Cell-to-cell propagation of infectious cytosolic protein aggregates

Abstract

Prions are self-templating protein conformers that replicate by recruitment and conversion of homotypic proteins into growing protein aggregates. Originally identified as causative agents of transmissible spongiform encephalopathies, increasing evidence now suggests that prion-like phenomena are more common in nature than previously anticipated. In contrast to fungal prions that replicate in the cytoplasm, propagation of mammalian prions derived from the precursor protein PrP is confined to the cell membrane or endocytic vesicles. Here we demonstrate that cytosolic protein aggregates can also behave as infectious entities in mammalian cells. When expressed in the mammalian cytosol, protein aggregates derived from the prion domain NM of yeast translation termination factor Sup35 persistently propagate and invade neighboring cells, thereby inducing a self-perpetuating aggregation state of NM. Cell contact is required for efficient infection. Aggregates can also be induced in primary astrocytes, neurons, and organotypic cultures, demonstrating that this phenomenon is not specific to immortalized cells. Our data have important implications for understanding prion-like phenomena of protein aggregates associated with human diseases and for the growing number of amyloidogenic proteins discovered in mammals.

Epigenetics and developmental programming of welfare and production traits in farm animals

“…Pioneering studies with prion proteins (PrP) in lower eukaryotes (i.e. yeast and filamentous fungi) have revealed that they can act as 'epigenetic' elements and can account, at least in part, for non-Mendelian patterns of inheritance for several traits (Hofmann et al 2013). Mammalian prions share many common features with their counterparts in yeast, but their function and patterns of inheritance are less well known.…”

Sequence-dependent Internalization of Aggregating Peptides

“…Recently, it has been demonstrated that several disease-associated aggregates, including human (1-3) and yeast prions (4), A␤ (5), Tau (6), ␣-synuclein (7), SOD1 (8), and PolyQ (9), can cross cellular membranes and spread aggregation from cell to cell (10). This has led to the notion that all of these proteins potentially possess a certain degree of prionoid behavior (8,11,12).…”

Glycosylphosphatidylinositol Anchoring Directs the Assembly of Sup35NM Protein into Non-fibrillar, Membrane-bound Aggregates

“…Tethering to membranes and clustering in lipid raft domains may increase the effective local concentration of GPI-anchored Sup35NM such that a critical concentration for spontaneous aggregation can be reached, as has been reported previously (77). Such spontaneous aggregates have not been observed in systems where Sup35 is expressed in the cytosol (57,58), possibly because in this environment, where proteins are less restricted, the local critical concentration required for aggregation is not GPI were stained without permeabilization with anti-GFP primary antibody and secondary antibody conjugated to HRP, which catalyzes the conversion of DAB substrate into a product detectable by TEM. Staining was present all along the surface membranes of transfected cells, with occasional small regions of more intense staining in both GFP GPI and Sup35-GFP GPI -Sol cells (arrowheads).…”

“…Ure2p) form amyloid in the yeast cytosol (56). In previous studies, we and others reported that Sup35NM is able to propagate as a prion in mammalian cells (47,57,58) and that GPI anchoring facilitates aggregate propagation between N2a cells, resembling mammalian prion behavior (47). In the present work, we go on to characterize the ultrastructural and biochemical features of GPI-anchored Sup35NM aggregates.…”