Giulio Taglialatela - US grants

DESCRIPTION CNS aging and neurodegenerative pathologies such as Alzheimer's disease are characterized by neuronal loss induced by a number of factors including decreased trophic factor signaling. The neurotrophins, NGF, BDNF, and NT-3 sustain survival of those neurons that are often affected by binding to specific tyrosine kinase receptors (trk), as well as to a common low affinity receptor (p75) whose function is not clear. NTs have been proposed as the basis for treatments to prevent neurodegeneration. A successful development of NT treatment requires a thorough characterization of the signal elements that transduce NT trophic action. This project focuses on the NGF-associated signal pathways involved in NGF mediated rescue from apoptosis. It is proposed that the stimulation of PKC-zeta and the activation of NF-kappa B are signal elements common to the activation of both NGF receptors. Using immortalized nigral and cerebellar cultured neurons transfected with either or both NGF receptors, Aim 1 will test whether binding to either Trk A or p75 may be sufficient to rescue cells from serum starved apoptosis. Aim 2 will test whether there are signal molecules associated with p75 that can affect apoptosis. Aim 3 will test whether PKC zeta activation or NF-kappa B translocation are signals common to both trk A and p75 receptors that are essential for rescue from apoptosis. Aim 5 will test whether the apoptosis which occurs in the aged rodent is associated with altered PKC or NF-kB signaling and confirm the in vitro observations. These experiments will elucidate mechanisms that mediate NT support of neurons and provide useful information as to the development of therapies to counteract age and pathology associated neuronal apoptosis.

[unreadable] DESCRIPTION (provided by applicant): Alzheimer's Disease (AD) is an age-associated dementia for which there is currently no cure. AD is characterized by memory deficits, loss of CNS neurons, and eventually death. Compelling evidence suggests that the prominent neurotoxic event in AD is the presence of the amyloid beta (Ab) peptide, the product of abnormal cleavage of a normal larger protein, and thus that preventing Ab toxicity would be an important therapeutic approach to AD. However, the cellular mechanisms mediating Ab toxicity are still unclear; understanding them should reveal molecular targets for treating AD. The objective of this project is to test one molecular mechanism mediating Ab neurotoxicity, and its behavioral consequences. The central hypothesis of this project is that a key intracellular mechanism mediating Ab neurotoxicity is the aberrant activation of the phosphatase calcineurin (CaN), a signaling element abundant in the CNS that plays a fundamental role in memory function. This project's specific goal is to determine whether the CaN inhibitor FK-506 prevents the detrimental impact of Ab on CNS neurons in vivo. This project will achieve its objective by pursuing the following specific aim: [unreadable] [unreadable] Identify the role of CaN in the onset and progression of cognitive deficits in a transgenic mouse model of Ab-induced neuropathology. The working hypothesis for this aim is that transgenic mice overexpressing mutant human APP will develop significant impairments in associative learning and memory that will be prevented or reversed by pharmacological inhibition of CaN. The results of these studies should identify CaN as a crucial element mediating Ab toxicity. This project will lay the foundation for future studies to develop FK506 as a clinical tool to prevent Ab-associated cognitive deficits. [unreadable] [unreadable] Health relevance: The buildup of the atypical amyloid beta (Ab) protein in the brain is thought to play a key role in the severe behavioral and cognitive impairments that are the most debilitating aspects of Alzheimer's Disease (AD), a terminal age-associated neurodegenerative disease affecting millions of elderly Americans; there is currently no effective treatment for AD. There is general agreement that blocking the neurotoxicity of Ab should decrease the mental impairment typical in AD patients. The goal of this project is to test one pharmacological approach to stop the detrimental effects of Ab on neurons. Specifically, this project will test whether FK506, a drug that inhibits calcineurin (an enzyme that could mediate Ab neurotoxicity), can decrease the adverse effects of Ab in the brains of mice with an AD-like condition. Importantly, since FK506 is already approved for human use as an immunosuppressant, successful results from this project should rapidly lead to clinical trials of this drug for the treatment of AD. [unreadable] [unreadable] [unreadable]

