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Cell survival and adaptation to chronic endoplasmic reticulum stress in thyrocytes

ABSTRACT: The large secretory glycoprotein, thyroglobulin, is the primary translation product of thyroid follicular cells. This difficult-to-fold protein is readily susceptible to structural alterations that render the misfolded thyroglobulin unable to be exported from the endoplasmic reticulum (ER) a known cause of congenital hypothyroidism, with severe, chronic thyrocyte ER stress. Nevertheless, patients with this disease commonly grow a goiter indicative of thyroid cell survival and adaptation. To model this, we have treated PCCl3 thyrocytes with continuous exposure to tunicamcyin (causing an ER stress that can be specifically attributed to thyroglobulin misfolding). In response, PCCl3 cells escape by downregulating expression of Mfsd2a (the tunicamycin transporter). By contrast, following CRISPR/Cas9-mediated deletion of Mfsd2a, PCCl3 cells cannot escape the continuous, chronic effects of high-dose tunicamycin (as demonstrated by persistent accumulation of unglycosylated thyroglobulin); nevertheless the thyrocytes live and grow. A comprehensive proteomic analysis of these cells adapted to chronic ER protein misfolding reveals many hundreds of up-regulated proteins, supporting stimulation of ER chaperones, oxidoreductases, and stress responses as well as lipid biosynthesis pathways. Further, we noted: a) increased phospho-AMP-kinase-B (suggesting upregulated AMPK activity) and decreased phospho-S6 and protein translation (suggesting decreased mTOR activity), consistent with conserved cell survival/adaptation pathways; and b) a suggestion of less differentiated thyrocyte phenotype with decreased PAX8, FOXE1, and TPO protein, as well as a significant decrease of thyroglobulin mRNA levels.

INSTRUMENT(S): Orbitrap Fusion ETD

ORGANISM(S): Homo Sapiens (ncbitaxon:9606)

SUBMITTER: Peter Arvan

PROVIDER: MSV000085006 | MassIVE | Tue Feb 25 07:30:00 GMT 2020

SECONDARY ACCESSION(S): PXD017724

REPOSITORIES: MassIVE

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Thyrocyte cell survival and adaptation to chronic endoplasmic reticulum stress due to misfolded thyroglobulin.

Morishita Yoshiaki Y Kabil Omer O Young Kelly Z KZ Kellogg Aaron P AP Chang Amy A Arvan Peter P

The Journal of biological chemistry 20200402 20

The large secretory glycoprotein thyroglobulin is the primary translation product of thyroid follicular cells. This difficult-to-fold protein is susceptible to structural alterations that disable export of the misfolded thyroglobulin from the endoplasmic reticulum (ER), which is a known cause of congenital hypothyroidism characterized by severe chronic thyrocyte ER stress. Nevertheless, individuals with this disease commonly grow a goiter, indicating thyroid cell survival and adaptation. To mode ...[more]

PMID: 32241916

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