SIRT1 Regulates Tau Expression and Tau Synaptic Pathology

Abstract

Background:

Amyloid plaques and neurofibrillary tangles are two pathological hallmarks of Alzheimer’s disease (AD). However, synaptic deficits occur much earlier and correlate stronger with cognitive decline than amyloid plaques and neurofibrillary tangles. Mislocalization of tau is an early hallmark of neurodegeneration and precedes aggregations. Sirtuin type 1 (SIRT1) is a deacetylase which acts on proteins including transcriptional factors and associates closely with AD.

Objective:

The present study investigated the association between SIRT1 and tau expression/tau localization in cells and in mice brains.

Methods:

Western blot was performed to detected tau, SIRT1, C/EBPα, and GAPDH protein levels. Immunological fluorescence assay was used to assess tau localization in primary cortical neuronal cells. Golgi staining was performed to evaluated dendritic spine morphology in mice brains.

Results:

In the present study, we found that SIRT1 negatively regulates expression of tau at the transcriptional level through transcriptional factor C/EBPα. Inhibition of the activity of SIRT1 limits the distribution of tau to the neurites. In the meantime, the alteration of dendritic spine morphology is also observed in the brains of SIRT1^+/– mice.

Conclusion:

SIRT1 may be a potential drug target for early intervention in AD.

Keywords

Alzheimer’s disease post-synapse SIRT1 tau

INTRODUCTION

Microtubule-associated protein tau is essential for microtubule assembly and stabilization [1, 2]. Neurofibrillary tangles comprised of aberrant hyperphosphorylated tau are one of the pathological hallmarks of Alzheimer’s disease (AD) [3].

Accumulating evidence reveals that expression levels of tau protein are associated with learning and memory. The total tau level in cerebrospinal fluid inversely correlates with memory scores in AD patients [4, 5]. Increasing plasma total tau levels result in mild cognitive impairment [6]. Elevated intracellular full-length wild-type human tau (hTau) exacerbates tau pathologies and leads to learning and memory deficits [7]. Reducing or eliminating tau has protective effects on human amyloid precursor protein (hAPP) transgenic mice expressing high levels of amyloid-β (Aβ) in the brain and prevents their learning and memory deficits [8]. Tau reduction also blocks deficits of synaptic plasticity in hAPP mice [9].

Most of tau locates in the axon, but a small amount of tau distributes in the soma and in the dendrites [10, 11]. In physiological and pathological conditions, tau exists both in the neuronal somatodendritic compartment and in pre- and post-synaptic sites [12], implying physiological functions of tau not only in the axon but also in the synapse [13 –15]. Synaptic tau takes charge of neuronal signaling and synaptic plasticity [13, 16]. Post-synaptic tau is important for long-term depression [14]. Tau plays a crucial physiological role in synapses which is declared by tau knockout mice [17]. Elevated tau in the dendrites may affected memory and synaptic plasticity. Tau overexpressed in cultured neurons and AD mice promotes its location in the somatodendritic compartment [18]. The physiological roles of tau in synapses need further detailed elucidation.

Reduction in the number of dendritic spines and alteration in their morphology occur at the earlier stage of AD before neurofibrillary tangle and amyloid plaque formation, and closely correlate with the extent of cognitive impairment in patients of AD [19 –22]. Dendritic spines are classified into three types based on their morphology: mushroom, thin, and stubby [23, 24]. Mushroom spines form strong synaptic connections and represent memory storage spines [25, 26], whereas thin spines act as learning spines for the formation of new memory [25]. Stubby spines are the remaining forms of eliminated mushroom spines [27]. Mushroom spine decline is related to memory loss in AD patients [28, 29]. The density of mushroom spines is decreased in various AD mice models [30 –32].

SIRT1 is one of the most evolutionally conserved members of Sirtuins (SIRT1–7), belonging to class III histone deacetylases (HDACs) [33, 34]. SIRT1 regulates diverse biological processes, such as cell differentiation [35], development [36], metabolism [37, 38], circadian rhythms [39], and so on in mammals. SIRT1 has protective effect on AD, Parkinson’s disease, and Huntington’s disease [40]. SIRT1 modulates synaptic plasticity and formation of synapse and memory [41]. Inerratic synaptic plasticity and memory appeared in mice expressing high levels of SIRT1 in brain [42]. On the contrary, SIRT1 deficiency causes cognitive deficits [42]. SIRT1 modulates these functions by deacetylating a variety of substrates, including a large number of transcription factors, such as the forkhead box class O (FoxO) family members [43], P53 [44], and nuclear factor κB (NF-κB) [45, 46]. It is reported that SIRT1 also deacetylates CREB at Lys136 to regulate its activity [47].

C/EBPα (CCAAT/enhancer-binding protein α) is a member of the basic leucine zipper transcription factor family, which has critical roles in cell growth and differentiation in various tissues [48 –50]. C/EBPα is one of the most well-studied isoforms in the six members of C/EBP family [49].

Whether and how SIRT1 regulates the expression and localization of tau remain elusive. In the present study, we found that SIRT1 inhibits the expression of tau at the transcriptional level through the transcriptional factor C/EBPα. Simultaneously, SIRT1 contributes to the redistribution of tau and changes the morphology of dendritic spine.

