Activation of HGF/Met Signaling Induces Delayed STAT3 Phosphorylation

Met is a receptor tyrosine kinase which mediates pleiotropic cellular responses following activation by its ligand, hepatocyte growth factor (HGF, also known as scatter factor). Activation of HGF-Met signaling is known to play potentially important roles in tumorigenesis. STATs mediate many of the cellular responses that occur following cytokine, growth factor, and hormone stimulation. STATs are activated by tyrosine and serine phosphorylation, which normally occurs as a tightly regulated process. Constitutively activated STATs have been found in many tumors. In this study, we observed delayed phosphorylation of STAT3 by activation of HGF-Met signaling in Sm Met transfected cells and Chang cells. NIH3T3 cell line was transfected with Trk-Met^(sm) and Trk-Metsm to exclude the effects of endogenous HGF and Met. The phosphorylation of STAT3 following treatment with NGF(100ng/ml) was checked by Western blot analysis. RT-PCR, 2D electrophoresis and MALDI-TOF analysis was performed to identify possible mediator(s). We found the tyrosine phosphorylation of STAT3 from 2 hours after the activation of HGF-Met signaling. The delayed phosphorylation of STAT3 was blocked by pretreatment with cycloheximide and actinomycin D. Interestingly, the conditioned media treated with NGF for 2 hour induced phosphorylation of STAT3 just within 15 miniute when applied to the new culture of NIH3T3 cells. Thus, we supposed that a newly synthesized product was released from the cells, which leads to the phosphorylation of STAT3 on themselves. when we treated human Chang liver cells with HGF, we could observe essentially the same results. To identify the soluble product, we performed RT-PCR for several cytokines which have known to induce activation of STATs. The results showed significant induction of IL-6 mRNA expression in the presence of the lignd. Furthermore, treatment of Chang cells with rhIL-6 resulted in STAT3 phosphorylation within 15 miniute. In addition, IL-6 neutralizing antibody dramatically reduced STAT3 phosphorylation, suggesting IL-6 was the secreted protein inducing delayed phosphorylation of STAT3 following the activation of HGF/Met signaling.

Author dc:creator

• 이, 복순

Contributors dc:contributor

• 이, 재호
• 대학원 의학과
• 104916

• Met
• HGF
• STAT3
• IL-6

Language dc:language

ko

Identifier

http://dcoll.ajou.ac.kr:9080/dcollection/jsp/common/DcLoOrgPer.jsp?sItemId=000000000222
000000000222

OAI identifier oai:identifier

oai:repository.ajou.ac.kr:201003/2311