C-terminal Globular Domain Research Articles

Purification and Assays of Tachylectin-5.

Tachylectin-5, a 41-kDa protein with a common fold of the C-terminal globular domain of the γ-chain of fibrinogen, is purified from horseshoe crab hemolymph plasma by affinity column chromatography, using acetyl-group-immobilized resin. Two types of isolectins, tachylectin-5A and tachylectin-5B, are obtained by stepwise elution with GlcNAc at 25 and 250mM, respectively. Tachylectins-5A and -5B exhibit extraordinarily strong hemagglutinating activity against all types of human erythrocytes (the minimum agglutinating concentration of 0.004-0.008μg/mL for tachylectin-5A and 0.077-0.27μg/mL for tachylectin-5B). Their hemagglutinating activities are inhibited by acetyl group-containing sugars and noncarbohydrates such as sodium acetate, acetylcholine, and acetyl CoA (the minimum inhibitory concentrations of 1.3-1.6mM), indicating that the acetyl group is required and sufficient for recognition by tachylectins-5A and -5B. EDTA inhibits their hemagglutinating activity, whereas the inhibition is overcome by adding an excess amount of Ca2+. Tachylectins-5A and -5B also exhibit bacterial agglutinating activity against both Gram-negative bacteria (the minimum agglutinating concentrations of 0.04-0.08μg/mL for tachylectin-5A and 0.05-0.11μg/mL for tachylectin-5B) and Gram-positive bacteria (the minimum agglutinating concentrations of 0.3-2.4μg/mL for tachylectin-5A and 15.1-26.8μg/mL for tachylectin-5B). Interestingly, tachylectins-5A and -5B enhance the antimicrobial activity of a hemocyte-derived peptide, big defensin.

YspD: A Potential Therapeutic Target for Drug Design to Combat Yersinia enterocolitica Infection

YspD is an annotated hydrophilic translocator of Ysa–Ysp type III secretion system of Yersinia enterocolitica. YspD has sequence, secondary structure and three-dimensional structure similar to other hydrophilic translocators. All hydrophilic translocators lack transmembrane region and possess intramolecular coiled-coil region. Disordered regions are mostly clustered at the N-terminal. Large loops provide flexibility, allowing conformational changes during oligomerization and protein–protein interaction. LcrV and PcrV have globular N-terminal and C-terminal domains, connected by intramolecular coiled-coil region. YspD, IpaD, SipD and BipD lack globular N-terminal and C-terminal domains. Their N-terminal and C-terminal domain have a bundle like structure connected by the intramolecular coiled-coil. The intramolecular coiled-coil regions (helix-5&9) of YspD showed maximum conservation, followed by helices at N-terminal. Polar interactions are mainly involved during dimerization of YspD, involving polar residues from helix-9 of both the YspD molecules. A methionine forms the boundary of interaction between the two YspD molecules. The two YspD molecules are arranged in antiparallel fashion to form the dimer. N-terminal of YspB interacted with C-terminal of YspD molecule to form a pentameric complex, consisting four YspD molecules and one YspB molecule. Sequence, structural similarity and presence of specific motifs in YspD (like chaperone protein) indicate the ability of N-terminal domain to show self-chaperoning activity and regulate folding and conformational state of YspD during its journey from the bacterial cytoplasm to the needle tip. Structural analysis of YspD and its mechanism of interaction with other proteins would enable us to design drugs against this hydrophilic protein to combat Yersinia infection.

Bipartite mechanism for laminin-integrin interactions: Identification of the integrin-binding site in LG domains of the laminin α chain

Laminins are major cell-adhesive proteins consisting of α, β, and γ chains, in which the three C-terminal globular domains of the α chain (LMα/LG1–3) and the C-terminal tail region of the γ1 chain (LMγ1-tail) are required for binding to integrin. Despite the recent progress on the role of LMγ1-tail in coordinating the metal ion-dependent adhesion site of the integrin β subunit, the mechanism by which LMα/LG1–3 interacts with integrin remains to be elucidated. We found that basic residues on the bottom face of LMα5/LG2 are required for binding laminin-511 to α6β1 integrin. Intermolecular cysteine scanning assays demonstrated that the basic residues in LMα5/LG2 were in contact with the acidic residues within the laminin-binding X1 region of the integrin α subunit in the laminin-integrin complex. These results indicate that LMα5/LG2 interacts directly with the integrin α subunit and comprises a bipartite integrin binding site of laminin-511 with the LMγ1-tail.

