Viral M45 and necroptosis-associated proteins form heteromeric amyloid assemblies.

The murine cytomegalovirus protein M45 protects infected mouse cells from necroptotic death and, when heterologously expressed, can protect human cells from necroptosis induced by tumour necrosis factor receptor (TNFR) activation. Here, we show that the N-terminal 90 residues of the M45 protein, which contain a RIP homotypic interaction motif (RHIM), are sufficient to confer protection against TNFR-induced necroptosis. This N-terminal region of M45 drives rapid self-assembly into homo-oligomeric amyloid fibrils and interacts with the RHIMs of the human kinases RIPK1 and RIPK3, and the Z-DNA binding protein 1 (ZBP1), to form heteromeric amyloid fibrils Mutation of the tetrad residues in the M45 RHIM attenuates homo- and hetero-amyloid assembly by M45, suggesting that the amyloidogenic nature of the M45 RHIM underlies its biological activity.

EspL is a bacterial cysteine protease effector that cleaves RHIM proteins to block necroptosis and inflammation.

Cell death signalling pathways contribute to tissue homeostasis and provide innate protection from infection. Adaptor proteins such as receptor-interacting serine/threonine-protein kinase 1 (RIPK1), receptor-interacting serine/threonine-protein kinase 3 (RIPK3), TIR-domain-containing adapter-inducing interferon-β (TRIF) and Z-DNA-binding protein 1 (ZBP1)/DNA-dependent activator of IFN-regulatory factors (DAI) that contain receptor-interacting protein (RIP) homotypic interaction motifs (RHIM) play a key role in cell death and inflammatory signalling. RHIM-dependent interactions help drive a caspase-independent form of cell death termed necroptosis.

Self-assembly of MPG1, a hydrophobin protein from the rice blast fungus that forms functional amyloid coatings, occurs by a surface-driven mechanism.

Rice blast is a devastating disease of rice caused by the fungus Magnaporthe oryzae and can result in loss of a third of the annual global rice harvest. Two hydrophobin proteins, MPG1 and MHP1, are highly expressed during rice blast infections. These hydrophobins have been suggested to facilitate fungal spore adhesion and to direct the action of the enzyme cutinase 2, resulting in penetration of the plant host.

Membrane-bound tetramer and trimer Aβ oligomeric species correlate with toxicity towards cultured neurons.

Amyloid beta (Aβ) peptide is the major constituent of the extracellular amyloid plaques deposited in the brains of Alzheimer's disease patients and is central to the pathogenic pathway causing this disease. The identity of the neurotoxic Aβ species remains elusive. We previously reported that Aβ toxicity correlates strongly with its neuronal cell binding leading us to hypothesize that neuronal cell death is caused by the binding of a specific oligomeric Aβ species.

Stabilization of nontoxic Aβ-oligomers: insights into the mechanism of action of hydroxyquinolines in Alzheimer's disease.

The extracellular accumulation of amyloid β (Aβ) peptides is characteristic of Alzheimer's disease (AD). However, formation of diffusible, oligomeric forms of Aβ, both on and off pathways to amyloid fibrils, is thought to include neurotoxic species responsible for synaptic loss and neurodegeneration, rather than polymeric amyloid aggregates. The 8-hydroxyquinolines (8-HQ) clioquinol (CQ) and PBT2 were developed for their ability to inhibit metal-mediated generation of reactive oxygen species from Aβ:Cu complexes and have both undergone preclinical and Phase II clinical development for the treatment of AD.

The N-terminal residues 43 to 60 form the interface for dopamine mediated α-synuclein dimerisation.

α-synuclein (α-syn) is a major component of the intracellular inclusions called Lewy bodies, which are a key pathological feature in the brains of Parkinson's disease patients. The neurotransmitter dopamine (DA) inhibits the fibrillisation of α-syn into amyloid, and promotes α-syn aggregation into SDS-stable soluble oligomers. While this inhibition of amyloid formation requires the oxidation of both DA and the methionines in α-syn, the molecular basis for these processes is still unclear.

Fungal Hydrophobin Proteins Produce Self-Assembling Protein Films with Diverse Structure and Chemical Stability.

Hydrophobins are small proteins secreted by fungi and which spontaneously assemble into amphipathic layers at hydrophilic-hydrophobic interfaces. We have examined the self-assembly of the Class I hydrophobins EAS and DewA, the Class II hydrophobin NC2 and an engineered chimeric hydrophobin. These Class I hydrophobins form layers composed of laterally associated fibrils with an underlying amyloid structure.

