Disruption of Heat Shock Protein 90 (Hsp90)-Protein Kinase Cδ (PKCδ) Interaction by (-)-Maackiain Suppresses Histamine H1 Receptor Gene Transcription in HeLa Cells

Background: The molecular mechanism of anti-allergic (-)-maackiain remains unknown. Results: (-)-Maackiain and Hsp90 inhibitors inhibited PKC delta activation and suppressed H1R gene expression. Conclusion: (-)-Maackiain is a novel Hsp90 pathway inhibitor, and its anti-allergic activity underlies the disruption of Hsp90-PKC delta interaction. Significance: Hsp90 is involved in H1R gene up-regulation, and its inhibition could be a novel therapeutic strategy for allergic rhinitis. The histamine H-1 receptor (H1R) gene is an allergic disease sensitive gene, and its expression level is strongly correlated with the severity of allergic symptoms. (-)-Maackiain was identified as a Kujin-derived anti-allergic compound that suppresses the up-regulation of the H1R gene. However, the underlying mechanism of H1R gene suppression remains unknown. Here, we sought to identify a target protein of (-)-maackiain and investigate its mechanism of action. A fluorescence quenching assay and immunoblot analysis identified heat shock protein 90 (Hsp90) as a target protein of (-)-maackiain. A pull-down assay revealed that (-)-maackiain disrupted the interaction of Hsp90 with PKC delta, resulting in the suppression of phorbol 12-myristate 13-acetate (PMA)-induced up-regulation of H1R gene expression in HeLa cells. Additional Hsp90 inhibitors, including 17-(allylamino)-17-demethoxygeldanamycin, celastrol, and novobiocin also suppressed PMA-induced H1R gene up-regulation. 17-(Allylamino)-17-demethoxygeldanamycin inhibited PKC delta translocation to the Golgi and phosphorylation of Tyr(311) on PKC delta. These data suggest that (-)-maackiain is a novel Hsp90 pathway inhibitor. The underlying mechanism of the suppression of PMA-induced up-regulation of H1R gene expression by (-)-maackiain and Hsp90 inhibitors is the inhibition of PKC delta activation through the disruption of Hsp90-PKC delta interaction. Involvement of Hsp90 in H1R gene up-regulation suggests that suppression of the Hsp90 pathway could be a novel therapeutic strategy for allergic rhinitis.