MATERIALS AND METHODS

Animals

SIRT1 heterozygous mice (SIRT1^+/–) were gifts from Professor Chuanming Hao, Department of nephropathy, Huashan Hospital Affiliated to Fudan University. This mouse strain was generated with deletion of one allele of SIRT1 (SIRT1^+/–) and further bred with C57BL/6J to generate heterozygous SIRT1 knockout mice and WT mice (SIRT1^+/+). Mice were housed in groups of 3 to 6 littermates in individually cages and had free access to water and food. Adult SIRT1^+/– mice and their littermates were enrolled in this study. The animal care and experimental protocols were approved by Animal Care and Use Committees of Nantong University.

Plasmids, lentivirus, and antibodies

pGL3-basic, pRL-Tk (thymidine kinase promoter driven Renilla luciferase), and dual luciferase assay kit were bought from Promega (Madison, WI, USA). A 1.0-kb fragment of the human tau genomic DNA from –695 – + 305 bp was amplified by PCR and cloned into pGL3-basic (Promega) by Kpn I and bgl II (New England Biolabs, Ipswich, MA, USA) to generate pGL3/tau1000 [51]. pcDNA3.1/SIRT1 was constructed by subcloning SIRT1 coding region which was PCR amplificated from Flag-SIRT1 plasmid purchased from Addgene (Cambridge, MA, USA) into mammalian expression vector pcDNA3.1 tagged with Myc at C-terminus by BamHI and NotI. Human siRNA of SIRT1 were from Santa Cruz Biotechnology (Santa Cruz, CA, USA). Mouse monoclonal anti-SIRT1 was from Cell Signaling Technology (Danves, MA, USA). Monoclonal antibody 43D, a gift from the New York State Institute for Basic Research in Developmental Disabilities, is phosphorylation-independent and specific to human tau. Polyclonal antibody 92e recognizes tau in mice or rats’ brains regardless of its phosphorylation state. Mouse monoclonal anti-actin antibody were from Sigma (St. Louis, MO, USA). Rabbit anti-GAPDH was purchased from Santa Cruz (Santa Cruz, CA, USA). Tetramethyl rhodamine isothiocyanate (TRITC)-conjugated goat anti-rabbit IgG, fluorescein isothiocyanate (FITC)-conjugated goat anti-mouse IgG. Peroxidase-conjugated anti-mouse and anti-rabbit IgG were obtained from Jackson. ImmunoResearch Laboratories (West Grove, PA, USA). The ECL kit was from ThermoFisher Scientific (Rockford, IL, USA).

Cell culture and transfection

HEK-293T cells were maintained in Dulbecco’s modified Eagle’s medium supplemented with 10% fetal bovine serum (Invitrogen, CA, USA) at 37°C (5% CO₂). Transfections were performed with Lipofectamine 2000 (Invitrogen, CA, USA), Lipofectamine 3000 (Invitrogen, CA, USA), or FuGene 6 (Promega, WI, USA), according to the manufacturer’s instructions. Primary cortical neuronal cells were obtained and cultured as described before [52]. Cortices were dissected from embryonic day 18 (E18) of Sprague Dawley (SD) rat brains. The rat embryos were dissected and dissociated in trypsin (0.05% with EDTA) and DNAse (10μg/mL) and then resuspended in neurobasal medium with 2% B27 and penicillin (20 U/ml) and streptomycin (5μg/ml) (Gibco, Rockville, MD, USA). Neurons were plated into 6 well culture plates and then infected by lentivirus of SIRT1 or its empty vectors.

Luciferase assay

HEK-293T cells were co-transfected with pcDNA3.1, pcDNA3.1/Myc-SIRT1, sh-C/EBPα, and pGL3/Tau1000, or their control vectors and pRL-Tk for 48 h. The cells were lysed using the passive lysis buffer (Promega). The luciferase activity was measured by the dual luciferase assay kit (Promega) according to manufacturer’s manuals. The firefly luciferase activity and Renilla luciferase activity were measured by the dual luciferase assay kit (Promega) according to manufacturer’s manuals. The firefly luciferase activity and Renilla luciferase activity were measured subsequently, and the firefly luciferase activity was normalized with Renilla luciferase activity.

Immunological fluorescence assay

Primary cortical neuronal cells from E18 fetal SD rat brain were plated in 24-well-plates onto glass bottom dishes (Thermo Fisher, MA, USA). The cells were treated with SIRT1 inhibitor Ex527 for 24 h before harvest and then subjected for immnunofluorescence study. The cells were washed with PBS and fixed with 4% paraformaldehyde in PB for 30 min at room temperature. After washing with PBS, the cells were blocked with 10% goat serum in 0.2% Triton X-100/PBS for 2 h at 37°C and incubated with rabbit anti-MAP2 and mouse anti-Tau overnight at 4°C. After washing with PBS and incubation with secondary antibodies (TRITC-conjugated goat anti-rabbit IgG and FITC-conjugated goat anti-mouse IgG, 1:200), the cells were washed extensively with PBS and incubated with 5μg/ml Hoechst 33342 for 5 min at room temperature. The cells were washed with PBS, mounted with Fluoromount-G, and visualized with a Leica TCS-SP5 dual photon laser-scanning confocal microscope.

