TY - JOUR
T1 - The p23 molecular chaperones act at a late step in intracellular receptor action to differentially affect ligand efficacies
AU - Freeman, Brian C.
AU - Felts, Sara J.
AU - Toft, David O.
AU - Yamamoto, Keith R.
PY - 2000
Y1 - 2000
N2 - Multiple molecular chaperones, including Hsp90 and p23, interact with members of the intracellular receptor (IR) family. To investigate p23 function, we compared the effects of three p23 proteins on IR activities, yeast p23 (sba1p) and the two human p23 homologs, p23 and tsp23. We found that Sba1p was indistinguishable from human p23 in assays of seven IR activities in both animal cells and in yeast; in contrast, certain effects of tsp23 were specific to that homolog. Transcriptional activation by two IRs was increased by expression of any of the p23 species, whereas activation by five other IRs was decreased by Sba1p or p23, and unaffected by tsp23, p23 was expressed in all tissues examined except striated and cardiac muscle, whereas tsp23 accumulated in a complementary pattern; hence, p23 proteins might contribute to tissue-specific differences in IR activities. Unlike Hsp90, which acts on IR aporeceptors to stimulate ligand potency (i.e., hormone-binding affinity), p23 proteins acted on IR holoreceptors to alter ligand efficiencies (i.e., transcriptional activation activity). Moreover, the p23 effects developed slowly, requiring prolonged exposure to hormone. In vitro, p23 interacted preferentially with hormone- receptor-response element ternary complexes, and stimulated receptor-DNA dissociation. The dissociation was reversed by addition of a fragment of the GRIP1 coactivator, suggesting that the two reactions may be in competition in vivo. Our findings suggest that p23 functions at one or more late steps in IR-mediated signal transduction, perhaps including receptor recycling and/or reversal of the response.
AB - Multiple molecular chaperones, including Hsp90 and p23, interact with members of the intracellular receptor (IR) family. To investigate p23 function, we compared the effects of three p23 proteins on IR activities, yeast p23 (sba1p) and the two human p23 homologs, p23 and tsp23. We found that Sba1p was indistinguishable from human p23 in assays of seven IR activities in both animal cells and in yeast; in contrast, certain effects of tsp23 were specific to that homolog. Transcriptional activation by two IRs was increased by expression of any of the p23 species, whereas activation by five other IRs was decreased by Sba1p or p23, and unaffected by tsp23, p23 was expressed in all tissues examined except striated and cardiac muscle, whereas tsp23 accumulated in a complementary pattern; hence, p23 proteins might contribute to tissue-specific differences in IR activities. Unlike Hsp90, which acts on IR aporeceptors to stimulate ligand potency (i.e., hormone-binding affinity), p23 proteins acted on IR holoreceptors to alter ligand efficiencies (i.e., transcriptional activation activity). Moreover, the p23 effects developed slowly, requiring prolonged exposure to hormone. In vitro, p23 interacted preferentially with hormone- receptor-response element ternary complexes, and stimulated receptor-DNA dissociation. The dissociation was reversed by addition of a fragment of the GRIP1 coactivator, suggesting that the two reactions may be in competition in vivo. Our findings suggest that p23 functions at one or more late steps in IR-mediated signal transduction, perhaps including receptor recycling and/or reversal of the response.
KW - Intracellular receptor
KW - Ligand efficacy
KW - Molecular chaperone
KW - P23
UR - http://www.scopus.com/inward/record.url?scp=0034102339&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0034102339&partnerID=8YFLogxK
M3 - Article
C2 - 10691735
AN - SCOPUS:0034102339
SN - 0890-9369
VL - 14
SP - 422
EP - 434
JO - Genes and Development
JF - Genes and Development
IS - 4
ER -