TGF-beta and HGF transmit the signals through JNK-dependent Smad2/3 phosphorylation at the linker regions.
Although hepatocyte growth factor (HGF) can act synergistically or antagonistically with transforming growth factor-beta (TGF-beta) signaling, molecular mechanism of their crosstalk remains unknown. Using antibodies which selectively distinguished receptor-regulated Smads (R-Smads) phosphorylated at linker regions from those at C-terminal regions, we herein showed that either HGF or TGF-beta treatment of normal stomach-origin cells activated the JNK pathway, thereafter inducing endogenous R-Smads phosphorylation at linker regions. However, the phosphorylation at their C-terminal regions was not induced by HGF treatment. The activated JNK could directly phosphorylate R-Smads in vitro at the same sites that were phosphorylated in response to TGF-beta or HGF in vivo. Thus, the linker regions of R-Smads were the common phosphorylation sites for HGF and TGF-beta signaling pathways. The phosphorylation induced by simultaneous treatment with HGF and TGF-beta allowed R-Smads to associate with Smad4 and to translocate into the nucleus. JNK pathway involved HGF and TGF-beta-mediated infiltration potency since a JNK inhibitor SP600125 caused the reduction of invasive capacity induced by HGF and TGF-beta signals. Moreover, a combined treatment with HGF and TGF-beta led to a potent increase in plasminogen activator inhibitor type 1 transcriptional activity through Smad3 phosphorylation at the linker region. In contrast, HGF treatment reduced TGF-beta-dependent activation of p15INK4B promoter, in which Smad3 phosphorylation at the C-terminal region was involved. In conclusion, HGF and TGF-beta transmit the signals through JNK-mediated R-Smads phosphorylation at linker regions.
Third Department of Internal Medicine, Kansai Medical University, 10-15 Fumizonocho, Moriguchi, Osaka 570-8507, Japan.
Shigeo
S
Mori
Koichi
K
Matsuzaki
Katsunori
K
Yoshida
Fukiko
F
Furukawa
Yoshiya
Y
Tahashi
Hideo
H
Yamagata
Go
G
Sekimoto
Toshihito
T
Seki
Hirofumi
H
Matsui
Mikio
M
Nishizawa
Jun-ichi
J
Fujisawa
Kazuichi
K
Okazaki
D000818:Animals; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005822:Genetic Vectors; D017228:Hepatocyte Growth Factor / Q000494:pharmacology*; D048031:JNK Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism*; D010766:Phosphorylation; D051381:Rats; D011994:Recombinant Proteins / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D051899:Smad2 Protein; D051900:Smad3 Protein; D013270:Stomach; D015534:Trans-Activators / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000494:pharmacology*
D004268:DNA-Binding Proteins; D011994:Recombinant Proteins; D051899:Smad2 Protein; C497784:Smad2 protein, rat; D051900:Smad3 Protein; C497787:Smad3 protein, rat; D015534:Trans-Activators; D016212:Transforming Growth Factor beta; D017228:Hepatocyte Growth Factor; D048031:JNK Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D020929:Mitogen-Activated Protein Kinase Kinases