Mammalian Origin Research Articles

Discovery of stylissatin A analogs exhibiting potent nitric oxide inhibition

The cyclic peptide stylissatin A(STA) was obtained from the Papua New Guinean marine spongeStylissamassaas a potent nitric oxide (NO) inhibitor.Among its reported analogs,cyclo-{Glu6, Ala2}-STA1potentlyinhibited theinterleukin-2 and proliferation of T-cells indicating position 2 of sequence playing important part in biological activities of this compound.In current studies, second generation analogs of STAwere synthesizedaround its most active analog1by screening position 2 of analog1with different amino acid. All analogs2–6were identified by mass, and NMR techniques.The synthesized analogswere also evaluated against NO generation by lipopolysaccharide (LPS)-stimulated murine J774.2macrophages, ROS inhibition from whole blood phagocytes, and T-cell proliferation from Jurkat cells.All analogswere found to be inactive towards interleukin-2, T-cells proliferation, and ROS inhibition. The analog2showed a potent suppression of NO (IC50 = 46.0 ± 2.2 µM) that was superior to the activityreported for natural product STA.Further attempts to optimizeanalog2afforded new nitric oxide inhibitors2a-2fwhich were found less active than2.The analog2also downregulated the transcription of pro-inflammatory molecules, tumor necrosis factor-α, interlukin-1β, caspase-1 and ASC which further highlights its anti-inflammatory and possible therapeutic potential. Analog2was non-toxic to BJ and Vero cell lines of normal mammalian origin.

Genome-wide screening for genes involved in the epigenetic basis of fragile X syndrome.

SummaryFragile X syndrome (FXS), the most prevalent heritable form of intellectual disability, is caused by the transcriptional silencing of the FMR1 gene. The epigenetic factors responsible for FMR1 inactivation are largely unknown. Here, we initially demonstrated the feasibility of FMR1 reactivation by targeting a single epigenetic factor, DNMT1. Next, we established a model system for FMR1 silencing using a construct containing the FXS-related mutation upstream to a reporter gene. This construct was methylated in vitro and introduced into a genome-wide loss-of-function (LOF) library established in haploid human pluripotent stem cells (PSCs), allowing the identification of genes whose functional loss reversed the methylation-induced silencing of the FMR1 reporter. Selected candidate genes were further analyzed in haploid- and FXS-patient-derived PSCs, highlighting the epigenetic and metabolic pathways involved in FMR1 regulation. Our work sheds light on the mechanisms responsible for CGG-expansion-mediated FMR1 inactivation and offers novel targets for therapeutic FMR1 reactivation.

A systematic comparison of optogenetic approaches to visual restoration

During inherited retinal degenerations (IRDs), vision is lost due to photoreceptor cell death; however, a range of optogenetic tools have been shown to restore light responses in animal models. Restored response characteristics vary between tools and the neuronal cell population to which they are delivered: the interplay between these is complex, but targeting upstream neurons (such as retinal bipolar cells) may provide functional benefit by retaining intraretinal signal processing. In this study, our aim was to compare two optogenetic tools: mammalian melanopsin (hOPN4) and microbial red-shifted channelrhodopsin (ReaChR) expressed within two subpopulations of surviving cells in a degenerate retina. Intravitreal adeno-associated viral vectors and mouse models utilising the Cre/lox system restricted expression to populations dominated by bipolar cells or retinal ganglion cells and was compared with non-targeted delivery using the chicken beta actin (CBA) promoter. In summary, we found bipolar-targeted optogenetic tools produced faster kinetics and flatter intensity-response relationships compared with non-targeted or retinal-ganglion-cell-targeted hOPN4. Hence, optogenetic tools of both mammalian and microbial origins show advantages when targeted to bipolar cells. This demonstrates the advantage of bipolar-cell-targeted optogenetics for vision restoration in IRDs. We therefore developed a bipolar-cell-specific gene delivery system employing a compressed promoter with the potential for clinical translation.

