Document Detail


Binding, uptake, and degradation of internalized thyroglobulin in cultured thyroid and non-thyroid cells.
MedLine Citation:
PMID:  20959721     Owner:  NLM     Status:  In-Data-Review    
Abstract/OtherAbstract:
Thyroid hormone release requires degradation of thyroglobulin (Tg) by thyroid epithelial cells, which occurs mainly in the lysosomal pathway following Tg endocytosis. Non-specific fluid-phase endocytosis is thought to be the main route of Tg uptake leading to degradation, whereas receptor- mediated endocytosis is believed to lead to post-endocytic pathways other than degradation. To gain more insights into these issues, we investigated handling of Tg by various cell types. Tg bound similarly to thyroid (FRTL-5, FRT) and non-thyroid (COS-7, IRPT) cells, indicating the presence of membrane-binding sites, presumably receptors, in both cell types. Tg was internalized and degraded by all cells and degradation paralleled uptake, with the exception of FRTL- 5 cells, in which a lower proportion of Tg was degraded, suggesting that in FRTL-5 cells mechanisms that target Tg to the various post-endocytic pathways (either receptors or postreceptorial factors) are differently represented. Immunoelectronmicroscopy showed a common path of endocytosis in FRTL-5, COS-7, and IRPT cells, namely the formation of pseudopods engulfing Tg, followed by internalization and accumulation of Tg in cytoplasmic vesicles and lysosomes. The fastest rate was observed in COS-7 cells, probably reflecting a lower impact of endocytic receptors. Our findings suggest that Tg uptake and degradation are not thyroid-specific, that Tg binding sites exist in different cell types, and that uptake and/or degradation are differently regulated in differentiated thyroid cells, presumably because of a different impact of endocytic receptors or post-endocytic mechanisms, which are probably responsible for the regulation of hormone release.
Authors:
R Botta; S Lisi; A Pinchera; A R Taddei; A M Fausto; F Giorgi; M Marinò
Publication Detail:
Type:  Journal Article     Date:  2010-10-15
Journal Detail:
Title:  Journal of endocrinological investigation     Volume:  34     ISSN:  1720-8386     ISO Abbreviation:  J. Endocrinol. Invest.     Publication Date:    2011 Jul-Aug
Date Detail:
Created Date:  2011-09-05     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  7806594     Medline TA:  J Endocrinol Invest     Country:  Italy    
Other Details:
Languages:  eng     Pagination:  515-20     Citation Subset:  IM    
Affiliation:
Department of Endocrinology and Metabolism, University of Pisa, Via Paradisa 2, 56124, Pisa, Italy.
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