[unreadable] DESCRIPTION (provided by applicant): Alzheimer's Disease (AD) is an age-associated dementia for which there is currently no cure. AD is characterized by memory deficits, loss of CNS neurons, and eventually death. Compelling evidence suggests that the prominent neurotoxic event in AD is the presence of the amyloid beta (Ab) peptide, the product of abnormal cleavage of a normal larger protein, and thus that preventing Ab toxicity would be an important therapeutic approach to AD. However, the cellular mechanisms mediating Ab toxicity are still unclear; understanding them should reveal molecular targets for treating AD. The objective of this project is to test one molecular mechanism mediating Ab neurotoxicity, and its behavioral consequences. The central hypothesis of this project is that a key intracellular mechanism mediating Ab neurotoxicity is the aberrant activation of the phosphatase calcineurin (CaN), a signaling element abundant in the CNS that plays a fundamental role in memory function. This project's specific goal is to determine whether the CaN inhibitor FK-506 prevents the detrimental impact of Ab on CNS neurons in vivo. This project will achieve its objective by pursuing the following specific aim: [unreadable] [unreadable] Identify the role of CaN in the onset and progression of cognitive deficits in a transgenic mouse model of Ab-induced neuropathology. The working hypothesis for this aim is that transgenic mice overexpressing mutant human APP will develop significant impairments in associative learning and memory that will be prevented or reversed by pharmacological inhibition of CaN. The results of these studies should identify CaN as a crucial element mediating Ab toxicity. This project will lay the foundation for future studies to develop FK506 as a clinical tool to prevent Ab-associated cognitive deficits. [unreadable] [unreadable] Health relevance: The buildup of the atypical amyloid beta (Ab) protein in the brain is thought to play a key role in the severe behavioral and cognitive impairments that are the most debilitating aspects of Alzheimer's Disease (AD), a terminal age-associated neurodegenerative disease affecting millions of elderly Americans; there is currently no effective treatment for AD. There is general agreement that blocking the neurotoxicity of Ab should decrease the mental impairment typical in AD patients. The goal of this project is to test one pharmacological approach to stop the detrimental effects of Ab on neurons. Specifically, this project will test whether FK506, a drug that inhibits calcineurin (an enzyme that could mediate Ab neurotoxicity), can decrease the adverse effects of Ab in the brains of mice with an AD-like condition. Importantly, since FK506 is already approved for human use as an immunosuppressant, successful results from this project should rapidly lead to clinical trials of this drug for the treatment of AD. [unreadable] [unreadable] [unreadable]

Alzheimer's Disease (AD) is an age-associated dementia for which there is currently no cure. AD is characterized by memory deficits, loss of CNS neurons, and eventually death. One of the prominent events in AD is the CNS presence of plaques that are mostly formed by large macromolecular aggregates of insoluble fibrillar amyloid beta (Aj3), a 40 or 42 aminoacid-Iong peptide resulting from atypical cleavage of the larger amyloid precursor protein (APP). However, mouse models of AD have shown that memory deficits occur in the absence of neuronal loss and long before plaque deposition;furthermore in humans, total CNS levels of Aj3, rather than number of amyloid plaques, correlate with the degree of disease severity, thus suggesting that soluble, non plaque associated, small forms of Aj3 may be the principal offender in the AD brain. Indeed, recent evidence has shown that specific oligomeric forms of Aj3 perturb synaptic plasticity, depress long term potentiation (L TP) and induce transient memory deficits in rodents. On this basis, there is consensus that preventing oligomeric Aj3 toxicity would be a significant therapeutic step to reverse cognitive deficits and hopefully prevent later neurodegeneration in AD. Thus, understanding the yet unclear cellular mechanisms mediating oligomeric Aj3-promoted memory deficits, the overall goal of this research, is important for the development of future therapies for AD. The central hypothesis of this project is that a key mechanism mediating oligomeric Aft neurotoxicity is the aberrant activation of the phosphatase calcineurin (CaN), a signaling element abundant in the CNS that plays a fundamental role in memory function. This hypothesis has been formulated based on preliminary data and published results showing that CaN is up-regulated in the CNS of APP transgenic mice (Tg2576), coincident with the appearance of oligomeric Aj3 and memory impairments, and that acute inhibition of CaN reverses memory deficits in these mice. The objective of this project is therefore to determine the role played by CaN in mediating the cognitive effects of oligomeric Aj3. This objective will be achieved by pursuing the following specific aim: test the hypothesis that there exist a causal link between the occurrence of oligomeric Aj3 and increased CaN activity in the CNS of ageing Tg2576 APP transgenic mice as a function of age, deteriorating cognitive performance and appearance of amyloid plaques. Once completed, this project will have identified CaN as a crucial element mediating the cognitive outcomes of oligomeric Aj3. Acquiring this new knowledge is important for the future development of effective therapies for AD.

