Model for localization of TRα1 isoforms to the mitochondria, plasma
membrane, and nucleus. TRα1 mRNA yields different forms of truncated TR
by internal translation initiation. Once synthesized in the cytosol, the
different forms localize to different intracellular compartments. TRα1
p28 and TRα1 p43 localize to the mitochondrial inner membrane and
matrix, respectively. TRα1 p30 localizes to the inner surface of the
plasma membrane, where it can bind to thyroid hormone to mediate thyroid hormone
signaling. The specific localization and function of TRα1 p33 remains
unknown. Full-length TRα1 (TRα1 p46) localizes to the nucleus
where it modulates target gene expression in response to thyroid hormone, in
association with corepressors and coactivators. Thyroid hormone enters the cell
through the monocarboxylate 8 and 10 transporters (MCT8/10).