UC Irvine

ABSTRACT OF THE DISSERTATION

Characterization of a pathogenic conformation of amyloid immunoreactivity in Alzheimer’s Disease and Cerebral Amyloid Angiopathy

By

Ricardo Albay III

Doctor of Philosophy in Biological Sciences

University of California, Irvine, 2018

Professor Charles G. Glabe, Chair

The deposition of the amyloid β protein (Aβ) in the brain as plaques and the formation of neurofibrillary tangles (NFT) filled with hyper-phosphorylated tau are the canonical histopathological hallmarks of Alzheimer’s disease (AD). The genetics of early onset, familial Alzheimer’s disease (fAD) supports a causal role of Aβ in AD pathogenesis. However, plaques do not correlate with dementia and therapeutic strategies inhibiting the production of soluble Aβ or leveraging monoclonal antibodies to target the removal of monomeric Aβ have produced disappointing results. Despite the therapeutic pitfalls that sequence specific antibodies have faced, conformation dependent monoclonal antibodies provide an invaluable tool to investigate specific conformations of protein aggregates whose relative abundance may prove significant to the pathogenesis of disease. By investigating the pathological significance of a unique subpopulation of vascular amyloid we addressed a knowledge gap that exists in understanding the role conformational diversity of amyloid structure plays in Alzheimer’s pathology. The data presented here demonstrate that monoclonal antibodies recognize deposits in human and transgenic mouse brain that are spatially, temporally, and morphologically diverse (Chapter 1). We report a unique immunoreactivity in vascular smooth muscle cells (VSMC) that correlates with plaque pathology and a loss of α-actin immunoreactivity in AD brains and transgenic mouse models of AD (Chapter 2). We investigated whether mOC31 immunoreactivity was associated with markers of inflammation, including the activation of microglia, presence of pro-inflammatory signals interleukin-1β (IL1β) and high-mobility group box 1 (HMGB1); we found that HMGB1 is colocalized with mOC31 immunoreactivity in the cytosol of VSMC (Chapter 2). To address the causative link between Aβ and mOC31 immunoreactivity with the observed loss of α-actin immunoreactivity we developed an in vitro model utilizing primary human brain vascular smooth muscle cells (HBVSMC). In this model, we found that exogenous treatment with Aβ40-WT and Aβ40-A21G was sufficient to induce the loss of α-actin immunoreactivity observed in human and transgenic mouse brain (Chapter 3). Furthermore, we report a loss of membrane integrity and a direct interaction between Aβ and α-actin. These results suggest that Aβ may have both indirect and direct effects on VSMC phenotype. Our findings demonstrate that amyloid heterogeneity is a significant factor to consider in the development of disease modifying therapeutics.