Soluble αKlotho interacts with Hsp90aa1 to inhibit the chaperone machinery-mediated Hif1α stabilization and alleviate CKD-induced vascular calcification.

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.