Molecular Characterization of Infectious Bronchitis Virus Strain HH06 Isolated in a Poultry Farm in Northeastern China.

Spike (S) glycoprotein is an important virulent factor for coronaviruses (CoVs), and variants of CoVs have been characterized based on S gene analysis. We present phylogenetic relationship of an isolated infectious bronchitis virus (IBV) strain with reference to the available genome and protein sequences based on network, multiple sequence, selection pressure, and evolutionary fingerprinting analysis in People's Republic of China. One hundred and elven strains of CoVs i.e., Alphacoronaviruses (Alpha-CoVs; n = 12), Betacoronaviruses (Beta-CoVs; n = 37), Gammacoronaviruses (Gamma-CoVs; n = 46), and Deltacoronaviruses (Delta-CoVs; n = 16) were selected for this purpose. Phylogenetically, SARS-CoV-2 and SARS-CoVs clustered together with Bat-CoVs and MERS-CoV of Beta-CoVs (C). The IBV HH06 of Avian-CoVs was closely related to Duck-CoV and partridge S14, LDT3 (teal and chicken host). Beluga whale-CoV (SW1) and Bottlenose dolphin-CoVs of mammalian origin branched distantly from other animal origin viruses, however, making group with Avian-CoVs altogether into Gamma-CoVs. The motif analysis indicated well-conserved domains on S protein, which were similar within the same phylogenetic class and but variable at different domains of different origins. Recombination network tree indicated SARS-CoV-2, SARS-CoV, and Bat-CoVs, although branched differently, shared common clades. The MERS-CoVs of camel and human origin spread branched into a different clade, however, was closely associated closely with SARS-CoV-2, SARS-CoV, and Bat-CoVs. Whereas, HCoV-OC43 has human origin and branched together with bovine CoVs with but significant distant from other CoVs like SARS CoV-2 and SARS-CoV of human origin. These findings explain that CoVs' constant genetic recombination and evolutionary process that might maintain them as a potential veterinary and human epidemic threat.

Ischemic tolerance and cardiac repair in the spiny mouse (Acomys)

Ischemic heart disease and by extension myocardial infarction is the primary cause of death worldwide, warranting regenerative therapies to restore heart function. Current models of natural heart regeneration are restricted in that they are not of adult mammalian origin, precluding the study of class-specific traits that have emerged throughout evolution, and reducing translatability of research findings to humans. Here, we present the spiny mouse (Acomys spp.), a murid rodent that exhibits bona fide regeneration of the back skin and ear pinna, as a model to study heart repair. By comparing them to ordinary mice (Mus musculus), we show that the acute injury response in spiny mice is similar, but with an associated tolerance to infarction through superior survivability, improved ventricular conduction, and near-absence of pathological remodeling. Critically, spiny mice display increased vascularization, altered scar organization, and a more immature phenotype of cardiomyocytes, with a corresponding improvement in heart function. These findings present new avenues for mammalian heart research by leveraging unique tissue properties of the spiny mouse.

Further Investigation of the 2‐Azido‐phenylselenylation of Glycals

AbstractDerivatives of 2‐azido‐2‐deoxysugars are widely applied as precursor of 2‐amino‐2‐deoxysugars in the synthesis of various oligosaccharides of bacterial, fungal and mammalian origin. Heterogeneous or homogeneous azidophenylselenylation (APS) of glycals, i. e., reaction of glycals with Ph2Se2, PhI(OAc)2 and NaN3 or TMSN3 as azide radical donors, is a straightforward way to phenyl 2‐azido‐2‐deoxy‐1‐selenoglycosides that can be directly used as glycosyl donors. However, heterogeneous APS is characterized by insufficient reproducibility and scalability. We have studied the effect of reaction conditions on the product distribution in heterogeneous APS of 3,4,6‐tri‐O‐acetyl‐d‐galactal and found the conditions that enabled reliable preparation of crystalline phenyl 2‐azido‐2‐deoxy‐1‐seleno‐α‐d‐galactopyranoside triacetate in yield of 58 % on the 3.7 mmol scale. APS of 3,4,6‐tri‐O‐acetyl‐d‐glucal under those conditions produced a ∼1 : 1 mixture of phenyl 2‐azido‐2‐deoxy‐1‐seleno‐α‐d‐gluco‐ and mannopyranosides in total yield of 78 %. Acetoxyphenylselenylation of differently protected galactals and 3,4,6‐tri‐O‐acetyl‐d‐glucal under the action of Ph2Se2 and PhI(OAc)2 has been shown to be a convenient method for the synthesis of 1‐O‐acetyl‐2‐seleno‐2‐deoxy derivatives, valuable intermediates in chemistry of 2‐deoxysugars. 2‐Seleno‐2‐deoxy sugars were characterized in detail by NMR data including 77Se chemical shifts and nJSe−H coupling constant values.