Mutations in Prion Protein Gene: Pathogenic Mechanisms in C-Terminal vs. N-Terminal Domain, a Review.

Inherited mutations in the Prion protein (PrP), encoded by the PRNP gene, have been associated with autosomal dominant neurodegenerative disorders, such as Creutzfeldt–Jacob disease (CJD), Gerstmann–Sträussler–Scheinker syndrome (GSS), and Fatal Familial Insomnia (FFI). Notably, PRNP mutations have also been described in clinical pictures resembling other neurodegenerative diseases, such as frontotemporal dementia. Regarding the pathogenesis, it has been observed that these point mutations are located in the C-terminal region of the PRNP gene and, currently, the potential significance of the N-terminal domain has largely been underestimated. The purpose of this report is to review and provide current insights into the pathogenic mechanisms of PRNP mutations, emphasizing the differences between the C- and N-terminal regions and focusing, in particular, on the lesser-known flexible N-terminal, for which recent biophysical evidence has revealed a physical interaction with the globular C-terminal domain of the cellular prion protein (PrPC).

C1Q/TNF-related protein 4 expression correlates with herpes simplex encephalitis progression.

Herpes simplex encephalitis (HSE), an acute inflammatory disease of the central nervous system is caused by the herpes simplex virus infection. HSE occurs at any age, and it is often accompanied by high mortality and neurological dysfunction. The C1Q/TNF-related protein (CTRP) family, usually contains a homotrimeric structure, which comprises the N-terminal signal peptide and the C-terminal C1q globular domain. It has been demonstrated that CTRPs play pivotal roles in the inflammation process. CTRP4 is a member of the CTRP family and contains two C1q globular domains. Moreover, evidence shows that the recombinant human CTRP4 (rhCTRP4) protein exerts satisfactory anti-inflammatory effects in experimental colitis models via the NF-κB pathway. However, its role in inflammation-related neurological diseases remains unknown. The purpose of this study is to evaluate the expression of CTRP4 and its correlation with HSE progression. We determined the serum CTRP4 levels in a normal brain, tuberculous meningitis (TBM), bacterial meningitis (BM) and HSE. We found that compared to a normal brain, TBM and BM, CTRP4 was significantly increased in HSE. Moreover, in the course of HSE, serum interleukin (IL-6) and necrosis factor-α (TNF-α) were also increased and were closely associated with CTRP4 expression. CTRP4 expression was examined by immunohistochemistry (IHC) in the normal control brain tissues, HSE, TBM and BM brain tissues. High positively expression of CTRP4 was found in HSE. In the normal brain tissue, TBM, and BM brain tissues, CTRP4 showed a weak expression. In the clinical evaluation, CTRP4 expression correlated closely with an ascending stage of the disease [mini-mental state examination (MMSE) evaluation, MRI imaging). Our findings suggest that CTRP4 is highly expressed in HSE and is closely related to the progression of HSE. Thus, CTRP4 may serve as a potential severity index for HSE and targeting CTRP4 might be a promising therapeutic strategy against HSE.

NMR structure of a full-length single-pass membrane protein NRADD.

Structural study of any single-pass membrane protein is both an important and challenging task. In this report, we present the structure of a neurotrophin receptor-alike death-domain protein. The structure and dynamics of the protein was investigated by conventional nuclear magnetic resonance techniques in the solution of phospholipid bicelles. The receptor contains two folded regions-α-helical transmembrane domain and globular C-terminal death domain with more than 50% of the rest of backbone being disordered. This is the first structure of a full-length single-pass membrane receptor-alike protein solved by the single method.