Golgi staining

Golgi staining was performed by using a Rapid GolgiStain kit according to the manufacturer’s protocol (FD NeuroTechnologies, Columbia, MD). Briefly, the mouse brain was immersed in a mixture of solution A and solution B at room temperature for 2 weeks. After that, the tissue was immersed in solution C and stored at room temperature in the dark for at least 72 h. The brain samples were coronally sliced to 100μm and mounted on 1% gelatin-coated glass slides. Slides were then allowed to air dry at room temperature, followed with rinsing in distilled water, dehydrating in absolute alcohol, clearing with xylene, mounting on slides, and covering with coverslips

Statistical analysis

Where appropriate, the data are presented as mean±S.E.M. Data points were compared by the unpaired two-tailed Student’s t-test for two groups’ comparison, one-way ANOVA, and two-way ANOVA. The calculated p-values are indicated in the figures.

RESULTS

SIRT1 negatively regulates the expression of tau

To investigate whether SIRT1 regulates the expression of tau, we overexpressed or knocked down SIRT1 in HEK-293T cells co-expressing tau₄₄₁ and then measured the tau protein level with 43D antibody against recombinant tau₄₄₁. We found that reducing protein level of tau was induced by overexpression of SIRT1, whereas knockdown of SIRT1 by siRNA dramatically increased protein level of tau (Fig. 1A, B). These data indicate that SIRT1 suppresses the protein expression of human tau. To further confirm the effect of SIRT1 on tau expression, we study the regulation of endogenous tau expression by SIRT1 in primary cortical neurons. Various concentration of lentivirus of SIRT1 was infected into cortical primary neuron cells and tau expression was measured at protein level with western blots. We found that gradient overexpression of SIRT1 caused a gradual decrease of tau protein level (Fig. 1C, 1D). Furthermore, we observed that total tau protein level was increased obviously in the brain of SIRT1 heterozygous mice (SIRT1^+/–) (Fig. 1E, F). Thus, we conclude that SIRT1 inhibits the protein expression level of tau in cells and in mice brains.

Fig. 1

Tau expression is modulated by SIRT1. A) tau protein level inversely correlated with SIRT1 expression. HEK-293T cells were transfected with pcDNA3.1, pcDNA/Myc-SIRT1 together with pEGFP/tau40 (left panel), or HEK-293T cells were transfected with siRNA or its vehicle of SIRT1 together with pEGFP/tau40 (right panel). Protein levels of SIRT1, tau, and β-actin were examined by western blot using anti-Myc, anti-SIRT1, anti-tau, and anti-actin antibody. B) Relative tau level was quantified after normalization with the protein level of β-actin and presented as mean±S.E.M. (n = 3), ^**p < 0.01. C) SIRT1 overexpression suppressed tau expression in primary cortical neuron cells. Primary rat E18 cortical neurons were infected with various concentration of SIRT1 overexpression lentivirus. After 48 h infection, tau or SIRT1 was detected by western blot using anti-tau (92e) [74] or anti-SIRT1 antibody and normalized with GAPDH. D) The data were represented as mean±S.E.M (n = 3). E) SIRT1 knock-down promoted tau expression in the SIRT1^+/^– mice. Brain homogenates from the SIRT1^+/^– mice and its control littermate mice were tested by western blot using anti-tau antibody and anti-SIRT1 antibody. F) The data were presented as mean±S.E.M. (n = 3), ^*p < 0.05.

SIRT1 modulates tau expression at transcriptional level through C/EBPα

Min et al. reported that SIRT1 deficiency increases acetylation of tau to interfere with ubiquitination of tau, resulting in reducing degradation of p-tau [53]. We want to know whether SIRT1 suppresses total tau level at transcriptional level. We investigate the transcriptional regulation of tau by using reporter plasmid of pGL3/tau1000 in which the promoter region of human tau, –695 – + 305, was inserted into pGL3-basic vector as described before [51]. pRL-Tk and pGL3/tau1000 were transfected together into HEK-293T cells co-expressing SIRT1 or not and then luciferase activity was measured using the dual luciferase assay. We found that luciferase activity was significantly decreased when SIRT1 was overexpressed (Fig. 2A), indicating that SIRT1 works on human tau promoter to inhibit the expression of tau.

Fig. 2

C/EBPα mediates the regulation of SIRT1 on tau expression. A) SIRT1 inhibited the luciferase activity driven by tau promoter depending on transcription factor C/EBPα. pGL3/tau1000 or pGL3-basic vector together with pRL-Tk were transfected into HEK-293T cells co-transfected with pcDNA/Myc-SIRT1 and shC/EBPα or its empty vector. After 48 h of transfection, the luciferase activity was measured and normalized with Renilla luciferase. The relative activity of luciferase was presented as mean±S.E.M. (n = 4); ^*p < 0.05. B) SIRT1 reduced tau protein expression through C/EBPα in cells. pCI-neo, shRNA of C/EBPα was transfected into HEK-293T cells overexpressing SIRT1 or not. Protein levels were detected by western blot using anti-Myc, anti-tau, anti-C/EBPα, or anti-GAPDH antibody. C) Relative tau level was quantified after normalization with the protein level of GAPDH and presented as mean±S.E.M (n = 3), ^*p < 0.05 versus control group.

