Organization of multi-binding to host proteins: The glyceraldehyde-3-phosphate dehydrogenase (GAPDH) of Mycoplasma pneumoniae

Marine-Derived Sulfated Glycans Inhibit the Interaction of Heparin with Adhesion Proteins of Mycoplasma pneumoniae

Mycoplasma pneumoniae, a notable pathogen behind respiratory infections, employs specialized proteins to adhere to the respiratory epithelium, an essential process for initiating infection. The role of glycosaminoglycans, especially heparan sulfate, is critical in facilitating pathogen-host interactions, presenting a strategic target for therapeutic intervention. In this study, we assembled a glycan library comprising heparin, its oligosaccharide derivatives, and a variety of marine-derived sulfated glycans to screen the potential inhibitors for the pathogen-host interactions. By using Surface Plasmon Resonance spectroscopy, we evaluated the library's efficacy in inhibiting the interaction between M. pneumoniae adhesion proteins and heparin. Our findings offer a promising avenue for developing novel therapeutic strategies against M. pneumoniae infections.

The complete genome sequence of unculturable Mycoplasma faucium obtained through clinical metagenomic next-generation sequencing

Introduction

Diagnosing Mycoplasma faucium poses challenges, and it's unclear if its rare isolation is due to infrequent occurrence or its fastidious nutritional requirements.

Methods

This study analyzes the complete genome sequence of M. faucium, obtained directly from the pus of a sternum infection in a lung transplant patient using metagenomic sequencing.

Results

Genome analysis revealed limited therapeutic options for the M. faucium infection, primarily susceptibility to tetracyclines. Three classes of mobile genetic elements were identified: two new insertion sequences, a new prophage (phiUMCG-1), and a species-specific variant of a mycoplasma integrative and conjugative element (MICE). Additionally, a Type I Restriction-Modification system was identified, featuring 5'-terminally truncated hsdS pseudogenes with overlapping repeats, indicating the potential for forming alternative hsdS variants through recombination.

Conclusion

This study represents the first-ever acquisition of a complete circularized bacterial genome directly from a patient sample obtained from invasive infection of a primary sterile site using culture-independent, PCR-free clinical metagenomics.

Analyzing the interaction of Helicobacter pylori GAPDH with host molecules and hemin: Inhibition of hemin binding

Glyceraldehyde 3-phosphate dehydrogenase (GAPDH) is a moonlighting enzyme. Apart from its primary role in the glycolytic pathway, in many bacterial species it is found in the extracellular milieu and also on the bacterial surface. Positioning on the bacterial surface allows the GAPDH molecule to interact with many host molecules such as plasminogen, fibrinogen, fibronectin, laminin and mucin etc. This facilitates the bacterial colonization of the host. Helicobacter pylori is a major human pathogen that causes a number of gastrointestinal infections and is the main cause of gastric cancer. The binding analysis of H. pylori GAPDH (HpGAPDH) with host molecules has not been carried out. Hence, we studied the interaction of HpGAPDH with holo-transferrin, lactoferrin, haemoglobin, fibrinogen, fibronectin, catalase, plasminogen and mucin using biolayer interferometry. Highest and lowest binding affinity was observed with lactoferrin (4.83 ± 0.70 × 10-9 M) and holo-transferrin (4.27 ± 2.39 × 10-5 M). Previous studies established GAPDH as a heme chaperone involved in intracellular heme trafficking and delivery to downstream target proteins. Therefore, to get insights into heme binding, the interaction between HpGAPDH and hemin was analyzed. Hemin binds to HpGAPDH with an affinity of 2.10 μM while the hemin bound HpGAPDH does not exhibit activity. This suggests that hemin most likely binds at the active site of HpGAPDH, prohibiting substrate binding. Blind docking of hemin with HpGAPDH also supports positioning of hemin at the active site. Metal ions were found to inhibit the activity of HpGAPDH, suggesting that it also possibly occupies the substrate binding site. Furthermore, with metal-bound HpGAPDH, hemin binding was not observed, suggesting metal ions act as an inhibitor of hemin binding. Since GAPDH has been identified as a heme chaperone, it will be interesting to analyse the biological consequences of inhibition of heme binding to GAPDH by metal ions.

