After decades of intense effort, two disease-modifying drugs for Alzheimer's disease (AD) have been recently
approved by the FDA: aducanumab and lecanemab. Although these drugs represent a major advance in AD
therapeutics, they have limitations: modest clinical benefit and side effects (brain edema and hemorrhage).
Additional therapies targeting new AD mechanisms are desperately needed to improve clinical benefit and
reduce side effects. Moreover, precision medicine for AD will require a panoply of drugs targeting different AD
mechanisms that will allow tailoring a combination therapy to the individual patient. The goal of this R01 is to
explore the therapeutic potential of inhibiting one such AD mechanism, that of Aβ-induced membrane damage.
Amyloid plaques consisting of the β-amyloid (Aβ) peptide and neurofibrillary tangles (NFTs) composed of
hyperphosphorylated tau protein are hallmarks of AD brain. Amyloid plaques accumulate many years before
NFTs arise. Aβ appears to be toxic to neurons surrounding plaques, causing molecular and cellular alterations
that lead to tau pathology, synapse loss, neuron death, and ultimately memory impairment and dementia.
However, the mechanism connecting Aβ with tau hyperphosphorylation and pathology is unknown and one of
the great mysteries of AD. A clue could come from dystrophic neurites (DNs), an understudied AD pathology
that is mostly of axonal origin and tightly associated with the borders of amyloid plaques. DN morphology
suggests that direct axon contact with the Aβ plaque is necessary for the formation of DNs. Our results indicate
that Aβ interaction with the axon plasma membrane causes plasmalemma damage, Ca2+ leakage, kinase
activation, microtubule disruption, axonal transport impairment, tau hyperphosphorylation, and DN formation.
Importantly, our preliminary results show that overexpression of the membrane repair protein annexin A6 in the
5XFAD mouse model of amyloid pathology reduces the formation of DNs and the accumulation of tau
phosphorylated at threonine 181 (p-tau181), an early biomarker of amyloid pathology in AD. Other work suggests
that DNs are crucibles of AD tau phosphorylation, seeding, and spreading. In this R01, we will investigate annexin
A6-mediated membrane repair following Aβ-induced membrane damage and DN formation (Aim 1) and reduction
of p-tau accumulation and the seeding and spreading of AD tau (Aim 2) in vitro and in vivo. Finally, we will
investigate recombinant annexin A6-mediated membrane repair and reduction of DN formation, p-tau
accumulation, and AD tau seeding and spreading (Aim 3). We will use a combination of molecular (immunoblot
analysis, biochemical assays), cellular (laser injury, dye penetration, immunohistochemistry, calcium imaging,
EM), electrophysiological (LTP) and cognitive (water maze, fear conditioning, novel object recognition, Y-maze)
approaches to accomplish these Aims. These experiments will serve as therapeutic proof-of-concept supporting
annexin A6 for the prevention or treatment of AD.