475 Impact of secretome derived from stool samples of patients with multiple system atrophy in alpha-synuclein oligomerization

Objectives/Goals: This study investigates the contribution of the stool secretome (the soluble factors secreted by microbes into extracellular space) to in vitro α-synuclein (αSyn) oligomerization using stool cultures from patients with multiple system atrophy (MSA), a rare neurodegenerative disease hallmarked by pathologic αSyn aggregates. Methods/Study Population: Stool samples from MSA patients (n = 20), household controls (n = 20), and healthy controls (n = 20) will be cultured using an adapted dilution-to-extinction approach. The goal is to reduce microbial complexity progressively to produce random secretome combinations that may affect αSyn oligomerization differentially. The original inoculant and dilutions will be cultured anaerobically to collect conditioned media (CM) enriched with microbial secretomes. CM will be used to expose a fluorescence resonance energy transfer (FRET) biosensor assay and a Gaussia luciferase protein complementation assay – both modified to quantify αSyn-αSyn interaction indicating oligomerization. Any CM-altering αSyn oligomerization will undergo multiomic characterization to identify potential causative agent(s). Results/Anticipated Results: Specific microbe-produced molecules from the literature are anticipated to modulate αSyn oligomerization, identified by targeted, reductionist studies that selected and tested separately single microbial factors on αSyn aggregation in vitro and in vivo. From these studies, lipopolysaccharide and bacterial amyloid protein are expected to increase αSyn oligomerization, while short-chain fatty acids, such as butyrate, are expected to interfere with and decrease oligomerization. As a complementary systemic approach, this study’s agnostic methods involving MSA stool culture combined with the proposed dilution-to-extinction method are expected to identify additional MSA stool secretome components modulating αSyn oligomerization that might otherwise be missed in earlier reductionist approaches. Discussion/Significance of Impact: Completion of this reverse-translational work will aid in discovering MSA stool secretome components modulating αSyn oligomerization. Identification of specific factors contributing to pathologic αSyn behavior might set the stage for patient screenings for identified stool markers and could lead to microbiome-based interventions for MSA.