REGULAR ARTICLES

Cell research (2004); 14(2):148-154

Binding activity of H-Ras is necessary for in vivo inhibition of ASK1 activity

Jun DU1, 2*, Shao Hui CAI3, 4, Zhe SHI3, Fumihiko NAGASE1

¹Department of Medical Technology, Nagoya University School of Health Sciences, Aichi 461-8673, Japan.
²School of Pharmaceutical Science, Sun Yat-Sen University, Guangzhou, 510089, China.
³Department of Immunology, Nagoya University Graduate and Faculty School of Medicine, Aichi, 466-8550, Japan.
⁴College of Pharmacy, Jinan University, Guangzhou, 510632, China.

Received, Jul 23, 2003    Revised, Dec 31, 2003    Accepted, Feb 2, 2004

Correspondence: Jun DU +81(52)719-1547 (phone) +81(52)719-1547 (fax) togun@met.nagoya-u.ac.jp

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H-Ras is well known as one of the essential components of Ras/Raf/MEK/ERK cascade, which is a critical prosurvival signaling mechanism in most eukaryotic cells. Ras targets Raf/MEK/ERK cascade by integrating and transmitting extracellular signals from growth factor receptors to Raf, leading to the propagation of signals to modulate a serious of cellular survival events. Apoptosis signal-regulating kinase1 (ASK1) serves as a general mediator of cell death because it is responsive to a variety of death signals. In this study, we found that H-Ras interacted with ASK1 to cause the inhibition of both ASK1 activity and ASK1-induced apoptosis in vivo, which was reversed only partially by addition of RafS621A, an antagonist of Raf, whereas MEK inhibitor, PD98059, and PI3K inhibitor, LY294002, did not disturb the inhibitory effect of H-Ras on ASK-1-induced apoptosis. Furthermore, by means of immunoprecipitate and kinase assays, we demonstrated that the interaction between H-Ras and ASK1 as well as the inhibition of ASK1 activity were dependent on the binding activity of H-Ras. These results suggest that a novel mechanism may be involved in H-Ras-mediated cell survival in addition to the well established MEK/ERK and PI3K/Akt kinase-dependent enhancement of cell survival.

Keywords: H-Ras, ASK1, apoptosis, binding activity.