FE65 in Alzheimer's disease: neuronal distribution and association with neurofibrillary tangles

Ying Yang 1 engagement in brain pathology

Herein, we discuss data concerning the involvement of transcription factor Yin Yang 1 (YY1) in the development of brain diseases, highlighting mechanisms of its pathological actions. YY1 plays an important role in the developmental and adult pathology of the nervous system. YY1 is essential for neurulation as well as maintenance and differentiation of neuronal progenitor cells and oligodendrocytes regulating both neural and glial tissues of the brain. Lack of a YY1 gene causes many developmental abnormalities and anatomical malformations of the central nervous system (CNS). Once dysregulated, YY1 exerts multiple neuropathological actions being involved in the induction of many brain disorders like stroke, epilepsy, Alzheimer's and Parkinson's diseases, autism spectrum disorder, dystonia, and brain tumors. Better understanding of YY1's dysfunction in the nervous system may lead to the development of novel therapeutic strategies related to YY1's actions.

Agent Clustering Strategy Based on Metabolic Flux Distribution and Transcriptome Expression for Novel Drug Development

The network module-based method has been used for drug repositioning. The traditional drug repositioning method only uses the gene characteristics of the drug but ignores the drug-triggered metabolic changes. The metabolic network systematically characterizes the connection between genes, proteins, and metabolic reactions. The differential metabolic flux distribution, as drug metabolism characteristics, was employed to cluster the agents with similar MoAs (mechanism of action). In this study, agents with the same pharmacology were clustered into one group, and a total of 1309 agents from the CMap database were clustered into 98 groups based on differential metabolic flux distribution. Transcription factor (TF) enrichment analysis revealed the agents in the same group (such as group 7 and group 26) were confirmed to have similar MoAs. Through this agent clustering strategy, the candidate drugs which can inhibit (Japanese encephalitis virus) JEV infection were identified. This study provides new insights into drug repositioning and their MoAs.

Roles of the MYST Family in the Pathogenesis of Alzheimer's Disease via Histone or Non-histone Acetylation

Alzheimer's disease (AD) is one of the most common neurodegenerative diseases and a major cause of death among elderly individuals. The etiology of AD involves a combination of genetic, environmental, and lifestyle factors. A number of epigenetic alterations in AD have recently been reported; for example, studies have found an increase in histone acetylation in patients with AD and the protective function of histone deacetylase inhibitors. The histone acetylases in the MYST family are involved in a number of key nuclear processes, such as gene-specific transcriptional regulation, DNA replication, and DNA damage response. Therefore, it is not surprising that they contribute to epigenetic regulation as an intermediary between genetic and environmental factors. MYST proteins also exert acetylation activity on non-histone proteins that are closely associated with the pathogenesis of AD. In this review, we summarized the current understanding of the roles of MYST acetyltransferases in physiological functions and pathological processes related to AD. Additionally, using published RNA-seq, ChIP-seq, and ChIP-chip data, we identified enriched pathways to further evaluate the correlation between MYST and AD. The recent research described in this review supports the importance of epigenetic modifications and the MYST family in AD, providing a basis for future functional studies.

Effects of the Pentapeptide P33 on Memory and Synaptic Plasticity in APP/PS1 Transgenic Mice: A Novel Mechanism Presenting the Protein Fe65 as a Target

Regulated intramembrane proteolysis (RIP) of the amyloid precursor protein (APP) leads to the formation of fragments, among which the intracellular domain of APP (AICD) was also identified to be a causative of early pathological events. AICD-counteracting proteins, such as Fe65, may serve as alternative therapeutic targets of Alzheimer’s disease (AD). The detection of elevated levels of Fe65 in the brains of both human patients and APP transgenic mice may further strengthen the hypothesis that influencing the interaction between Fe65 and APP may have a beneficial effect on the course of AD. Based on a PXP motif, proven to bind to the WW domain of Fe65, a new pentapeptide was designed and tested. The impedimental effect of P33 on the production of beta amyloid (Aβ) (soluble fraction and aggregated plaques) and on the typical features of the AD pathology (decreased dendritic spine density, synaptic markers, elevated inflammatory reactions) was also demonstrated. Significant enhancements of both learning ability and memory function were observed in a Morris water maze paradigm. The results led us to formulate the theory that P33 acts by altering the conformation of Fe65 via binding to its WW domain, consequently hindering any interactions between Fe65 and key members involved in APP processing.

