title: Phosphoinositide 3-kinase accelerates calpain-dependent proteolysis of fodrin during hypoxic cell death.
abstract: We have shown recently that phosphoinositide 3-kinase (PI 3-kinase) accelerates the hypoxia-induced necrotic cell death of H9c2, derived from rat cardiomyocytes, by enhancing metabolic acidosis. Here we show the downstream events of acidosis that cause hypoxic cell death. Hypoxia induces the proteolysis of fodrin, a substrate of calpain. Intracellular Ca(2+) chelation by BAPTA, and the addition of SJA6017, a specific peptide inhibitor of calpain, also reduces cell death and fodrin proteolysis, indicating that Ca(2+) influx and calpain activation might be involved in these events. The overexpression of wild type PI 3-kinase accelerates fodrin proteolysis, while dominant-negative PI 3-kinase reduces it. Both (N-ethyl-N-isopropyl)amiloride (EIPA), an inhibitor of the Na(+)/H(+) exchanger, and KB-R7943, an inhibitor of the Na(+)/Ca(2+) exchanger, reduce hypoxic cell death and fodrin proteolysis. The depletion of intracellular Ca(2+ )stores by thapsigargin, an inhibitor of endoplasmic reticulum Ca(2+)-ATPase, also reduces cell death and fodrin proteolysis, indicating that Ca(2+ )release from intracellular Ca(2+ )stores might be also involved. These results indicate that PI 3-kinase might accelerate hypoxic cell death by enhancing the calpain-dependent proteolysis of fodrin.
authors.affiliation: Department of Legal Medicine, Yamaguchi University School of Medicine, Minamikogushi, Ube, Yamaguchi 755-8505, Japan. taki@po.cc.yamaguchi-u.ac.jp
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Aki
authors.forename: Ken-ichi
authors.initials: K
authors.lastname: Yoshida
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Fujimiya
mesh_terms: D000138:Acidosis / Q000378:metabolism; D000818:Animals; D000963:Antimetabolites / Q000378:metabolism; D002021:Buffers; D002118:Calcium / Q000378:metabolism; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors / Q000378:metabolism; D002154:Calpain / Q000037:antagonists & inhibitors / Q000378:metabolism*; D016923:Cell Death / Q000502:physiology*; D015687:Cell Hypoxia; D002470:Cell Survival; D002478:Cells, Cultured; D002614:Chelating Agents / Q000378:metabolism; D003847:Deoxyglucose / Q000378:metabolism; D004151:Dipeptides / Q000378:metabolism; D004533:Egtazic Acid / Q000031:analogs & derivatives* / Q000378:metabolism; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000378:metabolism; D018014:Gene Transfer Techniques; D006531:HEPES / Q000378:metabolism; D032383:Myocytes, Cardiac / Q000166:cytology / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D051381:Rats; D019831:Sodium-Calcium Exchanger / Q000037:antagonists & inhibitors / Q000378:metabolism; D017923:Sodium-Hydrogen Exchangers / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D000963:Antimetabolites; D002021:Buffers; D002118:Calcium; D000252:Calcium-Transporting ATPases; D002154:Calpain; D002614:Chelating Agents; D003847:Deoxyglucose; D004151:Dipeptides; D004533:Egtazic Acid; D004791:Enzyme Inhibitors; D006531:HEPES; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D019831:Sodium-Calcium Exchanger; D017923:Sodium-Hydrogen Exchangers; C109145:N-(4-fluorophenylsulfonyl)-L-valyl-L-leucinal; C070379:1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid acetoxymethyl ester