Lipid mediator profiles of burn wound healing: Acellular cod fish skin grafts promote the formation of EPA and DHA derived lipid mediators following seven days of treatment

The use of acellular fish skin grafts (FSG) for the treatment of burn wounds is becoming more common due to its beneficial wound healing properties. In our previous study we demonstarted that FSG is a scaffold biomaterial that is rich in eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) conjugated to phosphatidylcholines. Here we investigated whether EPA and DHA derived lipid mediators are influenced during the healing of burn wounds treated with FSG. Deep partial and full thickness burn wounds (DPT and FT, respectively) were created on Yorkshire pigs (n = 4). DPT were treated with either FSG or fetal bovine dermis while FT were treated either with FSG or cadaver skin initially and followed by a split thickness skin graft. Punch biopsies were collected on days 7, 14, 21, 28 and 60 and analyzed in respect of changes to approximately 45 derivatives of EPA, DHA, arachidonic acid (AA), and linoleic acid (LA) employing UPLC-MS/MS methodology. Nine EPA and DHA lipid mediators, principally mono-hydroxylated derivatives such as 18-HEPE and 17-HDHA, were significantly higher on day 7 in the DPT when treated with FSG. A similar but non-significant trend was observed for the FT. The results suggest that the use of FSG in burn wound treatment can alter the formation of EPA and DHA mono hydroxylated lipid mediators in comparison to other grafts of mammalian origin. The differences observed during the first seven days after treatment indicates that FSG affects the early stages of wound healing.

The Microscopic Detection of Animal Proteins in Animal Feed Regarding Bovine Spongiform Encephalopathy

Abstract Due to the actuality of spongiform encephalopathies and their proven spreading by means of animal feed containing meat and bone meal, the description and measurement of osteocytic lacunae contributes to more easily distinguish bone fragments in meat and bone meal. Transmissible spongiform encephalopathies (TSEs) have attracted a lot of attention, especially after 1986, when the first case of BSE (bovine spongiform encephalopathy) was detected. Since the outbreak of spongiform encephalopathy (BSE), the use of animal protein including bone meal as an ingredient in animal feed has been controlled by several regulations including Regulation (EC) 999/2001, Regulation (EC) 1774/2002, and Regulation (EC) 1234/2003. The classical microscopic method is the only official method for detecting animal protein in animal feed in the European Union (Commission Regulation (EC) 152/2009). By applying the microscopic method to the animal feed samples, we performed detection in order to determine the presence of animal proteins that originate from mammals and fish. The microscopic analysis of all 421 samples, of which 115 were raw materials for the production of animal feed, 230 were concentrates for ruminant nutrition and 76 were concentrates for non-ruminant nutrition (32 concentrates for laying hens and 44 concentrates for pigs), did not provide positive results, that is, no remains of animal tissues of mammalian origin were found in any specimen. Whereas in 10 out of 32 (31.25%) concentrates intended for non-ruminant nutrition (laying hens), pieces of fish tissue were found. In these samples, we usually detected the presence of fish bones, gills and scales.

Glycoproteins of Predicted Amphibian and Reptile Lyssaviruses Can Mediate Infection of Mammalian and Reptile Cells.

