17-AAG

Colorectal cancer (CRC) exhibits dysregulated gene expression and signaling pathways. This study explores the role of HSP90 and its client protein METTL3 in CRC progression, revealing their overexpression in CRC tissues and a positive correlation between HSP90AA1 and METTL3 expression. HSP90 interacts with METTL3's MTA70 domain via its middle substrate-binding domain, stabilizing METTL3 and enhancing its protein levels. Inhibition of HSP90 by 17-AAG reduces METTL3 stability by increasing CHIP-mediated K48-linked polyubiquitination and degradation in both nucleus and cytoplasm, decreasing m⁶A modification on MYC mRNA and shortening its half-life without affecting METTL3 mRNA levels. RNA-seq identified 1158 genes with altered m⁶A levels and expression post-17-AAG treatment. HSP90 inhibition suppressed CRC cell proliferation, colony formation, stemness, invasion, and migration, effects partially reversed by the METTL3-METTL14 agonist MPCH. Similar outcomes followed METTL3 inhibition with STM2457, partially rescued by MYC-stabilizing compound NNK. These findings highlight HSP90's role in stabilizing METTL3 and MYC mRNA, proposing the HSP90-METTL3 axis as a promising therapeutic target for CRC.

Recent studies have highlighted the significance of soluble αKlotho in renal dysfunction-associated vascular health, however, the underlying molecular mechanisms by which soluble αKlotho maintains the vascular smooth muscle cells (VSMCs) phenotype and prevents vascular calcification remain unclear. Clinical analyses revealed an inverse correlation between circulating αKlotho levels and vascular calcification severity in early CKD patients. Recombinant protein or lentiviral vector transfection of soluble αKlotho significantly suppressed the osteogenic transdifferentiation of VSMCs in vitro. AAV-mediated overexpression of soluble αKlotho in VSMCs remarkably reduced vascular calcification without altering circulating soluble αKlotho levels or mineral metabolism in mice under a high-phosphate diet after nephrectomy. We also employed a combination of transcriptomics and proteomics approaches, as well as in vitro and in vivo vascular calcification models, and determined that soluble αKlotho specifically suppressed Hsp90aa1 activation-mediated osteogenic transdifferentiation of VSMCs and vascular calcification. The Hsp90aa1-specific inhibitor, 17-AAG, acted as an efficient therapeutic approach to attenuate vascular calcification in vivo and in vitro. Moreover, we revealed that the phosphorylation of Hsp90aa1 at Thr5/7 modulated its chaperone activity to stabilize Hif1α, thereby playing a causative role in the pathogenesis of vascular calcification. Upregulation of soluble αKlotho expression in VSMCs enhanced the interaction with Hsp90aa1 and blunted the phosphorylation of Hsp90aa1 at Thr5/7, which abolished Hsp90aa1-Hif1α axis activation in response to osteogenic induction. Our findings revealed a crucial pathway that soluble αKlotho interacts with Hsp90aa1 and suppresses the activation of the Hsp90aa1-Hif1α axis, which is involved in the osteogenic transdifferentiation of VSMCs and vascular calcification. Targeting Hsp90 may be a promising strategy for vascular calcification treatment, as various HSP90 inhibitors have been used for a range of clinical conditions.