Up-modulation of Hepatocyte Growth Factor/ c-Met Signaling by Protein Kinase C-g and its Mechanism

Protein kinase C (PKC) family is composed of 11 isoenzymes, and has been known to down-modulate the tyrosine kinase activity of c-Met, the receptor for hepaotcyte growth factor (HGF). However, specified roles by PKC isoenzymes on the regulation of HGF/c-Met signaling have never been addressed yet. In this study, attempts have been made to investigate the effect of PKC-γ, an isoenzyme of PKC, on the HGF/c-Met signaling and its mechanism. In PKC-γ-transfected NIH3T3 cells, c-Met autophosphorylation level was increased compared to that of the normal NIH3T3 cells, which was partly abolished by the pre-treatment of Go¨6976; an inhibitor of PKC-α, β1 and γ. Also, the Erk phosphorylation level was significantly increased in these cells with the treatment of HGF. The expression levels of both c-Met mRNA and protein were not altered in PKC-γ transfected cells. Translocation of PKC-γ to the membrane after HGF treatment was not observed either. Interestingly, a significant amount of PKC-γ revealed to be constitutively localized at the membrane, unlike PKC-α. Furthermore, co-immunoprecipitation assay revealed that PKC-γ interacts with c-Met constitutively. Treatment with HGF does not affect the association of PKC-γ with c-Met or the tyrosine phosphorylation level of PKC-γ. Instead, the serine phosporylation level of c-Met was increased. To define phosphorylation site of c-Met by PKC-γ, we perform in vitro kinase assay using various GST fusion proteins with different domains of cytosolic Met. This result indicates that juxtamembrane domain of c-Met is directly phosphorylated by PKC-γ. It seems that the up-modulation of c-Met signaling in PKC-γ transfected NIH3T3 cells is not associated with HGF-induced rapid change but with the constitutive association of c-Met with PKC-γ and effect on c-Met activation via phosphorylation of specific serine1020 residue in juxtamembrane domain.

Author dc:creator

• 김, 율

Contributors dc:contributor

• 이, 재호
• 대학원 의학과
• 200324254

• hepatocyte growth factor
• c-Met
• protein kinase C-γ
• up-modulation

Language dc:language

ko

Identifier

http://dcoll.ajou.ac.kr:9080/dcollection/jsp/common/DcLoOrgPer.jsp?sItemId=000000000207
000000000207

OAI identifier oai:identifier

oai:repository.ajou.ac.kr:201003/1488