title: A role for Hsp90 in retinoid receptor signal transduction.
abstract: The ubiquitous heat shock protein Hsp90 appears to participate directly in the function of a broad range of cellular signal transduction components, including steroid hormone receptors; however, an evolutionarily related subclass of intracellular receptors, exemplified by the retinoid receptors RAR and RXR, had been inferred from biochemical studies to function independently of Hsp90. To examine this issue genetically, we measured mammalian and avian retinoid receptor activity in a Saccharomyces cerevisiae strain in which the expression of the yeast Hsp90 homologue could be conditionally repressed approximately 20-fold relative to wild type. We tested transcriptional activation by RAR or RXR-RAR, from two types of retinoic acid response elements, triggered by three different agonist ligands. In every condition, we found that activation was severely compromised under conditions of low Hsp90 expression. We showed that the defect was in signal transduction rather than transcription activation per se, and that high affinity hormone binding was abolished in extracts of cells producing low levels of Hsp90. We suggest that Hsp90 may function in at least one step of signal transduction by all members of the intracellular receptor superfamily.
authors.affiliation: Department of Cellular and Molecular Pharmacology, University of California, San Francisco 94143-0450, USA.
authors.forename: S J
authors.initials: SJ
authors.lastname: Holley
authors.forename: K R
authors.initials: KR
authors.lastname: Yamamoto
mesh_terms: D000818:Animals; D001483:Base Sequence; D002645:Chickens; D003001:Cloning, Molecular; D003900:Desoxycorticosterone / Q000494:pharmacology; D005838:Genotype; D018841:HSP90 Heat-Shock Proteins / Q000096:biosynthesis / Q000502:physiology*; D006801:Humans; D008322:Mammals; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D009838:Oligodeoxyribonucleotides; D010957:Plasmids; D011401:Promoter Regions, Genetic; D018168:Receptors, Retinoic Acid / Q000096:biosynthesis / Q000502:physiology*; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000378:metabolism; D047488:Retinoid X Receptors; D012441:Saccharomyces cerevisiae / Q000502:physiology; D015398:Signal Transduction; D014157:Transcription Factors / Q000096:biosynthesis / Q000502:physiology*; D015533:Transcriptional Activation; D014212:Tretinoin / Q000494:pharmacology; D001616:beta-Galactosidase / Q000032:analysis / Q000096:biosynthesis
chemical_list: D018841:HSP90 Heat-Shock Proteins; D009838:Oligodeoxyribonucleotides; D018168:Receptors, Retinoic Acid; D011994:Recombinant Proteins; D047488:Retinoid X Receptors; D014157:Transcription Factors; D003900:Desoxycorticosterone; D014212:Tretinoin; D001616:beta-Galactosidase