERK by ?e14-PTHR was decreased significantly compared with PTHR. ?e14-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 ?e14-PTHR in endoplasmic reticulum, and diminished cAMP activation and ERK phosphorylation in response to challenge with PTH. ?e14-PTHR forms heterodimers with PTHR, which may account for cytoplasmic retention of PTHR in the presence of ?e14-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 ?e14-PTHR isoform. Thus ?e14-PTHR is a poorly functional receptor that acts as a dominant-negative of PTHR trafficking and signaling and may contribute to PTH resistance.

SUBMITTER: Alonso V

PROVIDER: S-EPMC3179322 | biostudies-literature | 2011 Jan

REPOSITORIES: biostudies-literature

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A naturally occurring isoform inhibits parathyroid hormone receptor trafficking and signaling.

Alonso Verónica V Ardura Juan A JA Wang Bin B Sneddon W Bruce WB Friedman Peter A PA

Journal of bone and mineral research : the official journal of the American Society for Bone and Mineral Research 20110101 1

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 ...[more]

PMID: 20578167

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Project description:The naturally occurring p53 isoform ∆40p53 lacks the first N-terminal transactivation domain of WTp53 and is implicated in mammalian aging. ∆40p53 is preferentially translated during cell stress. The ∆40p53 isoform oligomerizes with WTp53 to form hetero-tetramers with altered function compared to WTp53 tetramers. Co-expression of ∆40p53 and WTp53 results in the formation of a mixed population ∆40p53:WTp53 tetramers, including “contaminating” WTp53 tetramers. Here we implemented a strategy—based upon the native p53 tetramer structure—in which ∆40p53 was tethered to WTp53 (∆40p53:WTp53) as a single transcript, resulting in tetramers with a defined 2:2 ratio of Δ40p53 to WTp53. Using CRISPR/Cas9, human cell lines were generated in which ∆40p53:WTp53 (and controls) was inserted at the native TP53 locus. This enabled ∆40p53:WTp53 expression and induction in a physiologically relevant manner. As with WTp53, activation of ∆40p53:WTp53 with Nutlin-3a causes increased genome occupancy. However, unlike WTp53, precision run-on nuclear sequencing (PRO-seq) showed that increased ∆40p53:WTp53 occupancy does not correlate with robust transcriptional activation. Activated ∆40p53:WTp53 only induces transcription of a small subset of WTp53 enhancer RNAs (eRNAs) and other annotated regions. Defective eRNA production correlates with loss of downstream mature mRNA and p53-dependent cell-cycle arrest. Pathway analysis of ∆40p53:WTp53 induced transcriptional changes identified increased activation of stress and aging related pathways in ∆40p53:WTp53 compared to WTp53. However, these pathways never mature to full activation under Nutlin-3a treatment. Therefore, we propose a model where activation of ∆40p53 results in the transcription of a subset of WTp53 targets, setting the stage for synergistic pathway activation with other stress specific transcription factors driving cellular response in ways that differ from WTp53. Implications of these results provide an additional mechanistic layer of p53 regulation, in which expression of ∆40p53 isoform allows for modulation of WTp53 activities in a context dependent manner, tipping the scales towards activation of aging-associated pathways.

Dataset Information

A naturally occurring isoform inhibits parathyroid hormone receptor trafficking and signaling.

Publications

A naturally occurring isoform inhibits parathyroid hormone receptor trafficking and signaling.

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