Defined α-synuclein prion-like molecular assemblies spreading in cell culture

Background: α-Synuclein (α-syn) plays a central role in the pathogenesis of synucleinopathies, a group of neurodegenerative disorders that includes Parkinson disease, dementia with Lewy bodies and multiple system atrophy. Several findings from cell culture and mouse experiments suggest intercellular α-syn transfer.Results: Through a methodology used to obtain synthetic mammalian prions, we tested whether recombinant human α-syn amyloids can promote prion-like accumulation in neuronal cell lines in vitro. A single exposure to amyloid fibrils of human α-syn was sufficient to induce aggregation of endogenous α-syn in human neuroblastoma SH-SY5Y cells. Remarkably, endogenous wild-type α-syn was sufficient for the formation of these aggregates, and overexpression of the protein was not required.Conclusions: Our results provide compelling evidence that endogenous α-syn can accumulate in cell culture after a single exposure to exogenous α-syn short amyloid fibrils. Importantly, using α-syn short amyloid fibrils as seed, endogenous α-syn aggregates and accumulates over several passages in cell culture, providing an excellent tool for potential therapeutic screening of pathogenic α-syn aggregates

Defined \u3b1-synuclein prion-like molecular assemblies spreading in cell culture

BACKGROUND: \u3b1-Synuclein (\u3b1-syn) plays a central role in the pathogenesis of synucleinopathies, a group of neurodegenerative disorders that includes Parkinson disease, dementia with Lewy bodies and multiple system atrophy. Several findings from cell culture and mouse experiments suggest intercellular \u3b1-syn transfer. RESULTS: Through a methodology used to obtain synthetic mammalian prions, we tested whether recombinant human \u3b1-syn amyloids can promote prion-like accumulation in neuronal cell lines in vitro. A single exposure to amyloid fibrils of human \u3b1-syn was sufficient to induce aggregation of endogenous \u3b1-syn in human neuroblastoma SH-SY5Y cells. Remarkably, endogenous wild-type \u3b1-syn was sufficient for the formation of these aggregates, and overexpression of the protein was not required. CONCLUSIONS: Our results provide compelling evidence that endogenous \u3b1-syn can accumulate in cell culture after a single exposure to exogenous \u3b1-syn short amyloid fibrils. Importantly, using \u3b1-syn short amyloid fibrils as seed, endogenous \u3b1-syn aggregates and accumulates over several passages in cell culture, providing an excellent tool for potential therapeutic screening of pathogenic \u3b1-syn aggregates

Systemic α-synuclein injection triggers selective neuronal pathology as seen in patients with Parkinson’s disease

Parkinson’s disease (PD) is an α-synucleinopathy characterized by the progressive loss of specific neuronal populations. Here, we develop a novel approach to transvascularly deliver proteins of complex quaternary structures, including α-synuclein preformed fibrils (pff). We show that a single systemic administration of α-synuclein pff triggers pathological transformation of endogenous α-synuclein in non-transgenic rats, which leads to neurodegeneration in discrete brain regions. Specifically, pff-exposed animals displayed a progressive deterioration in gastrointestinal and olfactory functions, which corresponded with the presence of cellular pathology in the central and enteric nervous systems. The α-synuclein pathology generated was both time dependent and region specific. Interestingly, the most significant neuropathological changes were observed in those brain regions affected in the early stages of PD. Our data therefore demonstrate for the first time that a single, transvascular administration of α-synuclein pff can lead to selective regional neuropathology resembling the premotor stage of idiopathic PD. Furthermore, this novel delivery approach could also be used to deliver a range of other pathogenic, as well as therapeutic, protein cargos transvascularly to the brain

Wiring through tunneling nanotubes--from electrical signals to organelle transfer

