title: Import and export of nuclear proteins: focus on the nucleocytoplasmic movements of two different species of mammalian estrogen receptor.
abstract: There is a wealth of information regarding the import and export of nuclear proteins in general. Nevertheless, the available data that deals with the nucleocytoplasmic movement of steroid hormone receptors remains highly limited. Some research findings reported during the past five years have succeeded in identifying proteins related to the movement of estrogen receptor alpha from the cytoplasm to the nucleus. What is striking in these findings is the facilitatory role of estradiol in the transport process. A similar conclusion has been drawn from the studies on the plasma membrane-to nucleus movement of the alternative form of estrogen receptor, the non-activated estrogen receptor (naER). The internalization of naER from the plasma membrane takes place only in the presence of estradiol. While the gene regulatory functions of ER alpha appear to get terminated following its ubiquitinization within the nucleus, the naER, through its deglycosylated form, the nuclear estrogen receptor II (nER II) continues to remain functional even beyond its existence within the nucleus. Recent studies have indicated the possibility that the estrogen receptor that regulates the nucleo cytoplasmic transport of m RNP is the nERII. This appears to be the result of the interaction between nERII and three proteins belonging to a group of small nuclear ribonucleo proteins (snRNP). The interaction of nERII with two of this protein appears to activate the inherent Mg2+ ATPase activity of the complex, which leads to the exit of the RNP through the nuclear pore complex.
authors.affiliation: Rajiv Gandhi Center for Biotechnology, Thiruvanathapuram, Kerala, India.
authors.forename: Thomas
authors.initials: T
authors.lastname: Sebastian
authors.forename: S
authors.initials: S
authors.lastname: Sreeja
authors.forename: Raghava Varman
authors.initials: RV
authors.lastname: Thampan
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000187:drug effects; D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism*; D022163:Clathrin-Coated Vesicles / Q000378:metabolism; D004958:Estradiol / Q000494:pharmacology; D047628:Estrogen Receptor alpha; D047629:Estrogen Receptor beta; D006801:Humans; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D008954:Models, Biological; D022022:Nuclear Pore / Q000378:metabolism; D009687:Nuclear Proteins / Q000378:metabolism*; D010766:Phosphorylation; D011960:Receptors, Estrogen / Q000378:metabolism*; D048051:p38 Mitogen-Activated Protein Kinases; D020931:ran GTP-Binding Protein / Q000378:metabolism
chemical_list: D047628:Estrogen Receptor alpha; D047629:Estrogen Receptor beta; D009687:Nuclear Proteins; D011960:Receptors, Estrogen; D004958:Estradiol; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D020931:ran GTP-Binding Protein