Glyceraldehyde 3-Phosphate Dehydrogenase on the Surface of Candida albicans and Nakaseomyces glabratus Cells-A Moonlighting Protein That Binds Human Vitronectin and Plasminogen and Can Adsorb to Pathogenic Fungal Cells via Major Adhesins Als3 and Epa6

Candida albicans and other closely related pathogenic yeast-like fungi carry on their surface numerous loosely adsorbed "moonlighting proteins"-proteins that play evolutionarily conserved intracellular functions but also appear on the cell surface and exhibit additional functions, e.g., contributing to attachment to host tissues. In the current work, we characterized this "moonlighting" role for glyceraldehyde 3-phosphate dehydrogenase (GAPDH, EC 1.2.1.12) of C. albicans and Nakaseomyces glabratus. GAPDH was directly visualized on the cell surface of both species and shown to play a significant part in the total capacity of fungal cells to bind two selected human host proteins-vitronectin and plasminogen. Using purified proteins, both host proteins were found to tightly interact with GAPDH, with dissociation constants in an order of 10-8 M, as determined by bio-layer interferometry and surface plasmon resonance measurements. It was also shown that exogenous GAPDH tightly adheres to the surface of candidal cells, suggesting that the cell surface location of this moonlighting protein may partly result from the readsorption of its soluble form, which may be present at an infection site (e.g., due to release from dying fungal cells). The major dedicated adhesins, covalently bound to the cell wall-agglutinin-like sequence protein 3 (Als3) and epithelial adhesin 6 (Epa6)-were suggested to serve as the docking platforms for GAPDH in C. albicans and N. glabratus, respectively.

Hijacking of Host Plasminogen by Mesomycoplasma (Mycoplasma) hyopneumoniae via GAPDH: an Important Virulence Mechanism To Promote Adhesion and Extracellular Matrix Degradation

Mesomycoplasma hyopneumoniae is the etiological agent of mycoplasmal pneumonia of swine (MPS), which causes substantial economic losses to the world's swine industry. Moonlighting proteins are increasingly being shown to play a role in the pathogenic process of M. hyopneumoniae. Glyceraldehyde-3-phosphate dehydrogenase (GAPDH), a key enzyme in glycolysis, displayed a higher abundance in a highly virulent strain of M. hyopneumoniae than in an attenuated strain, suggesting that it may have a role in virulence. The mechanism by which GAPDH exerts its function was explored. Flow cytometry and colony blot analysis showed that GAPDH was partly displayed on the surface of M. hyopneumoniae. Recombinant GAPDH (rGAPDH) was able to bind PK15 cells, while the adherence of a mycoplasma strain to PK15 was significantly blocked by anti-rGAPDH antibody pretreatment. In addition, rGAPDH could interact with plasminogen. The rGAPDH-bound plasminogen was demonstrated to be activated to plasmin, as proven by using a chromogenic substrate, and to further degrade the extracellular matrix (ECM). The critical site for GAPDH binding to plasminogen was K336, as demonstrated by amino acid mutation. The affinity of plasminogen for the rGAPDH C-terminal mutant (K336A) was significantly decreased according to surface plasmon resonance analysis. Collectively, our data suggested that GAPDH might be an important virulence factor that facilitates the dissemination of M. hyopneumoniae by hijacking host plasminogen to degrade the tissue ECM barrier. IMPORTANCE Mesomycoplasma hyopneumoniae is a specific pathogen of pigs that is the etiological agent of mycoplasmal pneumonia of swine (MPS), which is responsible for substantial economic losses to the swine industry worldwide. The pathogenicity mechanism and possible particular virulence determinants of M. hyopneumoniae are not yet completely elucidated. Our data suggest that GAPDH might be an important virulence factor in M. hyopneumoniae that facilitates the dissemination of M. hyopneumoniae by hijacking host plasminogen to degrade the extracellular matrix (ECM) barrier. These findings will provide theoretical support and new ideas for the research and development of live-attenuated or subunit vaccines against M. hyopneumoniae.

