Published work from multiple groups indicates that tau phosphorylation causes tau to mis-‐localize to the soma and dendrites, where TIA-‐1 is present . Our preliminary data indicates that the TIA-‐1 binds the phosphorylated tau. Tau promotes formation of TIA-‐1 based SGs, and in the process, binding of Tau with TIA-‐1 stimulates tau misfolding. These data lead us to hypothesize that binding of tau protein to RNA binding proteins stimulate their aggregation to form stress granules, which concomitantly consolidates misfolded tau thereby providing the nidus for formation of tau pathology. The link between tau and SGs is particularly important because primary dysfunction of RNA binding proteins is known to cause neurodegenerative diseases, including Amyotrophic lateral sclerosis and frontotemporal dementia. We hypothesize that secondary dysfunction of RNA binding proteins, caused by tau-‐induced hyperactive stress granule formation, also causes neurodegeneration. This provides a clear mechanism through which tau pathology can elicit neurodegeneration, and if true, suggests that the interaction of tau with RNA binding proteins plays a pivotal role in the pathophysiology of AD.
Recently we observed that chronic suppression of monoacylglycerol lipase with the selective blocker JZL184 increased brain levels of endocannabinoid 2-arachidonoil glycerol (2-AG), restored long-term potentiation, improved cognition, and reduced brain levels of Aβ40 and Aβ42 in aged Ts65Dn mice, a model of ‘Alzheimer’s disease in Down syndrome’ (ADDS). In this proposal, we plan to examine the mechanisms responsible for the restoration of cognition and synaptic plasticity in the ADDS model mice. We suggest that two types of changes resulting from JZL184-treatment may contribute synergistically to the improvements in cognition and synaptic plasticity: (I) An increase of the level of 2-AG may result in a reduction of efficiency of the inhibitory GABAergic neurotransmission and, possibly, in improvement of adult neurogenesis. (II) The decrease of hippocampal levels of Aβ40 and Aβ42, which may reduce inhibitory efficiency and improve synaptic plasticity.
Working Hypothesis: Enhancement of synaptic plasticity and cognition in aged Ts65Dn mice by chronic blockade of monoacylglycerol lipase (MAGL) is caused by persistent alterations in properties of GABAergic synapses and changes in adult neurogenesis.
There is general agreement that beta amyloid (Aβ) is a likely causative agent in the development of Alzheimer’s disease. There is growing evidence that early in the disease an important target of Aβ is the synapse, the site of communication between neurons. We have found that exposure of synapses to Aβ causes synaptic loss. In this proposal we will examine the role played in this process by variant forms of synaptic proteins that have recently been identified by Dr. Tanzi in whole genome analysis of families with late-onset Alzheimer’s disease (LOAD). We hypothesize that the rare variants confer synapses with higher sensitivity to Aβ, thereby facilitating development of AD.
PICALM, the gene encoding phosphatidylinositol binding clathrin assembly (PICALM) protein, plays a key role in endocytosis, a process which regulates the function of cell receptors and synaptic transmission. Several GWAS studies of AD have replicated the association of PICALM with AD and shown relationships with neurodegenerative processes underlying disease. Additionally, low levels of PICALM in brain and cerebral microvessels have been recently shown in late onset AD. The role of PICALM in AD pathogenesis remains, however, elusive. A genome-wide screen for modifiers of Ab toxicity in yeast has identified the yeast homologue of PICALMand some other endocytotic factors as a functional link between Ab toxicity, endocytosis, and AD risk. PICALMhas been also shown to protect neurons against Ab toxicity by partially reversing Ab toxic effects on endocytotic trafficking. During YEAR 1, we showed that PICALM plays a central role in the molecular mechanism regulating Ab transcytosis and clearance across the blood-brain barrier (BBB). Using a human brain endothelial monolayer model of the BBB, we showed that PICALM binds to the cytoplasmic tail of LRP1 and is involved in clathrin-mediated Ab endocytosis and transport of Ab across the BBB controlled by Rab5 and Rab11 GTPases. We next showed that Picalmdeficiency diminishes Ab clearance across the murine BBB in vivo and reduces clearance of soluble Ab from the brain interstitial fluid (ISF) in APPsw/0mice accelerating Ab pathology and cognitive decline. These findings have established that PICALM controls AbBBB transcytosis and clearance from brain. In YEAR 2, we propose to continue these studies and determine i) the cell-specific role of PICALM in brain endothelium (AIM 1) and neurons (AIM 2) in vivo in relation to neuronal dysfunction and neurodegeneration within the Ab pathway and Ab-independent pathway using novel murine models of Picalmdeficiency; and ii) the effects of novel PICALMmutations on Ab BBB clearance using a human model of the BBB in vitro in collaboration with Dr. R. Tanzi. For AIMS 1 and 2, we will use Picalmlox/loxmice (generated by our collaborator Dr T. Maeda, Harvard Medical School) and will delete Picalmfrom endothelium and/or neurons to determine how these cell-specific deletions affect Ab metabolism, BBB integrity, neuronal function and neurodegeneration. We will use Ab clearance technique, multiphoton, confocal and light microscopy analysis, DTI MRI to evaluate brain structural and functional changes (tractography), DCE MRI for BBB integrity, and behavioral tests. Theproposedstudiesshouldadvanceour knowledge about the role of PICALM as a risk for AD and how novel PICALM mutations affect Abclearanceand trafficking across the BBB. We expect that the present findings will identify PICALM as an important new therapeutic target for Ab clearancetherapyand treatment of Alzheimer’s neurovascular and neurodegenerative disorder.
