title: Two distinct regions of the immunophilin-like protein XAP2 regulate dioxin receptor function and interaction with hsp90.
abstract: The dioxin (aryl hydrocarbon) receptor is a ligand inducible transcription factor, which mediates cellular responses to a variety of xenobiotic compounds such as dioxins. In the absence of ligand the receptor is associated with the molecular chaperone hsp90 and the tetratricopeptide repeat (TPR-) containing immunophilin-like protein XAP2. XAP2 has been implicated in regulation of the intracellular localization of the dioxin receptor and protection of the receptor against degradation. In this study a series of XAP2 mutants has been generated in order to identify the structural motif(s) mediating interaction with the dioxin receptor-hsp90 complex and modulation of receptor function. Immunoprecipitation experiments demonstrated that the C-terminal part of XAP2, including the TPR motifs and the region outside the TPR motifs, was required to directly contact hsp90. The N-terminal part of XAP2 was required for the stability of the ternary dioxin receptor-hsp90-XAP2 complex. In addition, the integrity of the N-terminal region of XAP2 was essential for XAP2 to regulate the intracellular localization of the dioxin receptor. In conclusion, these data demonstrate that two distinct regions of XAP2 modulate dioxin receptor function and interaction with hps90, illustrating the complexity in regulation of dioxin receptor signaling by the hsp90 molecular chaperone machinery.
authors.affiliation: Department of Cell and Molecular Biology, Karolinska Institute, S-171 77 Stockholm, Sweden.
authors.forename: Arunas
authors.initials: A
authors.lastname: Kazlauskas
authors.forename: Lorenz
authors.initials: L
authors.lastname: Poellinger
authors.forename: Ingemar
authors.initials: I
authors.lastname: Pongratz
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D001665:Binding Sites; D019556:COS Cells; D000939:Epitopes; D017353:Gene Deletion; D049452:Green Fluorescent Proteins; D018841:HSP90 Heat-Shock Proteins / Q000737:chemistry / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D015151:Immunoblotting; D020104:Immunophilins / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins; D008164:Luminescent Proteins / Q000378:metabolism; D008856:Microscopy, Fluorescence; D008957:Models, Genetic; D011233:Precipitin Tests; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000737:chemistry* / Q000378:metabolism; D018336:Receptors, Aryl Hydrocarbon / Q000378:metabolism / Q000502:physiology*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D000939:Epitopes; D018841:HSP90 Heat-Shock Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008164:Luminescent Proteins; D011506:Proteins; D018336:Receptors, Aryl Hydrocarbon; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; C103265:aryl hydrocarbon receptor-interacting protein; D049452:Green Fluorescent Proteins; D020104:Immunophilins