Direct interaction of DNMT inhibitors to PrPC suppresses pathogenic process of prion

The conversion of the normal cellular prion protein (PrPC) to the misfolded pathogenic scrapie prion protein (PrPSc) is the biochemical hallmark of prion replication. So far, various chemical compounds that inhibit this conformational conversion have been identified. Here, we report the novel anti-prion activity of SGI-1027 and its meta/meta analogue (M/M), previously known only as potent inhibitors of DNA methyltransferases (DNMTs). These compounds effectively decreased the level of PrPSc in cultured cells with permanent prion infection, without affecting PrPC at the transcriptional or translational levels. Furthermore, SGI-1027 prevented effective prion infection of the cells. In a PrP aggregation assay, both SGI-1027 and M/M blocked the formation of misfolded PrP aggregates, implying that binding of these compounds hinders the PrP conversion process. A series of binding and docking analyses demonstrated that both SGI-1027 and M/M directly interacted with the C-terminal globular domain of PrPC, but only SGI-1027 bound to a specific region of PrPC with high affinity, which correlates with its potent anti-prion efficacy. Therefore, we report SGI-1027 and related compounds as a novel class of potential anti-prion agents that preferentially function through direct interaction with PrPC.

Structural mechanism for versatile cargo recognition by the yeast class V myosin Myo2

Class V myosins are actin-dependent motors, which recognize numerous cellular cargos mainly via the C-terminal globular tail domain (GTD). Myo2, a yeast class V myosin, can transport a broad range of organelles. However, little is known about the capacity of Myo2-GTD to recognize such a diverse array of cargos specifically at the molecular level. Here, we solved crystal structures of Myo2-GTD (at 1.9-3.1 Å resolutions) in complex with three cargo adaptor proteins: Smy1 (for polarization of secretory vesicles), Inp2 (for peroxisome transport), and Mmr1 (for mitochondria transport). The structures of Smy1- and Inp2-bound Myo2-GTD, along with site-directed mutagenesis experiments, revealed a binding site in subdomain-I having a hydrophobic groove with high flexibility enabling Myo2-GTD to accommodate different protein sequences. The Myo2-GTD-Mmr1 complex structure confirmed and complemented a previously identified mitochondrion/vacuole-specific binding region. Moreover, differences between the conformations and locations of cargo-binding sites identified here for Myo2 and those reported for mammalian MyoVA (MyoVA) suggest that class V myosins potentially have co-evolved with their specific cargos. Our structural and biochemical analysis not only uncovers a molecular mechanism that explains the diverse cargo recognition by Myo2-GTD, but also provides structural information useful for future functional studies of class V myosins in cargo transport.

Impact of N-glycosylation site variants during human PrP aggregation and fibril nucleation

Misfolding and aggregation of the human prion protein (PrP) cause neurodegenerative transmissible spongiform encephalopathies such as Creutzfeldt-Jakob disease. Mature native PrP is composed of 209 residues and is folded into a C-terminal globular domain (residues 125–209) comprising a small two-stranded β-sheet and three α-helices. The N-terminal domain (residues 23–124) is intrinsically disordered. Expression of truncated PrP (residues 90–231) is sufficient to cause prion disease and residues 90/100–231 is comprising the amyloid-like fibril core of misfolded infectious PrP. During PrP fibril formation under native conditions in vitro, the disordered N-terminal domain slows down fibril formation likely due to a mechanism of initial aggregation forming morphologically disordered aggregates. The morphological disordered aggregate is a transient phase. Nucleation of fibrils occurs from this initial aggregate. The aggregate phase is largely circumvented by seeding with preformed PrP fibrils. In vivo PrP is N-glycosylated at positions Asn181 and Asn197. Little is known about the importance of these positions and their glycans for PrP stability, aggregation and fibril formation. We have in this study taken a step towards that goal by mutating residues 181 and 197 for cysteines to study the positional impact on these processes. We have further by organic synthetic chemistry and chemical modification generated synthetic glycosylations in these positions. Our data shows that residue 181 when mutated to a cysteine is a key residue for self-chaperoning, rendering a trap in the initial aggregate preventing conformational changes towards amyloid fibril formation. Position 197 is less involved in the aggregate trapping and is more geared towards β-sheet structure conversion within amyloid fibrils. As expected, synthetic glycosylated 197 is less affected towards fibril formation compared to glycosylated 181. Our data are rather compatible with the parallel in-register intermolecular β-sheet model structure of the PrP90–231 fibril and sheds light on the misfolding transitions of PrP in vitro. We hypothesize that glycosylation of position 181 is a key site for prion strain differentiation in vivo.

