Nuclear mitogen-activated protein kinase activation by protein kinase czeta during reoxygenation after ischemic hypoxia.
We examined the upstream kinases for mitogen-activated protein kinase (MAPK) activation during ischemic hypoxia and reoxygenation using H9c2 cells derived from rat cardiomyocytes. Protein kinase C (PKC)zeta, an atypical PKC isoform mainly expressed in rat heart, has been shown to act as an upstream kinase of MAPK during ischemic hypoxia and reoxygenation by analyses with PKC inhibitors, antisense DNA, a dominant negative kinase defective mutant, and constitutively active mutants of PKCzeta. Immunocytochemical observations show PKCzeta staining in the nucleus during ischemic hypoxia and reoxygenation when phosphorylated MAPK is also detected in the nucleus. This nuclear localization of PKCzeta is inhibited by treatment with wortmannin, a phosphoinositide 3-kinase inhibitor that also inhibits MAPK activation in a dose-dependent manner. This is supported by the inhibition of MAPK phosphorylation by another blocker of phosphoinositide 3-kinase, LY294002. An upstream kinase of MAPK, MEK1/2, is significantly phosphorylated 15 min after reoxygenation and observed mainly in the nucleus, whereas it is present in the cytoplasm in serum stimulation. The phosphorylation of MEK is blocked by PKC inhibitors and phosphoinositide 3-kinase inhibitors, as observed in the case of MAPK phosphorylation. These observations indicate that PKCzeta, which is activated by phosphoinositide 3-kinase, induces MAPK activation through MEK in the nucleus during reoxygenation after ischemic hypoxia.
Mizukami
Y
Y
First Department of Physiology and the Department of Legal Medicine, Yamaguchi University School of Medicine, Yamaguchi 755-8505, Japan. mizukami@po.cc.yamaguchi-u.ac.jp
Kobayashi
S
S
Uberall
F
F
Hellbert
K
K
Kobayashi
N
N
Yoshida
K
K
D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D002460:Cell Line; D002467:Cell Nucleus / Q000201:enzymology*; D016895:Culture Media, Serum-Free / Q000494:pharmacology; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005455:Fluorescent Antibody Technique; D005799:Genes, Dominant; D015151:Immunoblotting; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009154:Mutation; D017202:Myocardial Ischemia / Q000201:enzymology*; D015428:Myocardial Reperfusion Injury / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation / Q000187:drug effects; D011493:Protein Kinase C / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D013997:Time Factors; D014162:Transfection; D000077191:Wortmannin; D000099221:Protein Kinase C zeta
D000730:Androstadienes; D016895:Culture Media, Serum-Free; D004791:Enzyme Inhibitors; D020928:Mitogen-Activated Protein Kinases; D010100:Oxygen; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011493:Protein Kinase C; D000077191:Wortmannin; D000099221:Protein Kinase C zeta