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Article

Trace Amine-Associated Receptor 1 Trafficking to Cilia of Thyroid Epithelial Cells

Department of Life Sciences and Chemistry, Focus Area HEALTH, Jacobs University Bremen, Campus Ring 1, D-28759 Bremen, Germany
*
Author to whom correspondence should be addressed.
These authors contributed equally to this study.
Academic Editors: Gang Dong and William Tsang
Cells 2021, 10(6), 1518; https://doi.org/10.3390/cells10061518
Received: 14 May 2021 / Revised: 11 June 2021 / Accepted: 12 June 2021 / Published: 16 June 2021
(This article belongs to the Collection Cilia and Flagella: Structure, Function and Beyond)
Trace amine-associated receptor 1 (rodent Taar1/human TAAR1) is a G protein-coupled receptor that is mainly recognized for its functions in neuromodulation. Previous in vitro studies suggested that Taar1 may signal from intracellular compartments. However, we have shown Taar1 to localize apically and on ciliary extensions in rodent thyrocytes, suggesting that at least in the thyroid, Taar1 may signal from the cilia at the apical plasma membrane domain of thyrocytes in situ, where it is exposed to the content of the follicle lumen containing putative Taar1 ligands. This study was designed to explore mouse Taar1 (mTaar1) trafficking, heterologously expressed in human and rat thyroid cell lines in order to establish an in vitro system in which Taar1 signaling from the cell surface can be studied in future. The results showed that chimeric mTaar1-EGFP traffics to the apical cell surface and localizes particularly to spherical structures of polarized thyroid cells, procilia, and primary cilia upon serum-starvation. Moreover, mTaar1-EGFP appears to form high molecular mass forms, possibly homodimers and tetramers, in stably expressing human thyroid cell lines. However, only monomeric mTaar1-EGFP was cell surface biotinylated in polarized human thyrocytes. In polarized rat thyrocytes, mTaar1-EGFP is retained in the endoplasmic reticulum, while cilia were reached by mTaar1-EGFP transiently co-expressed in combination with an HA-tagged construct of the related mTaar5. We conclude that Taar1 trafficking to cilia depends on their integrity. The results further suggest that an in vitro cell model was established that recapitulates Taar1 trafficking in thyrocytes in situ, in principle, and will enable studying Taar1 signaling in future, thus extending our general understanding of its potential significance for thyroid autoregulation. View Full-Text
Keywords: cilia; G protein-coupled receptors; green fluorescent protein; thyroid auto-regulation; thyroid epithelial cells; trace amine-associated receptor 1; trafficking cilia; G protein-coupled receptors; green fluorescent protein; thyroid auto-regulation; thyroid epithelial cells; trace amine-associated receptor 1; trafficking
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MDPI and ACS Style

Qatato, M.; Venugopalan, V.; Al-Hashimi, A.; Rehders, M.; Valentine, A.D.; Hein, Z.; Dallto, U.; Springer, S.; Brix, K. Trace Amine-Associated Receptor 1 Trafficking to Cilia of Thyroid Epithelial Cells. Cells 2021, 10, 1518. https://doi.org/10.3390/cells10061518

AMA Style

Qatato M, Venugopalan V, Al-Hashimi A, Rehders M, Valentine AD, Hein Z, Dallto U, Springer S, Brix K. Trace Amine-Associated Receptor 1 Trafficking to Cilia of Thyroid Epithelial Cells. Cells. 2021; 10(6):1518. https://doi.org/10.3390/cells10061518

Chicago/Turabian Style

Qatato, Maria, Vaishnavi Venugopalan, Alaa Al-Hashimi, Maren Rehders, Aaron D. Valentine, Zeynep Hein, Uillred Dallto, Sebastian Springer, and Klaudia Brix. 2021. "Trace Amine-Associated Receptor 1 Trafficking to Cilia of Thyroid Epithelial Cells" Cells 10, no. 6: 1518. https://doi.org/10.3390/cells10061518

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