Bisleuconothine A Induces Autophagosome Formation by Interfering with AKT-mTOR Signaling Pathway

详细信息    查看全文

• 作者：Chin Piow Wong ; Ari Seki ; Kaori Horiguchi ; Tomokazu Shoji ; Takashi Arai ; Alfarius Eko Nugroho ; Yusuke Hirasawa ; Fumiaki Sato ; Toshio Kaneda ; Hiroshi Morita
• 刊名：Journal of Natural Products
• 出版年：2015
• 出版时间：July 24, 2015
• 年：2015
• 卷：78
• 期：7
• 页码：1656-1662
• 全文大小：502K
• ISSN：1520-6025

文摘

We have previously reported that bisleuconothine A (Bis-A), a novel bisindole alkaloid isolated from Leuconotis griffithii, showed cytostatic activity in several cell lines. In this report, the mechanism of Bis-A-induced cytostatic activity was investigated in detail using A549 cells. Bis-A did not cause apoptosis, as indicated by analysis of annexin V and propidium iodide staining. Expression of all tested apoptosis-related proteins was also unaffected by Bis-A treatment. Bis-A was found to increase LC3 lipidation in MCF7 cells as well as A549 cells, suggesting that Bis-A cytostatic activity may be due to induction of autophagy. Subsequent investigation via Western blotting and immunofluorescence staining indicated that Bis-A induced formation but prevented degradation of autophagosomes. Mechanistic studies showed that Bis-A down-regulated phosphorylation of protein kinase B (AKT) and its downstream kinase, PRAS40, which is an mTOR repressor. Moreover, phosphorylation of p70S6K, an mTOR-dependent kinase, was also down-regulated. Down-regulation of these kinases suggests that the increase in LC3 lipidation may be due to mTOR deactivation. Thus, the cytostatic activity shown by Bis-A may be attributed to its induction of autophagosome formation. The Bis-A-induced autophagosome formation was suggested to be caused by its interference with the AKT-mTOR signaling pathway.