JASPAR software analysis showed that there are potential C/EBPα elements in tau promoter. We hypothesize that SIRT1 may restrain transcription of tau though C/EBPα. To test this hypothesis, C/EBPα was knocked down by shRNA merely or SIRT1 was overexpressed simultaneously in HEK-293T cells which were transfected together with pGL3/tau1000. The dual luciferase assay was employed to check luciferase activity. We found that C/EBPα knockdown prevented the inhibition effect of SIRT1 on the luciferase activity driven by tau promoter (Fig. 2A). To further convince that SIRT1 regulates tau expression via C/EBPα, we transfected shRNA of C/EBPα alone or together with pcDNA3.1/Myc-SIRT1 into HEK-293T cells overexpressing tau. After 48 h transfection, cell lysates were analyzed by western blot using anti-tau antibody. As expected, the inhibitory activity of SIRT1 on tau expression was abrogated when C/EBPα was knocked down (Fig. 2B, C). These results suggested that C/EBPα is one of the major mediators in the inhibition of tau expression by SIRT1.

SIRT1 stabilizes the localization of tau in dendritic compartment of neurons

Since SIRT1 negatively regulates the protein level of tau, we want to identify whether the location of tau is influenced by SIRT1. The primary cortical neurons were treated with Ex527, the SIRT1 specific inhibitor, and followed by immunostaining with anti-Tau and anti-MAP2. The localization of tau was examined by confocal microscopy. We observed that tau protein localized in soma and neurite of the neurons (Fig. 3A), whereas inhibition the activity of SIRT1 by Ex527 suppressed the outgrowth of neurite and the ratio of tau intensity in the neurites versus soma (Fig. 3A-C). These data strongly suggest that the dendritic localization of tau is associated with SIRT1.

Fig. 3

Suppression of SIRT1 activity results in a shorter neurite outgrowth. A) Immunofluorescence staining of MAP2 (green) and tau (red). Arrow heads indicate the neurite localization of tau. B) Quantitative analysis of the fluorescence intensity of tau staining in neurites and the average length of neurites. Scale bars: 50μm. The data were presented as mean±S.E.M (n = 8), ^*p < 0.05, ^**p < 0.01.

The density of mushroom spine is accelerated in the brain of SIRT1^+/– mice

SIRT1 inhibits the expression of tau protein and influences the localization of tau. To examine whether SIRT1 has effect on the morphology of dendritic spines, we performed Golgi staining to reveal the morphology of dendritic spines in brain slices of SIRT1^+/– mice and their littermates. We classified spines into three groups: mushroom spines are big spines with a large mushroom-like head, thin spines are spines with a small head and long neck, and stubby spines are very short spines with almost no neck (Fig. 4A). We found that the density of mushroom spines was significantly increased in the brain of SIRT1^+/– mice compared with its control littermates. But no obvious alteration was observed in the density of stubby and thin spines in the brain of these two groups (Fig. 4B). These data suggest that SIRT1 negatively regulates the density of mushroom spines.

Fig. 4

SIRT1 knockout increases the density of mushroom spine but not the thin and stubby spine in SIRT1^+/^– mice. A) Representative images of spines in the brain slice of SIRT1^+/^– mice. The blue arrow represents a mushroom spine, the yellow arrow represents a stubby spine, and the red arrow represents a thin spine. B) The bar histogram summarizes the effect of SIRT1 knockout on the thin, mushroom, and stubby spine density in brain slices of SIRT1^+/^– mice and their control littermates. The data were represented as mean±S.E.M (n = 30); ^**p < 0.01.

DISCUSSION

AD is characterized by extracellular deposition of amyloid plaques and intracellular tau neurofibrillary tangles. The two pathological hallmarks are considered initially to contribute to neurotoxicity in AD patients [54, 55]. It is the neurofibrillary tangles but not amyloid plaques that are positively correlated with the cognitive deficits [56]. Soluble tau rather than tau aggregates is responsible for neurotoxicity [57, 58].

Positron emission tomography (PET) imaging of tau shows a closer correlation of tau alteration with cognitive decline and transition to mild cognitive impairment [59]. Mild cognitive impairment frequently occurs long before the clinical diagnosis of AD [60]. Hyperphosphorylation and mislocalization of tau are early events of neurodegeneration and precede overt neurodegeneration [61 –63]. In the present study, we found that activity inhibition of SIRT1 represses the elongation of dendrites and expression of tau in neurites (Fig. 3).

Overexpression of human tau causes the mislocalization of tau to the somatodendritic compartment [64, 65]. Kubo et al. also reported that the localization of tau is closely associated with the expression of tau, and the abnormal expression of tau may result in the pathogenesis of tauopathy [66]. In the present study, we found that SIRT1 negatively regulates the expression level of tau both in cells and in vivo (Fig. 1) and meanwhile inhibition of SIRT1 activity modulates the location of tau in neuron (Fig. 3). Our data are consistent with previous observations.

We previously reported that tau expression was negatively regulated by CREB [51]. It has also been confirmed that SIRT1 interacts with CREB [52, 53]. But in the present study, we found that SIRT1 inhibited the expression of tau not via CREB (data not shown). For the first time, data suggest that SIRT1 modulates the tau expression via C/EBPα.

Investigations indicate that tau acetylation destroys the stability of the cytoskeleton in the axon initial segment, contributing to axonal retention of tau by forming a barrier between the axon and the somatodendritic compartment and is mislocalized to the somatodendritic compartment [67]. Phosphorylation has been shown to be necessary for tau mislocalization into dendritic spines and subsequently for synaptic impairment [68]. Tau is hyperphosphorylated and mislocalizes to somatodendritic compartments in patient brain of AD [13 , 70]. How the expression of tau damages the polarized distribution of tau, the key early step in neurodegenerative diseases such as AD, is still unknown.