Lyssaviruses are neurotropic rhabdoviruses thought to be restricted to mammalian hosts, and to originate from bats. The identification of lyssavirus sequences from amphibians and reptiles by metatranscriptomics thus comes as a surprise and challenges the mammalian origin of lyssaviruses. The novel sequences of the proposed American tree frog lyssavirus (ATFLV) and anole lizard lyssavirus (ALLV) reveal substantial phylogenetic distances from each other and from bat lyssaviruses, with ATFLV being the most distant. As virus isolation has not been successful yet, we have here studied the functionality of the authentic ATFLV- and ALLV-encoded glycoproteins in the context of rabies virus pseudotype particles. Cryogenic electron microscopy uncovered the incorporation of the plasmid-encoded G proteins in viral envelopes. Infection experiments revealed the infectivity of ATFLV and ALLV G-coated RABV pp for a broad spectrum of cell lines from humans, bats, and reptiles, demonstrating membrane fusion activities. As presumed, ATFLV and ALLV G RABV pp escaped neutralization by human rabies immune sera. The present findings support the existence of contagious lyssaviruses in poikilothermic animals, and reveal a broad cell tropism in vitro, similar to that of the rabies virus.

Structural and biophysical aspects of l-asparaginases: a growing family with amazing diversity.

l-Asparaginases have remained an intriguing research topic since their discovery ∼120 years ago, especially after their introduction in the 1960s as very efficient antileukemic drugs. In addition to bacterial asparaginases, which are still used to treat childhood leukemia, enzymes of plant and mammalian origin are now also known. They have all been structurally characterized by crystallography, in some cases at outstanding resolution. The structural data have also shed light on the mechanistic details of these deceptively simple enzymes. Yet, despite all this progress, no better therapeutic agents have been found to beat bacterial asparaginases. However, a new option might arise with the discovery of yet another type of asparaginase, those from symbiotic nitrogen-fixing Rhizobia, and with progress in the protein engineering of enzymes with desired properties. This review surveys the field of structural biology of l-asparaginases, focusing on the mechanistic aspects of the well established types and speculating about the potential of the new members of this amazingly diversified family.

Antibiotic resistance profile and detection of degradative enzymes by Enterobacteriaceae isolated from raw goat milk.

Enterobacteriaceae are often reported as a typical bacterial population in raw milk from any mammalian origin. The frequent concern with bacteria, especially those related to this group of microorganisms, is their increasing resistance to antibiotics and the emergence of enzymes that degrade them. This study aimed to characterize isolates of Enterobacteriaceae from raw goat milk to expose associated safety problems and possible technological challenges. Isolates from 21 raw goat milk samples purchased in the State of Rio de Janeiro, Brazil, were identified by mass spectrometry, after isolation on Violet Red Bile Glucose agar. The isolates were subjected to evaluation of proteolytic, lipolytic, hemolytic, and biofilm producing activities. Furthermore, resistance profiles and production capacity of enzymes that degrade antimicrobials were evaluated. Almost half of the 59 isolates (48%) belonged to the Enterobacter genus, with a significant prevalence of the Serratia (20%) and Klebsiella (11%) genera. The majority showed biofilm-producing activity (90%), while the activity of degradative enzymes was observed in approximately 20%. Few isolates were found with a profile of resistance to antimicrobials, with only one isolate of Klebsiella variicola being classified as multidrug-resistant. However, chromogenic culture media showed high production of extended-spectrum beta-lactamases and carbapenemases (54% and 46%, respectively), as a presumptive identification. A considerable degree of virulence was observed in the Enterobacteriaceae isolates, as well as the potential for undesirable technological damage. The characterization and identification of the isolates contributes to the improvement of the risk monitoring process of goat's milk.

Identification and molecular profiling of a novel homolog of cystatin C from rock bream (Oplegnathus fasciatus) evidencing its transcriptional sensitivity to pathogen infections.

