A plasminogen-like protein, present in the apical extracellular environment of thyroid epithelial cells, degrades thyroglobulin in vitro.
The prothyroid hormone, thyroglobulin (Tg), is stored at high concentrations in the thyroid follicular lumen as a soluble 19S homo-dimer and as heavier soluble (27S and 37S) and insoluble (Tgm) forms. Follicular degradation of Tg may contribute to maintaining Tg concentrations compatible with follicle integrity. Here, we report on the presence of a plasminogen-like protein in the follicular lumen of normal human thyroids and its synthesis and apical secretion by cultured epithelial thyroid cells. Since all the main luminal forms of Tg are cleaved by this plasminogen-like protein, we suggest that it contributes to Tg degradation in the follicular lumen.
Giraud
Annie
A
INSERM U555, Faculté de Médecine, Université de la Méditerranée, 27 Bd. Jean Moulin, 13385 Marseille Cedex 5, France. Annie.Giraud@medecine.univ-mrs.fr
Dicristofaro
Julie
J
De Micco
Catherine
C
Lejeune
Pierre-Jean
PJ
Barbaria
Jocelyne
J
Mallet
Bernard
B
D000818:Animals; D002462:Cell Membrane / Q000378:metabolism*; D002478:Cells, Cultured; D004847:Epithelial Cells / Q000378:metabolism*; D045604:Extracellular Fluid / Q000378:metabolism*; D006801:Humans; D010958:Plasminogen / Q000378:metabolism*; D020033:Protein Isoforms / Q000378:metabolism; D013552:Swine; D013954:Thyroglobulin / Q000378:metabolism*; D013961:Thyroid Gland / Q000378:metabolism*
D020033:Protein Isoforms; D010958:Plasminogen; D013954:Thyroglobulin