Phosphorylated tau mislocalized to the somatodendritic compartment starts the reduction of dendritic spine density and alteration in morphology of dendrite spine both in mice model [71, 72] and in monkey model [73]. It is also reported that specific isoform of tau is retained in the somatodendritic compartment and accelerates spine and dendrite growth [18]. In our study, we show that SIRT1 implicates in tau expression and tau missorting and then the morphological change of dendrite spine (Fig. 4). But how dendritic spine morphology is affected by tau mislocalization in AD needs further investigation.

In summary, SIRT1 negatively regulates the expression of tau in cells and in vivo. SIRT1 may control the expression of tau at transcriptional level through the transcriptional factor C/EBPα, SIRT1 inhibits the expression of tau, simultaneously SIRT1 adjusts the localization of tau and the morphology of dendritic spines. This study provides a novel insight into the function of SIRT1 in tau modulating, which is crucial for the development of therapeutic strategies ameliorating synapse impairment and preventing AD pathogenesis.

Footnotes

ACKNOWLEDGMENTS

This work was supported in part by Nantong University and grants from National Natural Science Foundation of China (81872875, 81170317 and 81473218 to Wei Qian; 81503077 to Xiaomin Yin), the Priority Academic Program Development of Jiangsu Higher Education Institution (PAPD), and Jiangsu Province College Students’ innovation and entrepreneurship training program (202110304032Z).

Authors’ disclosures available online ().

References

Kirschner

, Suter

, Weingarten

, Littman

(1975) The role of rings in the assembly of microtubules in vitro. Ann N Y Acad Sci 253, 90–106.

Drechsel

, Hyman

, Cobb

, Kirschner

(1992) Modulation of the dynamic instability of tubulin assembly by the microtubule-associated protein tau. Mol Biol Cell 3, 1141–1154.

Kovacs

(2016) Molecular pathological classification of neurodegenerative diseases: Rurning towards precision medicine. Int J Mol Sci 17, 189.

, He

, Wang

, Duan

, Grundke-Iqbal

, Iqbal

, Wang

(2002) Levels of nonphosphorylated and phosphorylated tau in cerebrospinal fluid of Alzheimer’s disease patients: An ultrasensitive bienzyme-substrate-recycle enzyme-linked immunosorbent assay. Am J Pathol 160, 1269–1278.

Lin

, Cheng

, Yao

, Juo , Lo

, Lin

, Ger

, Lu

(2009) Increased total tau but not amyloid-beta(42) in cerebrospinal fluid correlates with short-term memory impairment in Alzheimer’s disease. J Alzheimers Dis 18, 907–918.

Mielke

, Hagen

, Wennberg

AMV

, Airey

, Savica

, Knopman

, Machulda

, Roberts

, Jack

Jr. , Petersen

, Dage

(2017) Association of plasma total tau level with cognitive decline and risk of mild cognitive impairment or dementia in the Mayo Clinic Study on Aging. JAMA Neurol 74, 1073–1080.

, Yin

, Zhang

, Wan

, Wang

, Zuo

, Gao

, Li

, Liu

, Ke

, Wang

(2020) Tau-induced upregulation of C/EBPbeta-TRPC1-SOCE signaling aggravates tauopathies: A vicious cycle in Alzheimer neurodegeneration. Aging Cell 19, e13209.

Roberson

, Scearce-Levie

, Palop

, Yan

, Cheng

, Wu

, Gerstein

, Yu

, Mucke

(2007) Reducing endogenous tau ameliorates amyloid beta-induced deficits in an Alzheimer’s disease mouse model. Science 316, 750–754.

Roberson

, Halabisky

, Yoo

, Yao

, Chin

, Yan

, Wu

, Hamto

, Devidze

, Yu

, Palop

, Noebels

, Mucke

(2011) Amyloid-beta/Fyn-induced synaptic, network, and cognitive impairments depend on tau levels in multiple mouse models of Alzheimer’s disease. J Neurosci 31, 700–711.

10.

Black

, Slaughter

, Moshiach

, Obrocka

, Fischer

(1996) Tau is enriched on dynamic microtubules in the distal region of growing axons. J Neurosci 16, 3601–3619.

11.

Mandell

and Banker

(1996) A spatial gradient of tau protein phosphorylation in nascent axons. J Neurosci 16, 5727–5740.

12.

Tai

, Wang

, Serrano-Pozo

, Frosch

, Spires-Jones

, Hyman

(2014) Frequent and symmetric deposition of misfolded tau oligomers within presynaptic and postsynaptic terminals in Alzheimer’s disease. Acta Neuropathol Commun 2, 146.

13.

Ittner

, Ke

, Delerue

, Bi

, Gladbach

, van Eersel

, Wolfing

, Chieng

, Christie

, Napier

, Eckert

, Staufenbiel

, Hardeman

, Gotz

(2010) Dendritic function of tau mediates amyloid-beta toxicity in Alzheimer’s disease mouse models. Cell 142, 387–397.

14.

Kimura

, Whitcomb

, Jo

, Regan

, Piers

, Heo

, Brown

, Hashikawa

, Murayama

, Seok

, Sotiropoulos

, Kim

, Collingridge

, Takashima

, Cho

(2014) Microtubule-associated protein tau is essential for long-term depression in the hippocampus. Philos Trans R Soc Lond B Biol Sci 369, 20130144.

