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Open AccessArticle

Procathepsin V Is Secreted in a TSH Regulated Manner from Human Thyroid Epithelial Cells and Is Accessible to an Activity-Based Probe

1
Department of Life Sciences and Chemistry, Jacobs University Bremen, D-28759 Bremen, Germany
2
School of Pharmacy, Queen’s University Belfast, Belfast BT9 7BL, UK
3
Institute of Physiological Chemistry, Martin Luther University Halle-Wittenberg, D-06114 Halle-Saale, Germany
4
Klinik für Endokrinologie, Diabetologie und Stoffwechsel, Universitätsklinikum Essen (AöR), Universität Duisburg-Essen, D-45177 Essen, Germany
5
Department of Pathology, Stanford University School of Medicine, Stanford, CA 94305-5324, USA
6
Patrick G. Johnston Centre for Cancer Research, School of Medicine, Dentistry and Biomedical Sciences, Queen’s University Belfast, Belfast BT9 7BL, UK
*
Author to whom correspondence should be addressed.
Int. J. Mol. Sci. 2020, 21(23), 9140; https://doi.org/10.3390/ijms21239140
Received: 31 October 2020 / Revised: 19 November 2020 / Accepted: 26 November 2020 / Published: 30 November 2020
(This article belongs to the Special Issue Biocatalysis: Mechanisms of Proteolytic Enzymes)
The significance of cysteine cathepsins for the liberation of thyroid hormones from the precursor thyroglobulin was previously shown by in vivo and in vitro studies. Cathepsin L is most important for thyroglobulin processing in mice. The present study aims at specifying the possible contribution of its closest relative, cysteine cathepsin L2/V, to thyroid function. Immunofluorescence analysis on normal human thyroid tissue revealed its predominant localization at the apical plasma membrane of thyrocytes and within the follicle lumen, indicating the secretion of cathepsin V and extracellular tasks rather than its acting within endo-lysosomes. To explore the trafficking pathways of cathepsin V in more detail, a chimeric protein consisting of human cathepsin V tagged with green fluorescent protein (GFP) was stably expressed in the Nthy-ori 3-1 thyroid epithelial cell line. Colocalization studies with compartment-specific markers and analyses of post-translational modifications revealed that the chimeric protein was sorted into the lumen of the endoplasmic reticulum and subsequently transported to the Golgi apparatus, while being N-glycosylated. Immunoblotting showed that the chimeric protein reached endo-lysosomes and it became secreted from the transduced cells. Astonishingly, thyroid stimulating hormone (TSH)-induced secretion of GFP-tagged cathepsin V occurred as the proform, suggesting that TSH upregulates its transport to the plasma membrane before it reaches endo-lysosomes for maturation. The proform of cathepsin V was found to be reactive with the activity-based probe DCG-04, suggesting that it possesses catalytic activity. We propose that TSH-stimulated secretion of procathepsin V is the default pathway in the thyroid to enable its contribution to thyroglobulin processing by extracellular means. View Full-Text
Keywords: cysteine cathepsins; green fluorescent protein tagging; protein trafficking; secretion; thyroid epithelial cells; thyroid stimulating hormone cysteine cathepsins; green fluorescent protein tagging; protein trafficking; secretion; thyroid epithelial cells; thyroid stimulating hormone
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MDPI and ACS Style

Al-Hashimi, A.; Venugopalan, V.; Rehders, M.; Sereesongsaeng, N.; Hein, Z.; Springer, S.; Weber, E.; Führer, D.; Bogyo, M.S.; Scott, C.J.; Burden, R.E.; Brix, K. Procathepsin V Is Secreted in a TSH Regulated Manner from Human Thyroid Epithelial Cells and Is Accessible to an Activity-Based Probe. Int. J. Mol. Sci. 2020, 21, 9140. https://doi.org/10.3390/ijms21239140

AMA Style

Al-Hashimi A, Venugopalan V, Rehders M, Sereesongsaeng N, Hein Z, Springer S, Weber E, Führer D, Bogyo MS, Scott CJ, Burden RE, Brix K. Procathepsin V Is Secreted in a TSH Regulated Manner from Human Thyroid Epithelial Cells and Is Accessible to an Activity-Based Probe. International Journal of Molecular Sciences. 2020; 21(23):9140. https://doi.org/10.3390/ijms21239140

Chicago/Turabian Style

Al-Hashimi, Alaa; Venugopalan, Vaishnavi; Rehders, Maren; Sereesongsaeng, Naphannop; Hein, Zeynep; Springer, Sebastian; Weber, Ekkehard; Führer, Dagmar; Bogyo, Matthew S.; Scott, Christopher J.; Burden, Roberta E.; Brix, Klaudia. 2020. "Procathepsin V Is Secreted in a TSH Regulated Manner from Human Thyroid Epithelial Cells and Is Accessible to an Activity-Based Probe" Int. J. Mol. Sci. 21, no. 23: 9140. https://doi.org/10.3390/ijms21239140

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