GAPDH Released from Lactobacillus johnsonii MG Enhances Barrier Function by Upregulating Genes Associated with Tight Junctions

Extracellular glyceraldehyde-3-phosphate dehydrogenase (GAPDH) has multiple interactions with various gut epithelial components. For instance, GAPDH in Lactobacillus johnsonii MG cells interacts with junctional adhesion molecule-2 (JAM-2) in Caco-2 cells and enhances tight junctions. However, the specificity of GAPDH toward JAM-2 and its role in the tight junctions in Caco-2 cells remain unclear. In the present study, we assessed the effect of GAPDH on tight junction regeneration and explored the GAPDH peptide fragments required for interaction with JAM-2. GAPDH was specifically bound to JAM-2 and rescued H₂O₂-damaged tight junctions in Caco-2 cells, with various genes being upregulated in the tight junctions. To understand the specific amino acid sequence of GAPDH that interacts with JAM-2, peptides interacting with JAM-2 and L. johnsonii MG cells were purified using HPLC and predicted using TOF-MS analysis. Two peptides, namely ¹¹GRIGRLAF¹⁸ at the N-terminus and ³²³SFTCQMVRTLLKFATL³³⁸ at the C-terminus, displayed good interactions and docking with JAM-2. In contrast, the long peptide ⁵²DSTHGTFNHEVSATDDSIVVDGKKYRVYAEPQAQNIPW⁸⁹ was predicted to bind to the bacterial cell surface. Overall, we revealed a novel role of GAPDH purified from L. johnsonii MG in promoting the regeneration of damaged tight junctions and identified the specific sequences of GAPDH involved in JAM-2 binding and MG cell interaction.

Reversion of mutations in a live mycoplasma vaccine alters its metabolism

The live attenuated temperature sensitive vaccine strain MS-H (Vaxsafe® MS, Bioproperties Pty. Ltd., Australia) is widely used to control disease associated with M. synoviae infection in commercial poultry. MS-H was derived from a field strain (86079/7NS) through N-methyl-N'-nitro-N-nitrosoguanidine (NTG)-induced mutagenesis. Whole genomic sequence analysis of the MS-H and comparison with that of the 86079/7NS have found that MS-H contains 32 single nucleotide polymorphisms (SNPs). Three of these SNPs, found in the obgE, oppF and gapdh genes, have been shown to be prone to reversion under field condition, albeit at a low frequency. Three MS-H reisolates containing the 86079/7NS genotype in obgE (AS2), obgE and oppF (AB1), and obgE, oppF and gapdh (TS4), appeared to be more immunogenic and transmissible compared to MS-H in chickens. To investigate the influence of these reversions in the in vitro fitness of M. synoviae, the growth kinetics and steady state metabolite profiles of the MS-H reisolates, AS2, AB1 and TS4, were compared to those of the vaccine strain. Steady state metabolite profiling of the reisolates showed that changes in ObgE did not significantly influence the metabolism, while changes in OppF was associated with significant alterations in uptake of peptides and/or amino acids into the M. synoviae cell. It was also found that GAPDH plays a role in metabolism of the glycerophospholipids as well as an arginine deiminase (ADI) pathway. This study underscores the role of ObgE, OppF and GAPDH in M. synoviae metabolism, and suggests that the impaired fitness arising from variations in ObgE, OppF and GAPDH contributes to attenuation of MS-H.