DESCRIPTION (provided by applicant): Alzheimer's disease (AD) is the most severe neurodegenerative dementia for which there is currently no cure. Abundant deposition of amyloid beta (A?) plaques and the presence of neurofibrillary tangles of hyper-phosphorylated tau protein are the two CNS lesions that, concomitant with synaptic disruption and preponderant insulin resistance, hallmark the onset and progression of AD. Some individuals, however, remain cognitively intact despite the presence of substantial AD neuropathology. The existence of these unusual cases (which we termed Non-Demented with Alzheimer's Neuropathology, NDAN) reveals that there is a natural way for the human brain to resist the neurotoxic events that normally lead to cognitive demise in AD. It follows that understanding the molecular mechanisms involved in such resistance would reveal a very effective target for treatment of cognitive decline in AD. Achieving this knowledge is the overarching goal of our research. We present compelling preliminary results supporting the hypothesis that NDAN individuals remain cognitively intact because A? oligomers do not bind to, and therefore, do not disrupt post-synaptic elements owing to increased insulin sensitivity that impacts the make-up of the PSD proteome rendering A? oligomer docking unlikely. The goal of this application is to establish that, as compared to demented AD, cognitive integrity of NDAN cases is collectively marked by a) molecular evidence of synaptic integrity; b) absence of A? oligomers from post-synaptic elements; c) increased insulin sensitivity; d) unique PSD proteome signature. We will test this hypothesis by pursuing the following three specific aims: 1) To demonstrate the presence (or absence) of A? oligomers at synapses in the hippocampus and cortex of AD and NDAN brains as a function of synaptic welfare, insulin sensitivity and cognitive competence; 2) To determine the existence of a causal link between sustained insulin signaling and the ability of synapses to reject the disfunctional binding of A? oligomers; 3) To determine and contrast the protein make-up of the PSD in control, AD and NDAN cases and in wt mice treated with the insulin sensitizing drug PTZ. Results will characterize the NDAN human synapse which is capable of escaping disruptive targeting by A? oligomers and maintaining increased insulin sensitivity and establish a molecular signature underscoring a causal relationship between sustained insulin signaling and the ability of synapses to reject detrimental A? oligomer binding. This new knowledge is necessary to lay solid foundations for the identification of potential pharmacological targets for the development of new, effective treatments for AD. We propose a multidisciplinary approach that brings together a uniquely qualified team of experts in neuronal molecular signaling in AD (Taglialatela), CNS electron microscopy (Carlton), behavior in APP Tg mouse models (Dineley), proteomics (Wiktorowicz), AD histopathology (Woltjer) and AD clinical aspects (Quinn).

PROJECT SUMMARY/ABSTRACT Alzheimer?s disease (AD) is the most common and severe age-associated neurodegenerative dementia for which finding a resolving cure is a pressing national priority. The discovery of resilient individuals who remain cognitively intact despite the presence of AD neuropathology normally associated with fully symptomatic stages of the disease, suggests that there is a way for the brain to evade dementia even in the face of AD. It follows that understanding the mechanism(s) involved in such extraordinary resistance would reveal targets for the development of a novel, effective therapeutic concept based on inducing cognitive resilience in anyone challenged with AD neuropathology. With this goal in mind, we have discovered that brain synapses in these unaffected individuals are resistant to the disrupting binding of toxic oligomers of both amyloid beta (A?) and tau (an event linked to onset of dementia in AD) and that this resistance is associated with the presence of higher numbers of neural stem cells (NSC) in the hippocampus as compared to either AD patients and control subjects. While these observations suggest a link between high NSC numbers and synaptic resistance to damaging amyloid oligomers, the involved mechanism (an obvious treatment target) remains unknown. Based on exciting new, compelling preliminary data involving exosomes specifically released from NSC as mediators of this phenomenon, in this project we will test the hypothesis that NSC-derived exosomes (via delivering specific microRNA cargoes to target neurons) render neuronal synapses resistant to the disrupting binding of A? and tau oligomers and thus protect from associated memory deficits. Employing both ex vivo and in vivo models of A? and tau oligomer-induced synaptic dysfunction and cognitive impairment, in Aim 1 we will test the hypothesis that NSC-derived exosomes reduce synaptic susceptibility to amyloid oligomers binding and its functional consequences. In Aim 2 we will characterize microRNAs uniquely present in NSC-exosomes responsible for these effects. In Aim 3 we will document the translational value of this novel mechanism employing human NSC and neurons derived from iPSCs. At the completion of the proposed studies we will have documented a previously unappreciated phenomenon of synaptic resistance to A? and tau oligomers mediated by NSC-exosomes and discovered specific miRNAs that can promote it. Given the translational value of miRNAs for drug development, this discovery will have a substantial impact in the field by illustrating targets for the development of an innovative treatment concept for AD centered on promoting synaptic resistance to toxic oligomers, a strategy expected to be effective in humans as suggested by the existence of NDAN subjects. A uniquely qualified investigative team has been assembled to successfully accomplish this project, bringing together expertise in AD molecular neurobiology (Taglialatela), NSC biology (Micci), biochemistry of amyloid proteins (Kayed), miRNA sequencing and analysis (Widen), electrophysiology and animal behavior (Krishnan) and neurobiology of NSC-derived exosomes and their miRNA cargoes (Cai, sub-contract PI).