Tunneling nanotubes (TNTs) represent a subset of F-actin-based transient tubular connections that allow direct communication between distant cells. Recent studies have provided new insights into the existence of TNTs in vivo, and this novel mechanism of intercellular communication is implicated in various essential processes, such as development, immunity, tissue regeneration and transmission of electrical signals. TNTs are versatile structures known to facilitate the transfer of various cargos, such as organelles, plasma membrane components, pathogens and Ca(2+). Recently, a new function of TNTs in the long-range transfer of electrical signals that involves gap junctions has been suggested. This indicates that different types of TNTs might exist, and supports the notion that TNTs might not be just passive open conduits but rather are regulated by gating mechanisms. Furthermore, TNTs have been found in different cell lines and are characterized by their diversity in terms of morphology. Here we discuss these novel findings in the context of the two models that have been proposed for TNT formation, and focus on putative proteins that could represent TNT specific markers. We also shed some light on the molecular mechanisms used by TNTs to transfer cargos, as well as chemical and electrical signals

Identification and characterization of tunneling nanotubes for intercellular trafficking

Tunneling nanotubes (TNTs) are thin membranous channels providing direct cytoplasmic connection between remote cells. They are commonly observed in different cell cultures and increasing evidence supports their role in intercellular communication and pathogen transfer. However, the study of TNTs presents several pitfalls (e.g., difficulty in preserving such delicate structures, possible confusionwith other protrusions, structural and functional heterogeneity, etc.) and therefore requires thoroughly designed approaches. The methods described in this unit represent a guideline for the characterization of TNTs (or TNT-like structures) in cell culture. Specifically, optimized protocols to (1) identify TNTs and the cytoskeletal elements present inside them; (2) evaluate TNT frequency in cell culture; (3) unambiguously distinguish them from other cellular connections or protrusions; and (4) monitor their formation in living cells are provided. Finally, this unit describes how to assess TNT-mediated cell-to-cell transfer of cellular components, which is a fundamental criterion for identifying functional TNTs

Tunneling nanotubes: A possible highway in the spreading of tau and other prion-like proteins in neurodegenerative diseases

The mechanisms of intercellular spreading of amyloidogenic proteins involved in neurodegenerative diseases have yet to be fully elucidated. While secretion has been implicated in the transfer of many proteins, including prions and α-synuclein, tunneling nanotubes (TNTs) have also been demonstrated for prions and mutant Huntingtin. Here, we provide further evidence that Tau aggregates, which have been demonstrated to predominantly be transferred via secretion, can also be found in TNTs. Additionally, cells that have taken up Tau have increased TNT formation. Coupled with previous evidence that other amyloidogenic aggregates also induce TNT formation we propose that misfolded protein aggregates can, through a common mechanism, promote the formation of TNTs and thereby their own intercellular transfer, contributing to the propagation of pathology

Transfer of mitochondria via tunneling nanotubes rescues apoptotic PC12 cells

Tunneling nanotubes (TNTs) are F-actin-based membrane tubes that form between cells in culture and in tissues. They mediate intercellular communication ranging from electrical signalling to the transfer of organelles. Here, we studied the role of TNTs in the interaction between apoptotic and healthy cells. We found that pheochromocytoma (PC) 12 cells treated with ultraviolet light (UV) were rescued when cocultured with untreated PC12 cells. UV-treated cells formed a different type of TNT with untreated PC12 cells, which was characterized by continuous microtubule localized inside these TNTs. The dynamic behaviour of mCherry-tagged end-binding protein 3 and the accumulation of detyrosinated tubulin in these TNTs indicate that they are regulated structures. In addition, these TNTs show different biophysical properties, for example, increased diameter allowing dye entry, prolonged lifetime and decreased membrane fluidity. Further studies demonstrated that microtubule-containing TNTs were formed by stressed cells, which had lost cytochrome c but did not enter into the execution phase of apoptosis characterized by caspase-3 activation. Moreover, mitochondria colocalized with microtubules in TNTs and transited along these structures from healthy to stressed cells. Importantly, impaired formation of TNTs and untreated cells carrying defective mitochondria were unable to rescue UV-treated cells in the coculture. We conclude that TNT-mediated transfer of functional mitochondria reverse stressed cells in the early stages of apoptosis. This provides new insights into the survival mechanisms of damaged cells in a multicellular context