Cystatins are reversible inhibitors of cysteine proteases which show an omnipresent distribution in the life on earth. Although, cystatins with mammalian origin were well characterized and their roles in physiology were reported in details, those from teleostean origin are still underrepresented in literature. However, role of cystatins in fish physiology and immune defense is highlighted in few recent reports. In this study, a cystatin C holmologue from rock bream (Oplegnathus fasciatus); termed RbCytC was identified and molecularly characterized. The complete coding sequence of RbCytC was 387bp in length, which codes for a polypeptide with 129 amino acids, including a signal peptide of 19 amino acids. The consensus cystatin family signatures including a G residue, turning up towards the N-terminus region, QVVAG motif, locating at the middle of the sequence and the PW motif at the c terminal region was found to be well conserved in RbCytC. Phylogenetic analysis using different cystatin counterparts affirmed the close evolutionary relationship of RbCytC with its teleostan homologs which belong to family 2 cystatins. The predicted molecular model of RbCytC resembled most of the structural features of empirically elucidated tertiary structures for chicken egg white cystatin. According to the qPCR assays, RbCytC showed detectable expression in all fish tissues used in the experiment, with markedly pronounced expression level in liver. Moreover, its basal mRNA expression was up-regulated in liver and spleen tissues by experimental rock bream iridovirus infection, whereas down regulated in the same tissues, post live Edwardsiella tarda injection. Collectively, outcomes of our study validate the structural homology of RbCytC with known cystatin C similitudes, especially those of teleosts and suggest its potential roles in proteolytic processes of rock bream physiology as well as in host immune defense mechanisms.

Screening of Mosquitoes for West Nile Virus and Usutu Virus in Croatia, 2015-2020.

In the period from 2015 to 2020, an entomological survey for the presence of West Nile virus (WNV) and Usutu virus (USUV) in mosquitoes was performed in northwestern Croatia. A total of 20,363 mosquitoes were sampled in the City of Zagreb and Međimurje county, grouped in 899 pools and tested by real-time RT-PCR for WNV and USUV RNA. All pools were negative for WNV while one pool each from 2016 (Aedes albopictus), 2017 (Culex pipiens complex), 2018 (Cx. pipiens complex), and 2019 (Cx. pipiens complex), respectively, was positive for USUV. The 2018 and 2019 positive pools shared 99.31% nucleotide homology within the USUV NS5 gene and both clustered within USUV Europe 2 lineage. The next-generation sequencing of one mosquito pool (Cx. pipiens complex) collected in 2018 in Zagreb confirmed the presence of USUV and revealed several dsDNA and ssRNA viruses of insect, bacterial and mammalian origin.

Crystallographic and modeling study of the human inorganic pyrophosphatase 1: A potential anti-cancer drug target.

Inorganic pyrophosphatases (PPases) catalyze the hydrolysis of pyrophosphate to phosphates. PPases play essential roles in growth and development, and are found in all kingdoms of life. Human possess two PPases, PPA1 and PPA2. PPA1 is present in all tissues, acting largely as a housekeeping enzyme. Besides pyrophosphate hydrolysis, PPA1 can also directly dephosphorylate phosphorylated c-Jun N-terminal kinases 1 (JNK1). Upregulated expression of PPA1 has been linked to many human malignant tumors. PPA1 knockdown induces apoptosis and decreases proliferation. PPA1 is emerging as a potential prognostic biomarker and target for anti-cancer drug development. In spite of the biological and physiopathological importance of PPA1, there is no detailed study on the structure and catalytic mechanisms of mammalian origin PPases. Here we report the crystal structure of human PPA1 at a resolution of 2.4Å. We also carried out modeling studies of PPA1 in complex with JNK1 derived phosphor-peptides. The monomeric protein fold of PPA1 is similar to those found in other family I PPases. PPA1 forms a dimeric structure that should be conserved in animal and fungal PPases. Analysis of the PPA1 structure and comparison with available structures of PPases from lower organisms suggest that PPA1 has a largely pre-organized and relatively rigid active site for pyrophosphate hydrolysis. Results from the modeling study indicate the active site of PPA1 has the potential to accommodate double-phosphorylated peptides from JNK1. In short, results from the study provides new insights into the mechanisms of human PPA1 and basis for structure-based anti-cancer drug developments using PPA1 as the target.