Functional amyloid: widespread in Nature, diverse in purpose.

Amyloids are insoluble fibrillar protein deposits with an underlying cross-β structure initially discovered in the context of human diseases. However, it is now clear that the same fibrillar structure is used by many organisms, from bacteria to humans, in order to achieve a diverse range of biological functions. These functions include structure and protection (e.

The interplay between lipids and dopamine on α-synuclein oligomerization and membrane binding.

The deposition of α-syn (α-synuclein) as amyloid fibrils and the selective loss of DA (dopamine) containing neurons in the substantia nigra are two key features of PD (Parkinson's disease). α-syn is a natively unfolded protein and adopts an α-helical conformation upon binding to lipid membrane. Oligomeric species of α-syn have been proposed to be the pathogenic species associated with PD because they can bind lipid membranes and disrupt membrane integrity.

Guanidine hydrochloride denaturation of dopamine-induced α-synuclein oligomers: a small-angle X-ray scattering study.

Alpha-synuclein (α-syn) forms the amyloid-containing Lewy bodies found in the brain in Parkinson's disease. The neurotransmitter dopamine (DA) reacts with α-syn to form SDS-resistant soluble, non-amyloid, and melanin-containing oligomers. Their toxicity is debated, as is the nature of their structure and their relation to amyloid-forming conformers of α-syn.

SERF protein is a direct modifier of amyloid fiber assembly.

The inherent cytotoxicity of aberrantly folded protein aggregates contributes substantially to the pathogenesis of amyloid diseases. It was recently shown that a class of evolutionary conserved proteins, called MOAG-4/SERF, profoundly alter amyloid toxicity via an autonomous but yet unexplained mode. We show that the biological function of human SERF1a originates from its atypical ability to specifically distinguish between amyloid and nonamyloid aggregation.

The amyloid precursor protein copper binding domain histidine residues 149 and 151 mediate APP stability and metabolism.

One of the key pathological hallmarks of Alzheimer disease (AD) is the accumulation of the APP-derived amyloid β peptide (Aβ) in the brain. Altered copper homeostasis has also been reported in AD patients and is thought to increase oxidative stress and to contribute to toxic Aβ accumulation and regulate APP metabolism. The potential involvement of the N-terminal APP copper binding domain (CuBD) in these events has not been investigated.

The hypoxia imaging agent CuII(atsm) is neuroprotective and improves motor and cognitive functions in multiple animal models of Parkinson's disease.

Parkinson's disease (PD) is a progressive, chronic disease characterized by dyskinesia, rigidity, instability, and tremors. The disease is defined by the presence of Lewy bodies, which primarily consist of aggregated α-synuclein protein, and is accompanied by the loss of monoaminergic neurons. Current therapeutic strategies only give symptomatic relief of motor impairment and do not address the underlying neurodegeneration.

The neuroprotective domains of the amyloid precursor protein, in traumatic brain injury, are located in the two growth factor domains.

The amyloid precursor protein (APP) is known to increase following traumatic brain injury (TBI). This increase in levels of APP may be deleterious to outcome due to the production of neurotoxic Aβ. Conversely, this upregulation may be beneficial as cleavage of APP via the alternative non-amyloidogenic pathway produces the soluble α form of APP (sAPPα), which is known to have many neuroprotective and neurotrophic functions.

A structural model for apolipoprotein C-II amyloid fibrils: experimental characterization and molecular dynamics simulations.

The self-assembly of specific proteins to form insoluble amyloid fibrils is a characteristic feature of a number of age-related and debilitating diseases. Lipid-free human apolipoprotein C-II (apoC-II) forms characteristic amyloid fibrils and is one of several apolipoproteins that accumulate in amyloid deposits located within atherosclerotic plaques. X-ray diffraction analysis of aligned apoC-II fibrils indicated a simple cross-β-structure composed of two parallel β-sheets.

The structure of dopamine induced alpha-synuclein oligomers.

Inclusions of aggregated alpha-synuclein (alpha-syn) in dopaminergic neurons are a characteristic histological marker of Parkinson's disease (PD). In vitro, alpha-syn in the presence of dopamine (DA) at physiological pH forms SDS-resistant non-amyloidogenic oligomers. We used a combination of biophysical techniques, including sedimentation velocity analysis, small angle X-ray scattering (SAXS) and circular dichroism spectroscopy to study the characteristics of alpha-syn oligomers formed in the presence of DA.

