Lack of association between the hepatocyte growth factor receptor, c-met, and the anti-apoptotic action of bag-1 in endothelial cells.
Bag-1 is a novel multifunctional protein. It was identified based on its ability to bind the anti-apoptotic protein, bcl-2, and also reported to interact with the heat shock protein 70 kDa (Hsp70). Thus, bag-1 may modulate apoptosis and the chaperone activity. More interestingly, bag-1 can bind to several growth factor receptors or steroid hormone receptors and regulate their function and signaling. The receptor of hepatocyte growth factor (HGF), c-met, associated with bag-1 in a study measuring immunoprecipitation in endothelial cells, we decided to investigate the contribution of bag-1 to the anti-apoptotic action of HGF. Endogenous expression of bag-1 in endothelial cells was confirmed mainly in the cytosol fraction. The treatment of human recombinant HGF (rHGF) increased tyrosine kinase and ERK phosphorylation, whereas over-expression of bag-1 had no effect on this phosphorylation. In DNA synthesis as assessed by thymidine incorporation, over-expression of bag-1 also did not induce any additional increase. In contrast, in an assay of cell death as assessed by caspase activity and lactate dehydrogenase release, over-expression of bag-1 alone attenuated serum-free and tumor necrosis factor-alpha-induced cell death in endothelial cells. No synergistic effect was observed between bag-1 and rHGF. To further study the association of HGF and bag-1, we examined the effect of a deletion mutant of the bag-1 C-terminal region (CTR), because bag-1 CTR is necessary to bind to c-met. Unexpectedly, over-expression of bag-1 CTR also attenuated the endothelial cell death, similar to rHGF. Taken together, these results indicate that over-expression of bag-1 has an anti-apoptotic effect on endothelial cells independent of HGF signaling.
Nakagami
Hironori
H
Department of Geriatric Medicine, Osaka University Graduate School of Medicine, Yamadaoka, Suita, Japan.
Morishita
Ryuichi
R
Nishikawa
Tomoyuki
T
Shimizu
Hideo
H
Iguchi
Sota
S
Matsumoto
Kunio
K
Nakamura
Toshikazu
T
Kaneda
Yasufumi
Y
Ogihara
Toshio
T
D000818:Animals; D001011:Aorta; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D002352:Carrier Proteins / Q000235:genetics / Q000494:pharmacology / Q000502:physiology*; D002417:Cattle; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D004268:DNA-Binding Proteins; D004357:Drug Synergism; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D017353:Gene Deletion; D017228:Hepatocyte Growth Factor / Q000494:pharmacology; D006801:Humans; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009154:Mutation; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D019859:Proto-Oncogene Proteins c-met / Q000378:metabolism*; D011994:Recombinant Proteins / Q000494:pharmacology; D014157:Transcription Factors
C091732:BCL2-associated athanogene 1 protein; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D011994:Recombinant Proteins; D014157:Transcription Factors; D017228:Hepatocyte Growth Factor; D011505:Protein-Tyrosine Kinases; D019859:Proto-Oncogene Proteins c-met; D020928:Mitogen-Activated Protein Kinases