R482L Mutation of the LMNA Gene Affects Dynamics of C2C12 Myogenic Differentiation and Stimulates Formation of Intramuscular Lipid Droplets.

Mutations in the LMNA gene resulting in the substitution of the highly conserved arginine 482 residue in the globular C-terminal domain of lamin A/C are associated with the Dunnigan-type familial partial lipodystrophy (FPLD2) often accompanied by impairments in the muscle tissue development. The mechanisms underlying these impairments remain unknown. The purpose of our work was to investigate the effects of the LMNA gene mutation R482L on the muscle differentiation and intramuscular fat accumulation using C2C12 mouse myoblasts transduced with the lentiviral constructs carrying the wild-type human LMNA gene (LMNA-WT) or the LMNA-R482L mutant gene. After stimulation of myogenesis and adipogenesis in the transduced cell, expression of muscle and adipose tissue differentiation markers, morphology of differentiated myotubes, and formation of intramuscular lipid droplets were analyzed. C2C12 cells carrying the LMNA-R482L construct exhibited upregulated desmin expression at all stages of muscle differentiation and transformed into hypertrophied myotubules (in comparison with C2C12 myoblasts transduced with LMNA-WT). Reduced expression levels of the myogenic transcription factor Myf6 in the cells with the LMNA-R482L mutant indicated delayed maturation of muscle fibers. These cells more actively accumulated fat in response to the stimulation of adipose differentiation than myoblasts modified with the wild-type LMNA; they also expressed the markers of lipid droplets, such as FABP4 (fatty acid-binding protein 4), ATGL (adipose triglyceride lipase), and PLIN2 (perilipin 2). Therefore, the R482L mutation of the LMNA gene affects the dynamics of C2C12 myoblast differentiation into myotubules and stimulates formation of fat deposits in the myoblasts and myotubules in a tissue-specific manner.

A recessive lethal chondrodysplasia in a miniature zebu family results from an insertion affecting the chondroitin sulfat domain of aggrecan

BackgroundCongenital skeletal malformations represent a heterogeneous group of disorders affecting bone and cartilage development. In cattle, particular chondrodysplastic forms have been identified in several miniature breeds. In this study, a phenotypic characterization was performed of an affected Miniature Zebu calf using computed tomography, necropsy and histopathological examinations, whole genome sequencing of the case and its parents on an Illumina NextSeq 500 in 2 × 150 bp paired-end mode and validation using Sanger sequencing and a Kompetitive Allele Specific PCR assay. Samples from the family of an affected Miniature Zebu with bulldog syndrome including parents and siblings, 42 healthy Miniature Zebu not related with members of the herd and 88 individuals from eight different taurine cattle breeds were available for validation.ResultsA bulldog-like Miniature Zebu calf showing a large bulging head, a short and compressed body and extremely short and stocky limbs was delivered after a fetotomy. Computed tomography and necropsy revealed severe craniofacial abnormalities including a shortening of the ventral nasal conchae, a cleft hard palate, rotated limbs as well as malformed and fused vertebrae and ribs. Histopathologic examination showed a disorganization of the physeal cartilage with disorderly arranged chondrocytes in columns and a multifocal closed epiphyseal plate. Whole-genome sequencing of this malformed Miniature Zebu calf, its dam and sire and subsequent comparative sequence analysis revealed a one base pair insertion (ACAN:c.5686insC) located within the cartilage development gene aggrecan (ACAN) exclusively homozygous in the affected calf and heterozygous in its parents. This variant was predicted to cause a frameshift (p.Val1898fsTer9) and thus a truncation of the chondroitin sulfate domain as well as a loss of the C-terminal globular domain of ACAN. It perfectly co-segregated with the lethal bulldog syndrome in Miniature Zebus.ConclusionsWe found a novel mutation in ACAN causing a recessive lethal chondrodysplasia in Miniature Zebu cattle. A diagnostic test for this mutation is now available for Miniature Zebu breeders preventing further cases of bulldog syndrome by targeted matings. To the authors’ best knowledge, this is the first case of a Miniature Zebu associated with an ACAN mutation.