Moonlighting proteins: beacon of hope in era of drug resistance in bacteria

Moonlighting proteins (MLPs) are ubiquitous and provide a unique advantage to bacteria performing multiple functions using the same genomic content. Targeting MLPs can be considered as a futuristic approach in fighting drug resistance problem. This review follows the MLP trail from its inception to the present-day state, describing a few bacterial MLPs, viz., glyceraldehyde 3'-phosphate dehydrogenase, phosphoglucose isomerase glutamate racemase (GR), and DNA gyrase. Here, we carve out that targeting MLPs are the beacon of hope in an era of increasing drug resistance in bacteria. Evolutionary stability, structure-functional relationships, protein diversity, possible drug targets, and identification of new drugs against bacterial MLP are given due consideration. Before the final curtain calls, we provide a comprehensive list of small molecules that inhibit the biochemical activity of MLPs, which can aid the development of novel molecules to target MLPs for therapeutic applications.

Genomic Diversity of a Globally Used, Live Attenuated Mycoplasma Vaccine

The Mycoplasma synoviae live attenuated vaccine strain MS-H (Vaxsafe MS; Bioproperties Pty., Ltd., Australia) is commonly used around the world to prevent chronic infections caused by M. synoviae in birds and to minimize economic losses in the poultry industry. MS-H is a temperature-sensitive strain that is generated via the chemical mutagenesis of a virulent M. synoviae isolate, 86079/7NS. 32 single nucleotide polymorphisms have been found in the genome of MS-H compared to that of 86079/7NS, including 25 in predicted coding sequences (CDSs). There is limited information on the stability of these mutations in MS-H in vitro during the propagation of the vaccine manufacturing process or in vivo after the vaccination of chickens. Here, we performed a comparative analysis of MS-H genomes after in vitro and in vivo passages under different circumstances. Studying the dynamics of the MS-H population can provide insights into the factors that potentially affect the health of vaccinated birds. The genomes of 11 in vitro laboratory passages and 138 MS-H bird reisolates contained a total of 254 sequence variations. Of these, 39 variations associated with CDSs were detected in more than one genome (range = 2 to 62, median = 2.5), suggesting that these sequences are particularly prone to mutations. From the 25 CDSs containing previously characterized variations between MS-H and 86079/7NS, 7 were identified in the MS-H reisolates and progenies examined here. In conclusion, the MS-H genome contains individual regions that are prone to mutations that enable the restoration of the genotype or the phenotype of wild-type 86079/7NS in those regions. However, accumulated mutations in these regions are rare. IMPORTANCE Preventative measures, such as vaccination, are commonly used for the control of mycoplasmal infections in poultry. A live attenuated vaccine strain (Vaxsafe MS; MS-H; Bioproperties Pty. Ltd., Australia) is used for the prevention of disease caused by M. synoviae in many countries. However, information on the stability of previously characterized mutations in the MS-H genome is limited. In this study, we performed a comparative analysis of the whole-genome sequences of MS-H seeds used for vaccine manufacturing, commercial batches of the vaccine, cultures minimally passaged under small-scale laboratory and large-scale manufacturing conditions, MS-H reisolated from specific-pathogen-free (SPF) chickens that were vaccinated under controlled conditions, and MS-H reisolated from vaccinated commercial poultry flocks around the world. This study provides a comprehensive assessment of genome stability in MS-H after in vitro and in vivo passages under different circumstances and suggests that most of the mutations in the attenuated MS-H vaccine strain are stable.

