Purpose. Transthyretin (TTR) is a 55 kD tetrameric protein which binds thyroxine (T4) as well as the complex formed by retinol and retinol binding protein. TTR could play a role in the intraocular cycling of vitamin A and thyroxine. This study was performed to determine the intracellular localization of TTR in cultured and native human retinal pigment epithelial cells (HRPE). Methods. Immunoreactivity to TTR was localized at the electron microscopic level in fixed monolayer cultures and native tissue isolated from adult human donor tissue, using monoclonal antibodies (mAbs) (6E5-2 and 14D1-1) against TTR in a post-embedding immunogold technique. Tissues were embedded with Lowicryl K4M, and labeling was performed with 20 nm gold-tagged goat anti-mouse IgG. Results. Immunoreactivity was observed over the nucleus and mitochondria. In the cytoplasm, reaction product was detected in a non-vesicle bound, random distribution. Immunoreactivity was also detected on the plasma membrane. It was observed on both apical and basolateral surfaces, but was most abundant apically. The labeling pattern was the same in cultured and native preparations and for both mAbs. Mouse IgG, used as a negative control, did not exhibit labeling. Conclusions. The subcellular localization of TTR in HRPE cells grown in culture parallels that of native HRPE cells, and suggests an intracellular function for TTR, possibly in association with T4; in addition to its previously hypothesized role in retinol transport.
|Original language||English (US)|
|Journal||Investigative Ophthalmology and Visual Science|
|State||Published - Feb 15 1996|
ASJC Scopus subject areas
- Sensory Systems
- Cellular and Molecular Neuroscience