Age-associated evolution of plasmatic amyloid in mouse lemur primates: relationship with intracellular amyloid deposition

Alzheimer's disease (AD) is the most common age-related neurodegenerative disorder. Amyloid-β peptide (Aβ) deposition in the brain is one of its hallmarks, and the measure of plasma Aβ is considered to be a biomarker for anti-amyloid drug efficacy in animal models of AD. However, age-associated plasmatic Aβ modulation in animal models is practically never addressed in the literature. Mouse lemur primates are used as a model of normal and AD-like cerebral aging. Here, we studied the effect of age on plasmatic Aβ in 58 mouse lemurs aged from 1 to 10 years. A subset of animals presented high plasmatic Aβ, and the proportion of animals with high plasmatic Aβ was higher in aged animals as compared with young ones. Histologic evaluation of the brain of some of these animals was carried out to assess extracellular and intracellular amyloid load. In aged lemurs, plasmatic Aβ was negatively correlated with the density of neurons accumulating deposits of Aβ.

Total body 100-mGy X-irradiation does not induce Alzheimer's disease-like pathogenesis or memory impairment in mice

The cause and progression of Alzheimer's disease (AD) are poorly understood. Possible cognitive and behavioral consequences induced by low-dose radiation are important because humans are exposed to ionizing radiation from various sources. Early transcriptional response in murine brain to low-dose X-rays (100 mGy) has been reported, suggesting alterations of molecular networks and pathways associated with cognitive functions, advanced aging and AD. To investigate acute and late transcriptional, pathological and cognitive consequences of low-dose radiation, we applied an acute dose of 100-mGy total body irradiation (TBI) with X-rays to C57BL/6J Jms mice. We collected hippocampi and analyzed expression of 84 AD-related genes. Mouse learning ability and memory were assessed with the Morris water maze test. We performed in vivo PET scans with (11)C-PIB, a radiolabeled ligand for amyloid imaging, to detect fibrillary amyloid beta peptide (Aβ) accumulation, and examined characteristic AD pathologies with immunohistochemical staining of amyloid precursor protein (APP), Aβ, tau and phosphorylated tau (p-tau). mRNA studies showed significant downregulation of only two of 84 AD-related genes, Apbb1 and Lrp1, at 4 h after irradiation, and of only one gene, Il1α, at 1 year after irradiation. Spatial learning ability and memory were not significantly affected at 1 or 2 years after irradiation. No induction of amyloid fibrillogenesis or changes in APP, Aβ, tau, or p-tau expression was detected at 4 months or 2 years after irradiation. TBI induced early or late transcriptional alteration in only a few AD-related genes but did not significantly affect spatial learning, memory or AD-like pathological change in mice.

Association of AICD and Fe65 with Hirano bodies reduces transcriptional activation and initiation of apoptosis

Hirano bodies are cytoplasmic inclusions predominantly found in the central nervous system associated with various conditions including aging and Alzheimer's disease (AD). Since most studies of Hirano bodies have been performed in post-mortem samples, the physiological roles of Hirano bodies have not been investigated. Astrocytoma H4 cells were employed to test the hypothesis that Hirano bodies interact with and modulate signaling by the C-terminal fragment of amyloid-β precursor protein (AICD). We demonstrated by immunofluorescence and immunoprecipitation that model Hirano bodies accumulate AICD. Since stimulation of transcription by AICD is dependent on its interaction with the nuclear adaptor protein Fe65, we examined localization of Fe65, and employed a dual luciferase reporter assay to test the effects of Hirano bodies on AICD- and Fe65-dependent modulation of gene expression. We find that both AICD and Fe65 are co-localized in model Hirano bodies. Model Hirano bodies also down-regulate both AICD-dependent apoptosis and AICD- and Fe65-dependent transcriptional activity. Thus, association of AICD and Fe65 with Hirano bodies impedes their function in promoting apoptosis and modulating transcription.

