mir-331 negatively regulates thyroglobulin secretion via ERp29

Abstract

We investigated the effect of endoplasmic reticulum ER protein 29 ERp29 on thyroglobulin Tg secretion and its negative regulation by microRNAs miRNAs . ERp29 overexpression promoted Tg secretion from thyrocytes of PCCL3 cells via activation of ER stress sensors, including activation of transcription factor 6 fragmentation, XBP1 mRNA splicing by inositol-requiring enzyme 1, and phosphorylation of eukaryotic initiation factor 2 alpha as downstream actions of RNA-dependent protein kinase-like ER kinase. Thyroid hormone receptor beta is a target gene of mir-331, one of the most abundant miRNAs observed in ERp29-overexpressing cells. mir-331 negatively regulated Tg expression and secretion by ~70% compared with the control. To overcome hypothyroidism, Tg secretion at the molecular level is required to counteract negative regulation of intracellular mir-331. Our findings may provide insight into the treatment of diseases caused by poor ER protein secretion, including ER storage diseases.