Alzheimer's disease is the most common form of dementia, affecting over 5 million people in the United States alone; it is the sixth-leading cause of death and is expected to cost the nation over $200 billion in 2013, with costs projected to exceed $1 trillion by 2050. Currently, there is no cure for Alzheimer's disease, nor are there effective treatments that delay or improve symptoms. Progress in understanding the underlying etiology and molecular mechanisms that cause progressive neuronal cell death has been hampered by a lack of research models that faithfully recapitulate the disease, including mouse models carrying genetic mutations that predispose humans to Alzheimer's disease. The brief lifespan of mice (age of onset for Alzheimer's is usually over 65) and intrinsic differences between mouse and human neuron physiology are two factors that likely contribute to the failure of mouse models. These obstacles were particularly difficult, or impossible, to overcome until recently.
Advances in stem cell technology have given researchers new hope by making it possible to study cultured human neurons derived from Alzheimer's patient fibroblasts. Here, we will take advantage of these technological advances to examine neurons from patients carrying mutations in MAPT(Microtubule-Associated Protein Tau), which encodes the tau protein. Postmortem brains from a broad range of dementia patients, including Alzheimer's and frontotemporal dementia (FTD) patients, show altered tau biology that includes tau tangles and elevated levels of hyperphosphorylated tau. To determine how tau misregulation perturbs normal neuronal function and leads to neurodegeneration, we will perform a comprehensive biochemical and cell biological analysis of tau-mutant human neurons and compare to gene-edited isogenic controls. In addition to examining neurons longitudinally, we will assess changes that may occur in response to premature aging. Finally, we aim to determine whether tau is required for AP-induced toxicity in human neurons, as has been reported for mouse neurons, and whether MAPT mutations sensitize neurons to AP-induced degeneration . We expect this research to provide new insights into tau biology in Alzheimer's disease and to potentially reveal novel disease mechanisms that could be beneficial for developing therapeutics for treating dementia.
Absence of biomarkers has posed a formidable challenge in the development of effective treatment for Alzheimer disease (AD). Blood-based biomarkers could offer advantages that allow for early AD diagnosis and are critical in monitoring efficacy in clinical studies. Proposed studies aim to identify a set of novel blood biomarkers and examine their potential application as diagnostic agents. Phage display is a powerful approach to engineer peptides or proteins for binding to targets of interest. Therefore, we will apply phage display technology to identify peptides that selectively interact with molecules in AD blood samples, not in the age matched controls. In Aim 1, we will identify potential biomarkers by screening two libraries with a diversity of approximately 2 billion peptides against AD and control blood samples. To overcome the anticipated kinetic limitations with monovalent peptides, we will polymerize them by conjugation to dendrimers combined with functional moieties including fluorescent dyes for validation studies in Aim 2. These studies will identify a set of peptides that can be potentially used as diagnostic agents for AD. Furthermore, the proposed research is highly transformative and can be widely applied for biomarker studies in other human disorders. Overall, these proposed studies address a critical unmet medical need in AD by providing large sets of new biomarkers for rapid and accurate non-invasive diagnosis of AD using innovative approaches.
