Keith A. Vossel - US grants

DESCRIPTION (provided by applicant): Alzheimer's disease (AD) and other age-related neurodegenerative disorders are a major source of morbidity and mortality. In the U.S. alone, some 5 million people have AD, a relentless and fatal condition that devastates the mind and engenders feelings of hopelessness in caregivers. The urgency in finding a cure for AD has never been stronger. AD is associated with an increased incidence of seizures as well as cognitive decline. Seizures and subclinical excitatory neuronal activity may contribute to cognitive deficits. We propose to investigate neuroprotective strategies to counter neuronal overexcitation and seizures in AD and identify a population who could benefit from such therapies. The laboratory investigation focuses on the axonal transport of two cellular components that tightly regulate neuronal activity-mitochondria and the voltage-gated potassium channel Kv1.1. The neurotoxic peptide amyloid-[unreadable] (A[unreadable]) impairs axonal transport of mitochondria, and reduction of the microtubule-associated protein tau completely abolishes this effect. Tau reduction also protects against seizures and behavioral deficits in transgenic mouse models of AD. These findings suggest a pathogenic mechanism for A[unreadable] and tau involving axonal transport and neuronal excitability. In Aim 1, we will investigate mechanisms by which tau and A[unreadable] regulate the axonal transport of mitochondria and Kv1.1, and study the effects of tau reduction on axonal transport of these cargoes in vivo in a mouse model of AD. Aim 2 is a translational clinical investigation of the extent of subclinical epileptiform activity in people with mild cognitive impairment and AD with an eye toward future therapeutic trials using antiepileptic medications or tau-targeted strategies. The candidate is a physician-scientist with a strong commitment to a career in academic neurology focused on identifying novel therapies for AD and related dementias. The candidate has an MSc in biomedical engineering and an MD with clinical training in neurology and subspecialty training in behavioral neurology and neurodegenerative dementias. The research proposal and career development plan build upon his training in neuroscience, aging, and neurodegenerative diseases to provide expertise in transgenic mouse models of AD, histology, cell culture, microfluidics chambers, time-lapse microscopy, transcranial two-photon imaging, and translational clinical trials. Dr. Lennart Mucke, a physician-scientist who cares for patients with dementia and specializes in transgenic mouse models of neurodegenerative disease, is the candidate's sponsor. The mentoring and research experience described in this proposal will facilitate the candidate's goal of developing a strong independent research career. PUBLIC HEALTH RELEVANCE: Projected increases in the prevalence of dementia with the aging of the American population are a major threat to our healthcare system, and the development of novel therapeutic approaches is a critical goal. This project is designed to uncover mechanisms by which tau reduction is protective against neural network dysfunction and seizures in mouse models of AD and to identify people in the early stages of AD who have subclinical epileptiform activity and who could benefit from tau-targeted strategies or antiepileptic drugs. A host of FDA-approved antiepileptic medications are already available that could be tested in future clinical trials.

PROJECT SUMMARY Up to 60% of patients with Alzheimer?s disease (AD) exhibit seizures and network hyperactivity, leading to a faster cognitive decline. Therefore, seizures in AD should be an important focus for therapeutic interventions. The microtubule-associated protein tau, a central factor in AD pathogenesis, mediates seizures and associated memory loss in models of AD, suggesting that targeting tau could effectively treat seizures in AD. However, there is a fundamental gap in understanding how tau contributes to seizures in these models. Broadly reducing tau levels successfully prevents seizures; however, reducing tau also causes deleterious effects in aged mice and the safety of this approach in the adult human brain is unknown. Therefore, a better understanding of how tau contributes to seizures is needed in order to develop more precise therapies targeting tau. The overall objective here is to identify a mechanism by which tau mediates seizures and related functional deficits in mouse models of AD and genetic epilepsy. The applicant has obtained preliminary data indicating that blocking tau?s interactions with SRC Homology 3 (SH3)-containing proteins can prevent seizures and associated memory loss in AD. The central hypothesis, based on the applicant?s preliminary data, is that tau binds to SH3-containing enzymes on its proline-rich region, and regulates network activity by modulating the activity or cellular localization of these enzymes. Previous studies, supportive of this concept, have indicated that binding between tau and the tyrosine kinase Fyn, which regulates excitatory receptors, are involved in tau?s ability to regulate seizures. The applicant?s preliminary data expands on these findings to indicate additional SH3-containing enzymes that bind tau and are involved in this phenomenon. The rationale for the proposed research is that, once it is known which enzymes are important for tau?s ability to mediate seizures, tau?s binding affinity with these enzymes can be manipulated pharmacologically, resulting in new and innovative approaches to the prevention and treatment of seizures and associated memory loss in AD. Guided by strong preliminary data in which the applicant created two novel mutant tau knockin mouse models, this hypothesis will be tested by pursuing two specific aims: 1) Determine the influence of variants in the proline-rich region of tau that prevent its binding to SH3-containing enzymes on signal transduction initiated by A? oligomers, which are epileptogenic peptides linked to AD, and excitotoxins, and 2) Determine the extent to which these variants in tau prevent seizures, behavioral deficits, and premature mortality in mouse models of AD and genetic epilepsy. The proposed research is innovative because it represents a substantive departure from the status quo by shifting focus to tau?s upstream modulation of cell signaling related to A? and excitotoxicity. This contribution is expected to be significant because it will have broad translational importance in the prevention and treatment of seizures and associated memory loss in AD.