Transcriptional regulation of human FE65, a ligand of Alzheimer's disease amyloid precursor protein, by Sp1

FE65 is a neuronal-enriched adaptor protein that binds to the Alzheimer's disease amyloid precursor protein (APP). FE65 forms a transcriptionally active complex with the APP intracellular domain (AICD). The precise gene targets for this complex are unclear but several Alzheimer's disease-linked genes have been proposed. Additionally, evidence suggests that FE65 influences APP metabolism. The mechanism by which FE65 expression is regulated is as yet unknown. To gain insight into the regulatory mechanism, we cloned a 1.6 kb fragment upstream of the human FE65 gene and found that it possesses particularly strong promoter activity in neurones. To delineate essential regions in the human FE65 promoter, a series of deletion mutants were generated. The minimal FE65 promoter was located between -100 and +5, which contains a functional Sp1 site. Overexpression of the transcription factor Sp1 potentiates the FE65 promoter activity. Conversely, suppression of the FE65 promoter was observed in cells either treated with an Sp1 inhibitor or in which Sp1 was knocked down. Furthermore, reduced levels of Sp1 resulted in downregulation of endogenous FE65 mRNA and protein. These findings reveal that Sp1 plays a crucial role in transcriptional control of the human FE65 gene.

Classification and basic pathology of Alzheimer disease

The lesions of Alzheimer disease include accumulation of proteins, losses of neurons and synapses, and alterations related to reactive processes. Extracellular Abeta accumulation occurs in the parenchyma as diffuse, focal or stellate deposits. It may involve the vessel walls of arteries, veins and capillaries. The cases in which the capillary vessel walls are affected have a higher probability of having one or two apoepsilon 4 alleles. Parenchymal as well as vascular Abeta deposition follows a stepwise progression. Tau accumulation, probably the best histopathological correlate of the clinical symptoms, takes three aspects: in the cell body of the neuron as neurofibrillary tangle, in the dendrites as neuropil threads, and in the axons forming the senile plaque neuritic corona. The progression of tau pathology is stepwise and stereotyped from the entorhinal cortex, through the hippocampus, to the isocortex. The neuronal loss is heterogeneous and area-specific. Its mechanism is still discussed. The timing of the synaptic loss, probably linked to Abeta peptide itself, maybe as oligomers, is also controversial. Various clinico-pathological types of Alzheimer disease have been described, according to the type of the lesions (plaque only and tangle predominant), the type of onset (focal onset), the cause (genetic or sporadic) and the associated lesions (Lewy bodies, vascular lesions, hippocampal sclerosis, TDP-43 inclusions and argyrophilic grain disease).

The Yin and Yang of YY1 in the nervous system

The transcription factor Yin Yang 1 (YY1) is a multifunctional protein that can activate or repress gene expression depending on the cellular context. YY1 is ubiquitously expressed and highly conserved between species. However, its role varies in diverse cell types and includes proliferation, differentiation, and apoptosis. This review will focus on the function of YY1 in the nervous system including its role in neural development, neuronal function, developmental myelination, and neurological disease. The multiple functions of YY1 in distinct cell types are reviewed and the possible mechanisms underlying the cell specificity for these functions are discussed.

Alzheimer's disease-related changes in diseases characterized by elevation of intracranial or intraocular pressure

In this review, we focus on the coexistence of Alzheimer's disease-related changes in brain diseases, such as normal pressure hydrocephalus and traumatic brain injury, and in glaucoma at the level of the retinal ganglion cells. This is a group of diseases that affect central nervous system tissue and are characterized by elevation of intracranial or intraocular pressure and/or local shear stress and strain. In considering possible mechanisms underlying Alzheimer-type changes in these diseases, we briefly summarize recent evidence indicating that caspase activation and abnormal processing of beta-amyloid precursor protein, which are important events in Alzheimer's disease, may play a role both in glaucoma and following traumatic brain injury. With regard to normal pressure hydrocephalus, evidence suggests that changes in cerebrospinal fluid circulatory dynamics ultimately may result in reduced clearance of neurotoxins, such as beta-amyloid peptides and tau protein, that play a role in the pathogenesis of Alzheimer's disease. Data presented in this review could be interpreted to suggest that Alzheimer-type changes in these diseases may result at least in part from exposure of central nervous system tissue to increased levels of mechanical stress. Evidence for such a relationship is of major importance because it may support an association between elevated mechanical load and the development of Alzheimer-type lesions. Further studies are warranted, however, especially to elucidate the role of elevated mechanical forces in Alzheimer's disease neuropathogenesis.

