Soh J W, Mao Y, Liu L, Thompson W J, Pamukcu R, Weinstein I B
Department of Medicine, Herbert Irving Comprehensive Cancer Center, College of Physicians & Surgeons, Columbia University, New York, New York 10032, USA.
J Biol Chem. 2001 May 11;276(19):16406-10. doi: 10.1074/jbc.C100079200. Epub 2001 Mar 14.
We recently obtained evidence that treatment of human colon cancer cells with exisulind (sulindac sulfone) and related compounds induces apoptosis by activation of protein kinase G (PKG) and c-Jun kinase (JNK1). The present study further explores this mechanism. We demonstrate that in NIH3T3 cells a constitutively active mutant of PKG causes a dose-dependent activation of JNK1 and thereby transactivates c-Jun and stimulates transcription from the AP-1 enhancer element. The activation of JNK1 and the transactivation of c-Jun by this mutant of PKG were inhibited by a dominant negative MEKK1. In vitro assays showed that a purified PKG directly phosphorylated the N-terminal domain of MEKK1. PKG also directly phosphorylated a full-length MEKK1, and this was associated with enhanced MEKK1 phosphorylation. Thus, it appears that PKG activates JNK1 through a novel PKG-MEKK1-SEK1-JNK1 pathway, by directly phosphorylating and activating MEKK1.
我们最近获得的证据表明，用依索昔康（舒林酸砜）及相关化合物处理人结肠癌细胞可通过激活蛋白激酶G（PKG）和c-Jun激酶（JNK1）诱导细胞凋亡。本研究进一步探究了这一机制。我们证明，在NIH3T3细胞中，一种组成型活性PKG突变体可引起JNK1的剂量依赖性激活，从而反式激活c-Jun并刺激AP-1增强子元件的转录。PKG的这种突变体对JNK1的激活以及对c-Jun的反式激活受到显性负性MEKK1的抑制。体外实验表明，纯化的PKG可直接磷酸化MEKK1的N端结构域。PKG还可直接磷酸化全长MEKK1，这与MEKK1磷酸化增强有关。因此，PKG似乎通过直接磷酸化并激活MEKK1，经由一条新的PKG-MEKK1-SEK1-JNK1途径激活JNK1。
