title: Activation of mitochondrial μ-calpain increases AIF cleavage in cardiac mitochondria during ischemia-reperfusion.
abstract: Ubiquitous calpains (calpain I and II) are generally recognized as cytosolic proteins. Recently, mitochondrial localized calpain I (μ-calpain) has been identified. Activation of mito-μ-calpain cleaves apoptosis inducing factor (AIF), a flavoprotein located within the mitochondrial intermembrane space, in liver mitochondria, but not in brain mitochondria. We first tested if activation of mito-μ-calpain cleaves AIF in isolated heart mitochondria. A decrease in AIF content within mitochondria increases cardiac injury during ischemia-reperfusion by augmenting oxidative stress. We hypothesize that the activation of mito-μ-calpain by calcium overload during ischemia-reperfusion results in decreased AIF content within mitochondria by cleaving AIF. The μ-calpain was present within mouse heart mitochondria, mostly in the intermembrane space. Exogenous calcium treatment induced a calpain-dependent decrease of mitochondrial AIF content in isolated mouse heart mitochondria. This process was blocked by a calpain inhibitor (MDL-28170). The Mitochondrial μ-calpain activity was increased by 160 ± 15% during ischemia-reperfusion compared to time control. In contrast, the mitochondrial AIF content was decreased by 52 ± 7% during reperfusion vs. time control in the buffer perfused mouse heart. Inhibition of mito-μ-calpain using MDL-28170 decreased cardiac injury by preserving AIF content within mitochondria during ischemia-reperfusion. Thus, activation of mito-μ-calpain is required to release AIF from cardiac mitochondria. Inhibition of calpains using MDL-28170 decreases cardiac injury by inhibiting both cytosolic calpains and mito-μ-calpain during ischemia-reperfusion.
authors: Department of Medicine, Division of Cardiology, Virginia Commonwealth University, Richmond, VA 23298, United States.
authors: Qun
authors: Q
authors: Chen
authors: Melanie
authors: M
authors: Paillard
authors: Ludovic
authors: L
authors: Gomez
authors: Thomas
authors: T
authors: Ross
authors: Ying
authors: Y
authors: Hu
authors: Aijun
authors: A
authors: Xu
authors: Edward J
authors: EJ
authors: Lesnefsky
mesh_terms: D000818:Animals; D051033:Apoptosis Inducing Factor / Q000378:metabolism*; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004151:Dipeptides / Q000494:pharmacology; D004789:Enzyme Activation; D051379:Mice; D008928:Mitochondria / Q000201:enzymology*; D008929:Mitochondria, Heart / Q000201:enzymology*; D015428:Myocardial Reperfusion Injury / Q000201:enzymology*
chemical_list: D051033:Apoptosis Inducing Factor; D015853:Cysteine Proteinase Inhibitors; D004151:Dipeptides; C058076:calpain inhibitor III