Knocking down Cabin1 induces glomerular podocyte injury

Background Podocyte damage exerts a key role in proteinuria. We have demonstrated that calcineurin-binding protein 1 (Cabin1) upregulated during podocyte injury, yet its function in podocyte is still unclear. Methods We established 5/6 nephrectomized rats and angiotensin II (AngII)-injured podocyte, as well as knocked down Cabin1 with siRNA in cultured podocytes. Rats were killed at 4 or 8 weeks after 5/6 nephrectomy. The localization of podocyte cytoskeleton was detected after immunofluorescence staining. Podocyte mitochondrial morphology was observed under electron microscopy. Podocyte mitochondrial transmembrane potential (MMP) was measured with MitoCapture kit. Cabin1 and cytochrome c protein expression were detected by western blot. Results Massive proteinuria, as well as obvious segmental glomerular sclerosis, was found in rats at 8 weeks after nephrectomy, accompanied with the disruption of synaptopodin. Moreover, mitochondria changed from large and ellipsoid shape to the small, long, and irregular shape in rats at 4 weeks after operation. At 8 weeks, mitochondria were swollen and cristae were remarkably dissolved. Compared to sham-operated rats, Cabin1 protein expression was obviously upregulated in rats at 8 weeks. AngII induced the decrease in MMP, as well as the overexpression of Cabin1 and cytochrome c protein in podocytes. Knocking down Cabin1 induced the disruption of F-actin and overexpression of cytochrome c (1.81 ± 0.21 in siRNA group vs. 0.86 ± 0.11 in negative control group). Conclusions Knocking down Cabin1 induces the disruption of cytoskeleton and mitochondrial dysfunction in podocyte. Cabin1 could be a crucial factor in podocyte damage.