ESTRADIOL BINDING AFTER SIALIDASE AND SIALYLTRANSFERASE TREATMENT OF MCF-7 CELLS

Sialyltransferase activity and serum sialic acid concentration are hig her in certain malignancies. Also the estrogen receptor can be modifie d post-translationally. We have investigated the effect of sialidase a nd sialyltransferase on estrogen receptors from MCF-7 cytosol. Specifi c estradiol binding was measured using the radioligand essay. Although the K-d values (0.7 +/- 0.2 nM) remained essentially unaltered, wheth er treated or not with sialidase or sialyltransferase (p>0.06), the sp ecific binding capacity changed from 27.2 +/- 5 fmol mg(-1) protein (u ntreated) to 42.0 +/- 4 and 17.0 +/- 2 following treatment with sialid ase and sialyltransferase respectively. Positive and negative correlat ions were respectively obtained with increasing concentrations of sial idase (r=0.9429) or sialyltransferase (r=-1.0000) with specific estrad iol binding. These results suggest that the specific binding of estrad iol to estrogen receptors can be post-translationally altered by siali dase and sialyltransferase treatment.