A d-enantiomeric peptide interferes with heteroassociation of amyloid-β oligomers and prion protein

Alzheimer's disease (AD) is a progressive neurodegenerative disorder that affects millions of people worldwide. One AD hallmark is the aggregation of β-amyloid (Aβ) into soluble oligomers and insoluble fibrils. Several studies have reported that oligomers rather than fibrils are the most toxic species in AD progression. Aβ oligomers bind with high affinity to membrane-associated prion protein (PrP), leading to toxic signaling across the cell membrane, which makes the Aβ-PrP interaction an attractive therapeutic target. Here, probing this interaction in more detail, we found that both full-length, soluble human (hu) PrP(23-230) and huPrP(23-144), lacking the globular C-terminal domain, bind to Aβ oligomers to form large complexes above the megadalton size range. Following purification by sucrose density-gradient ultracentrifugation, the Aβ and huPrP contents in these heteroassemblies were quantified by reversed-phase HPLC. The Aβ:PrP molar ratio in these assemblies exhibited some limited variation depending on the molar ratio of the initial mixture. Specifically, a molar ratio of about four Aβ to one huPrP in the presence of an excess of huPrP(23-230) or huPrP(23-144) suggested that four Aβ units are required to form one huPrP-binding site. Of note, an Aβ-binding all-d-enantiomeric peptide, RD2D3, competed with huPrP for Aβ oligomers and interfered with Aβ-PrP heteroassembly in a concentration-dependent manner. Our results highlight the importance of multivalent epitopes on Aβ oligomers for Aβ-PrP interactions and have yielded an all-d-peptide-based, therapeutically promising agent that competes with PrP for these interactions.

Interfacial Behavior of Recombinant Spider Silk Protein Parts Reveals Cues on the Silk Assembly Mechanism.

The mechanism of silk assembly, and thus the cues for the extraordinary properties of silk, can be explored by studying the simplest protein parts needed for the formation of silk-like materials. The recombinant spider silk protein 4RepCT, consisting of four repeats of polyalanine and glycine-rich segments (4Rep) and a globular C-terminal domain (CT), has previously been shown to assemble into silk-like fibers at the liquid-air interface. Herein, we study the interfacial behavior of the two parts of 4RepCT, revealing new details on how each protein part is crucial for the silk assembly. Interfacial rheology and quartz crystal microbalance with dissipation show that 4Rep interacts readily at the interfaces. However, organized nanofibrillar structures are formed only when 4Rep is fused to CT. A strong interplay between the parts to direct the assembly is demonstrated. The presence of either a liquid-air or a liquid-solid interface had a surprisingly similar influence on the assembly.

High-Level Production of High-Purity Human and Murine Recombinant Prion Proteins Functionally Compatible to In Vitro Seeding Assay.