Modulation of alpha-synuclein aggregation by dopamine: a review.

Parkinson's disease (PD) is a progressive neurodegenerative disorder that is characterized by (1) the selective loss of dopaminergic neurons in the substantia nigra and (2) the deposition of misfolded alpha-synuclein (alpha-syn) as amyloid fibrils in the intracellular Lewy bodies in various region of the brain. Current thinking suggests that an interaction between alpha-syn and dopamine (DA) leads to the selective death of neuronal cells and the accumulation of misfolded alpha-syn. However, the exact mechanism by which this occurs is not fully defined.

Dopamine and the dopamine oxidation product 5,6-dihydroxylindole promote distinct on-pathway and off-pathway aggregation of alpha-synuclein in a pH-dependent manner.

The deposition of alpha-synuclein (alpha-syn) aggregates in dopaminergic neurons is a key feature of Parkinson's disease. While dopamine (DA) can modulate alpha-syn aggregation, it is unclear which other factors can regulate the actions of DA on alpha-syn. In this study, we investigated the effect of solution conditions (buffer, salt and pH) on the oligomerization of alpha-syn by DA.

Formation of dopamine-mediated alpha-synuclein-soluble oligomers requires methionine oxidation.

alpha-Synuclein is the major component of the intracellular Lewy body inclusions present in Parkinson disease (PD) neurons. PD involves the loss of dopaminergic neurons in the substantia nigra and the subsequent depletion of dopamine (DA) in the striatum. DA can inhibit alpha-synuclein fibrillization in vitro and promote alpha-synuclein aggregation into soluble oligomers.

MLPA diagnostics of complex microbial communities: relative quantification of bacterial species in oral biofilms.

A multitude of molecular methods are currently used for identification and characterization of oral biofilms or for community profiling. However, multiplex PCR techniques that are able to routinely identify several species in a single assay are not available. Multiplex Ligation-dependent Probe Amplification (MLPA) identifies up to 45 unique fragments in a single tube PCR.

Cu2+ binding modes of recombinant alpha-synuclein--insights from EPR spectroscopy.

The interaction of the small (140 amino acid) protein, alpha-synuclein (alphaS), with Cu(2+) has been proposed to play a role in Parkinson's disease (PD). While some insight from truncated model complexes has been gained, the nature of the corresponding Cu(2+) binding modes in the full length protein remains comparatively less well characterized. This work examined the Cu(2+) binding of recombinant human alphaS using Electron Paramagnetic Resonance (EPR) spectroscopy.

Apolipoprotein C-II amyloid fibrils assemble via a reversible pathway that includes fibril breaking and rejoining.

Alzheimer's and several other diseases are characterized by the misfolding and assembly of protein subunits into amyloid fibrils. Current models propose that amyloid fibril formation proceeds via the self-association of several monomers to form a nucleus, which then elongates by the addition of monomer to form mature fibrils. We have examined the concentration-dependent kinetics of apolipoprotein C-II amyloid fibril formation and correlated this with the final size distribution of the fibrils determined by sedimentation velocity experiments.

Phospholipid interaction induces molecular-level polymorphism in apolipoprotein C-II amyloid fibrils via alternative assembly pathways.

A common feature of many of the most important and prominent amyloid-forming proteins is their ability to bind lipids and lipid complexes. Lipids are ubiquitous components of disease-associated amyloid plaques and deposits in humans, yet the specific roles of lipid in the process of amyloid fibril formation are poorly understood. This study investigated the effect of phospholipids on amyloid fibril formation by human apolipoprotein (apo) C-II using phosphatidylcholine derivatives comprising acyl chains of up to 14 carbon atoms.

Oxidized cholesterol metabolites found in human atherosclerotic lesions promote apolipoprotein C-II amyloid fibril formation.

Apolipoprotein amyloid deposits and lipid oxidation products are colocalized in human atherosclerotic tissue. In this study we show that the primary ozonolysis product of cholesterol, 3beta-hydroxy-5-oxo-5,6-secocholestan-6-al (KA), rapidly promotes human apolipoprotein (apo) C-II amyloid fibril formation in vitro. Previous studies show that hydrophobic aldehydes, including KA, modify proteins by the formation of a Schiff base with the lysine epsilon-amino group or N-terminal amino group.