Biology subjects

Basore, K.

Publications and source records attributed to Basore, K..

3 recordsLinked to original sources

bioRxiv2026

Intrastriatal injection of amplified Lewy body dementia (LBD) fibrils in mice results in accumulation of fibrils with LBD structure and neurodegeneration

The defining neuropathologic feature of Lewy body dementia (LBD) and Parkinson's disease (PD) is alpha-synuclein (Asyn) fibril accumulation in Lewy bodies (LBs) and Lewy neurites (LNs). Recently, we developed a method to amplify Asyn fibrils derived from human post-mortem LBD brain tissue and determined that the structure of amplified Asyn fibrils is highly similar to the structure of fibrils directly isolated from LBD brain tissue. We examined whether injection of these fibrils into humanized Asyn mice recapitulates pathologic Asyn fibril accumulation with human LBD Asyn fibril structure. We utilized mice containing a null allele in the mouse Snca gene and a human SNCA transgene. Intrastriatal injection of amplified Asyn fibrils derived from 3 different LBD autopsy cases resulted in cytoplasmic and neuritic phospho-Asyn accumulation in the striatum, cortex, and amygdala bilaterally at 3mpi. Fibril injections produced a reduction in the number of dopaminergic neurons in the substantia nigra, with LB-like inclusions in surviving neurons, and produced impaired sensorimotor function as measured on the accelerating rotarod test. Fibril accumulation increased 3.6-fold between 1 and 3 months post-injection (mpi) and was relatively stable between 3 and 5 mpi. We amplified fibrils from mouse brain tissue 5 mpi and collected single-particle cryo-EM data. High resolution 3D structural information could not be obtained because of the lack of helical twist, but comparison of the cryo-EM 2D class averages with those derived from amplified fibrils prepared from human LBD tissue revealed multiple matching classes, indicating that the Lewy fold is maintained in the fibrils that accumulate in mouse brain tissue. Our findings demonstrate an approach to model the accumulation of Asyn fibrils with LBD structure in mice, providing a platform for investigating disease mechanisms, imaging biomarkers, and therapeutics targeting Asyn in PD/LBD.

neuroscience↗

bioRxiv2023

C-terminus induced asymmetry within a Rad52 homodecamer dictates single-position Rad51 nucleation in homologous recombination

Homologous recombination (HR) is a pathway for the accurate repair of double-stranded DNA breaks. These breaks are resected to yield single-stranded DNA (ssDNA) that are coated by Replication Protein A (RPA). Saccharomyces cerevisiae Rad52 is a mediator protein that promotes HR by facilitating formation of Rad51 nucleoprotein filaments on RPA-coated ssDNA. Canonically, Rad52 has been described to function by displacing RPA to promote Rad51 binding. However, in vitro, Rad51 readily forms a filament by displacing RPA in the absence of Rad52. Yet, in vivo, Rad52 is essential for HR. Here, we resolve how Rad52 functions as a mediator using single-particle cryo-electron microscopy and biophysical approaches. We show that Rad52 functions as a homodecamer and catalyzes single-position nucleation of Rad51. The N-terminal half of Rad52 is a well-ordered ring, while the C-terminal half is disordered. An intrinsic asymmetry within Rad52 is observed, where one or a few of the C-terminal halves interact with the ordered N-terminal ring. Within the C-terminal half, we identify two conserved charged patches that harbor the Rad51 and RPA interacting motifs. Interactions between these two charged patches regulate a ssDNA binding. These features drive Rad51 binding to a single position on the Rad52 decameric ring. We propose a Rad52 catalyzed single-position nucleation model for the formation of pre-synaptic Rad51 filaments in HR.

biochemistry↗

bioRxiv2023

Structure of alpha-synuclein fibrils derived from human Lewy body dementia tissue

The defining feature of Parkinson disease (PD) and Lewy body dementia (LBD) is the accumulation of alpha-synuclein (Asyn) fibrils in Lewy bodies and Lewy neurites. We developed and validated a novel method to amplify Asyn fibrils extracted from LBD postmortem tissue samples and used solid state nuclear magnetic resonance (SSNMR) studies to determine atomic resolution structure. Amplified LBD Asyn fibrils comprise two protofilaments with pseudo-21 helical screw symmetry, very low twist and an interface formed by antiparallel beta strands of residues 85-93. The fold is highly similar to the fold determined by a recent cryo-electron microscopy study for a minority population of twisted single protofilament fibrils extracted from LBD tissue. These results expand the structural landscape of LBD Asyn fibrils and inform further studies of disease mechanisms, imaging agents and therapeutics targeting Asyn.

neuroscience↗