Hydrogen peroxide mediates Rac1 activation of S6K1.
We previously reported that hydrogen peroxide (H2O2) mediates mitogen activation of ribosomal protein S6 kinase 1 (S6K1) which plays an important role in cell proliferation and growth. In this study, we investigated a possible role of H2O2 as a molecular linker in Rac1 activation of S6K1. Overexpression of recombinant catalase in NIH-3T3 cells led to the drastic inhibition of H2O2 production by PDGF, which was accompanied by a decrease in S6K1 activity. Similarly, PDGF activation of S6K1 was significantly inhibited by transient transfection or stable transfection of the cells with a dominant-negative Rac1 (Rac1N17), while overexpression of constitutively active Rac1 (Rac1V12) in the cells led to an increase in basal activity of S6K1. In addition, stable transfection of Rat2 cells with Rac1N17 dramatically attenuated the H2O2 production by PDGF as compared with that in the control cells. In contrast, Rat2 cells stably transfected with Rac1V12 produced high level of H2O2 in the absence of PDGF, comparable to that in the control cells stimulated with PDGF. More importantly, elimination of H2O2 produced in Rat2 cells overexpressing Rac1V12 inhibited the Rac1V12 activation of S6K1, indicating the possible role of H2O2 as a mediator in the activation of S6K1 by Rac1. However, H2O2 could be also produced via other pathway, which is independent of Rac1 or PI3K, because in Rat2 cells stably transfected with Rac1N17, H2O2 could be produced by arsenite, which has been shown to be a stimulator of H2O2 production. Taken together, these results suggest that H2O2 plays a pivotal role as a mediator in Rac1 activation of S6K1.
College of Pharmacy, Sungkyunkwan University, Suwon 440-746, South Korea.
Gyu-Un
GU
Bae
Yong Kee
YK
Kim
Hyoung-Keun
HK
Kwon
Jong Woo
JW
Park
Eun Kyung
EK
Lee
Se Jin
SJ
Paek
Wahn Soo
WS
Choi
In Duk
ID
Jung
Hoi Young
HY
Lee
Eun-Jung
EJ
Cho
Hyang Woo
HW
Lee
Jeung-Whan
JW
Han
D000818:Animals; D002374:Catalase / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000378:metabolism*; D051379:Mice; D041681:NIH 3T3 Cells; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010982:Platelet-Derived Growth Factor / Q000378:metabolism; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000378:metabolism*; D020830:rac1 GTP-Binding Protein / Q000378:metabolism*
D010982:Platelet-Derived Growth Factor; D006861:Hydrogen Peroxide; D002374:Catalase; D019869:Phosphatidylinositol 3-Kinases; D038762:Ribosomal Protein S6 Kinases, 70-kDa; C448901:ribosomal protein S6 kinase, 70kD, polypeptide 1; D020830:rac1 GTP-Binding Protein