缺血性卒中后DAPK1死亡信號介導(dǎo)突觸損傷的機(jī)制研究
[Abstract]:[background]
Stroke is the primary cause of brain injury. Ischemic stroke is a serious neurological disease caused by the interruption of cerebral blood flow, resulting in local cerebral ischemia. The patients suffer from language impairment, visual loss, paralysis and even death. The incidence, mortality and disability rate of stroke remain high. With the aging of the population, the incidence of stroke is increasing. The rate is rising and is recognized as a common refractory disease that seriously endangers human health and life safety. Currently, the treatment for cerebral ischemia damage is very limited, and the only effective treatment is thrombolytic therapy with tissue plasminogen activator (tPA). However, safety considerations and thrombolytic therapy are considered. The treatment window is narrow (4.5 hours), and most patients can only get symptomatic support treatment. Therefore, it is very important to explore new intervention methods and treatment methods to combat brain injury and protect nerve cells against ischemic stroke.
Neuronal synaptic damage after ischemia (including presynaptic and postsynaptic damage) is the early pathophysiological basis of synaptic transmission disorders and neuronal death. Our previous study found that death-associated protein kinase (DAPKl) is a Ca2+/calmodulin-dependent serine/threonine. Kinases, which are activated in ischemic brain regions and mediate neuronal death, are abundantly expressed in the somas and processes of neurons, mainly by promoting microtubule assembly to maintain axonal transport, neuronal morphology and signal exchange between neurons. Many serine/threonine kinases (including DAPK1) are involved in abnormal hyperphosphorylation of Tau protein in neurodegenerative disorders. However, whether DAPKl affects Tau phosphorylation during ischemic brain injury and which damage effects of DAPK1 on neurons are mediated by Tau have not been reported so far. As a protein abundantly expressed in presynaptic, n can regulate glutamate transmission, participate in neuronal synaptic apoptosis, and cause neurodegenerative changes and neuronal death. Whether activated DAPK1 acts with Caytaxin and induces Caytaxin phosphorylation, which mediates presynaptic injury after ischemic stroke, remains unclear.
[Objective]
(1) To elucidate the cellular and molecular mechanisms of DAPK1 interacting with Tau, DAPKl and Caytaxin mediating neuronal death after ischemic stroke, and to provide evidence that Tau and Caytaxin are downstream specific substrates of DAPK1 and participate in neuronal death after ischemic stroke. Activated DAPK1 causes abnormal phosphorylation of Tau protein after ischemic stroke Abnormal dendritic spine aggregation leads to the loss of dendritic spine, and the pre-synaptic activation of DAPK1 phosphorylated Caytaxin promotes the expression of Cayatxin, causing synaptic transmission dysfunction.
(2) To explore the therapeutic strategy of ischemic stroke by blocking the interaction between DAPK1 and Tau by synthesizing small molecular polypeptides, so as to lay a theoretical foundation for the development of therapeutic drugs for ischemic stroke.
Middle cerebral artery embolization (MCAO) and light ischemia (PT) were used to construct cerebral ischemia model in 4-month-old mice or sham-operated mice as control. C57BL/6J mice, CaMK II alpha-Cre mice, DAPK1-KD loxp/loxp, DAPK1-KD-/-mice were used as study objects. CaMK II a-Cre mice were hybridized with DAPK1-KD loxp/loxp mice and PCR was used to identify positive. DAPK1-KD-/- mice were induced by tamoxifen; cerebral blood flow during MCAO was monitored by Doppler Cerebral Blood Flowmeter and Laser Speckle Cerebrovascular Imaging; cerebral ischemic area was detected by magnetic resonance (MRI) and TTC staining; degeneration was identified by Fluoro-Jade C (FJ) staining and TUNEL staining, respectively. Number of degenerative and apoptotic neurons; Adeno-associated virus (AAV-EGFP) was used to infect dendritic spines; Western blot (WB) was used to detect DAPK1, Phospho-myosin light chain (pMLC), Tau, Caytaxin, sheared-caspase 3, synapse-related protein PSD95, GluR1, SynapIsin and other eggs after ischemia. The interaction between DAPK1 and Tau, DAPK1 and Caytaxin was studied in vivo and in vitro by immunofluorescence double labeling and immunoprecipitation. The expression system was constructed in HEK293T cells to co-transfect different mutants of DAPK1 (DAPK1 KD, DAPK1 CaM, DAPK1 DD, DAPK1K42A) with Tau, and the interaction between DAPK1 and Tau was identified. Structural domains of DAPK1 immunoprecipitated phosphorylated proteins were detected by mass spectrometry; DAPK1-KD+/+ primary neurons were infected by AAV-Tau-WT and rAAV-Tau-S262A viruses, and DAPK1-KD-/-primary neurons were infected by 1AAV-Tau-WT. The damage of dendritic spines was observed and the AMPA receptor-mediated miniature excitatory postsynaptic potentials (mEPs) were recorded. The amplitude and frequency of EPSC, synthetic peptides blocked the interaction between DAPK1 and Tau, and intravenously injected TAT-R1D small molecule peptides to observe whether they reversed stroke injury. Behavioral methods such as water maze and open field were used to detect the learning, memory and activity of cerebral ischemic mice and those after TAT-R1D polypeptide treatment.