15.

Regan

, Piers

, Yi

, Kim

, Huh

, Park

, Ryu

, Whitcomb

, Cho

(2015) Tau phosphorylation at serine 396 residue is required for hippocampal LTD. J Neurosci 35, 4804–4812.

16.

Chen

, Zhou

, Zhang

, Wang

, Zhang

, Zhong

, Xu

, Chen

, Li

, Yu

(2012) Tau protein is involved in morphological plasticity in hippocampal neurons in response to BDNF. Neurochem Int 60, 233–242.

17.

, Brown

, Whitehead

, Piers

, Lee

, Perez

, Regan

, Whitcomb

, Cho

(2017) Glucocorticoids activate a synapse weakening pathway culminating in tau phosphorylation in the hippocampus. Pharmacol Res 121, 42–51.

18.

Zempel

, Dennissen

FJA

, Kumar

, Luedtke

, Biernat

, Mandelkow

(2017) Axodendritic sorting and pathological missorting of Tau are isoform-specific and determined by axon initial segment architecture. J Biol Chem 292, 12192–12207.

19.

DeKosky

and Scheff

(1990) Synapse loss in frontal cortex biopsies in Alzheimer’s disease: Correlation with cognitive severity. Ann Neurol 27, 457–464.

20.

Terry

, Masliah

, Salmon

, Butters

, DeTeresa

, Hill

, Hansen

, Katzman

(1991) Physical basis of cognitive alterations in Alzheimer’s disease: Synapse loss is the major correlate of cognitive impairment. Ann Neurol 30, 572–580.

21.

Koffie

, Hyman

, Spires-Jones

(2011) Alzheimer’s disease: Synapses gone cold. Mol Neurodegener 6, 63.

22.

Selkoe

(2002) Alzheimer’s disease is a synaptic failure. Science 298, 789–791.

23.

Bourne

and Harris

(2008) Balancing structure and function at hippocampal dendritic spines. Annu Rev Neurosci 31, 47–67.

24.

Kasai

, Matsuzaki

, Noguchi

, Yasumatsu

, Nakahara

(2003) Structure-stability-function relationships of dendritic spines. Trends Neurosci 26, 360–368.

25.

Bourne

and Harris

(2007) Do thin spines learn to be mushroom spines that remember? Curr Opin Neurobiol 17, 381–386.

26.

Hayashi

and Majewska

(2005) Dendritic spine geometry: Functional implication and regulation. Neuron 46, 529–532.

27.

Hering

and Sheng

(2001) Dendritic spines: Structure, dynamics and regulation. Nat Rev Neurosci 2, 880–888.

28.

Tackenberg

, Ghori

, Brandt

(2009) Thin, stubby or mushroom: Spine pathology in Alzheimer’s disease. Curr Alzheimer Res 6, 261–268.

29.

Popugaeva

, Bezprozvanny

(2013) Role of endoplasmic reticulum Ca2+signaling in the pathogenesis of Alzheimer disease. Front Mol Neurosci 6, 29.

30.

Sun

, Zhang

, Liu

, Popugaeva

, Xu

, Feske

, White

3rd , Bezprozvanny

(2014) Reduced synaptic STIM2 expression and impaired store-operated calcium entry cause destabilization of mature spines in mutant presenilin mice. Neuron 82, 79–93.

31.

Zhang

, Wu

, Pchitskaya

, Zakharova

, Saito

, Saido

, Bezprozvanny

(2015) Neuronal store-operated calcium entry and mushroom spine loss in amyloid precursor protein knock-in mouse model of Alzheimer’s disease. J Neurosci 35, 13275–13286.

32.

Saito

, Matsuba

, Mihira

, Takano

, Nilsson

, Itohara

, Iwata

, Saido

(2014) Single App knock-in mouse models of Alzheimer’s disease. Nat Neurosci 17, 661–663.

33.

Anderson

, Green

, Huynh

, Wagner

, Hirschey

(2014) SnapShot: Mammalian sirtuins. Cell 159, 956–956e951.

34.

Michishita

, Park

, Burneskis

, Barrett

, Horikawa

(2005) Evolutionarily conserved and nonconserved cellular localizations and functions of human SIRT proteins. Mol Biol Cell 16, 4623–4635.

35.

Fulco

, Cen

, Zhao

, Hoffman

, McBurney

, Sauve

, Sartorelli

(2008) Glucose restriction inhibits skeletal myoblast differentiation by activating SIRT1 through AMPK-mediated regulation of Nampt. Dev Cell 14, 661–673.

36.

Cheng

, Mostoslavsky

, Saito

, Manis

, Gu

, Patel

, Bronson

, Appella

, Alt

, Chua

(2003) Developmental defects and p53 hyperacetylation in Sir2 homolog (SIRT1)-deficient mice. Proc Natl Acad Sci U S A 100, 10794–10799.

37.

Picard

, Kurtev

, Chung

, Topark-Ngarm

, Senawong

, Machado De Oliveira

, Leid

, McBurney

, Guarente

(2004) Sirt1 promotes fat mobilization in white adipocytes by repressing PPAR-gamma. Nature 429, 771–776.

38.

