Abstract 1338: Blockage of nucleocytoplasmic transport by wheat germ agglutinin (WGA) induces autophagy and cell death

Abstract

Abstract The nuclear pore complex (NPC) is a primary conduit for cellular communication between the nucleus and cytoplasm, which is essential for cellular survival and proliferation. During carcinogenesis, many oncoproteins are activated and have to send their signals into nucleus to regulate gene expression. In response to the signals, many genes are upregulated, which results in transcription of many RNA. Because both inward of transcriptional factors and outward of RNAs require interaction of these molecules with NPC, blockage of NPC may provoke serious cellular distress. Wheat germ agglutinin (WGA), a lectin that specifically binds to N-acetyl-d-glucosamine (GlcNAc) and N-acetyl-d-neuraminic acid (NeuNAc) residues on the cell surface, was reported to disrupt the function of NPC via interaction with POM121. We found that FITC-WGA had located around the cell membrane 0.5 hour after administration to culture media and reached the paranuclear region 4 hours later. The accumulation of WGA around the nucleus subsequently induced a nucleocytoplasmic transport blockage that prevented export of tRNA and import of signaling proteins (NF-κB and Nrf2) into the nucleus. Beyond the concentration of 5 μg/ml, WGA dose- and time-dependently induced cell death in HeLa, SiHa and CaSKi cell lines. The SiHa cells had more intake of WGA than HeLa and CaSKi cells did and became more sensitive to WGA treatment compared to the other two cells. After treatment with WGA in the three cells, we observed that the expression of autophagic markers (ATG5, ATG7 and LC3) are induced in 24 hours and last to 96 hours. On the contrary, the apoptotic protein caspases 3 and downstream substrates, such as poly(ADP-ribose) polymerase (PARP) were only marginally induced. Furthermore, Transmission Electron Microscopy (TEM) imaging disclosed multi-membrane vesicles (autophagosomes and autolysosomes) inside the cytoplasm after WGA treatment, confirming that the autophagy response was fully induced. These findings suggest that blockage of NPC by WGA may induced autophagy-related cell death and targeting NPC may be warranting further development into a new anti-cancer modality. Citation Format: Tsung-Lin Tsai, Chun-Hua Hung, Hao-Chen Wang, Dar-Bin Shieh, Wu-Chou Su, Chien-Chung Lin. Blockage of nucleocytoplasmic transport by wheat germ agglutinin (WGA) induces autophagy and cell death. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1338. doi:10.1158/1538-7445.AM2014-1338