Abstract
The calcineurin inhibitors cyclosporine A (CsA) and tacrolimus are widely used in the treatment of proteinuria diseases. As the direct target of these drugs, calcineurin has previously been demonstrated to play a role in proteinuria diseases. However, aside from its immune-related effects, the local status of calcineurin in renal inherent cells has not been fully explored in the settings of proteinuria disease and podocyte injury. In this study, calcineurin activity and protein expression in the well-known puromycin aminonucleoside (PAN)-induced podocyte injury model were examined. Interestingly, we found that calcineurin activity was abnormally increased in PAN-treated podocytes, whereas the expression of the full-length 60-kDa calcineurin protein was decreased. This result suggests that there may be another activated form of calcineurin that is independent of the full-length phosphatase. To investigate whether calpain is involved in regulating calcineurin, we exposed PAN-treated podocytes to both pharmacological inhibitors of calpain and specific siRNAs against calpain. Calpain blockade reduced the enhanced calcineurin activity and restored the down-regulated expression of 60-kDa calcineurin. In addition, purified calpain protein was incubated with podocyte extracts, and a 45-kDa fragment of calcineurin was identified; this finding was confirmed in PAN-induced podocyte injury and calpain inhibition experiments. We conclude that calcineurin activity is abnormally increased during PAN-induced podocyte injury, whereas the expression of the full-length 60-kDa calcineurin protein is down-regulated due to over-activated calpain that cleaves calcineurin to form a 45-kDa fragment.
Highlights
The immunosuppressive drugs cyclosporine A (CsA) and tacrolimus are widely used in renal proteinuria diseases, including minimal change disease (MCD), to reduce excessive protein levels in urine [1,2,3,4]
These results suggest that a podocyte injury model was successfully generated with the application of puromycin aminonucleoside (PAN)
Calcineurin is clinically important as a direct target of the immunosuppressive drugs CsA and tacrolimus [16]
Summary
The immunosuppressive drugs cyclosporine A (CsA) and tacrolimus are widely used in renal proteinuria diseases, including minimal change disease (MCD), to reduce excessive protein levels in urine [1,2,3,4]. The initial motivation for using these drugs was based on the understanding that MCD pathogenesis involves dysregulated production of several circulating immune factors by T cells, which are eventually deposited in glomeruli [5]. Many studies have shown that abnormalities in glomerular inherent cells, including podocytes, play key roles in PLOS ONE | DOI:10.1371/journal.pone.0155504. Calpain Cleaved Calcineurin in Podocyte Injury data collection and analysis, decision to publish, or preparation of the manuscript Many studies have shown that abnormalities in glomerular inherent cells, including podocytes, play key roles in PLOS ONE | DOI:10.1371/journal.pone.0155504 May 12, 2016
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
