PARP-1Impairs Recognition Of Mice By Regulating Tau Protein Phosphorylation

Tau protein is a microtubule-associated protein that can promote microtubule assembly and maintain its stabilizing. Tau molecule contains multiple Thr/Ser phosphorylation sites, and is subjected to the regulation of intracellular multiple kinases and phosphotases. Phosphorylation and dephosphorylation of these sites can regulate the affinity of Tau and microtubule. Abnormal hyperphosphorylation of Tau results in affinity of Tau with microtubule decreasing significantly, and that microtubule structure is unstable. Hyperphosphorylation of Tau is easy to gather into a tangle of silk. Those changes affect intracellular transport and cell morphology, and lead to Tau pathology. The Akt/GSK-3β signaling pathway plays an important role in the regulation of Tau protein phosphorylation, but its upstream factors are still unclear.The latest studies have shown that PARP-1may be an upstream regulating factor of the Akt/GSK-3β signaling pathway. This study intends to explore the effects and mechanisms of PARP-1involving in Tau phosphorylation and functional regulation by using PARP-1activator MNNG and its inhibitor PJ34.In this study, experiments were conducted at the cellular level and animal level. At the cellular level, HEK293/Tau441cells were dealt with10μM MNNG separately, or with10μM MNNG and2μM PJ34interval of2h. After24h, we detected the levels and activity of PARP-1, Akt, GSK-3β as well as Tau phosphorylation by immunoblotting. The results showed that:(1) Compared with the control, MNNG treatment significantly enhanced PAR modification of PARP-1itself, and PARP-1was activated(p<0.01). PARP-1activity of MNNG+PJ34group decreased significantly than the MNNG group (p<0.01).(2) Compared with the control, MNNG treatment significantly reduced Akt activity by phosphorylation of Ser473site (p<0.01), and PJ34attenuated MNNG’s effect.(p<0.05).(3) Compared with the control, MNNG processing significantly inhibited the phosphorylation of the negative active site Ser9of GSK-3β, and raised GSK-3β activity0<0.01), while the overactivity of GSK-3β was provented by PJ34(p<0.05).(4) The attenuatin of PJ34combated the MNNG-induced hyperphosphorylation of Tau at Thr205, Thr231and Ser396observed by Western Blotting. But it is surprising that the Tau hyperphosphorylation at Ser214was decreased after MNNG appication and increased by using PJ34. A further study was applied in Kunming mice by Lateral ventricle positioning injection of22.5mM MNNG8μL or30mM MNNG6μL+2mM PJ342μL. Then the animals behaviors was detected by Morris Water Maze and Elevated Plus Maze. The results indicated that:(1) The escape time to reach the platform of MNNG group mouse was significantly longer than control(p<0.01), the path of searching platform was disorderly, and the time stayed in the target quadrant was significantly shorter(p<0.05). While PJ34could increase the scores of water maze performance significantly(p<0.05).(2) We also observed that enteries to open arm of MNNG group were more often(p<0.05), the residence time was longer(p<0.05) and residence time in the closed arm was shorter(p<0.05), while PJ34provented the role of MNNG.(3) Finally, we made hippocampal homogenates to detect the level and activity of PARP-1, Akt and GSK-3β, and Tau protein phosphorylation level, the results coincided with the cellular results. Conclusion:MNNG led activation of PARP-1, then regulated the phosphorylation of Tau protein through the Akt/GSK-3β signaling cascade, and at last Tau protein hyperphosphorylation of mice depressed spatial cognitive function and mood regulation. This study provides new information for the upstream regulating mechanism of Tau protein phosphorylation and a reference for the treatment of Tau pathology diseases induced by hyperphosphorylation of Tau protein.