Rapid Tau Protein Dephosphorylation and Differential Rephosphorylation during Cardiac Arrest-Induced Cerebral Ischemia and Reperfusion

Abstract

The effects of cerebral ischemia/reperfusion on phosphorylation of microtubule-associated tau proteins were assessed in a canine model of cardiac arrest. As tau proteins are phosphorylated by kinases involved in different transduction signal pathways, their phosphorylation state is an excellent marker of neuronal homeostasis and microtubule dynamics. Canine brain tau proteins were characterized by immunoblotting using phosphorylation-dependent antibodies and antisera raised against different amino- and carboxy-terminal tau sequences. The present study reports a complete dephosphorylation of tau proteins during ischemia, which is shown by a higher electrophoretic mobility and the almost (if not total) disappearance of phosphorylation-dependent monoclonal antibody labeling. After 2-hour restoration of spontaneous circulation, a decrease in the electrophoretic mobility was observed, and after 24 hours of reperfusion, a full restoration of the phosphorylation was visualized using phosphorylation-dependent monoclonal antibodies directed against Ser/Thr-Pro sites. However, one particular phosphorylation site involved in tau binding to microtubules, located on Ser262/356, was never fully significantly rephosphorylated, suggesting that microtubule metabolism was still affected after 24 hours of reperfusion. Thus, the sequential and differential recovery of tau phosphorylation after ischemia followed by reperfusion is a useful marker with which to monitor neuronal integrity after brain ischemia.

Induction of Dickkopf-1, a Negative Modulator of the Wnt Pathway, Is Required for the Development of Ischemic Neuronal Death

“…Although tau phosphorylation was not examined here, it is noteworthy that changes in tau phosphorylation have been observed during cardiac arrest-induced cerebral ischemia and reperfusion (Mailliot et al, 2000), transient forebrain ischemia in rats (Shackelford and Yeh, 1998), and in cortical slices subjected to hypoxia combined with glucose deprivation (Burkhart et al, 1998).…”

Differential Changes in Phosphorylation of Tau at PHF-1 and 12E8 Epitopes During Brain Ischemia and Reperfusion in Gerbils

“…Rapid dephosphorylation of tau has been reported in post mortem rat and human brain tissues [17,18] indicating that phosphorylation state of tau is a very dynamic process. The effects of ischemia and reperfusion on tau metabolism have been studied in rats [19,20] and dogs [21] but not in gerbils. Yet gerbils are a long established model of reversible ischemia [22][23][24] used in a number of biochemical studies [1][2][3][4][5].…”

Acute changes in the axonal cytoskeleton after mild stretching of the rat brachial plexus

“…The preferential expression of 65 kDa tau protein with several isoforms in the brachial plexus was consistent with that in the rat sciatic nerve [19]. Because transient cerebral ischemia caused the dephosphorylation or phosphorylation of tau proteins [5,13,14,16], we measured their phosphorylation using phospho-specific antibodies. When the phosphorylation levels were divided by the amount of tau protein, the levels in the control and stretch groups were not significantly different.…”