Recombinant (rec) prion protein (PrP) is an extremely useful resource for studying protein misfolding and subsequent protein aggregation events. Here, we report mass production of high-purity rec-polypeptide encoding the C-terminal globular domain of PrP; (90-230) for human and (89-231) for murine PrP. These proteins were expressed as His-tagged fusion proteins in E. coli cultured by a high cell-density aerobic fermentation method. RecPrPs recovered from inclusion bodies were slowly refolded under reducing conditions. Purification was performed by a sequence of metal-affinity, cation-exchange, and reverse-phase chromatography. The current procedure yielded several dozens of milligrams of recPrP per liter with ＞95% purity. The purified recPrPs predominantly adopted an α-helix-rich conformation and were functionally sufficient as substrates to measure the seeding activity of human and animal prions. Establishment of a procedure for high-level production of high-purity recPrP supports the advancement of in vitro investigations of PrP including diagnosis for prion diseases.

Structural analysis of the ternary complex between lamin A/C, BAF and emerin identifies an interface disrupted in autosomal recessive progeroid diseases.

Lamins are the main components of the nucleoskeleton. Whereas their 3D organization was recently described using cryoelectron tomography, no structural data highlights how they interact with their partners at the interface between the inner nuclear envelope and chromatin. A large number of mutations causing rare genetic disorders called laminopathies were identified in the C-terminal globular Igfold domain of lamins A and C. We here present a first structural description of the interaction between the lamin A/C immunoglobulin-like domain and emerin, a nuclear envelope protein. We reveal that this lamin A/C domain both directly binds self-assembled emerin and interacts with monomeric emerin LEM domain through the dimeric chromatin-associated Barrier-to-Autointegration Factor (BAF) protein. Mutations causing autosomal recessive progeroid syndromes specifically impair proper binding of lamin A/C domain to BAF, thus destabilizing the link between lamin A/C and BAF in cells. Recent data revealed that, during nuclear assembly, BAF’s ability to bridge distant DNA sites is essential for guiding membranes to form a single nucleus around the mitotic chromosome ensemble. Our results suggest that BAF interaction with lamin A/C also plays an essential role, and that mutations associated with progeroid syndromes leads to a dysregulation of BAF-mediated chromatin organization and gene expression.

Gene expression levels of Casein kinase 1 (CK1) isoforms are correlated to adiponectin levels in adipose tissue and site-specific phosphorylation mediated by CK1 influences multimerization of adiponectin

Adiponectin, an adipocytokine with anti-inflammatory, antidiabetic, anti-atherogenic, and anti-cancer features, is mainly secreted by adipose tissue. Human adiponectin has an N-terminal collagenous domain and a C-terminal globular domain and builds characteristic homomeres including trimers, hexamers and high molecular weight (HMW) 12 – 18-mers. The beneficial effects of adiponectin in humans are primarily mediated by its HMW isoform. Posttranslational modifications play an important role in regulating activity and complex formation of adiponectin. Phosphorylation is considered to be another most common posttranslational modification that may alter the activity, life span, or cellular localization of proteins.

Hidden Structural Codes in Protein Intrinsic Disorder

Protein intrinsic disorder is a major structural category in biology yet its definition is often limited to the absence of folding. The explosion of information in the genomic era showed that it may account for over 30% of coding regions across life domains, and it is particularly overrepresented in viruses. Papillomaviruses are an unparalleled case for sequence to structure correlation analysis because of the existence of hundreds of anciently evolved and stable virus types which are divergent enough in sequence, but conserving the function of each protein. E7, the main transforming oncoprotein from human papillomaviruses, is a paradigmatic example of an intrinsically disordered protein with pathological moonlighting activities evolved for hijacking cell cycle control. Despite of being intrinsically disordered, the N-terminal domain shows more conserved residues than the globular C-terminal domain. Mutation of five hyper conserved residues precisely distributed along the sequence lead to a marked increase in both α-helix and ß-sheet structural content, reflected by drastic effects on equilibrium propensities and oligomerization kinetics. These results strongly suggest the existence of local nuclei, yet to be defined in structural terms, that oppose to canonical folding as expected for globular proteins. Moreover, direct coupling analysis pinpoint interactions surprisingly coincident with the proposed nuclei. In addition, these match with regions of helix propensities found in TFE/NMR experiments.