Novel modulators of amyloid-beta precursor protein processing

Proteolytic processing of the amyloid precursor protein (APP) is modulated by the action of enzymes alpha-, beta- and gamma-secretases, with the latter two mediating the amyloidogenic production of amyloid-beta (Abeta). Cellular modulators of APP processing are well known from studies of genetic mutations (such as those found in APP and presenilins) or polymorphisms (such as the apolipoprotein E4 epsilon-allele) that predisposes an individual to early or late-onset Alzheimer's disease. In recent years, several classes of molecule with modulating functions in APP processing and Abeta secretion have emerged. These include the neuronal Munc-18 interacting proteins (Mints)/X11s, members of the reticulon family (RTN-3 and RTN-4/Nogo-B), the Nogo-66 receptor (NgR), the peptidyl-prolyl isomerase Pin1 and the Rho family GTPases and their effectors. Mints and NgR bind to APP directly, while RTN3 and Nogo-B interact with the beta-secretase BACE1. Phosphorylated APP is a Pin1 substrate, which binds to its phosphor-Thr668-Pro motif. These interactions by and large resulted in a reduction of Abeta generation both in vitro and in vivo. Inhibition of Rho and Rho-kinase (ROCK) activity may underlie the ability of non-steroidal anti-inflammatory drugs and statins to reduce Abeta production, a feat which could also be achieved by Rac1 inhibition. Detailed understanding of the underlying mechanisms of action of these novel modulators of APP processing, as well as insights into the molecular neurological basis of how Abeta impairs leaning and memory, will open up multiple avenues for the therapeutic intervention of Alzheimer's disease.

The cytosolic domain of APP induces the relocalization of dynamin 3 in hippocampal neurons

Amyloid precursor protein (APP) has been the subject of intense research to uncover its implication in Alzheimer's disease. Its physiological function is, however, still poorly understood. Herein, we investigated its possible influence on the development of cultured hippocampal neurons. A peptide corresponding to the APP intracellular domain linked to a cell-penetrating peptide was used to alter the interactions of APP with its cytosolic partners. This treatment promoted the concentration of the cytosolic GTPase dynamin 3 (Dyn3) in neurite segments when most untreated cells displayed a homogenous punctate distribution of Dyn3. The Dyn3-labelled segments were excluded from those revealed by APP staining after aldehyde fixation. Interestingly, after aldehyde fixation MAP2 also labelled segments excluded from APP-stained segments. Thus APP is also a marker for the spacing pattern of neurites demonstrated by Taylor & Fallon (2006)J. Neurosci., 26, 1154-4463.

Expression of human FE65 in amyloid precursor protein transgenic mice is associated with a reduction in beta-amyloid load

FE65 is an adaptor protein that interacts with the cytoplasmic tail of the amyloid precursor protein (APP). In cultured non-neuronal cells, the formation of the FE65-APP complex is a key element for the modulation of APP processing, signalling and beta-amyloid (Abeta) production. The functions of FE65 in vivo, including its role in the metabolism of neuronal APP, remain to be investigated. In this study, transgenic mice expressing human FE65 were generated and crossbred with APP transgenic mice, known to develop Abeta deposits at 6 months of age. Compared with APP mice, APP/FE65 double transgenic mice exhibited a lower Abeta accumulation in the cerebral cortex as demonstrated by immunohistochemistry and immunoassay, and a lower level of APP-CTFs. The reduced accumulation of Abeta in APP/FE65 double transgenics, compared with APP mice, could be linked to the low Abeta42 level observed at 4 months of age and to the lower APP-CTFs levels. The present work provides evidence that FE65 plays a role in the regulation of APP processing in an in vivo model.

Activation of Akt/PKB, increased phosphorylation of Akt substrates and loss and altered distribution of Akt and PTEN are features of Alzheimer's disease pathology

Studies suggest that activation of phosphoinositide 3-kinase-Akt may protect against neuronal cell death in Alzheimer's disease (AD). Here, however, we provide evidence of increased Akt activation, and hyperphosphorylation of critical Akt substrates in AD brain, which link to AD pathogenesis, suggesting that treatments aiming to activate the pathway in AD need to be considered carefully. A different distribution of Akt and phospho-Akt was detected in AD temporal cortex neurons compared with control neurons, with increased levels of active phosphorylated-Akt in particulate fractions, and significant decreases in Akt levels in AD cytosolic fractions, causing increased activation of Akt (phosphorylated-Akt/total Akt ratio) in AD. In concordance, significant increases in the levels of phosphorylation of total Akt substrates, including: GSK3beta(Ser9), tau(Ser214), mTOR(Ser2448), and decreased levels of the Akt target, p27(kip1), were found in AD temporal cortex compared with controls. A significant loss and altered distribution of the major negative regulator of Akt, PTEN (phosphatase and tensin homologue deleted on chromosome 10), was also detected in AD neurons. Loss of phosphorylated-Akt and PTEN-containing neurons were found in hippocampal CA1 at end stages of AD. Taken together, these results support a potential role for aberrant control of Akt and PTEN signalling in AD.

