Majd S, Power JHT, Koblar SA, Grantham HJM. The impact of tau hyperphosphorylation at Ser
262 on memory and learning after global brain ischaemia in a rat model of reversible cardiac arrest.
IBRO Rep 2016;
2:1-13. [PMID:
30135928 PMCID:
PMC6084925 DOI:
10.1016/j.ibror.2016.12.002]
[Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2016] [Revised: 12/12/2016] [Accepted: 12/21/2016] [Indexed: 01/12/2023] Open
Abstract
An increase in phosphorylated tau (p-tau) is associated with Alzheimer's disease (AD), and brain hypoxia. Investigation of the association of residue-specific tau hyperphosphorylation and changes in cognition, leads to greater understanding of its potential role in the pathology of memory impairment. The aims of this study are to investigate the involvement of the main metabolic kinases, Liver Kinase B1 (LKB1) and Adenosine Monophosphate Kinase Protein Kinase (AMPK), in tau phosphorylation-derived memory impairment, and to study the potential contribution of the other tau kinases and phosphatases including Glycogen Synthase Kinase (GSK-3β), Protein kinase A (PKA) and Protein Phosphatase 2A (PP2A). Spatial memory and learning were tested in a rat global brain ischemic model of reversible cardiac arrest (CA). The phosphorylation levels of LKB1, AMPK, GSK-3β, PP2A, PKA and tau-specific phosphorylation were assessed in rats, subjected to ischaemia/reperfusion and in clinically diagnosed AD and normal human brains. LKB1 and AMPK phosphorylation increased 4 weeks after CA as did AMPK related p-tau (Ser262). The animals showed unchanged levels of GSK-3β specific p-tau (Ser202/Thr205), phospho-PP2A (Tyr307), total GSK-3β, PP2A, phospho-cAMP response element-binding protein (CREB) which is an indicator of PKA activity, and no memory deficits. AD brains had hyperphosphorylated tau in all the residues of Ser262, Ser202 and Thr205, with increased phosphorylation of both AMPK (Thr172) and GSK-3β (Ser9), and reduced PP2A levels. Our data suggests a crucial role for a combined activation of tau kinases and phosphatases in adversely affecting memory and that hyperphosphorylation of tau in more than one specific site may be required to create memory deficits.
Short-term brain ischaemia causes AMPK activation and tau phosphorylation at its AMPK-sensitive site (Ser262).
Activation of GSK-3β, PP2A and PKA are remained unchanged in short-term brain ischaemia/reperfusion.
In clinical cases of AD, activation of AMPK, GSK-3β, PP2A and multiple site hyperphosphorylation of tau are observed.
Hyperphosphorylation of tau (Ser262) alone without involving the other tau kinases/phosphatase does not affect memory.
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