PROJECT SUMMARY Lewy body dementias (LBD), including Parkinson?s disease dementia (PDD) and dementia with Lewy bodies (DLB), are the second most common type of degenerative dementia in the world. Unfortunately, there are currently no therapies to slow or halt the progression of LBD. Seizures associated with LBD deserve more attention because, despite the harmful impact on the patients, seizure activity can go unrecognized and untreated. Seizures or myoclonus occur in over half of DLB patients, and these symptoms hasten cognitive decline. Our preliminary studies indicate that abnormal ?-synuclein (?S), a key component of Lewy bodies, causes cognitive deficits preceded by epileptic activity. We also show that ?S-dependent synaptic and cognitive deficits and epileptic activity require endogenous tau expression. This is reminiscent of data showing that the tau-dependence of cognitive deficits and epileptic activity in the mouse models of Alzheimer?s disease (AD). Preventing epileptic activity with antiseizure drugs improves memory in models of AD, and antiseizure drugs are currently in early phase clinical trials for AD. However, antiseizure drugs have not been well investigated for ?- synucleinopathy. To better define the role of seizure activity in LBD, the following aims are proposed: Aim 1, Determine the causal relationship between the epileptiform activity and ?S-dependent cognitive deficits; Aim 2, Determine if ?S fibril inoculation model of PDD/DLB causes tau-dependent cognitive deficits mediated by epileptiform activity; and Aim 3, Define the circuitry and cellular signaling mechanisms contributing to epileptiform activity in mutant ?S models. The results of this investigation could lead to new strategies, such as antiseizure drugs and reducing tau levels, as therapies for LBD.

Alzheimer?s disease (AD) is a complex age-dependent disorder. It requires multiple approaches to comprehensively understand at a molecular level in order to develop novel diagnostics and disease modifying treatments. Astrocytes and neurons coexist in the brain and both major cell types are known to contribute to AD. The cellular phase of AD is proposed to comprise feedback and feedforward signaling between diverse brain cells as a link between the initial emergence of molecular pathology (abnormal tau and A?) and subsequent disease manifestations. Known glial cell proteins that contribute to this cellular phase are APOE and TREM2, and are associated with significantly increased risk of AD. Moreover, known astrocyte mechanisms include reactivity, which is a complex, non-binary phenomenon with sequelae that depends on context. In the past, most disease related studies have evaluated astrocytes or neurons using assessments of physiology, markers, or with gene expression evaluations. Astrocytes and neurons have not been studied in detail together or with cell-type specific proteomic methods, as proposed here and as requested by the FOA. As a result, despite advances, we have little precise information about the proteomes of astrocytes and neurons during aging in brain areas relevant to AD or in brain regions relevant to specific and defined abnormalities such as seizure activity in AD. Our overarching hypothesis is that astrocytes and neurons display protein dynamics during normal ageing and in mouse models of AD and that these changes reflect signaling between these dominant brain cells during the cellular phase of AD pathogenesis and during aberrant seizure activity and its associated cognitive decline in AD. Aim 1 will characterize cell, brain region, and compartment (plasma membrane versus cytosol) specific proteomic methods for astrocytes and neurons. Aim 2 will determine astrocyte and neuron proteomic dynamics during normal aging in mice. Aim 3 will determine astrocyte and neuron proteomic dynamics during aberrant network activity in AD model mice. Understanding the identities and the extent of cell, brain region, and compartment-specific protein changes for the major brain cell types (astrocytes and neurons) using data-driven unbiased approaches could be foundational and catalytic with regards to new opportunities for translational and mechanistic work.

PROJECT SUMMARY Up to 60% of patients with Alzheimer?s disease (AD) exhibit seizures and network hyperactivity, leading to a faster cognitive decline. Therefore, seizures in AD should be an important focus for therapeutic interventions. The microtubule-associated protein tau, a central factor in AD pathogenesis, mediates seizures and associated memory loss in models of AD, suggesting that targeting tau could effectively treat seizures in AD. However, there is a fundamental gap in understanding how tau contributes to seizures in these models. Broadly reducing tau levels successfully prevents seizures; however, reducing tau also causes deleterious effects in aged mice and the safety of this approach in the adult human brain is unknown. Therefore, a better understanding of how tau contributes to seizures is needed in order to develop more precise therapies targeting tau. The overall objective here is to identify a mechanism by which tau mediates seizures and related functional deficits in mouse models of AD and genetic epilepsy. The applicant has obtained preliminary data indicating that blocking tau?s interactions with SRC Homology 3 (SH3)-containing proteins can prevent seizures and associated memory loss in AD. The central hypothesis, based on the applicant?s preliminary data, is that tau binds to SH3-containing enzymes on its proline-rich region, and regulates network activity by modulating the activity or cellular localization of these enzymes. Previous studies, supportive of this concept, have indicated that binding between tau and the tyrosine kinase Fyn, which regulates excitatory receptors, are involved in tau?s ability to regulate seizures. The applicant?s preliminary data expands on these findings to indicate additional SH3-containing enzymes that bind tau and are involved in this phenomenon. The rationale for the proposed research is that, once it is known which enzymes are important for tau?s ability to mediate seizures, tau?s binding affinity with these enzymes can be manipulated pharmacologically, resulting in new and innovative approaches to the prevention and treatment of seizures and associated memory loss in AD. Guided by strong preliminary data in which the applicant created two novel mutant tau knockin mouse models, this hypothesis will be tested by pursuing two specific aims: 1) Determine the influence of variants in the proline-rich region of tau that prevent its binding to SH3-containing enzymes on signal transduction initiated by A? oligomers, which are epileptogenic peptides linked to AD, and excitotoxins, and 2) Determine the extent to which these variants in tau prevent seizures, behavioral deficits, and premature mortality in mouse models of AD and genetic epilepsy. The proposed research is innovative because it represents a substantive departure from the status quo by shifting focus to tau?s upstream modulation of cell signaling related to A? and excitotoxicity. This contribution is expected to be significant because it will have broad translational importance in the prevention and treatment of seizures and associated memory loss in AD.