The utilization of small non-mammals in traumatic brain injury research: A systematic review.

Traumatic brain injury (TBI) is the leading cause of death and disability worldwide and has complicated underlying pathophysiology. Numerous TBI animal models have been developed over the past decade to effectively mimic the human TBI pathophysiology. These models are of mostly mammalian origin including rodents and non‐human primates. However, the mammalian models demanded higher costs and have lower throughput often limiting the progress in TBI research. Thus, this systematic review aims to discuss the potential benefits of non‐mammalian TBI models in terms of their face validity in resembling human TBI. Three databases were searched as follows: PubMed, Scopus, and Embase, for original articles relating to non‐mammalian TBI models, published between January 2010 and December 2019. A total of 29 articles were selected based on PRISMA model for critical appraisal. Zebrafish, both larvae and adult, was found to be the most utilized non‐mammalian TBI model in the current literature, followed by the fruit fly and roundworm. In conclusion, non‐mammalian TBI models have advantages over mammalian models especially for rapid, cost‐effective, and reproducible screening of effective treatment strategies and provide an opportunity to expedite the advancement of TBI research.

Amylin and Calcitonin: Potential Therapeutic Strategies to Reduce Body Weight and Liver Fat.

The hormones amylin and calcitonin interact with receptors within the same family to exert their effects on the human organism. Calcitonin, derived from thyroid C cells, is known for its inhibitory effect on osteoclasts. Calcitonin of mammalian origin promotes insulin sensitivity, while the more potent calcitonin extracted from salmon additionally inhibits gastric emptying, promotes gallbladder relaxation, increases energy expenditure and induces satiety as well as weight loss. Amylin, derived from pancreatic beta cells, regulates plasma glucose by delaying gastric emptying after meal ingestion, and modulates glucagon secretion and central satiety signals in the brain. Thus, both hormones seem to have metabolic effects of relevance in the context of non-alcoholic fatty liver disease (NAFLD) and other metabolic diseases. In rats, studies with dual amylin and calcitonin receptor agonists have demonstrated robust body weight loss, improved glucose tolerance and a decreased deposition of fat in liver tissue beyond what is observed after a body weight loss. The translational aspects of these preclinical data currently remain unknown. Here, we describe the physiology, pathophysiology, and pharmacological effects of amylin and calcitonin and review preclinical and clinical findings alluding to the future potential of amylin and calcitonin-based drugs for the treatment of obesity and NAFLD.

Evaluation of natural endosymbiosis for progress towards artificial endosymbiosis

Endosymbiosis or symbiogenesis is a process where a cell hosts another cell that is acquired through phagocytosis or natural entry of the cell within its cytoplasm. Endosymbiosis has a profound effect on the survival of the host cell by conferring nutritional and/or biosynthetic advantage. Therefore, attempts of artificial endosymbiosis have become one of the most challenging projects in synthetic biology. In this paper, we review the process of endosymbiosis, its levels, requirements and mechanisms. We then review the unique cases of ‘natural endosymbiosis’. Furthermore, we describe and evaluate the recent cases of attempted artificial endosymbiosis. Subsequently, we assess the potential barriers to the possibility of endosymbiosis of highly evolved cell types such as mammalian cells that are known for their high inflexibility towards hosting potentially even the most ‘benign endosymbionts’. The paper concludes with possibilities and methodologies that may have not been evaluated or tried in the past, but may be used to increase the chance of artificial endosymbiosis of host cells such as those from mammalian origin that are not permissive to even benign endosymbionts. Artificial endosymbiosis is worth revisiting in this post-genomic, synthetic biology era because the tools and techniques currently available at our disposal have significantly advanced to make this grand challenge a possibility.

Structural Organization and Protein-Protein Interactions in Human Adenovirus Capsid.

