Glial cells in the mammalian CNS are subject to environmental stress resulting from a variety of neuropathological conditions. In this study, we have examined the activation of a stress signal responsive kinase, i.e., stress-activated protein kinase (SAPK) or cJun N-terminal kinase (JNK), in primary
Thrombin activates two stress-activated protein kinases, c-Jun N-terminal kinase and p38, in HepG2 cells
β Scribed by Hiroshi Mitsui; Toshiyuki Maruyama; Satoshi Kimura; Yoh Takuwa
- Publisher
- John Wiley and Sons
- Year
- 1998
- Tongue
- English
- Weight
- 237 KB
- Volume
- 27
- Category
- Article
- ISSN
- 0270-9139
No coin nor oath required. For personal study only.
β¦ Synopsis
Recently identified c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase are activated by stimuli of various cellular stresses, cytokines, and growth factors. Strong activation of JNK was reported in the regenerating liver, implicating JNK in growth stimulation of hepatocytes. However, it is not known which factors regulate JNK activity in liver cells. In this study, we examined activation of JNK and p38 in HepG2 cells stimulated with heterotrimeric G protein-coupled receptor agonists known as mitogens. Thrombin, lysophosphatidic acid (LPA), and bradykinin (BK) stimulated extracellular signal-regulated protein kinase to similar extents, indicating that HepG2 cells have cell surface receptors for these agonists, which are coupled to intracellular signaling pathways. In contrast, only thrombin strongly activated JNK and p38. Thrombin-induced activation of JNK and p38 peaked at 30 minutes and 15 minutes with maximal stimulation of 13- and 4-fold increases, respectively. LPA and BK failed to activate JNK at all and activated p38 only slightly. Interestingly, thrombin-induced JNK activation was inhibited by protein kinase C down-regulation and the addition of a specific protein kinase C inhibitor. Short-term stimulation of cells with an active phorbol ester also induced JNK activation in HepG2 cells. These results indicate that thrombin is a relatively strong activator for JNK and p38 and might play a role in the regulation of activities of JNK and p38 in liver cells.
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