Follicular thyroglobulin induces cathepsin H expression and activity in thyrocytes

Journal Article · Sun Jan 29 04:00:00 EST 2017 · Biochemical and Biophysical Research Communications

DOI:https://doi.org/10.1016/J.BBRC.2016.12.109· OSTI ID:22696838

Oda, Kenzaburo ^[1]; Luo, Yuqian ^[1]; Yoshihara, Aya ^[1]; Ishido, Yuko ^[1]; Sekihata, Kengo ^[1]; others, and

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1. Department of Clinical Laboratory Science, Faculty of Medical Technology, Teikyo University, 2-11-1 Kaga, Itabashi, Tokyo 173-8605 (Japan)

Thyroglobulin (Tg) stored in thyroid follicles exerts a potent negative-feedback effect on each step of pre-hormone biosynthesis, including Tg gene transcription and iodine uptake and organification, by suppressing the expression of specific transcription factors that regulate these steps. Pre-hormones are stored in the follicular colloid before being reabsorbed. Following lysosomal proteolysis of its precursor, thyroid hormone (TH) is released from thyroid follicles. Although the suppressive effects of follicular Tg on each step of pre-hormone biosynthesis have been extensively characterized, whether follicular Tg accumulation also affects hormone reabsorption, proteolysis, and secretion is unclear. In this study we explored whether follicular Tg can regulate the expression and function of the lysosomal endopeptidases cathepsins. We found that in the rat thyroid cell line FRTL-5 follicular Tg induced cathepsin H mRNA and protein expression, as well as cathepsin H enzyme activity. Double immunofluorescence staining showed that Tg endocytosis promoted cathepsin H translocalization into lysosomes where it co-localized with internalized Tg. These results suggest that cathepsin H is an active participant in lysosome-mediated pre-hormone degradation, and that follicular Tg stimulates mobilization of pre-hormones by activating cathepsin H-associated proteolysis pathways. - Highlights: • Follicular Tg increases cathepsin H mRNA and protein levels in rat thyroid cells. • Follicular Tg increases cathepsin H enzyme activity in rat thyroid cells. • After Tg stimulation cathepsin H co-localizes to lysosomes with follicular Tg. • Cathepsin H promotes hormone secretion by lysosome-mediated mechanisms.

• OSTI ID: 22696838
• Journal Information: Biochemical and Biophysical Research Communications, Journal Name: Biochemical and Biophysical Research Communications Journal Issue: 1 Vol. 483; ISSN BBRCA9; ISSN 0006-291X
• Country of Publication: United States
• Language: English

Related Subjects

60 APPLIED LIFE SCIENCES
CATHEPSINS
ENZYME ACTIVITY
LYSOSOMES
PROTEOLYSIS
RATS
THYROGLOBULIN
THYROID CELLS
THYROID HORMONES
TRANSCRIPTION FACTORS