Interaction of Tau with Fe65 links tau to APP

The beta-amyloid precursor protein APP and the microtubule-associated protein Tau play a crucial role in the pathogenesis of Alzheimer's disease (AD). However, the possible molecular events linking these two proteins are still unknown. Here, we show that Fe65, one of the ligands of the APP cytodomain, is associated with Tau in vivo and in vitro, as demonstrated by co-immunoprecipitation, co-localization, and FRET experiments. Deletion studies indicated that the N-terminal domain of Tau and the PTB1 domain of Fe65 are required for this association. This interaction is regulated by the phosphorylation of Tau at selected sites, by glycogen synthase kinase-3beta (GSK3beta) and cyclin-dependent kinase 5 (Cdk5), and requires an intact microtubule network. Furthermore, laser scanner microscopy and co-immunoprecipitation experiments provide preliminary evidence of possible complex(es) involving Tau, Fe65, APP. These findings open new perspectives for the study of the possible crosstalk between these proteins in the pathogenesis of AD.

Accumulation of flotillin-1 in tangle-bearing neurones of Alzheimer's disease

The protein flotillin-1 is associated with the 'lipid rafts', that is, membrane microdomains that are enriched in cholesterol and sphingolipids. We compared flotillin-1 immunoreactivity in the hippocampus, amygdala and isocortex (Brodmann area 22) of six controls and 13 Alzheimer's disease (AD) cases (10 sporadic and three familial). A diffuse labelling of the neuropil was observed in most of the samples. The intensity of this labelling was not correlated with the density of neurofibrillary tangles (NFT) or of senile plaques. Some neuronal cell bodies were diffusely labelled in patients as in controls. Immunostained granular bodies were found in the cell body of a few neurones. The density of neuronal profiles containing large granular bodies (diameter > or =2 microm) was significantly higher in AD cases and was correlated with the density of NFTs in the three regions that were studied. Sections stained by double immunofluorescence methods and examined with confocal microscopy suggested that flotillin-1 accumulated most often in tangle-bearing neurones (76% of flotillin-1-positive neurones contained a NFT). Flotillin-1 immunoreactivity, even when found in a tangle-bearing neurone, was not colocalized with tau protein indicating that the two proteins were not in close contact and probably in different subcellular compartments. Flotillin-1-positive granular bodies were also found in neurones containing Pin1-positive vesicles but were not colocalized with them. Flotillin-1 immunoreactivity was colocalized with cathepsin D, a lysosomal marker. These data indicate that flotillin-1, a marker of rafts, accumulates in lysosomes of tangle-bearing neurones in the course of AD.

Real-time PCR quantitation of FE65 a beta-amyloid precursor protein-binding protein after traumatic brain injury in rats

In cases of traumatic brain injury (TBI) in which the patient survived for only a short period of time and was without macroscopic changes at autopsy, it is difficult to diagnose TBI. To detect early diagnostic markers of diffuse axonal injury (DAI), real-time quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) in an experimental head trauma model of rat was chosen. The beta-amyloid precursor protein (beta-APP) is a well-known diagnostic marker of DAI which can be detected by immunolabeling as early as 1.5 h after injury. beta-APP has a binding protein, FE65, which is expressed in the brain of Alzheimer's disease patients along with beta-APP, but no involvement with brain injury has been reported. Neuron-specific enolase (NSE) is also a useful marker of DAI. We found that FE65 expression increased dramatically as early as 30 min after injury and decreased after peaking 1 h post-injury, although NSE showed no significant changes. These results suggest that real-time PCR of FE65 mRNA is useful for the diagnosis of DAI in forensic cases.

