title: Early glycogen synthase kinase-3β and protein phosphatase 2A independent tau dephosphorylation during global brain ischaemia and reperfusion following cardiac arrest and the role of the adenosine monophosphate kinase pathway.
abstract: Abnormal tau phosphorylation (p-tau) has been shown after hypoxic damage to the brain associated with traumatic brain injury and stroke. As the level of p-tau is controlled by Glycogen Synthase Kinase (GSK)-3β, Protein Phosphatase 2A (PP2A) and Adenosine Monophosphate Kinase (AMPK), different activity levels of these enzymes could be involved in tau phosphorylation following ischaemia. This study assessed the effects of global brain ischaemia/reperfusion on the immediate status of p-tau in a rat model of cardiac arrest (CA) followed by cardiopulmonary resuscitation (CPR). We reported an early dephosphorylation of tau at its AMPK sensitive residues, Ser(396) and Ser(262) after 2 min of ischaemia, which did not recover during the first two hours of reperfusion, while the tau phosphorylation at GSK-3β sensitive but AMPK insensitive residues, Ser(202) /Thr(205) (AT8), as well as the total amount of tau remained unchanged. Our data showed no alteration in the activities of GSK-3β and PP2A during similar episodes of ischaemia of up to 8 min and reperfusion of up to 2 h, and 4 weeks recovery. Dephosphorylation of AMPK followed the same pattern as tau dephosphorylation during ischaemia/reperfusion. Catalase, another AMPK downstream substrate also showed a similar pattern of decline to p-AMPK, in ischaemic/reperfusion groups. This suggests the involvement of AMPK in changing the p-tau levels, indicating that tau dephosphorylation following ischaemia is not dependent on GSK-3β or PP2A activity, but is associated with AMPK dephosphorylation. We propose that a reduction in AMPK activity is a possible early mechanism responsible for tau dephosphorylation.
authors.affiliation: Centre for Neuroscience, Neuronal Injury and Repair Laboratory, School of Medicine, Flinders University of South Australia, Adelaide, SA, 5042, Australia.
authors.forename: Shohreh
authors.initials: S
authors.lastname: Majd
authors.affiliation: Department of Human Physiology, School of Medicine, Flinders University of South Australia, Adelaide, SA, Australia.
authors.forename: John H T
authors.initials: JH
authors.lastname: Power
authors.affiliation: School of Medicine, The Queen Elizabeth Hospital (TQEH) Campus, University of Adelaide, Adelaide, SA, Australia.
authors.forename: Simon A
authors.initials: SA
authors.lastname: Koblar
authors.affiliation: Centre for Neuroscience, Neuronal Injury and Repair Laboratory, School of Medicine, Flinders University of South Australia, Adelaide, SA, 5042, Australia.
authors.forename: Hugh J M
authors.initials: HJ
authors.lastname: Grantham
mesh_terms: D000091162:AMP-Activated Protein Kinase Kinases; D000818:Animals; D002545:Brain Ischemia / Q000209:etiology / Q000378:metabolism*; D002374:Catalase / Q000378:metabolism; D005260:Female; D000071679:Glycogen Synthase Kinase 3 beta / Q000378:metabolism*; D006323:Heart Arrest / Q000150:complications / Q000378:metabolism*; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism*; D054648:Protein Phosphatase 2 / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D051381:Rats; D017207:Rats, Sprague-Dawley; D015427:Reperfusion Injury / Q000209:etiology / Q000378:metabolism*; D016875:tau Proteins / Q000378:metabolism*
chemical_list: D016875:tau Proteins; D002374:Catalase; D011494:Protein Kinases; D000071679:Glycogen Synthase Kinase 3 beta; D000091162:AMP-Activated Protein Kinase Kinases; D054648:Protein Phosphatase 2
keywords: adenosine monophosphate kinase protein; glycogen synthase kinase-3β; microtubule-associated protein; neuronal energy stress; phosphorylation; protein phosphatase 2A