Effect of the knockdown of Cabin1 on p53 in glomerular podocyte

Cabin1 involves in renal tubular epithelial cells mitochondrial dysfunction through SIRT1/p53 pathway

Background: Angiotensin II (AngII) induced Calcineurin binding protein 1 (Cabin1) protein expression significantly increased during Renal tubular epithelial cells (RTEC) injury. However, the detailed function of Cabin1 protein in RTEC was not characterized well. In this study, we aimed to explore the downstream target of Cabin1 in vitro model.Methods: Rat kidney epithelial cells were cultured and stimulated with AngII. Electron microscopy was performed to observe mitochondrial morphology change. Immunofluorescence staining was detected to observe the distribution of cytoskeleton and Cabin1. Mitochondrial morphology change and protein expression were detected by electrical microscopy and western blot.Results: AngII induced the disruption of cytoskeleton at 24 and 48 h. Western blot analysis showed AngII significantly induced the overexpression of Cabin1. AngII induced a great deal of small, long and irregular mitochondria in RTEC, aspect ratio which reflects the length-to-width ratio of mitochondria remarkably increased at 12 and 24 h. Knocking down Cabin1 aggravated mitochondrial morphological abnormality in AngII treated RTEC. In comparison with control, Cabin1, p53 and cyto C level were significantly increased in AngII treated cells, while SIRT1 level was obviously decreased. Knocked down Cabin1 plus AngII stimulated, SIRT1 was further decreased, while p53 and cyto C were significantly increased.Conclusions: Cabin1 involves in RTEC mitochondrial dysfunction through SIRT1/p53 pathway. Cabin1 may be used as a new marker for the mechanisms of RTEC injury.

The Use of High-Throughput Transcriptomics to Identify Pathways with Therapeutic Significance in Podocytes

Podocytes have a unique structure that supports glomerular filtration function, and many glomerular diseases result in loss of this structure, leading to podocyte dysfunction and ESRD (end stage renal disease). These structural and functional changes involve a complex set of molecular and cellular mechanisms that remain poorly understood. To understand the molecular signature of podocyte injury, we performed transcriptome analysis of cultured human podocytes injured either with PAN (puromycin aminonucleoside) or doxorubicin/adriamycin (ADR). The pathway analysis through DE (differential expression) and gene-enrichment analysis of the injured podocytes showed Tumor protein p53 (P53) as one of the major signaling pathways that was significantly upregulated upon podocyte injury. Accordingly, P53 expression was also up-regulated in the glomeruli of nephrotoxic serum (NTS) and ADR-injured mice. To further confirm these observations, cultured podocytes were treated with the P53 inhibitor pifithrin-α, which showed significant protection from ADR-induced actin cytoskeleton damage. In conclusion, signaling pathways that are involved in podocyte pathogenesis and can be therapeutically targeted were identified by high-throughput transcriptomic analysis of injured podocytes.

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.

The Emerging Roles of the Calcineurin-Nuclear Factor of Activated T-Lymphocytes Pathway in Nervous System Functions and Diseases

The ongoing epidemics of metabolic diseases and increase in the older population have increased the incidences of neurodegenerative diseases. Evidence from murine and cell line models has implicated calcineurin-nuclear factor of activated T-lymphocytes (NFAT) signaling pathway, a Ca²⁺/calmodulin-dependent major proinflammatory pathway, in the pathogenesis of these diseases. Neurotoxins such as amyloid-β, tau protein, and α-synuclein trigger abnormal calcineurin/NFAT signaling activities. Additionally increased activities of endogenous regulators of calcineurin like plasma membrane Ca²⁺-ATPase (PMCA) and regulator of calcineurin 1 (RCAN1) also cause neuronal and glial loss and related functional alterations, in neurodegenerative diseases, psychotic disorders, epilepsy, and traumatic brain and spinal cord injuries. Treatment with calcineurin/NFAT inhibitors induces some degree of neuroprotection and decreased reactive gliosis in the central and peripheral nervous system. In this paper, we summarize and discuss the current understanding of the roles of calcineurin/NFAT signaling in physiology and pathologies of the adult and developing nervous system, with an emphasis on recent reports and cutting-edge findings. Calcineurin/NFAT signaling is known for its critical roles in the developing and adult nervous system. Its role in physiological and pathological processes is still controversial. However, available data suggest that its beneficial and detrimental effects are context-dependent. In view of recent reports calcineurin/NFAT signaling is likely to serve as a potential therapeutic target for neurodegenerative diseases and conditions. This review further highlights the need to characterize better all factors determining the outcome of calcineurin/NFAT signaling in diseases and the downstream targets mediating the beneficial and detrimental effects.