Differential impact of tetratricopeptide repeat proteins on the steroid hormone receptors.
BACKGROUND
Tetratricopeptide repeat (TPR) motif containing co-chaperones of the chaperone Hsp90 are considered control modules that govern activity and specificity of this central folding platform. Steroid receptors are paradigm clients of Hsp90. The influence of some TPR proteins on selected receptors has been described, but a comprehensive analysis of the effects of TPR proteins on all steroid receptors has not been accomplished yet.


RESULTS
We compared the influence of the TPR proteins FK506 binding proteins 51 and 52, protein phosphatase-5, C-terminus of Hsp70 interacting protein, cyclophillin 40, hepatitis-virus-B X-associated protein-2, and tetratricopeptide repeat protein-2 on all six steroid hormone receptors in a homogeneous mammalian cell system. To be able to assess each cofactor's effect on the transcriptional activity of on each steroid receptor we employed transient transfection in a reporter gene assay. In addition, we evaluated the interactions of the TPR proteins with the receptors and components of the Hsp90 chaperone heterocomplex by coimmunoprecipitation. In the functional assays, corticosteroid and progesterone receptors displayed the most sensitive and distinct reaction to the TPR proteins. Androgen receptor's activity was moderately impaired by most cofactors, whereas the Estrogen receptors' activity was impaired by most cofactors only to a minor degree. Second, interaction studies revealed that the strongly receptor-interacting co-chaperones were all among the inhibitory proteins. Intriguingly, the TPR-proteins also differentially co-precipitated the heterochaperone complex components Hsp90, Hsp70, and p23, pointing to differences in their modes of action.


CONCLUSIONS
The results of this comprehensive study provide important insight into chaperoning of diverse client proteins via the combinatorial action of (co)-chaperones. The differential effects of the TPR proteins on steroid receptors bear on all physiological processes related to steroid hormone activity.
Schülke
Jan-Philip
JP
Chaperone Research Group, Max Planck Institute of Psychiatry, Munich, Germany.
Wochnik
Gabriela Monika
GM
Lang-Rollin
Isabelle
I
Gassen
Nils Christian
NC
Knapp
Regina Theresia
RT
Berning
Barbara
B
Yassouridis
Alexander
A
Rein
Theo
T
D000818:Animals; D002460:Cell Line; D045744:Cell Line, Tumor; D000081406:Peptidyl-Prolyl Isomerase F; D021983:Cyclophilins / Q000235:genetics / Q000378:metabolism; D050956:HSP40 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D006360:Heat-Shock Proteins; D006801:Humans; D015151:Immunoblotting; D047468:Immunoprecipitation; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D018832:Molecular Chaperones; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D010749:Phosphoprotein Phosphatases / Q000235:genetics / Q000378:metabolism; D011944:Receptors, Androgen / Q000235:genetics / Q000378:metabolism; D011960:Receptors, Estrogen / Q000235:genetics / Q000378:metabolism; D011965:Receptors, Glucocorticoid / Q000235:genetics / Q000378:metabolism; D018161:Receptors, Mineralocorticoid / Q000235:genetics / Q000378:metabolism; D011980:Receptors, Progesterone / Q000235:genetics / Q000378:metabolism; D011987:Receptors, Steroid / Q000235:genetics / Q000378:metabolism*; D022021:Tacrolimus Binding Proteins / Q000235:genetics / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism
D000081406:Peptidyl-Prolyl Isomerase F; C485782:DNAJC7 protein, human; D050956:HSP40 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D047908:Intracellular Signaling Peptides and Proteins; D018832:Molecular Chaperones; D009687:Nuclear Proteins; C000631446:PPIF protein, mouse; D011944:Receptors, Androgen; D011960:Receptors, Estrogen; D011965:Receptors, Glucocorticoid; D018161:Receptors, Mineralocorticoid; D011980:Receptors, Progesterone; D011987:Receptors, Steroid; C103265:aryl hydrocarbon receptor-interacting protein; C467728:STUB1 protein, human; D044767:Ubiquitin-Protein Ligases; D010749:Phosphoprotein Phosphatases; C089641:protein phosphatase 5; D021983:Cyclophilins; D022021:Tacrolimus Binding Proteins