The present project continues to address the characterization of iodide transport in thyroid. The current emphasis is to clone proteins in thyroid that are involved in the transport of iodide across the membrane. This project involves the use of rat thyroid cells in culture, and the use of cells that are unable to transport iodide; these cells are transfected with specific clones enabling them to transport iodide. Selection of the initial clones was based on the property of stilbene binding, since stilbenes interact with iodide transport. These clones were transfected into COS-7 cells and to non-iodide transporting thyroid cells. The results using these methods show that the transfected cells do not demonstrate the major iodide uptake system of thyroid, but rather the property involved relates to acid/base regulation and maintenance of internal pH. The transfected cells have characteristics of pH-dependent loss of iodide. The effort to clone the major iodide-transport protein has led to the use of a different approach. These new methods depend on RNA- expression libraries. Initial studies are complex and time-consuming but offer a promising approach to further understand iodide transport. Furthermore, in co-ordination with Dr. Ashwell, this laboratory is completing work involving the glycosylation of thyroglobulin, the major secretory product of thyroid. These studies show that thyroglobulin glycosylation is TSH-regulated, plays a role in some forms of congenital goiter, and finally is essential to understand critical aspects of thyroid hormone formation. Finally, biochemical studies on thyroid tissue from iodine-deficiency goiters relate iodine utilization, growth and thyroid hormone synthesis.
