Involvement of the CDKL5-SOX9 signaling axis in rhabdomyolysis-associated acute kidney injury.

Acute kidney injury (AKI) is a common clinical syndrome associated with adverse short- and long-term sequelae. Renal tubular epithelial cell (RTEC) dysfunction and cell death are among the key pathological features of AKI. Diverse systemic and localized stress conditions such as sepsis, rhabdomyolysis, cardiac surgery, and nephrotoxic drugs can trigger RTEC dysfunction. Through an unbiased RNA inhibition screen, we recently identified cyclin-dependent kinase-like 5 (Cdkl5), also known as serine/threonine kinase-9, as a critical regulator of RTEC dysfunction associated with nephrotoxic and ischemia-associated AKI. In the present study, we examined the role of Cdkl5 in rhabdomyolysis-associated AKI. Using activation-specific antibodies and kinase assays, we found that Cdkl5 is activated in RTECs early during the development of rhabdomyolysis-associated AKI. Furthermore, we found that RTEC-specific Cdkl5 gene ablation mitigates rhabdomyolysis-associated renal impairment. In addition, the small-molecule kinase inhibitor AST-487 alleviated rhabdomyolysis-associated AKI in a Cdkl5-dependent manner. Mechanistically, we demonstrated that Cdkl5 phosphorylates the transcriptional regulator sex-determining region Y box 9 (Sox9) and suppresses its protective function under stress conditions. On the basis of these results, we propose that, by suppressing the protective Sox9-directed transcriptional program, Cdkl5 contributes to rhabdomyolysis-associated renal impairment. All together, the present study identified Cdkl5 as a critical stress-induced kinase that drives RTEC dysfunction and kidney injury linked with distinct etiologies.