Diverse mechanisms of myocardial p38 mitogen-activated protein kinase activation: evidence for MKK-independent activation by a TAB1-associated mechanism contributing to injury during myocardial ischemia.
The ischemic activation of p38alpha mitogen-activated protein kinase (p38alpha-MAPK) is thought to contribute to myocardial injury. Under other circumstances, activation is through dual phosphorylation by MAPK kinase 3 (MKK3). Therefore, the mkk3-/- murine heart should be protected during ischemia. In retrogradely perfused mkk3-/- and mkk3+/+ mouse hearts subjected to 30 minutes of global ischemia and 120 minutes of reperfusion, infarction/risk volume was similar (50+/-5 versus 51+/-4, P=0.93, respectively), as was intraischemic p38-MAPK phosphorylation (10 minutes ischemia as percent basal, 608+/-224 versus 384+/-104, P=0.43, respectively). This occurred despite undetectable activation of MKK3/6 in mkk3-/- hearts. However, tumor necrosis factor (TNF)-induced p38-MAPK phosphorylation was markedly diminished in mkk3-/- vs mkk3+/+ hearts (percent basal, 127+/-23 versus 540+/-267, respectively, P=0.04), suggesting an MKK-independent activation mechanism by ischemia. Hence, we examined p38-MAPK activation by TAB1-associated autophosphorylation. In wild-type mice and mkk3-/- mice, the p38-MAPK catalytic site inhibitor SB203580 (1 micromol/L) diminished phosphorylation during ischemia versus control (10 minutes ischemia as percent basal, 143+/-2 versus 436+/-96, P=0.003, and 122+/-25 versus 623+/-176, P=0.05, respectively) and reduced infarction volume (infarction/risk volume, 57+/-5 versus 36+/-3, P<0.001, and 50+/-5 versus 29+/-3, P=0.003, respectively) but did not alter TNF-induced activation, although in homogenates of ischemic hearts but not TNF-exposed hearts, p38-MAPK was associated with TAB1. Furthermore, adenovirally expressed wild-type and drug-resistant p38alpha-MAPK, lacking the SB203580 binding site, was phosphorylated when H9c2 myoblasts were subjected to simulated ischemia. However, SB203580 (1 micromol/L) did not prevent the phosphorylation of resistant p38alpha-MAPK. These findings suggest the ischemic activation of p38-MAPK contributing to myocardial injury is by TAB1-associated autophosphorylation.
Tanno
Masaya
M
Department of Cardiology, Guy's, King's and St Thomas' School of Medicine, King's College London, The Rayne Institute, St Thomas' Hospital, London, UK.
Bassi
Rekha
R
Gorog
Diana A
DA
Saurin
Adrian T
AT
Jiang
Jie
J
Heads
Richard J
RJ
Martin
Jody L
JL
Davis
Roger J
RJ
Flavell
Richard A
RA
Marber
Michael S
MS
D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D002478:Cells, Cultured; D018450:Disease Progression; D004789:Enzyme Activation / Q000187:drug effects / Q000235:genetics; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007093:Imidazoles / Q000494:pharmacology; D066298:In Vitro Techniques; D047908:Intracellular Signaling Peptides and Proteins; D048371:MAP Kinase Kinase 3; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000235:genetics; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D020929:Mitogen-Activated Protein Kinase Kinases / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D032446:Myoblasts / Q000166:cytology / Q000378:metabolism; D009203:Myocardial Infarction / Q000209:etiology / Q000473:pathology; D017202:Myocardial Ischemia / Q000150:complications / Q000378:metabolism* / Q000473:pathology; D010766:Phosphorylation / Q000187:drug effects; D011505:Protein-Tyrosine Kinases / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D011725:Pyridines / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D048051:p38 Mitogen-Activated Protein Kinases
D002352:Carrier Proteins; D004791:Enzyme Inhibitors; D007093:Imidazoles; D047908:Intracellular Signaling Peptides and Proteins; D011725:Pyridines; C099510:TAB1 protein, MAPKKK activator, vertebrate; D014409:Tumor Necrosis Factor-alpha; D011505:Protein-Tyrosine Kinases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D048371:MAP Kinase Kinase 3; C482531:Map2k3 protein, mouse; D020929:Mitogen-Activated Protein Kinase Kinases; C093642:SB 203580