Study on the mechanisms of PPE8-induced apoptosis through endoplasmic reticulum stress

• Main Authors: Chih-Hsiang Tseng, 曾智祥
• Other Authors: Te-Ling Lu
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/7bt847

碩士 === 中國醫藥大學 === 藥學系碩士班 === 101 === The endoplasmic reticulum (ER) is a multifunctional organelle that controls important cellular processes, including Ca2+ homoeostasis, protein synthesis and protein folding. Disturbance in the homeostasis of protein folding triggers unfolding protein response (UPR) and causes ER stress. When unfolded proteins accumulate in the ER, binding immunoglobulin protin (Bip)/ glucose-regulated protein 78 (GRP78) chaperone releases IRE1. The released IRE1 is phosphorylated and recruits kinase ASK1. The IRE1-ASK1 complex induces JNK phosphorylation, leading to cell apoptosis. The Vitamin K analogs, naphthoquinones, have been reported to inhibit cell growth. A series of naphthoquinone related compounds, PPE 1-29, were synthesized and were tested for antitumor activity in human lung carcinoma cell lines. The IC50 of PPE8 for H1299 (p53 null) and A549 (p53 wild type) cells were 3.2 uM and 10 uM, respectively, indicating that H1299 cells were more sensitive to PPE8 than A549 cells. We found that PPE8 induced ER expansion by using ER stain in H1299 cells. GRP78 was increased after 5 uM PPE8 treatment for 2 to 8 h. IRE1 was phosphorylated and recruited to ASK1, leading JNK phosphorylation. Knockdown of IRE1 expression by siRNA reduced PPE8-induced JNK phosphorylation in H1299 cells. In contrast, 5 uM PPE8 could not induce GRP 78 expression and JNK phosphorylation in A549 cells. However, knockdown of p53 expression by RNAi in A549 cells induced GRP78 expression and JNK phosphorylation. These results indicate that PPE8-induced ER stress is more potently in p53 null cells.