[results]
1. the damage of dendritic spine was earlier than that of apoptosis during cerebral ischemia.
The dendritic spine density decreased significantly from 2 h to 24 h after reperfusion in MCAO group, and the synaptic related proteins PSD95, GluR1 and Synapsin I also decreased significantly. The number of TUNEL positive cells increased significantly from 6 h to 24 h after reperfusion, and the number of shear Caspase 3 increased significantly at 12 h after reperfusion.
2.DAPK1 interacts with Tau through kinase domain, and DAPK1 and Caytaxin interact at presynaptic level.
The results of immunofluorescence double labeling and immunoprecipitation confirmed that DAPK1 and Tau and DAP K1 and Caytaxin interacted to form a complex under hypoxic-ischemic condition, but the expression of DAPK1 and Tau did not change after ischemia, while the expression of Caytaxin increased significantly on the ischemic side compared with the contralateral side. DAPK1 specifically binds to Tau via the amino-terminal kinase domain in the cell line expression system; DAPK1 and Caytaxin co-localize in neurons by immunofluorescence double labeling; both immunofluorescence and immunoblotting show that DAPK1 and Caytaxin are pre-synaptic; interaction between DAPK1 and Caytaxin after ischemic stroke and hydrogen peroxide treatment in neurons Obviously enhanced.
3. DAPK1 was activated during cerebral ischemia, phosphorylation of Tau Ser262 site and phosphorylation of Caytaxin Ser46 site.
After MCAO, the activity of DAPK1 was significantly higher than that of sham-operated group, which showed that the level of pMLC was significantly increased; GPS21 software predicted that DAPK1 might phosphorylate Tau Ser262 site; MS results showed that DAPK1 phosphorylated Tau Ser262 site, phosphorylated Caytaxin Ser46HEK293T cells co-transfected DAPK1 and Tau-WT group, Tau pS262 and shear type. Caspase 3 levels were significantly elevated, but not in DAPK1 and Tau-S262A co-transfected mice; Tau pS262 levels were elevated in C57BL/6J mice after 2 and 24 hours of MCAO, while pS202, pS422, and GSK3P levels were not significantly changed.
4. phosphorylation of Tau Ser262 site results in dendritic spine injury.
After 9 days of culture, primary neurons infected with rAAV-Tau-WT virus showed loss of dendritic spines, elevated levels of Tau pS262, decreased levels of synaptic-related proteins such as PSD95, GluRl and Synapsin I, and decreased amplitudes and frequencies of AMPA receptor-mediated miniature excitatory postsynaptic potentials (mEPSC). On the contrary, AV-Tau-S262A infection resulted in a decrease in the formation of dendritic spines. Tau-WT was infected with DAPK1-KD-/-primitive primordial primordial primordial primordial primordial primordial primordial primordial primordial primordial primordial primordial primordial primordial primordial primordial primordial primordial primordial primordial primordial primordial primordial primordial primordial primordial primordial primordial primordial pri
5. knocking out DAPK1 kinase domain to alleviate ischemic injury
The body weight, cerebral blood vessels, blood flow, brain structure and emotions of DAPK1-KD-/- mice did not change significantly compared with wild-type mice in the same nest, suggesting that conditioned knockout of DAPK1 kinase domain did not affect the phenotype of mice; MCAO1-hour ischemia, reperfusion 24 hours, magnetic resonance imaging and TTC staining showed that the ischemic area of DAPK1-KD mice was larger than that of DAPK1-K mice. In Dloxp/loxp mice, the levels of Tau pS262 and degeneration and apoptosis of DAPK1-KD-/- mice were observed by FJ staining and TUNEL at 3 and 7 days after reperfusion. The loss of dendritic spines was also alleviated, and the neurological function score and motor coordination were improved.
Therapeutic effect of 6.TAT-R1D on stroke injury
A peptide TAT-R1D was synthesized according to the site of interaction between DAPK1 and Tau. Fluorescence microscopy showed that TAT-R1D was absorbed by neurons instead of microglia or astrocytes. Immunocoprecipitation results showed that TAT-R1D could be used in brain tissue at the dose of intravenous TAT-R1D2mg/kg within 6 hours of reperfusion. Tau pS262 decreased, synapse-related proteins PSD-95, GluR1 and Synapsin-1 were up-regulated compared with the control group, TTC staining was performed 3 days later, and the ischemic area was reduced; moreover, TAT-R1D significantly increased the neural function of the mice 7 days after TMCAO. Able to score and behave in behavior such as water maze and open field.
[Conclusion]
We found for the first time that the interaction between DAPK1 and Tau in ischemic stroke mice mediated the loss of dendritic spines and subsequent neuronal death after stroke. The activation of DAPK1 phosphorylated Tau at the site of Ser262 triggered Tau aggregation in the dendritic spines. Blocking the interaction between DAPK1 and Tau protects dendritic spines from loss and reverses neurological impairment. Furthermore, we preliminarily investigated that the interaction between DAPK1 and Caytaxin in ischemic stroke may mediate poststroke presynaptic dysfunction. Row intervention is likely to provide new therapeutic targets and strategies for the treatment of ischemic stroke.
【學(xué)位授予單位】:華中科技大學(xué)
【學(xué)位級別】:博士
【學(xué)位授予年份】:2015
【分類號】:R743.3
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