First identification of Nocardia seriolae GapA adhesion function and its three B-cell epitopes with cell-binding activity

Fish nocardiosis mainly caused by Nocardia seriolae (N. seriolae) is a serious threat to aquaculture. Bacterial adhesion to host cells mediated by adhesin is an initial step of pathogenesis. But it is not clear whether glyceraldehyde-3-phosphate dehydrogenase (GapA) is an adhesin of N. seriolae. Here, recombinant GapA protein (rGapA) was prokaryotic expressed, and its role in the bacterial adhesion to Ctenopharyngodon idella kidney cells was investigated by indirect immunofluorescence, protein-binding assay and adhesion inhibition assay. The results showed that an obvious green fluorescence was observed on the surface of the cells co-incubated with rGapA protein; the cytomembrane proteins of the cells pretreated with rGapA could react with anti-rGapA antibody; and the antibody significantly inhibited the adhesion ability of the bacteria. Subsequently, B-cell linear epitopes of GapA protein were identified by using a immunoinformatics approach combined with peptide ELISA and Western blot for the first time. It was found that four predicted epitopes (Ep_58-69 , Ep_139-150 , Ep_186-197 , Ep_318-329 ) could all react with anti-rGapA antibody and obviously inhibit the immunoreactivity between rGapA and anti-rGapA antibody, and they were confirmed as indeed B-cell linear epitopes of the protein. Furthermore, flow cytometry analysis found the percentage of positive cells co-incubated with FITC-labelled epitope peptides (Ep_139-150 , Ep_186-197 , Ep_318-329 ) was significantly higher than those in the FITC-labelled Ep_58-69 , unrelated control peptide and cell control. Collectively, GapA is an adhesin of N. seriolae, and epitope peptides (Ep_139-150 , Ep_186-197 , Ep_318-329 ) possess cell-binding activity, which are potential candidates for developing a multiple epitopes-based adhesin vaccine against fish nocardiosis.

Virulence factors of Mycoplasma synoviae: Three genes influencing colonization, immunogenicity, and transmissibility

Infections caused by Mycoplasma synoviae are major welfare and economic concerns in poultry industries worldwide. These infections cause chronic respiratory disease and/or synovitis in chickens and turkeys leading to reduced production and increased mortality rates. The live attenuated vaccine strain MS-H (Vaxsafe® MS), commonly used for protection against M. synoviae infection in many countries, contains 32 single nucleotide variations compared to its wildtype parent strain, 86079/7NS. Genomic analysis of vaccine strains reisolated from flocks following the administration of MS-H has identified reversions to the original 86079/7NS sequence in the obgE, oppF and gapdh genes. Here, three MS-H field reisolates containing the 86079/7NS genotype in obgE (AS2), obgE and oppF (AB1), and obgE, oppF and gapdh (TS4), as well as the vaccine MS-H and the parental strain 86079/7NS were experimentally inoculated to chickens. The strains were assessed for their ability to infect and elicit immune responses in the recipient chickens, as well as in naïve in-contact chickens. Despite the loss of temperature sensitivity phenotype and colonization of the reisolates in the lower respiratory tract, there was no significant differences detected in the microscopic mucosal thickness of the middle or lower trachea of the inoculated chickens. Concurrent reversions in ObgE, OppF and GAPDH proteins were associated with higher gross air sac lesion scores and increased microscopic upper-tracheal mucosal thickness in chickens directly inoculated with the reisolates following intratracheal administration of a virulent strain of infectious bronchitis virus. The gross air sac lesions of the chickens in-contact with those inoculated with reisolates were not significantly different to those of chickens in-contact with MS-H inoculated chickens, suggesting that horizontal transmission of the reisolates in the poultry flock will not lead to higher pathogenicity or clinical signs. These results suggest a significant role of GAPDH and/or cumulative effect of ObgE, OppF and GAPDH on M. synoviae pathogenicity. Future experiments will be required to investigate the effect of single mutations in gapdh or oppF gene on pathogenicity of M. synoviae.

