Upon stimulation by a steroid hormone, the glucocorticoid receptor moves from the cytoplasm to specific sites in the nucleus, but the mechanism of this transport either within the cytoplasm or within the nucleus is unknown. To address these issues, we are using time-lapse microscopy to visualize and quantify the receptor translocation process. We have taken two approaches. First, we attached gluocorticoid receptor to 20 nm fluorescent beads, and injected these beads into the cytoplasm of cells. A low percentage of the beads moved along linear paths, suggestive of directional transport. However, this directional motion may not have been specific to the glucocorticoid receptor, since control beads coated only with BSA also occasionally exhibited directional motion. In the second approach, we treated cells with drugs known to disrupt either microtubules or microfilaments, and then measured transport of glucocorticoid receptor to the nucleus in living cells containing a GFP tagged form of the receptor. We were unable to detect differences in transport rates between control and drug treated cells, suggesting that simple diffusion may be sufficient to localize the receptor to the nucleus. - hormone, receptor, transport, - Neither Human Subjects nor Human Tissues
