Requirement of protein kinase (Krs/MST) activation for MT-21-induced apoptosis

Abstract

Fas is a well characterized apoptosis-inducing factor. One of our synthetic compounds, MT-21, induced apoptosis in human leukemia HL-60 cells similar to Fas. MT-21 activated caspase-3, an important cysteine aspartic protease for apoptosis induction. MT-21 also activated c-Jun-NH 2 -terminal kinase (JNK), a member of mitogen activated protein kinase (MAPK) superfamily that is involved in the regulation of cell growth, di erentiation and cell death. Moreover, MT-21 treatment resulted in the activation of a 36 kDa kinase which uses myelin basic protein (MBP) as a substrate. However, MAPK and p38 were not activated by treatment with MT-21. The 36 kDa MBP kinase was shown to be a proteolytic product derived from the Krs protein with a molecular weight of 60 kDa. The Krs protein is a Ser/Thr protein kinase whose activity is enhanced by digestion of its C-terminal regulatory domain by caspase-3. When a kinase-inactive mutant form of Krs protein was overexpressed in HL-60 cells, JNK activation and apoptosis induction by MT-21 were suppressed. Furthermore, overexpression of dominant negative c-Jun also suppressed apoptosis induction by MT-21. These ®ndings indicate that MT-21 induces apoptosis by the activation of JNK via the Krs protein, which is activated by caspase cleavage.

Life and death decisions: regulation of apoptosis by proteolysis of signaling molecules

“…Ectopic expression of MST induces apoptosis, and a kinase-dead mutant in HL-60 cells inhibits both JNK activation and apoptosis. 57 Similar results are obtained when BJAB or 293T cells are used. The physiologic targets of activated MST are unknown, although transfection of 293T cells with MST1 activates MKK7, MKK6, SAPK, and p38 MAPK.…”

Activation of MST/Krs and c-Jun N-terminal Kinases by Different Signaling Pathways during Cytotrienin A-induced Apoptosis

“…Camptothecin, etoposide, mitomycin C, doxorubicin, bleomycin, staurosporine, actinomycin D, colcemid, taxol, and 5-fluorouracil were purchased from Wako Pure Chemicals, Ltd. (Osaka, Japan). Cloning of human fulllength MST/krs1 and MST/krs2 cDNA and constructions of expression vectors of kinase-inactive MST/krs1 and MST/krs2 were performed as described previously (17).…”

“…It is possible that most apoptotic signals including the Fas-mediated signal and the cytotrienin-induced signal activate several pathways for apoptosis in a target cell. Unlike these apoptosis inducers, MT-21 (3-acetyl-4,5-dimethyl-5-octyloxy-3-pyrrolin-2-one), our synthetic apoptosis inducer, activates the signal from caspase-3, MST/Krs to JNK in a rather simple manner (16,17). In the present study, we have investigated the caspase-mediated proteolytic activation of MST/Krs proteins in cytotrienin A-sensitive and -resistant human tumor cell lines.…”

Ajoene-induced cell death in human promyeloleukemic cells does not require JNK but is amplified by the inhibition of ERK

“…The stimuli reported to induce JNK-dependent cell death are stress inducers such as UV-and g-irradiation (Chen et al, 1996;Zanke et al, 1996;Butterfield et al, 1997;Tournier et al, 2000) as well as cytotoxic drugs (Chen et al, 1999;Shiah et al, 1999Shiah et al, , 2001Watabe et al, 1999;Eichhorst et al, 2000;Mandlekar et al, 2000;SanchezPerez et al, 2000;Wang et al, 2000) and anticarcinogenic compounds such as isothiocyanates (Chen et al, 1998). Thus, JNK has been suggested to be required for stress-induced mitochondrial death signaling pathways (Tournier et al, 2000).…”

“…Activation of mitogen-activated protein kinases (MAPKs) is considered to be a pivotal step in ROS-induced signaling pathways. In fact, it has been shown that increased ROS production in leukemic cells leads to the activation of MAPKs and cell death (Chen et al, 1998;Shiah et al, 1999;Watabe et al, 1999;Zhuang et al, 2000).…”