Garlid AO 2012 Abstract Bioblast
Garlid AO, Garlid KD (2012) Na,K-ATPase Signaling to Mitochondria. Mitochondr Physiol Network 17.12. |
Link: MiPNet17.12 Bioblast 2012 - Open Access
Event: Bioblast 2012
Binding of cardiac glycosides to the Na,K-ATPase has two effects: increased contractility (inotropy) and cardioprotection against ischemia-reperfusion injury [1]. Cardioprotection is mediated by caveolar vesicles (signalosomes) that bud off the plasma membrane, move to mitochondria, and use a terminal kinase to phosphorylate an outer membrane protein. This activates inner membrane PKCΞ΅s, causing opening of the mitochondrial ATP-sensitive K+ channel (mitoKATP) and inhibition of the mitochondrial permeability transition (MPT). These events are assayed in vitro using purified signalosomes from treated hearts and mitochondria from untreated hearts [2].
The terminal kinase of GPCR signalosomes is PKG [2]; however PKG does not mediate cardioprotection by ouabain, so we set out to determine the terminal kinases used by the ouabain signalosome. Rat hearts perfused with ouabain yielded a signalosome fraction that was caveolar in nature and enriched with caveolins 1 and 3, Src, PKCΞ΅ and the Ξ±-1-subunit of the Na+,K+-ATPase. Electron microscopy of purified signalosomes revealed vesicles approximately 140 nM in diameter that were found by immunogold labeling to be decorated with caveolin-3. Ouabain signalosomes from heart opened mitoKATP in mitochondria isolated from untreated hearts and liver. The terminal kinases of the ouabain signalosome are Src and PKCΞ΅, which together phosphorylated an endogenous outer membrane p38MAPK. We conclude (1) that ouabain cardioprotection utilizes the signalosome mechanism; (2) that the terminal kinases acting on mitochondria are Src and PKCΞ΅, (3) that this is a general mechanism of cell signaling, given that signalosomes from rat heart open mitoKATP in rat liver mitochondria. (4) that ouabain cardioprotection acts via a mitochondrial p38 MAPK.
Digitalis has been used in the treatment of heart failure since 1785. It was thought for many years that its efficacy was due to its positive inotropic effect. This may not be the case. Cardioprotection in both rat and rabbit is seen with concentrations of ouabain that have no inotropic effect.
β’ Keywords: Na/K ATPase, Signaling, Ouabain, Cardioprotection, p38 MAPK, Digitalis
Labels:
Stress:Ischemia-Reperfusion; Preservation"Ischemia-Reperfusion; Preservation" is not in the list (Cell death, Cryopreservation, Ischemia-reperfusion, Permeability transition, Oxidative stress;RONS, Temperature, Hypoxia, Mitochondrial disease) of allowed values for the "Stress" property. Organism: Rat Tissue;cell: Cardiac muscle"Cardiac muscle" is not in the list (Heart, Skeletal muscle, Nervous system, Liver, Kidney, Lung;gill, Islet cell;pancreas;thymus, Endothelial;epithelial;mesothelial cell, Blood cells, Fat, ...) of allowed values for the "Tissue and cell" property. Preparation: Intact Organ"Intact Organ" is not in the list (Intact organism, Intact organ, Permeabilized cells, Permeabilized tissue, Homogenate, Isolated mitochondria, SMP, Chloroplasts, Enzyme, Oxidase;biochemical oxidation, ...) of allowed values for the "Preparation" property., Isolated Mitochondria"Isolated Mitochondria" is not in the list (Intact organism, Intact organ, Permeabilized cells, Permeabilized tissue, Homogenate, Isolated mitochondria, SMP, Chloroplasts, Enzyme, Oxidase;biochemical oxidation, ...) of allowed values for the "Preparation" property.
Affiliations and author contributions
Anders O Garlid, Keith D Garlid
Department of Biology, Portland State University, Portland, Oregon, USA; Email: [email protected]
Figure 1
Signaling to mitochondria via signalosome. Upon binding to their respective receptors, bradykinin and ouabain trigger formation of caveolar signaling platforms that are encapsulated in signalosomes. Signalosomes bind to and phosphorylate mitochondrial outer membrane (MOM) receptors via specific terminal kinases. This causes the signal to be transmitted across the MOM and intermembrane space, to PKCΞ΅1 on the mitochondrial inner membrane and trigger the intramitochondrial signaling pathway, leading to activation of PKCΞ΅2 and inhibition of MPT. The terminal kinase of the bradykinin signalosome is PKG, which phosphorylates a MOM receptor (R1) of unknown identity. The terminal kinases of the ouabain signalosome are Src and PKCe acting in concert to phosphorylate a MOM p38MAPK.