Bax translocates to mitochondria of heart cells during simulated ischaemia: involvement of AMP-activated and p38 mitogen-activated protein kinases.
The cytosolic protein Bax plays a key role in apoptosis by migrating to mitochondria and releasing proapoptotic proteins from the mitochondrial intermembrane space. The present study investigates the movement of Bax in isolated rat neonatal cardiomyocytes subjected to simulated ischaemia (minus glucose, plus cyanide), using green fluorescent protein-tagged Bax as a means of imaging Bax movements. Simulated ischaemia induced Bax translocation from the cytosol to mitochondria, commencing within 20 min of simulated ischaemia and progressing for several hours. Under the same conditions, there was an increase in the active, phosphorylated forms of p38 MAPK (mitogen-activated protein kinase) and AMPK (AMP-activated protein kinase). The AMPK activators AICAR (5-aminoimidazole-4-carboxamide ribonucleoside) and metformin also stimulated Bax translocation. Inhibition of p38 MAPK with SB203580 attenuated the phosphorylation of the downstream substrates, MAPK-activated protein kinases 2 and 3, but not that of the upstream MAPK kinase 3, nor of AMPK. Under all conditions (ischaemia, AICAR and metformin), SB203580 blocked Bax translocation completely. It is concluded that Bax translocation to mitochondria is an early step in ischaemia and that it occurs in response to activation of p38 MAPK downstream of AMPK.
Capano
Michela
M
Department of Biochemistry and Molecular Biology, University College London, Gower Street, London WC1E 6BT, UK.
Crompton
Martin
M
D055372:AMP-Activated Protein Kinases; D000620:Aminoimidazole Carboxamide / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D002478:Cells, Cultured; D003600:Cytosol / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000378:metabolism; D008687:Metformin / Q000494:pharmacology; D008929:Mitochondria, Heart / Q000378:metabolism*; D009097:Multienzyme Complexes / Q000378:metabolism*; D017202:Myocardial Ischemia / Q000139:chemically induced / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology*; D032383:Myocytes, Cardiac / Q000378:metabolism* / Q000473:pathology; D010766:Phosphorylation / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D021381:Protein Transport / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D012265:Ribonucleotides / Q000494:pharmacology; D051028:bcl-2-Associated X Protein / Q000378:metabolism*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
D009097:Multienzyme Complexes; D012265:Ribonucleotides; D051028:bcl-2-Associated X Protein; D049452:Green Fluorescent Proteins; D000620:Aminoimidazole Carboxamide; D008687:Metformin; D017346:Protein Serine-Threonine Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D055372:AMP-Activated Protein Kinases; C031143:AICA ribonucleotide