Thyroid Stimulating Hormone Upregulates Secretion of Cathepsin B from Thyroid Epithelial Cells
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Martin Linke
Abstract
Constant levels of thyroid hormones in the blood are principal requirements for normal vertebrate development. Their release depends on the regulated proteolysis of thyroglobulin which is extracellularly stored in the follicle lumen under resting conditions. Thyroglobulin is proteolytically degraded to a major part in lysosomes, but in part also extracellularly leading to the release of thyroxine. Extracellularly occurring lysosomal enzymes are most probably involved in the proteolytic release of thyroxine. In this study we have analyzed the secretion of cathepsin B by thyroid follicle cells (primary cells as well as FRTL-5 cells) and its regulation by thyroid stimulating hormone, which stimulated the secretory release of the proenzyme as well as of mature cathepsin B. Within one to two hours of stimulation with thyroid stimulating hormone, the cathepsin B activity associated with the plasma membrane increased significantly. This increase correlated closely with the localization of lysosomes in close proximity to the plasma membrane of cultured thyrocytes as well as with the thyroxine liberating activity of thyrocyte secretion media. These observations indicate that thyroid stimulating hormone induces the secretion of cathepsin B, which contributes to the extracellular release of thyroxine by thyrocytes.
Copyright © 2002 by Walter de Gruyter GmbH & Co. KG
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Articles in the same Issue
- Nobuhiko Katunuma: An Outstanding Scientific and Professional Career of a Warm-Hearted Person. Reflections on the Occasion of his 75th Birthday
- Structural and Functional Diversity of Connexin Genes in the Mouse and Human Genome
- Congopain from Trypanosoma congolense: Drug Target and Vaccine Candidate
- Biosynthesis of Lysosomal Proteinases in Health and Disease
- Calpain Function in the Differentiation of Mesenchymal Stem Cells
- Ku Antigen Supports Termination of Mammalian rDNA Replication by Transcription Termination Factor TTF-I
- Thyroid Stimulating Hormone Upregulates Secretion of Cathepsin B from Thyroid Epithelial Cells
- Selective Release of Calpain Produced αII-Spectrin (α-Fodrin) Breakdown Products by Acute Neuronal Cell Death
- Altered Storage of Proteases in Mast Cells from Mice Lacking Heparin: A Possible Role for Heparin Carboxypeptidase A Processing
- Clustering-Induced Signaling of CEACAM1 in PC12 Cells
- Spin Adducts of Superoxide, Alkoxyl, and Lipid-Derived Radicals with EMPO and Its Derivatives
- Glutathione S-Transferase of the Malarial Parasite Plasmodium falciparum: Characterization of a Potential Drug Target
- Analysis of the Structural Determinants for RNA Binding of the Human Protein AUF1/hnRNP D
- Effect of Cysteine Proteinase Inhibitors on Murine B16 Melanoma Cell Invasion in vitro
- Stage-Specific Antimalarial Activity of Cysteine Protease Inhibitors
- Epoxysuccinyl Peptide-Derived Cathepsin B Inhibitors: Modulating Membrane Permeability by Conjugation with the C-Terminal Heptapeptide Segment of Penetratin
- Design of Inhibitors for Human Tissue Kallikrein Using Non-Natural Aromatic and Basic Amino Acids
- Amyloid Fibril Formation by Human Stefin B in vitro: Immunogold Labelling and Comparison to Stefin A
- Lysosomal Peptidases and Glycosidases in Rheumatoid Arthritis
