SERCA2 deficiency in tubular epithelial cells drives ferroptosis in acute kidney injury regulating endoplasmic reticulum mitochondrial calcium homeostasis via voltage dependent anion channel 1 oligomerization.

INTRODUCTION: Cellular calcium homeostasis is essential for maintaining kidney function. Sarcoplasmic/endoplasmic reticulum calcium ATPase 2 (SERCA2), the primary calcium pump responsible for transporting cytosolic calcium ions back into the endoplasmic reticulum, is a key regulator of endoplasmic reticulum stress and intracellular calcium balance. However, its specific role in acute kidney injury (AKI) and the underlying regulatory mechanisms remain poorly understood.

METHODS: SERCA2 expression was measured in biopsies of patients with AKI, animal models, and cellular assays. AKI models were established using SERCA2 conditional knockdown and overexpression mice, HK-2 cells and primary kidney tubular epithelial cells in vitro. To investigate the underlying mechanisms, we integrated approaches including RNA-sequencing, transmission electron microscopy, immunofluorescence, and Seahorse analyses.

RESULTS: Transcriptomic and histopathological analyses revealed reduced SERCA2 expression in proximal tubules of both patient AKI biopsies and murine models. Proximal tubule-specific SERCA2 knockdown exacerbated kidney dysfunction and tubular injury in murine AKI, while SERCA2 allosteric activation with CDN1163 or its overexpression attenuated these injuries. Mechanistically, SERCA2 deficiency disrupted endoplasmic reticulum calcium homeostasis, leading to endoplasmic reticulum stress and promoting voltage dependent anion channel 1 (VDAC1) oligomerization through impaired mitochondria-associated endoplasmic reticulum membranes. These changes led to mitochondrial permeability transition pore opening, mitochondrial calcium overload, oxidative stress, and ferroptosis. Importantly, stopping VDAC1 oligomerization with small molecule inhibitor VBIT-4 or blocking ferroptosis with ferrostatin-1 restored mitochondrial function and mitigated ferroptosis in SERCA2-deficient models.

CONCLUSIONS: Our study identifies the SERCA2-VDAC1 axis as a critical regulator of endoplasmic reticulum-mitochondrial calcium homeostasis in AKI. Both SERCA2 activation and inhibition of VDAC1 oligomerization conferred substantial renoprotection, highlighting this pathway as a promising therapeutic target for attenuating tubular damage in AKI.