DnaK Functions as a Moonlighting Protein on the Surface of Mycoplasma hyorhinis Cells

Mycoplasma hyorhinis is a common pathogen of swine and is also associated with various human tumors. It causes systemic inflammation, typically polyserositis and polyarthritis, in some infected pigs. However, the pathogenic mechanism of M. hyorhinis remains unclear. DnaK is a highly conserved protein belonging to the heat-shock protein 70 family of molecular chaperones, which plays important roles as a moonlighting protein in various bacteria. In the present study, we identified the surface exposure of M. hyorhinis DnaK. Two virulent strains expressed more DnaK on their surface than the avirulent strain. Thereafter, the potential moonlighting functions of DnaK were investigated. Recombinant M. hyorhinis DnaK (rMhr-DnaK) was found to be able to adhere to swine PK-15 cells and human NCI-H292 cells. It also bound to four extracellular matrix components-fibronectin, laminin, type IV collagen, and vitronectin-in a dose-dependent manner. ELISA demonstrated an interaction between rMhr-DnaK and plasminogen, which was significantly inhibited by a lysine analog, ε-aminocaproic acid. rMhr-DnaK-bound plasminogen was activated by tissue-type plasminogen activator (tPA), and the addition of rMhr-DnaK significantly enhanced the activation. Finally, a DnaK-specific antibody was detected in the serum of pigs immunized with inactivated vaccines, which indicated good immunogenicity of it. In summary, our findings imply that DnaK is an important multifunctional moonlighting protein in M. hyorhinis and likely participates extensively in the infection and pathogenesis processes of M. hyorhinis.

The variable lipoprotein family participates in the interaction of Mycoplasma hyorhinis with host extracellular matrix and plasminogen

Mycoplasma hyorhinis (Mhr) infects pigs, typically causing polyserositis and polyarthritis. It has also been reported in various human tumors. The variable lipoprotein (Vlp) family is a vital surface component mediating the immune evasion of Mhr. We have previously reported its functions in the adherence of Mhr to pig cells. Herein, we further evaluated its role in interacting with host extracellular matrix (ECM) components (fibronectin, collagen type Ⅳ and laminin) and plasminogen. Consequently, the recombinant Vlp proteins of all the seven members (VlpA-VlpG) were able to bind most of the tested host molecules. Further experiment showed that region Ⅱ of all Vlp members has a strong binding ability, while the binding ability of region Ⅲ of each member varied between different host molecules. Comparing the Vlps containing short (rVlpX3) or long (rVlpX12) region Ⅲ, we found that the ability of most Vlps binding NCI-H292 cell membrane proteins became weaker as the molecule grows, except VlpG. However, the binding of VlpA, VlpB, VlpC and VlpG to tested ECM components and plasminogen tended to increase as Vlps became longer, and those of VlpE and VlpF decreased, and that of VlpD did not change. Furthermore, the activation of Vlp-bound plasminogen was proved. In summary, the Vlp family participates in the interaction of Mhr with host ECM and plasminogen in addition to cytoadhesion. The size variation of Vlps is likely to further regulate these interactions. The results may help to elucidate the roles of Vlps in the persistent infection of Mhr.

Pathogenicity & virulence of Mycoplasma hyopneumoniae

Mycoplasma hyopneumoniae: is the etiological agent of porcine enzootic pneumonia (EP), a disease that impacts the swine industry worldwide. Pathogen-induced damage, as well as the elicited host-response, contribute to disease. Here, we provide an overview of EP epidemiology, control and prevention, and a more in-depth review of M. hyopneumoniae pathogenicity determinants, highlighting some molecular mechanisms of pathogen-host interactions relevant for pathogenesis. Based on recent functional, immunological, and comparative “omics” results, we discuss the roles of many known or putative M. hyopneumoniae virulence factors, along with host molecules involved in EP. Moreover, the known molecular bases of pathogenicity mechanisms, including M. hyopneumoniae adhesion to host respiratory epithelium, protein secretion, cell damage, host microbicidal response and its modulation, and maintenance of M. hyopneumoniae homeostasis during infection are described. Recent findings regarding M. hyopneumoniae pathogenicity determinants also contribute to the development of novel diagnostic tests, vaccines, and treatments for EP.

