Beclin-1-mediated Autophagy Protects Against Cadmium-activated Apoptosis via the Fas/FasL Pathway in Primary Rat Proximal Tubular Cell Culture

Gang Liu,Zongping Liu,Mengfei Long,Tongwang Luo,Lin Wang,Yan Yuan,Jianchun Bian,Xuezhong Liu,Hui Zou,Ruilong Song,Jianhong Gu,Yi Wang

doi:10.1038/s41598-017-00997-w

Gang Liu, Zongping Liu + Show 10 more

Open Access

https://doi.org/10.1038/s41598-017-00997-w

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Abstract

The Fas/FasL signaling pathway is one of the primary apoptosis pathways, but the involvement and regulatory mechanism of this pathway by autophagy remain unclear. Here we demonstrated that cadmium (Cd) activated the Fas/FasL apoptosis pathway in rat proximal tubular (rPT) cells; this was accompanied by simultaneous activation of autophagy resulted in reduced apoptosis. In this model, we induced autophagy through RAPA and further demonstrated that autophagy protects against activation of Fas/FasL signaling and apoptosis. The antiapoptotic effect of autophagy was blocked by 3-MA, an autophagy inhibitor. The interactions between Beclin-1 and Fas, FasL, FADD, caspase-8 and BID/tBID were relatively weak, with the exception of cleaved caspase-8, indicated that minimal interactions between these proteins and Beclin-1 are involved in maintaining the balance of autophagy and apoptosis. Beclin-1 precipitated with cleaved caspase-8 in a dose-dependent mannter, and the expression was increased by siRNA against Beclin-1. These data suggested that Beclin-1-mediated autophagy impairs the expression and function of cleaved caspase-8 to protect against Cd-induced activation of apopotosis through Fas/FasL signaling pathway.

Highlights

The Fas/FasL signaling pathway is one of the primary apoptosis pathways, but the involvement and regulatory mechanism of this pathway by autophagy remain unclear
Proteins that are associated with the Fas/FasL apoptosis pathway were detected by immunoblotting, and Fas, FasL, FADD, and cleaved caspase-8 were significantly increased in a dose-dependent manner after 12-h treatment with 2.5 μmol/L and 5 μmol/L Cd (Fig. 1B)
These results illustrated that the Fas/FasL apoptosis pathway can be activated by Cd in rat proximal tubular (rPT) cells

Summary

Introduction

The Fas/FasL signaling pathway is one of the primary apoptosis pathways, but the involvement and regulatory mechanism of this pathway by autophagy remain unclear. We demonstrated that cadmium (Cd) activated the Fas/FasL apoptosis pathway in rat proximal tubular (rPT) cells; this was accompanied by simultaneous activation of autophagy resulted in reduced apoptosis. In this model, we induced autophagy through RAPA and further demonstrated that autophagy protects against activation of Fas/FasL signaling and apoptosis. Beclin-1 precipitated with cleaved caspase-8 in a dose-dependent mannter, and the expression was increased by siRNA against Beclin-1 These data suggested that Beclin-1-mediated autophagy impairs the expression and function of cleaved caspase-8 to protect against Cd-induced activation of apopotosis through Fas/FasL signaling pathway. Overexpression of Beclin-1 induces autophagy in mammalian cells[17], and knockout of the Beclin-1 gene results in embryonic lethality in mice[19]

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Conclusion