, Zhang

, Blander

, Tse

, Krieger

, Guarente

(2007) SIRT1 deacetylates and positively regulates the nuclear receptor LXR. Mol Cell 28, 91–106.

39.

Asher

, Gatfield

, Stratmann

, Reinke

, Dibner

, Kreppel

, Mostoslavsky

, Alt

, Schibler

(2008) SIRT1 regulates circadian clock gene expression through PER2 deacetylation. Cell 134, 317–328.

40.

Zhang

, Wang

, Gan

, Vosler

, Gao

, Zigmond

, Chen

(2011) Protective effects and mechanisms of sirtuins in the nervous system. Prog Neurobiol 95, 373–395.

41.

Gao

, Wang

, Mao

, Graff

, Guan

, Pan

, Mak

, Kim

, Su

, Tsai

(2010) A novel pathway regulates memory and plasticity via SIRT1 and miR-134. Nature 466, 1105–1109.

42.

Michan

, Li

, Chou

, Parrella

, Ge

, Long

, Allard

, Lewis

, Miller

, Xu

, Mervis

, Chen

, Guerin

, Smith

, McBurney

, Sinclair

, Baudry

, de Cabo

, Longo

(2010) SIRT1 is essential for normal cognitive function and synaptic plasticity. J Neurosci 30, 9695–9707.

43.

Brunet

, Sweeney

, Sturgill

, Chua

, Greer

, Lin

, Tran

, Ross

, Mostoslavsky

, Cohen

, Hu

, Cheng

, Jedrychowski

, Gygi

, Sinclair

, Alt

, Greenberg

(2004) Stress-dependent regulation of FOXO transcription factors by the SIRT1 deacetylase. Science 303, 2011–2015.

44.

Huang

and Tindall

(2007) Dynamic FoxO transcription factors. J Cell Sci 120, 2479–2487.

45.

Chen

, Zhou

, Mueller-Steiner

, Chen

, Kwon

, Yi

, Mucke

, Gan

(2005) SIRT1 protects against microglia-dependent amyloid-beta toxicity through inhibiting NF-kappaB signaling. J Biol Chem 280, 40364–40374.

46.

Yeung

, Hoberg

, Ramsey

, Keller

, Jones

, Frye

, Mayo

(2004) Modulation of NF-kappaB-dependent transcription and cell survival by the SIRT1 deacetylase. EMBO J 23, 2369–2380.

47.

Qiang

, Lin

, Kim-Muller

, Welch

, Gu

, Accili

(2011) Proatherogenic abnormalities of lipid metabolism in SirT1 transgenic mice are mediated through Creb deacetylation. Cell Metab 14, 758–767.

48.

Johnson

(2005) Molecular stop signs: Regulation of cell-cycle arrest by C/EBP transcription factors. J Cell Sci 118, 2545–2555.

49.

Nerlov

(2007) The C/EBP family of transcription factors: A paradigm for interaction between gene expression and proliferation control. Trends Cell Biol 17, 318–324.

50.

McKnight

(2001) McBindall–a better name for CCAAT/enhancer binding proteins? Cell 107, 259–261.

51.

Liu

, Jin

, Yin

, Jin

, Liu

, Qian

(2015) PKA-CREB signaling suppresses tau transcription. J Alzheimers Dis 46, 239–248.

52.

, Yin

, Wang

, Gu

, Huang

, Jin

, Chu

, Xu

, Liu

, Qian

(2020) SIRT1 regulates O-GlcNAcylation of tau through OGT. Aging (Albany NY) 12, 7042–7055.

53.

Min

, Cho

, Zhou

, Schroeder

, Haroutunian

, Seeley

, Huang

, Shen

, Masliah

, Mukherjee

, Meyers

, Cole

, Ott

, Gan

(2010) Acetylation of tau inhibits its degradation and contributes to tauopathy. Neuron 67, 953–966.

54.

Blennow

, de Leon

, Zetterberg

(2006) Alzheimer’s disease. Lancet 368, 387–403.

55.

Alzheimer

, Stelzmann

, Schnitzlein

, Murtagh

(1995) An English translation of Alzheimer’s 1907 paper, “Uber eine eigenartige Erkankung der Hirnrinde”. Clin Anat 8, 429–431.

56.

Arriagada

, Growdon

, Hedley-Whyte

, Hyman

(1992) Neurofibrillary tangles but not senile plaques parallel duration and severity of Alzheimer’s disease. Neurology 42, 631–639.

57.

Santacruz

, Lewis

, Spires

, Paulson

, Kotilinek

, Ingelsson

, Guimaraes

, DeTure

, Ramsden

, McGowan

, Forster

, Yue

, Orne

, Janus

, Mariash

, Kuskowski

, Hyman

, Hutton

, Ashe

(2005) Tau suppression in a neurodegenerative mouse model improves memory function. Science 309, 476–481.

58.

Oddo

, Vasilevko

, Caccamo

, Kitazawa

, Cribbs

, LaFerla

(2006) Reduction of soluble Abeta and tau, but not soluble Abeta alone, ameliorates cognitive decline in transgenic mice with plaques and tangles. J Biol Chem 281, 39413–39423.

59.

Hanseeuw

, Betensky

, Jacobs

HIL

, Schultz

, Sepulcre

, Becker

, Cosio

DMO

, Farrell

, Quiroz

, Mormino

, Buckley

, Papp

, Amariglio

, Dewachter

, Ivanoiu

, Huijbers

, Hedden

, Marshall

, Chhatwal

, Rentz

, Sperling

, Johnson

(2019) Association of amyloid and tau with cognition in preclinical Alzheimer disease: A longitudinal study. JAMA Neurol 76, 915–924.