Human adenoviruses (HAdVs) are large (150 MDa), complex, nonenveloped dsDNA viruses that cause self-limiting respiratory, ocular and enteric infections. They are significant health hazard in young, elderly and immuno-compromised populations. Moreover, various adenoviruses (AdVs) of mammalian origin are being used as vectors in gene, vaccine and cancer therapies. Multiple copies of at least 13 different proteins, all in all ~2800 protein molecules, come together to form an adenovirus virion packaging the ~36Kbp geome. The details of structural organization of the adenovirus capsid and underlying network of protein-protein interactions provide clues into designing the modified and novel adenovirus vectors with desired functionalities and/or targeting specificities. The advancements in 3D structure determination by cryo-electron microscopy (cryo-EM) in the past decade have enabled unveiling of the complex organization of adenovirus architecture at near atomic resolution. Specifically, these studies revealed the structures and the network of interactions involving cement/minor proteins in stabilizing the AdV icosahedral architecture, which appear to be mostly conserved among human adenoviruses. In this chapter, we describe the current state of knowledge on the structure and organization of human adenoviruses.

Biological Functions of Prokaryotic Amyloids in Interspecies Interactions: Facts and Assumptions.

Amyloids are fibrillar protein aggregates with an ordered spatial structure called “cross-β”. While some amyloids are associated with development of approximately 50 incurable diseases of humans and animals, the others perform various crucial physiological functions. The greatest diversity of amyloids functions is identified within prokaryotic species where they, being the components of the biofilm matrix, function as adhesins, regulate the activity of toxins and virulence factors, and compose extracellular protein layers. Amyloid state is widely used by different pathogenic bacterial species in their interactions with eukaryotic organisms. These amyloids, being functional for bacteria that produce them, are associated with various bacterial infections in humans and animals. Thus, the repertoire of the disease-associated amyloids includes not only dozens of pathological amyloids of mammalian origin but also numerous microbial amyloids. Although the ability of symbiotic microorganisms to produce amyloids has recently been demonstrated, functional roles of prokaryotic amyloids in host–symbiont interactions as well as in the interspecies interactions within the prokaryotic communities remain poorly studied. Here, we summarize the current findings in the field of prokaryotic amyloids, classify different interspecies interactions where these amyloids are involved, and hypothesize about their real occurrence in nature as well as their roles in pathogenesis and symbiosis.

Solubility, Stability, and Avidity of Recombinant Antibody Fragments Expressed in Microorganisms.

Solubility of recombinant proteins (i.e., the extent of soluble versus insoluble expression in heterogeneous hosts) is the first checkpoint criterion for determining recombinant protein quality. However, even soluble proteins often fail to represent functional activity because of the involvement of non-functional, misfolded, soluble aggregates, which compromise recombinant protein quality. Therefore, screening of solubility and folding competence is crucial for improving the quality of recombinant proteins, especially for therapeutic applications. The issue is often highlighted especially in bacterial recombinant hosts, since bacterial cytoplasm does not provide an optimal environment for the folding of target proteins of mammalian origin. Antibody fragments, such as single-chain variable fragment (scFv), single-chain antibody (scAb), and fragment antigen binding (Fab), have been utilized for numerous applications such as diagnostics, research reagents, or therapeutics. Antibody fragments can be efficiently expressed in microorganisms so that they offer several advantages for diagnostic applications such as low cost and high yield. However, scFv and scAb fragments have generally lower stability to thermal stress than full-length antibodies, necessitating a judicious combination of designer antibodies, and bacterial hosts harnessed with robust chaperone function. In this review, we discuss efforts on not only the production of antibodies or antibody fragments in microorganisms but also scFv stabilization via (i) directed evolution of variants with increased stability using display systems, (ii) stabilization of the interface between variable regions of heavy (VH) and light (VL) chains through the introduction of a non-native covalent bond between the two chains, (iii) rational engineering of VH-VL pair, based on the structure, and (iv) computational approaches. We also review recent advances in stability design, increase in avidity by multimerization, and maintaining the functional competence of chimeric proteins prompted by various types of chaperones.