Evidence against posttranslational glycosylation of rat glucocorticoid receptors

The observed M(r) of the rat glucocorticoid receptor on denaturing polyacrylamide gels is 7-11 kDa higher than that deduced from the cloned cDNA sequence of the receptor. Posttranslational modification of the receptor, such as glycosylation, could account for this difference in mol wt. Indeed, several reports have appeared in the literature suggesting that glucocorticoid receptors contain sugar moieties. We have used a variety of methods to determine whether the receptor is glycosylated, i.e., digestion of affinity labeled receptors with various glycosidases, immunoadsorption of receptors after whole cell labeling with [3H]D-glucosamine, and ion exchange and lectin column chromatography of affinity labeled receptors. With each of these methods, there was no evidence for glycosylation of the receptor protein. We therefore conclude that there is no significant amount of either N-linked glycosylation, or O-linked glycosylation with D-glucosamine, of the rat glucocorticoid receptor.