Transient Covalent Interactions of Newly Synthesized Thyroglobulin with Oxidoreductases of the Endoplasmic Reticulum

• Published in: The Journal of biological chemistry Vol. 289; no. 16; pp. 11488 - 11496
• Main Authors: Di Jeso, Bruno, Morishita, Yoshiaki, Treglia, Antonella S., Lofrumento, Dario D., Nicolardi, Giuseppe, Beguinot, Francesco, Kellogg, Aaron P., Arvan, Peter
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 18.04.2014; American Society for Biochemistry and Molecular Biology
• Subjects: Calcium-Binding Proteins - genetics; Calcium-Binding Proteins - metabolism; Cell Line; Disulfide; Disulfides - metabolism; Endoplasmic Reticulum (ER); Humans; Membrane Glycoproteins - genetics; Membrane Glycoproteins - metabolism; Molecular Chaperone; Multiprotein Complexes - genetics; Multiprotein Complexes - metabolism; Protein Disulfide-Isomerases - genetics; Protein Disulfide-Isomerases - metabolism; Protein Folding; Protein Structure and Folding; Thyroglobulin - biosynthesis; Thyroglobulin - genetics; Thyroid; Molecular Chaperone; Protein Folding; Disulfide; Endoplasmic Reticulum (ER); Thyroid
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M113.520767

Newly synthesized thyroglobulin (Tg), the thyroid prohormone, forms detectable high molecular weight mixed disulfide adducts: until now, only Tg “adduct B” was identified as primarily engaging the endoplasmic reticulum oxidoreductases ERp57 and protein disulfide isomerase. Here, we demonstrate that the faster migrating Tg adduct C primarily engages the CaBP1/P5 oxidoreductase, whereas the slower migrating Tg adduct A primarily engages ERp72. Upon siRNA-mediated knockdown of CaBP1/P5 or ERp72, adducts C or A, respectively, are decreased. Within the three Tg adduct bands that do not exhibit a precursor-product relationship, Tg exhibits distinct oxidation patterns. We present evidence suggesting that disulfide maturation occurs within Tg monomers engaged in each of the adduct bands. Moreover, the same Tg substrate molecules can form simultaneous mixed disulfides with both CaBP1/P5 and protein disulfide isomerase, although these are generally viewed as components of distinct oxidoreductase-chaperone protein complexes. Such substrate-oxidoreductase combinations offer Tg the potential for simultaneous oxidative maturation along different parallel tracks leading to the native state. Background: Secretory proteins acquire their native three-dimensional conformation through repeated brief interactions with ER chaperones and oxidoreductases. Results: We have captured and defined previously unidentified disulfide adducts of newly synthesized thyroglobulin with ERp72 and CaBP1/P5. Conclusion: Multiple oxidoreductases simultaneously engage thyroglobulin during its early folding in the ER. Significance: Distinct chaperone/oxidoreductase partners coordinately engage this multi-domain secretory protein to promote its advancement to the native state.