Goat endometrial heat shock protein-90 (Hsp-90): Development of an expedient method for its purification and observations on its intracellular movement

An expedient method has been developed by which goat uterine Hsp-90 could be isolated and purified to homogeneity in less than 1 day. The yield is roughly 1 mg from 60 g tissue. This method takes into advantage three of our earlier observation that (a) Hsp-90 gets linked to the non-activated estrogen receptor (naER) in the presence of 10 mM sodium molybdate; (b) naER, but not Hsp-90 binds to phosphocellulose and (c) exposure to estradiol facilitates dissociation of Hsp-90 from naER through estradiol binding to naER and the possible change in naER conformation. Intracellular movement of Hsp-90 and naER was monitored in goat endometrial cells in culture following exposure of the cells to estradiol. Confocal microscopic analysis revealed a clear presence of both proteins within the nucleus within 3 h after exposure to estradiol. Whether Hsp-90 has its own nuclear-transport machinery is debatable. Being an actin-binding protein, there is a distinct possibility that the nuclear entry of Hsp-90 is actin dependent. The functional significance of the nuclear entry of Hsp-90, along with naER, remains to be determined; it may, however, be speculated that the Hsp-90 might be directly involved in the naER to nER II transformation by functioning as a molecular chaperone and helping the protein in re-orienting its structural organization.