60.

Liao

, Miller

, Teravskis

(2014) Tau acts as a mediator for Alzheimer’s disease-related synaptic deficits. Eur J Neurosci 39, 1202–1213.

61.

Braak

and Braak

(1994) Morphological criteria for the recognition of Alzheimer’s disease and the distribution pattern of cortical changes related to this disorder. Neurobiol Aging 15, 355–356; discussion 379-380.

62.

Giannakopoulos

, Herrmann

, Bussiere

, Bouras

, Kovari

, Perl

, Morrison

, Gold

, Hof

(2003) Tangle and neuron numbers, but not amyloid load, predict cognitive status in Alzheimer’s disease. Neurology 60, 1495–1500.

63.

Gomez-Isla

, Hollister

, West

, Mui

, Growdon

, Petersen

, Parisi

, Hyman

(1997) Neuronal loss correlates with but exceeds neurofibrillary tangles in Alzheimer’s disease. Ann Neurol 41, 17–24.

64.

Gotz

, Probst

, Spillantini

, Schafer

, Jakes

, Burki

, Goedert

(1995) Somatodendritic localization and hyperphosphorylation of tau protein in transgenic mice expressing the longest human brain tau isoform. EMBO J 14, 1304–1313.

65.

Spittaels

, Van den Haute

, Van Dorpe

, Bruynseels

, Vandezande

, Laenen

, Geerts

, Mercken

, Sciot

, Van Lommel

, Loos

, Van Leuven

(1999) Prominent axonopathy in the brain and spinal cord of transgenic mice overexpressing four-repeat human tau protein. Am J Pathol 155, 2153–2165.

66.

Kubo

, Ueda

, Yamane

, Wada-Kakuda

, Narita

, Matsuyama

, Nomori

, Takashima

, Kato

, Onodera

, Goto

, Ito

, Tomiyama

, Mori

, Murayama

, Ihara

, Misonou

, Miyasaka

(2019) Ectopic expression induces abnormal somatodendritic distribution of tau in the mouse brain. J Neurosci 39, 6781–6797.

67.

Sohn

, Tracy

, Son

, Zhou

, Leite

, Miller

, Seeley

, Grinberg

, Gan

(2016) Acetylated tau destabilizes the cytoskeleton in the axon initial segment and is mislocalized to the somatodendritic compartment. Mol Neurodegener 11, 47.

68.

Hoover

, Reed

, Su

, Penrod

, Kotilinek

, Grant

, Pitstick

, Carlson

, Lanier

, Yuan

, Ashe

, Liao

(2010) Tau mislocalization to dendritic spines mediates synaptic dysfunction independently of neurodegeneration. Neuron 68, 1067–1081.

69.

Avila

, Lucas

, Perez

, Hernandez

(2004) Role of tau protein in both physiological and pathological conditions. Physiol Rev 84, 361–384.

70.

Zempel

, Thies

, Mandelkow

(2010) Abeta oligomers cause localized Ca(2+) elevation, missorting of endogenous tau into dendrites, tau phosphorylation, and destruction of microtubules and spines. J Neurosci 30, 11938–11950.

71.

Messing

, Decker

, Joseph

, Mandelkow

(2013) Cascade of tau toxicity in inducible hippocampal brain slices and prevention by aggregation inhibitors. Neurobiol Aging 34, 1343–1354.

72.

Muller-Thomsen

, Borgmann

, Morcinek

, Schroder

, Dengler

, Moser

, Neumaier

, Schneider

, Schroder

, Huggenberger

(2020) Consequences of hyperphosphorylated tau on the morphology and excitability of hippocampal neurons in aged tau transgenic mice. Neurobiol Aging 93, 109–123.

73.

Crimins

, Puri

, Calakos

, Yuk

, Janssen

WGM

, Hara

, Rapp

, Morrison

(2019) Synaptic distributions of pS214-tau in rhesus monkey prefrontal cortex are associated with spine density, but not with cognitive decline. J Comp Neurol 527, 856–873.

74.

Pei

, Gong

, Iqbal

, Grundke-Iqbal

, Wu

, Winblad

, Cowburn

(1998) Subcellular distribution of protein phosphatases and abnormally phosphorylated tau in the temporal cortex from Alzheimer’s disease and control brains. J Neural Transm (Vienna) 105, 69–83.

SIRT1 Regulates Tau Expression and Tau Synaptic Pathology

Abstract

Background:

Objective:

Methods:

Results:

Conclusion:

Keywords

INTRODUCTION

MATERIALS AND METHODS

Animals

Plasmids, lentivirus, and antibodies

Cell culture and transfection

Luciferase assay

Immunological fluorescence assay

Golgi staining

Statistical analysis

RESULTS

SIRT1 negatively regulates the expression of tau

SIRT1 modulates tau expression at transcriptional level through C/EBPα

SIRT1 stabilizes the localization of tau in dendritic compartment of neurons

The density of mushroom spine is accelerated in the brain of SIRT1+/– mice

DISCUSSION

Footnotes

ACKNOWLEDGMENTS

References

The density of mushroom spine is accelerated in the brain of SIRT1^+/– mice