Abstract
Rasfonin is a fungal secondary metabolite with demonstrated antitumor effects. However, the underlying mechanism of the regulatory role in autophagy initiated by rasfonin is largely unknown. Moreover, the function of Akt to positively mediate the induced autophagy remains elusive. In the present study, we observed that rasfonin induced autophagy concomitant with the upregulation of Akt phosphorylation. Both the inhibition of Akt by small molecule inhibitors and genetic modification partially reduced rasfonin-dependent autophagic flux and PARP-1 cleavage. The overexpression of myrAkts (constant active form) promoted rasfonin-induced apoptosis and autophagy in a cell type- and Akt isoform-specific manner. Using quantitative PCR and immunoblotting, we observed that rasfonin increased the expression of glycolytic gene PFKFB3, and this increased expression can be suppressed in the presence of Akt inhibitor. The inhibition of PFKFB3 suppressed rasfonin-activated autophagy with enhanced PARP-1 cleavage. In the case of glucose uptake was disrupted, which mean the glycolytic pathway was fully blocked, the rasfonin-induced autophagy and PARP-1 cleavage were downregulated. Collectively, these results demonstrated that Akt positively regulated rasfonin-enhanced autophagy and caspase-dependent apoptosis primarily through affecting the glycolytic pathway.
Highlights
Accumulating evidence suggests the existence of several molecular connections among apoptosis, necrosis, and autophagy.[3,4] Macroautophagy, an evolutionarily conserved catabolic and intracellular membrane trafficking process, is involved in the delivery of cytoplasmic contents and organelles to lysosomes for degradation.[5]
We demonstrated that rasfonin induces autophagy, which contributes to apoptosis
Immunoblotting analysis showed that rasfonin induced cleavage of PARP-1 (Figure 1c), PARP-1 is one of the main cleavage targets of caspase-3 in vivo, and cleavage of PARP-1 serves as a marker of cells undergoing apoptosis,[27,28] suggesting the activation of caspase-dependent apoptotic pathway
Summary
Accumulating evidence suggests the existence of several molecular connections among apoptosis, necrosis, and autophagy.[3,4] Macroautophagy (hereafter called autophagy), an evolutionarily conserved catabolic and intracellular membrane trafficking process, is involved in the delivery of cytoplasmic contents and organelles to lysosomes for degradation.[5]. Received 11.8.15; revised 20.10.15; accepted 27.10.15; Edited by M Agostini several mechanisms, such as increasing the expression of glucose transporters, enhancing the coupling between oxidative phosphorylation and glycolysis, promoting the accumulation of HIF1α and HK2, and activating phosphofructokinase-2 (PFK-2).[18] Here, ACHN cell line was selected as the experiment material, as renal cell carcinoma (RCC) is a model for the role of Warburg effect leading to malignancy.[22]
Sign-in/Register to view highlights & summary 
Published Version (
Free)
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 call