Keywords:Variable domain of heavy-chain antibody Inhibition of protein misfolding and aggregation Protein misfolding diseases Amyloidoses V H H Nanobody a b s t r a c tThe deposition of misfolded peptides and proteins in the form of amyloid fibrils is the hallmark of nearly fifty medical disorders, including Alzheimer's disease, Parkinson's disease, prion diseases and type II diabetes. These disorders, referred to as amyloidoses, generally become apparent late in life. Their psycho-sociological and economic incidence in western societies will be therefore considerable in the coming decades due to the ageing of the population. Neither preventing nor curative treatments are available yet. These disorders constitute therefore a medical challenge of great importance. Thus, an extensive research is being carried out to understand, at the molecular level, (i) how amyloidogenic proteins misfold and convert from their soluble form into amyloid fibrils, and (ii) how these aggregates or some of their oligomeric precursor species are toxic. The formation of amyloid fibrils proceeds through a complex nucleation/polymerisation mechanism with the formation of various species, including small oligomers. In this review, we focus on how V H Hs or nanobodies, the antigen-binding domains of camelid heavy-chain antibodies, are being increasingly used to characterise each of the species formed on the pathway of fibril formation in terms of structure, stability, kinetics of formation and toxicity. We first introduce the characteristic features of nanobodies compared to those of conventional antibody fragments. Thereafter, we discuss how nanobodies, due to their unique properties, are used as probes to dissect the molecular mechanisms of misfolding and aggregation of six proteins associated with diseases, i.e. human lysozyme, b2-microglobulin, a-synuclein, prion, polyadenylate binding protein nuclear 1 and amyloid b-peptide. A brief general presentation of each disease and the associated peptide/protein is also provided. In addition, we discuss how nanobodies could be used as early diagnostic tools and as novel strategies to treat diseases associated with protein misfolding and aggregation.© 2015 Elsevier B.V. and Societe Française de Biochimie et Biologie Moleculaire (SFBBM). All rights reserved.Abbreviations: Ab, antibody; Ab, amyloid b-peptide; AD, Alzheimer's disease; ANS, anilino naphthalene-sulfonic acid; AP, alkaline phosphatase; APP, amyloid precursor protein; aSyn, a-synuclein; b2m, b2-microglobulin; BBB, bloodebrain barrier; CDR, complementarity determining region; C m , concentration of mid-denaturation; CR, Congo red; CSF, cerebrospinal fluid; DN6b2m, a truncated form of b2m lacking the six N-terminal amino acids; DLS, dynamic light scattering; DRA, dialysis-related amyloidosis; FR, framework; FTIR, Fourier transform infrared spectroscopy; Fv, variable fragment made of the VH and VL domains of conventional antibodies; GFP, green fluorescent protein; HCAb, heavy-chain antibody; H/D, hydrogen/deuterium; HSQC, heteronuclear s...

We report here the detailed characterisation of a non-naturally occurring variant of human lysozyme, I59T, which possesses a destabilising point mutation at the interface of the alpha- and beta-domains. Although more stable in its native structure than the naturally occurring variants that give rise to a familial form of systemic amyloidosis, I59T possesses many attributes that are similar to these disease-associated species. In particular, under physiologically relevant conditions, I59T populates transiently an intermediate in which a region of the structure unfolds cooperatively; this loss of global cooperativity has been suggested to be a critical feature underlying the amyloidogenic nature of the disease-associated lysozyme variants. In the present study, we have utilised this variant to provide direct evidence for the generic nature of the conformational transition that precedes the ready formation of the fibrils responsible for lysozyme-associated amyloid disease. This non-natural variant can be expressed at higher levels than the natural amyloidogenic variants, enabling, for example, singly isotopically labelled protein to be generated much more easily for detailed structural studies by multidimensional NMR spectroscopy. Moreover, we demonstrate that the I59T variant can readily form fibrils in vitro, similar in nature to those of the amyloidogenic I56T variant, under significantly milder conditions than are needed for the wild-type protein.

Background information. The TSPO (18 kDa translocator protein) is a mitochondrial transmembrane protein involved in cholesterol transport in organs that synthesize steroids and bile salts. Different natural and synthetic highaffinity TSPO ligands have been characterized through their ability to stimulate cholesterol transport, but also to stimulate other physiological functions including cell proliferation, apoptosis and calcium-dependent transepithelial ion secretion. Here, we investigate the localization and functions of TSPO in the small intestine.Results. TSPO was present in enterocyte mitochondria but not in rat intestinal goblet cells. Enterocyte cytoplasm also contained the endogenous TSPO ligand, polypeptide DBI (diazepam-binding inhibitor). Whereas intestinal TSPO had high affinity for the synthetic ligand PK 11195, the pharmacological profile of TSPO in the duodenum was distinct from the jejunum and ileum. Specifically, benzodiazepine Ro5-4864 and protoporphyrin IX showed 5-13-fold lower affinity for duodenal TSPO. The mRNA and protein ratios of TSPO to other mitochondrial membrane proteins VDAC (voltage-dependent anion channel) and ANT (adenine nucleotide transporter) were significantly different. PK 11195 stimulated calcium-dependent chloride secretion in the duodenum and calcium-dependent chloride absorption in the ileum, but did not affect jejunum ion transport.Conclusions. The functional differences in subpopulations of TSPO in different regions of the intestine could be related to structural organization of mitochondrial protein complexes that mediate the ability of TSPO to modulate either chloride secretion or absorption in the duodenum and ileum respectively.

A rapid and simple method for lysing anerobic Gram‐positive rods is described. It is based on the simultaneous action of lysozyme and achromopeptidase (each at 5 mg/g wet weight of cells), followed by the action of SDS (0.2%). The efficiency of the bacterial lysis is measured by the yield of DNA obtained with Marmur's modified procedure. This method permits effective lysis of small amounts of anaerobic rods (200 mg wet weight) independent of their growth phase, and extraction of DNA for further analysis. It is particularly useful for strains with low growth such as certain species of Actinomyces and Bifidobacterium and it saves considerable time.