Large, poorly soluble aggregates of the amyloid-beta peptide form the senile plaques that are a pathological hallmark of Alzheimer’s disease, but the extent of plaque deposition correlates only moderately with dementia; for example many middle aged and elderly people have extensive plaque deposition without any signs of dementia. Instead, several types of smaller water soluble amyloid-beta oligomers have been found to be more toxic than either plaques or amyloid-beta peptide monomers. Our collaborative group has recently developed a sensitive, specific, quantitative and high-throughput assay for amyloid-beta oligomers. We propose to use this assay to facilitate purification of amyloid-beta oligomers from human brain tissue. We expect that there will be substantial complexity in the Alzheimer’s disease brain, with multiple oligomeric species having varying structural properties and toxicities. Once purified, we will use mass spectrometry to characterize the structure and cell-based toxicity assays to quantitatively assess the function of each distinct type of oligomer. The first major outcome will be identification of critical post-translational modifications, associated proteins, and conformational epitopes in amyloid-beta oligomers that could be targeted by innovative therapeutics. The second major outcome will be determining which (if any) animal models accurately reproduce the amyloid-beta oligomers found in the human brain so that candidate therapeutics targeting these oligomers can be tested appropriately in vivo. It may be that entirely new animal models will be needed. Thus, if successful, this project will facilitate an entirely new wave of preclinical and clinical therapeutic development for Alzheimer’s disease.
Alzheimer’s disease (AD) is a major cause of dementia in elderly. The amyloid-β (Aβ) peptides deposit in the brain parenchyma as senile plaques and in the cerebrovasculature as cerebral amyloid angiopathy (CAA), both are hallmarks of AD pathology. Epidemiologically, cerebrovascular damages caused by diabetes mellitus or stroke increase the risk for AD. Cerebral hypoperfusion precedes cognitive decline and neurodegeneration in AD. Our recent work has also demonstrated that cerebrovasculature plays critical roles in Aβ clearance. Therefore, we aim to develop novel regenerative therapy for AD by restoring cerebral vasculature function and neural integrity through transplantation of induced pluripotent stem cell (iPSC)-derived specialty cells. Specifically, we will co-inject iPSC-derived vascular progenitor cells (VPCs) and neural stem cells (NSCs) into mouse brain to promote synergistic effects for regeneration of both cerebral vessels and neurons as neurovascular interactions play critical roles in neurogenesis and angiogenesis. Therefore, the overall goal of this proposed study is to investigate the effects of regenerative therapy through transplantation of iPSC-derived VPCs and neurospheres on Aβ clearance, amyloid pathology and cognitive function in amyloid model mice. Our innovative approach could lead to development of novel therapeutic methods to treat AD.
The amyloid Aß peptide is deposited in at least two distinct locations in AD brain: Parenchymal plaques and vascular amyloid deposits in the wall of arterioles, where it is associated with vascular smooth muscle cell degeneration and stroke (Congophilic amyloid angiopathy, CAA). While CAA is commonly found in AD brain, some human mutations within the Aß domain of the amyloid precursor protein (APP) cause CAA and stroke, rather than AD indicating that these diseases can occur independently. Using a conformation-dependent monoclonal antibody, M31, we have discovered a structurally unique type of Abeta deposit that is specifically associated with vessels. This shows that a subset of the vascular amyloid is conformationally unique and raises the hypothesis that it may be associated with a unique type of pathogenesis. The goal of this proposal is to examine the relationship of this unique vascular amyloid to AD and CAA pathogenesis and obtain preliminary data to support an NIH application with more mechanistic and translational aims. The results of this study may lead to the development of immunological strategies to therapeutically target CAA and image its accumulation in human brain, allowing the pre-mortem diagnosis of vascular amyloidosis and the stratification of patients for human clinical trials for both AD and CAA.
In neurodegenerative diseases known as the tauopathies (e.g. progressive supranuclear palsy, Alzheimer disease), there is progressive degeneration of specific brain regions that account for the symptoms and signs of each disease. Accumulation of aggregated forms of the protein tau in structures known as neurofibrillary tangles and dystrophic neurites in these brain regions correlates well with functional decline in cognition, motor, and other functions. Cell to cell transmission of tau aggregates leading to brain dysfunction is one hypothesis which may account for spread of pathology and progressive brain dysfunction. Our recent data, now “in press”, showing the effectiveness of certain anti-tau antibodies as a potential therapy, supports this hypothesis. One difficulty in assessing the effects of therapies for neurodegeneration in animals is the lack of a strong, quantifiable, physiologically relevant phenotype. Here, we seek to further characterize preliminary findings that a mouse model of tauopathy (P301S Tau Tg mice) develops both decreased NREM sleep as well as a marked decline in delta power during non-REM (NREM) sleep. In addition, we will determine whether an anti-tau antibody, HJ8.5, that we have found to strongly decrease tau pathology, will prevent this sleep phenotype when administered peripherally.