T-kininogen inhibits kinin-mediated activation of ERK in endothelial cells.
Serum levels of T-kininogen increase dramatically as rats approach the end of their lifespan. Stable expression of the protein in Balb/c 3T3 fibroblasts leads to a dramatic inhibition of cell proliferation, as well as inhibition of the ERK signaling pathway. T-kininogen is a potent inhibitor of cysteine proteinases, and we have described that the inhibition of ERK activity occurs, at least in part, via stabilization of the MAP kinase phosphatase, MKP-1. Since fibroblasts are not a physiological target of T-kininogen, we have now purified the protein from rat serum, and used it to assess the effect of T-kininogen on endothelial cells. Adding purified T-kininogen to EAhy 926 hybridoma cells resulted in inhibition of basal ERK activity levels, as estimated using appropriate anti-phospho ERK antibodies. Furthermore, exogenously added T-kininogen inhibited the activation of the ERK pathway induced by either bradykinin or T-kinin. We conclude that the age-related increase in hepatic T-kininogen gene expression and serum levels of the protein could have dramatic consequences on endothelial cell physiology, both under steady state conditions, and after activation by cell-specific stimuli. Our results are consistent with T-kininogen being an important modulator of the senescent phenotype in vivo.
Leiva-Salcedo
Elias
E
Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile Independencia 1027, Santiago, Chile.
Perez
Viviana
V
Acuña-Castillo
Claudio
C
Walter
Robin
R
Sierra
Felipe
F
D000367:Age Factors; D000818:Animals; D015153:Blotting, Western; D001920:Bradykinin / Q000031:analogs & derivatives* / Q000494:pharmacology; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D015853:Cysteine Proteinase Inhibitors / Q000097:blood / Q000494:pharmacology*; D004730:Endothelium, Vascular / Q000166:cytology / Q000201:enzymology*; D004789:Enzyme Activation / Q000187:drug effects; D007704:Kininogens / Q000097:blood / Q000494:pharmacology*; D007705:Kinins / Q000494:pharmacology; D020928:Mitogen-Activated Protein Kinases / Q000187:drug effects* / Q000378:metabolism; D051381:Rats; D011914:Rats, Inbred BN; D015398:Signal Transduction
D015853:Cysteine Proteinase Inhibitors; D007704:Kininogens; D007705:Kinins; C039065:T-kinin; D020928:Mitogen-Activated Protein Kinases; D001920:Bradykinin