Article

Radicicol leads to selective depletion of Raf kinase and disrupts K-Ras-activated aberrant signaling pathway

Nagoya University, Nagoya, Aichi, Japan
Journal of Biological Chemistry (Impact Factor: 4.57). 02/1998; 273(2):822-8. DOI: 10.1074/jbc.273.2.822
Source: PubMed

ABSTRACT Activation of Ras leads to the constitutive activation of a downstream phosphorylation cascade comprised of Raf-1, mitogen-activated protein kinase (MAPK) kinase, and MAPK. We have developed a yeast-based assay in which the Saccharomyces cerevisiae mating pheromone-induced MAPK pathway relied on co-expression of K-Ras and Raf-1. Radicicol, an antifungal antibiotic, was found to inhibit the K-ras signaling pathway reconstituted in yeast. In K-ras-transformed, rat epithelial, and K-ras-activated, human pancreatic carcinoma cell lines, radicicol inhibited K-Ras-induced hyperphosphorylation of Erk2. In addition, the level of Raf kinase was significantly decreased in radicicol-treated cells, whereas the levels of K-Ras and MAPK remained unchanged. These results suggest that radicicol disrupts the K-Ras-activated signaling pathway by selectively depleting Raf kinase and raises the possibility that pharmacological destabilization of Raf kinase could be a new and powerful approach for the treatment of K-ras-activated human cancers.

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    • "The nonaketide compound Radicicol (Rad) (Fig. 1) was first isolated from Monocillium nordinii and named initially monorden [16]. Rad was reported to reverse oncogene-induced cell transformation [10] and to inhibit the 90-kDa molecular chaperone heat shock protein (Hsp)-90 activity by a direct interaction with its structural ATP-binding motif [55] [59]. Formation of the Rad-Hsp90 complex leads to the disruption of the interaction between Hsp90 and its client proteins resulting in their rapid destabilization and degradation by the proteasome. "
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    ABSTRACT: Constitutive tyrosine kinase activity of the breakpoint cluster region (Bcr)-Abl fusion protein is characteristic of chronic myelogenous leukemia (CML). As resistance against Imatinib a Bcr-abl inhibitor used in CML, was described, Heat shock protein (Hsp90) became an alternative target as inhibition of Bcr-Abl-Hsp90 complex leads to proliferation arrest. Here, we used natural product Radicicol (Rad), a macrocyclic antifungal, as an Hsp90 inhibitor to investigate the effect of Bcr-Ab1 inactivation on erythroid gene expression and subsequently on the transcription factors involved in their regulation. We showed that all erythroid genes studied were over-expressed after Rad treatment while Bcr-Abl expression was inhibited. Specific transcription factor NF-E2 was induced in Rad-treated cells as well as GATA-1 cofactors Friend of GATA (FOG)1 and SP1, whereas PU.1 was downregulated. Moreover, p38 mitogen activated protein kinase (MAPK) inhibition prevented Rad-mediated differentiation of K562 in correlation with decreased γ-globin expression and suppression of Rad-mediated inhibition of PU.1. In conclusion, our results show that Radicicol leads to Bcr-Abl inactivation via Hsp90 inhibition inducing reactivation of the erythroid program in K562 cells.
    BioFactors 01/2008; 34(4):313-329. DOI:10.1002/biof.5520340407 · 3.00 Impact Factor
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    • "The nonaketide compound Radicicol (Rad) (Fig. 1) was first isolated from Monocillium nordinii and named initially monorden [16]. Rad was reported to reverse oncogene-induced cell transformation [10] and to inhibit the 90-kDa molecular chaperone heat shock protein (Hsp)-90 activity by a direct interaction with its structural ATP-binding motif [55] [59]. Formation of the Rad-Hsp90 complex leads to the disruption of the interaction between Hsp90 and its client proteins resulting in their rapid destabilization and degradation by the proteasome. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Constitutive tyrosine kinase activity of the breakpoint cluster region (Bcr)-Abl fusion protein is characteristic of chronic myelogenous leukemia (CML). As resistance against Imatinib a Bcr-abl inhibitor used in CML, was described, Heat shock protein (Hsp90) became an alternative target as inhibition of Bcr-Abl-Hsp90 complex leads to proliferation arrest. Here, we used natural product Radicicol (Rad), a macrocyclic antifungal, as an Hsp90 inhibitor to investigate the effect of Bcr-Abl inactivation on erythroid gene expression and subsequently on the transcription factors involved in their regulation. We showed that all erythroid genes studied were over-expressed after Rad treatment while Bcr-Abl expression was inhibited. Specific transcription factor NF-E2 was induced in Rad-treated cells as well as GATA-1 cofactors Friend of GATA (FOG)1 and SP1, whereas PU.1 was downregulated. Moreover, p38 mitogen activated protein kinase (MAPK) inhibition prevented Rad-mediated differentiation of K562 in correlation with decreased gamma-globin expression and suppression of Rad-mediated inhibition of PU.1. In conclusion, our results show that Radicicol leads to Bcr-Abl inactivation via Hsp90 inhibition inducing reactivation of the erythroid program in K562 cells.
    BioFactors 01/2008; 34(4):313-29. DOI:10.3233/BIO-2009-1085 · 3.00 Impact Factor
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    • "Neckers (2002) Geldanamycin-testosterone Specific Hsp90 inhibition in tumours Kosan Bioscience (www.kosan.com) Harvey et al. (2002) Radicicol Hsp90 inhibition Kyowa Hakko Kogyo Ltd. (www.kyowa.co.jp) Soga et al. (1998) "
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    Aging Cell 03/2003; 2(1):39-45. DOI:10.1046/j.1474-9728.2003.00031.x · 5.94 Impact Factor
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