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Control of PTH secretion by the TRPC1 ion channel
Marta Onopiuk, … , Leonidas Tsiokas, Kai Lau
Marta Onopiuk, … , Leonidas Tsiokas, Kai Lau
Published March 26, 2020
Citation Information: JCI Insight. 2020;5(8):e132496. https://doi.org/10.1172/jci.insight.132496.
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Research Article Cell biology Endocrinology

Control of PTH secretion by the TRPC1 ion channel

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Abstract

Familial hypocalciuric hypercalcemia (FHH) is a genetic condition associated with hypocalciuria, hypercalcemia, and, in some cases, inappropriately high levels of circulating parathyroid hormone (PTH). FHH is associated with inactivating mutations in the gene encoding the Ca2+-sensing receptor (CaSR), a GPCR, and GNA11 encoding G protein subunit α 11 (Gα11), implicating defective GPCR signaling as the root pathophysiology for FHH. However, the downstream mechanism by which CaSR activation inhibits PTH production/secretion is incompletely understood. Here, we show that mice lacking the transient receptor potential canonical channel 1 (TRPC1) develop chronic hypercalcemia, hypocalciuria, and elevated PTH levels, mimicking human FHH. Ex vivo and in vitro studies revealed that TRPC1 serves a necessary and sufficient mediator to suppress PTH secretion from parathyroid glands (PTGs) downstream of CaSR in response to high extracellular Ca2+ concentration. Gα11 physically interacted with both the N- and C-termini of TRPC1 and enhanced CaSR-induced TRPC1 activity in transfected cells. These data identify TRPC1-mediated Ca2+ signaling as an essential component of the cellular apparatus controlling PTH secretion in the PTG downstream of CaSR.

Authors

Marta Onopiuk, Bonnie Eby, Vasyl Nesin, Peter Ngo, Megan Lerner, Caroline M. Gorvin, Victoria J. Stokes, Rajesh V. Thakker, Maria Luisa Brandi, Wenhan Chang, Mary Beth Humphrey, Leonidas Tsiokas, Kai Lau

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Figure 6

Gα11 physically interacts with TRPC1 and increases its activity.

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Gα11 physically interacts with TRPC1 and increases its activity.
(A and ...
(A and B) Gα11 increases TRPC1-mediated Ca2+ signaling in HEK293 cells. Cells were transiently transfected with CaSR and TRPC1α or CaSR, TRPC1α, and Gα11. Both groups were cotransfected with the fluorescent Ca2+ indicator, GCaMP3, and fluorescence intensity was determined by single-cell Ca2+ imaging. Changes in intracellular Ca2+ concentration (F/F0) in response to spermine (1 mM) were determined under physiological conditions (1.8 mM extracellular Ca2+, A) or in Ca2+-free ECS followed by Ca2+ readdition (2 mM, B). Data were pooled from 74 (black) or 85 (red) cells from 2 independent transfections (A) and 318 (black) or 261 (red) cells from 4 independent transfections (B). (C) HEK293T cells were transiently transfected with the long form of TRPC1ε, short form of TRPC1ε, short form of TRPC1α, long form of TRPC1α, or the same TRPC1 plasmids plus myc-tagged Gα11 (top 3 rows) or GαS (bottom 3 rows). Gα11 was immunoprecipitated using α-myc, and GαS was immunoprecipitated using α-GαS. TRPC1 was detected in the complexes using anti-TRPC1 (top). TRPC1 input is shown in middle panels, and immunoprecipitated Gα11 or GαS is shown in bottom panels. (D) Truncation mutants of TRPC1α (GST alone, GST-N(α)-ter, GST-N(ε)-ter, GST-ΔNΔC, GST-C-ter, GST-ΔN) shown in E tagged with GST (blue cylinders) were cotransfected with WT Gα11 or GαS. Protein-protein interactions were determined by GST pulldowns followed by immunoblotting. Gα11 (first panel), but not GαS (third panel), interacted with the cytosolic N- or C-tail of TRPC1. Gα11 input is shown in second panel, GαS input is shown in fourth panel, and immunoprecipitated mutants of TRPC1 are shown.

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