The ASC Protein Controls the Severity of Systemic AA Amyloidosis in Mice
Abstract
The apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) protein is a component of inflammasomes, inflammation-mediating complexes that include Nucleotide-Binding Oligomerization Domain, Leucine Rich Repeat And Pyrin Domain Containing 3 (NLRP3). ASC and NLRP3 components aggregate to form ASC specks, which can cross-seed Aβ aggregation in Alzheimer’s disease (AD). Here we asked whether ASC is involved in additional protein misfolding diseases (PMDs). AA amyloidosis is a severe complication of chronic inflammatory conditions caused by the aggregation of Serum Amyloid A (SAA) protein. Since AA and Aβ aggregates share similar biochemical properties, such as β-sheet structures, we hypothesized that ASC inflammasomes may be involved in SAA/AA recruitment, aggregation, processing and removal. We therefore investigated the role of ASC in AA amyloidosis in vivo , employing a murine AA amyloidosis model in Asc -ablated mice. We show that ASC exerts a crucial role in SAA recruitment in the presence of AA fibrils, that splenic AA amyloid load was decreased in Asc -/- mice, that the presence of ASC accelerates SAA fibril formation and that ASC is important for SAA-activated phagocytosis of macrophages. We conclude that ASC modulates both SAA serum levels and the severity of AA amyloidosis in mice. ASC may represent a therapeutic target in AA as well as other amyloidosis entities.
