Regulation of steroid receptor subcellular trafficking.

Cellular responses to external signals often reflect alterations in gene expression. The activation of cell surface hormone or growth factor receptors upon the binding of appropriate ligands mobilizes signal transduction cascades that can ultimately impact the activity of defined sets of transcription factors. The interpretation of hormonal signals can also be initiated intracellularly, as is the case for steroid hormone receptors. In addition to recognizing specific hormones, steroid hormone receptors also function as transcription factors and directly transduce hormonal signals to activation or repression of unique target genes. The delivery of activated steroid receptors to high-affinity genomic sites must be efficient to account for the rapidity and selectivity of many transcriptional responses to steroid hormones. Thus, the signal transduction capacity of steroid hormone receptors will be affected by the efficiency of receptor trafficking both between different subcellular compartments (i.e., the cytoplasm and nucleus) and within a specific compartment (i.e., the nucleus). This article will highlight the recent advances in our understanding of subcellular and subnuclear trafficking of steroid receptors.