Expression of the Fe65 adapter protein in adult and developing mouse brain

Fe65 is a multimodular adaptor protein expressed mainly in the nervous system. Fe65 binds to the Alzheimer's disease amyloid precursor protein (APP) and the interaction is mediated via a phosphotyrosine binding domain in Fe65 and the carboxy-terminal cytoplasmic domain of APP. Fe65 modulates trafficking and processing of APP, including production of the beta-amyloid peptide that is believed to be central to the pathogenesis of Alzheimer's disease. Fe65 also facilitates translocation of a carboxy-terminal fragment of APP to the nucleus and is required for APP-mediated transcription events. In addition, Fe65 functions in regulation of the actin cytoskeleton and cell movement. Here we report the distribution profile of Fe65 immunoreactivity in adult mouse brain. Fe65 expression was found to be widespread in neurones in adult brain. The areas of highest expression included regions of the hippocampus in which the earliest abnormalities of Alzheimer's disease are detectable. Fe65 was also highly expressed in the cerebellum, thalamus and selected brain stem nuclei. Fe65 was evident in a sub-set of astrocytes within the stratum oriens and radiatum in the hippocampus. Expression of Fe65 was found to be developmentally regulated with levels reducing after embryonic day 15 and increasing again progressively from post-partum day 10 up to adulthood, a developmental pattern that partially parallels that of APP. These data indicate a widespread distribution of Fe65 in neurones throughout mouse brain and also suggest that Fe65 may have functions independent of APP and any potential role in the pathogenesis of Alzheimer's disease.

Aberrant activation of focal adhesion proteins mediates fibrillar amyloid beta-induced neuronal dystrophy

Neuronal dystrophy is a pathological hallmark of Alzheimer's disease (AD) that is not observed in other neurodegenerative disorders that lack amyloid deposition. Treatment of cortical neurons with fibrillar amyloid beta (Abeta) peptides induces progressive neuritic dystrophy accompanied by a marked loss of synaptophysin immunoreactivity (Grace et al., 2002). Here, we report that fibrillar Abeta-induced neuronal dystrophy is mediated by the activation of focal adhesion (FA) proteins and the formation of aberrant FA structures adjacent to Abeta deposits. In the AD brain, activated FA proteins are observed associated with the majority of senile plaques. Clustered integrin receptors and activated paxillin (phosphorylated at Tyr-31) and focal adhesion kinase (phosphorylated at Tyr-297) are mainly detected in dystrophic neurites surrounding Abeta plaque cores, where they colocalize with hyperphosphorylated tau. Deletion experiments demonstrated that the presence of the LIM domains in the paxillin C terminus and the recruitment of the protein-Tyr phosphatase (PTP)-PEST to the FA complex are required for Abeta-induced neuronal dystrophy. Therefore, both paxillin and PTP-PEST appear to be critical elements in the generation of the dystrophic response. Paxillin is a scaffolding protein to which other FA proteins bind, leading to the formation of the FA contact and initiation of signaling cascades. PTP-PEST plays a key role in the dynamic regulation of focal adhesion contacts in response to extracellular cues. Thus, in the AD brain, fibrillar Abeta may induce neuronal dystrophy by triggering a maladaptive plastic response mediated by FA protein activation and tau hyperphosphorylation.

Aberrant activation of focal adhesion proteins mediates fibrillar amyloid beta-induced neuronal dystrophy

Neuronal dystrophy is a pathological hallmark of Alzheimer's disease (AD) that is not observed in other neurodegenerative disorders that lack amyloid deposition. Treatment of cortical neurons with fibrillar amyloid beta (Abeta) peptides induces progressive neuritic dystrophy accompanied by a marked loss of synaptophysin immunoreactivity (Grace et al., 2002). Here, we report that fibrillar Abeta-induced neuronal dystrophy is mediated by the activation of focal adhesion (FA) proteins and the formation of aberrant FA structures adjacent to Abeta deposits. In the AD brain, activated FA proteins are observed associated with the majority of senile plaques. Clustered integrin receptors and activated paxillin (phosphorylated at Tyr-31) and focal adhesion kinase (phosphorylated at Tyr-297) are mainly detected in dystrophic neurites surrounding Abeta plaque cores, where they colocalize with hyperphosphorylated tau. Deletion experiments demonstrated that the presence of the LIM domains in the paxillin C terminus and the recruitment of the protein-Tyr phosphatase (PTP)-PEST to the FA complex are required for Abeta-induced neuronal dystrophy. Therefore, both paxillin and PTP-PEST appear to be critical elements in the generation of the dystrophic response. Paxillin is a scaffolding protein to which other FA proteins bind, leading to the formation of the FA contact and initiation of signaling cascades. PTP-PEST plays a key role in the dynamic regulation of focal adhesion contacts in response to extracellular cues. Thus, in the AD brain, fibrillar Abeta may induce neuronal dystrophy by triggering a maladaptive plastic response mediated by FA protein activation and tau hyperphosphorylation.