Project Summary: In this project we seek to stimulate talented undergraduate students from Hispanic Serving Institutions, Historically Black College/Universities, Minority Serving Institutions, and other colleges with high populations of disadvantaged students, women and veterans. We propose to provide a ten-week research experience in the neurosciences with a focus on Pain, Addiction, mild Traumatic Brain Injury, and other Neurodegenerative Diseases such as Alzheimer?s and Parkinson?s disease. Students will work in affinity research groups in a supportive and challenging environment on real world problems designed to inspire, and provide enhanced neuroscience training with the goal of retaining these students in a STEM pipeline to diversify the NIH workforce. This grant will support a student population of approximately 50 percent female and at least 50 percent underrepresented minority students. With the integration of Tinto?s model, our work on core competences, and our track record of excellence in mentoring we propose a near 100 percent retention rate of these students in their fields of study.

PROJECT SUMMARY/ABSTRACT Alzheimer?s disease (AD) is the most common and severe age-associated neurodegenerative dementia of our times for which there is no cure. Synaptic dysfunction induced by the dysfunctional targeting toxic oligomers of both Ab and Tau (the two hallmark amyloids in AD) is recognized as one of the earliest events in AD, driving initial cognitive decline and clinical manifestation. Preventing such oligomer disrupting action on synapses would thus be an effective and comprehensive therapy for AD, blocking the combined driving toxicity of both A? and tau. However, a strategy to achieve this important goal remains elusive. In the present project we wish to address this critical knowledge gap by testing the hypothesis that activation of calcineurin (CN) mediates the synergistic effect of A? and tau oligomers on synapses. CN is a CNS-abundant phosphatase critically involved in synaptic function and memory formation. CN activity is abnormally increased the brain of AD patients as well as tg mouse models of AD, and inhibition of CN with FK506 (an FDA-approved immunosuppressant drug) protects synapses from A? oligomers and restores memory in transgenic AD mouse models. Most notably, we showed that the incidence of AD in solid organ transplant recipients chronically treated with FK506 is dramatically reduced as compared to the general population. This is highly significant in light of recent evidence showing that overexpression of hTau induces elevated CN in the CNS, and that tau oligomers induce synaptic deficits and memory dysfunction in synergy with A? oligomers, strongly suggesting that the two species impinge upon a common molecular target mediating their combined key role in AD onset and clinical progression. We propose that such common target is CN and that CN inhibition is an effective approach to block the combined toxicity of tau and A? oligomers that drive AD. In the present project will employ in vitro, ex vivo and in vivo models and autopsy human brain specimens to mechanistically test our hypothesis by characterizing the role of CN in mediating the disruptive effects of tau oligomers (Aim 1) and by establishing CN as the common target mediating the combined, synergistic impact of tau and Ab oligomers on synaptic and memory function (Aim 2). At the completion of the proposed studies we will have documented a previously unappreciated role of CN as the point of molecular convergence of the toxic oligomers of the two amyloid proteins that hallmark AD neuropathology, tau and A?, and illustrated the beneficial effects of FK506 in preventing their combined toxicity. Given the translational value of FK506 (an FDA-approved drug) this discovery will have a substantial impact in the field by promoting the development of an innovative treatment concept for AD centered on simultaneous blockade of tau and A? toxic species, a strategy expected to be effective in humans as suggested by the resilience to AD of transplanted patients chronically treated with FK506.