Inactivation of Mechanically Activated Piezo1 Ion Channels Is Determined by the C-Terminal Extracellular Domain and the Inner Pore Helix

SUMMARYPiezo proteins form mechanically activated ion channels that are responsible for our sense of light touch, proprioception, and vascular blood flow. Upon activation by mechanical stimuli, Piezo channels rapidly inactivate in a voltage-dependent manner through an unknown mechanism. Inactivation of Piezo channels is physiologically important, as it modulates overall mechanical sensitivity, gives rise to frequency filtering of repetitive mechanical stimuli, and is itself the target of numerous human disease-related channelopathies that are not well understood mechanistically. Here, we identify the globular C-terminal extracellular domain as a structure that is sufficient to confer the time course of inactivation and a single positively charged lysine residue at the adjacent inner pore helix as being required for its voltage dependence. Our results are consistent with a mechanism for inactivation that is mediated through voltage-dependent conformations of the inner pore helix and allosteric coupling with the C-terminal extracellular domain.

Transcriptional response after exposure to domoic acid-producing Pseudo-nitzschia in the digestive gland of the mussel Mytilus galloprovincialis

Bivalve molluscs are filter feeding species that can accumulate biotoxins in their body tissues during harmful algal blooms. Amnesic Shellfish Poisoning (ASP) is caused by species of the diatom genus Pseudo-nitzschia, which produces the toxin domoic acid. The Mytilus galloprovincialis digestive gland transcriptome was de novo assembled based on the sequencing of 12 cDNA libraries, six obtained from control mussels and six from mussels naturally exposed to domoic acid-producing diatom Pseudo-nitzschia australis. After de novo assembly 94,727 transcripts were obtained, with an average length of 1015 bp and a N50 length of 761 bp. The assembled transcripts were clustered (homology > 90%) into 69,294 unigenes. Differential gene expression analysis was performed (DESeq2 algorithm) in the digestive gland following exposure to the toxic algae. A total of 1158 differentially expressed unigenes (absolute fold change > 1.5 and p-value < 0.05) were detected: 686 up-regulated and 472 down-regulated. Several membrane transporters belonging to the family of the SLC (solute carriers) were over-expressed in exposed mussels. Functional enrichment was performed using Pfam annotations obtained from the genes differentially expressed, 37 Pfam families were found to be significantly (FDR adjusted p-value < 0.1) enriched. Some of these families (sulfotransferases, aldo/keto reductases, carboxylesterases, C1q domain and fibrinogen C-terminal globular domain) could be putatively involved in detoxification processes, in the response against of the oxidative stress and in immunological processes. Protein network analysis with STRING algorithm found alteration of the Notch signaling pathway under the action of domoic acid-producing Pseudo-nitzschia. In conclusion, this study provides a high quality reference transcriptome of M. galloprovincialis digestive gland and identifies potential genes involved in the response to domoic acid.

Cellular prion protein targets amyloid-β fibril ends via its C-terminal domain to prevent elongation

Oligomeric forms of the amyloid-β (Aβ) peptide are thought to represent the primary synaptotoxic species underlying the neurodegenerative changes seen in Alzheimer's disease. It has been proposed that the cellular prion protein (PrPC) functions as a cell-surface receptor, which binds to Aβ oligomers and transduces their toxic effects. However, the molecular details of the PrPC-Aβ interaction remain uncertain. Here, we investigated the effect of PrPC on polymerization of Aβ under rigorously controlled conditions in which Aβ converts from a monomeric to a fibrillar state via a series of kinetically defined steps. We demonstrated that PrPC specifically inhibited elongation of Aβ fibrils, most likely by binding to the ends of growing fibrils. Surprisingly, this inhibitory effect required the globular C-terminal domain of PrPC, which has not been previously implicated in interactions with Aβ. Our results suggest that PrPC recognizes structural features common to both Aβ oligomers and fibril ends and that this interaction could contribute to the neurotoxic effect of Aβ aggregates. Additionally, our results identify the C terminus of PrPC as a new and potentially more druggable molecular target for treating Alzheimer's disease.