THYROID-HORMONE REGULATES PROTEIN EXPRESSION IN C6 GLIOMA-CELLS

Thyroid hormone (T-3) is essential to normal brain development. Previo usly, we have shown that T-3 induces cerebellar astrocyte proliferatio n. This effect is accompanied by alteration in glial fibrillary acidic protein (GFAP) and fibronectin organization. In the present study, we report that the C6 glioma cell line, which expresses GFAP and is clas sified as an undifferentiated astrocytic cell type, is a target for Tg action. The C6 monolayers were treated with 50 nM T-3 for 3 days, aft er which the cells were maintained for 2 days without medium changes. In C6 cells, Tg induced the expression of proteins of 107, 73 and 62 k Da. The hormone also up-regulated protein bands of 100 (+50%), 37 (+50 %) and 25.5 kDa (+50%) and down-regulated proteins of 94 (-100%), 86.5 (-100%), 68 (-100%), 60 (-100%), 54 (-33%), 51 (-33%) and 43.5 kDa (- 33%). We suggest, on the basis of molecular mass, that the 54-, 51- an d 43.5-kDa proteins could be the cytoskeletal proteins vimentin, GFAP and actin, respectively. The down-regulation of these proteins may be involved in the effects of thyroid hormone on C6 differentiation.