PROJECT SUMMARY/ABSTRACT Finding a resolving cure for Alzheimer?s Disease (AD), is an urgent critical need. There is ample consensus that successful treatments should target early pathological events in AD. Among these, synaptic dysfunction induced by oligomers of both A? and tau is recognized as one of the earliest key driving events in AD and thus an attractive treatment target, but an effective strategy is still missing. Our long-term goal is to help develop therapeutically useful approaches to increase synaptic resilience to A? and tau oligomers for the clinical treatment of AD patients. With this goal in mind, we recently reported that exosomes specifically released by hippocampal neural stem cells (NSC-exo) render CNS synapses resilient to the disruptive impact of A? oligomers via selected micro RNA (miRNA) cargoes, a mechanism likely at play in the human brain as suggested by reports of aged individuals with high numbers of NSC and synapses resilient to A? oligomers who remain cognitively intact despite the CNS presence of extensive AD neuropathology. Whether such mechanism of resilience is also effective against synaptic disruption brought about by tau oligomers- a recognized major player in the onset and clinical progression of AD- remain to be established. Thus, the overall objective in this application, is to evaluate the link between NSC (and their released exosomes) and increased synaptic resilience to the toxic actions of tau oligomers as a function of aging, the strongest AD risk factor. Based of rigorous previous literature reports and compelling preliminary results, our central hypothesis is that NSC-exo, via delivering unique miRNA cargoes, render synapses resistant to toxic tau oligomers and that such protective mechanism fails during aging owing to the well-documented age-related loss of NSC, leaving the aged brain more vulnerable to the AD toxic amyloids (and therefore more at risk of developing clinically manifest AD). The rationale for this project is that a determination of the preclinical therapeutic efficacy and associated mechanisms of NSC-exo (and their miRNA cargoes) as a function of aging is likely to offer a strong scientific framework whereby a new strategy centered on promoting synaptic resilience to AD pathological oligomers could be developed. To obtain the overall objective, we will pursue three specific aims that will evaluate the efficacy of NSC-exo in promoting synaptic resilience to Tau oligomers (Aim 1), determine the invoved miRNA cargoes and their impact on key synaptic proteins (Aim 2) and evaluate the impact of aging on such protective mechanisms as a function of decreasing numbers of resident NSC and their released exosomes (Aim 3). At the completion of the proposed studies, it is our expectation that we will have documented a previously unappreciated phenomenon of synaptic resistance to toxic oligomers mediated by NSC-exo and their miRNA cargo that fails during aging. This discovery will illustrate targets for the development of an innovative treatment concept for AD centered on sustaining synaptic resistance to toxic oligomers in an aging environment, a strategy expected to be effective in humans as suggested by the existence of aged resilient subjects with high NSC numbers and synapses that reject oligomers.

PROJECT SUMMARY/ABSTRACT Finding a resolving cure for Alzheimer's Disease (AD) is an urgent critical need and there is ample consensus that successful treatments should target early disease events. Among these, synaptic dysfunction induced by soluble oligomers of tau (TauO) is recognized as one of the earliest key events in AD and related disorders, where disease-specific TauO conformers (strains) may drive the diverse clinical presentations. Thus, blocking synaptic demise induced by TauO conformers is a highly desirable therapeutic strategy, its potential effectiveness supported by the existence of resilient individuals who remain Non-Demented despite the CNS presence of late-stage Braak AD Neuropathology (here termed NDAN) that present with functional synapses devoid of TauO. Notably, late Braak stage pathology paralleled by intact synapses in NDAN suggests the novel concept that trans-synaptic spreading of tau and tau-driven synaptic toxicity are two distinct phenomena that coexist in AD and other symptomatic tauopathies but not in NDAN, where the toxic impact of TauO on synapses (but not spreading) is curbed. While such evidence indicates that rejecting synaptic tau toxic impact as a protective mechanism can be effectively enabled in the human brain despite the spread of AD neuropathology, a therapeutic strategy to achieve such a game-changing goal remains missing. Filling this critical knowledge gap by laying the molecular foundations for the development of such therapeutic strategy is the overall objective of the present project. Our central hypothesis is that dysfunctional engagement of synapses by TauO is determined by the type of tau strain and its binding to LRP1 (a synaptic receptor essential for tau uptake and spreading), which differentially affects LRP1-containing protein complexes in vulnerable vs. resilient synapses. We will test our central hypothesis by evaluating binding dynamic and functional impact of disease-specific brain-derived TauO conformers on human synapses as a function of LRP1-mediated toxicity (Aim 1) and by evaluating the functional response of human synapses from different tauopathies (AD, PSP) and resilience status (NDAN, PART) to TauO as a function of the synaptic LRP1 (Aim 2). At the completion of the proposed studies, we expect to have documented a previously unappreciated mechanism of synaptic interaction of TauO conformers as well as a phenomenon of synaptic resistance modulated by LRP1. This discovery will have a significant impact in the development of an innovative treatment concept for AD centered on sustaining synaptic resistance to toxic oligomers, a strategy expected effective as demonstrated by NDAN subjects. A uniquely qualified investigative team has been assembled to successfully accomplish this project, bringing together expertise in AD molecular neurobiology (Taglialatela), human synaptic physiology (Limon) and function (Krishnan) and biochemistry of tau oligomers (Kayed).