Pathogen Moonlighting Proteins: From Ancestral Key Metabolic Enzymes to Virulence Factors

Moonlighting and multitasking proteins refer to proteins with two or more functions performed by a single polypeptide chain. An amazing example of the Gain of Function (GoF) phenomenon of these proteins is that 25% of the moonlighting functions of our Multitasking Proteins Database (MultitaskProtDB-II) are related to pathogen virulence activity. Moreover, they usually have a canonical function belonging to highly conserved ancestral key functions, and their moonlighting functions are often involved in inducing extracellular matrix (ECM) protein remodeling. There are three main questions in the context of moonlighting proteins in pathogen virulence: (A) Why are a high percentage of pathogen moonlighting proteins involved in virulence? (B) Why do most of the canonical functions of these moonlighting proteins belong to primary metabolism? Moreover, why are they common in many pathogen species? (C) How are these different protein sequences and structures able to bind the same set of host ECM protein targets, mainly plasminogen (PLG), and colonize host tissues? By means of an extensive bioinformatics analysis, we suggest answers and approaches to these questions. There are three main ideas derived from the work: first, moonlighting proteins are not good candidates for vaccines. Second, several motifs that might be important in the adhesion to the ECM were identified. Third, an overrepresentation of GO codes related with virulence in moonlighting proteins were seen.

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) moonlights as an adhesin in Mycoplasma hyorhinis adhesion to epithelial cells as well as a plasminogen receptor mediating extracellular matrix degradation

Mycoplasma hyorhinis infects pigs causing polyserositis and polyarthritis, and has also been reported in a variety of human tumor tissues. The occurrence of disease is often linked with the systemic invasion of the pathogen. Glyceraldehyde-3-Phosphate Dehydrogenase (GAPDH), one of the key enzymes of glycolysis, was reported as a surface multifunctional molecule in several bacteria. Here, we investigated whether GAPDH could manifest binary functions; as an adhesin to promote colonization as well as a plasminogen receptor functioning in extracellular matrix (ECM) degradation to promote systemic invasion. The surface localization of GAPDH was observed in M. hyorhinis with flow cytometry and colony blot analysis. Recombinant GAPDH (rGAPDH) was found to be able to bind porcine-derived PK-15 and human-derived NCI-H292 cells. The incubation with anti-GAPDH antibody significantly decreased the adherence of M. hyorhinis to both cell lines. To investigate its function in recruiting plasminogen, firstly, the interaction between rGAPDH and plasminogen was demonstrated by ELISA and Far-Western blot assay. The activation of the rGAPDH-bound plasminogen into plasmin was proved by using a chromogenic substrate, and furtherly confirmed to degrade extracellular matrix by using a reconstituted ECM. Finally, the ability of rGAPDH to bind different ECM components was demonstrated, including fibronectin, laminin, collagen type IV and vitronectin. Collectively, our data imply GAPDH as an important adhesion factor of M. hyrohinis and a receptor for hijacking host plasminogen to degrade ECM. The multifunction of GAPDH to bind both plasminogen and ECM components is believed to increase the targeting of proteolysis and facilitate the dissemination of M. hyorhinis.

Infection strategies of mycoplasmas: Unraveling the panoply of virulence factors

Mycoplasmas, the smallest bacteria lacking a cell wall, can cause various diseases in both humans and animals. Mycoplasmas harbor a variety of virulence factors that enable them to overcome numerous barriers of entry into the host; using accessory proteins, mycoplasma adhesins can bind to the receptors or extracellular matrix of the host cell. Although the host immune system can eradicate the invading mycoplasma in most cases, a few sagacious mycoplasmas employ a series of invasion and immune escape strategies to ensure their continued survival within their hosts. For instance, capsular polysaccharides are crucial for anti-phagocytosis and immunomodulation. Invasive enzymes degrade reactive oxygen species, neutrophil extracellular traps, and immunoglobulins. Biofilm formation is important for establishing a persistent infection. During proliferation, successfully surviving mycoplasmas generate numerous metabolites, including hydrogen peroxide, ammonia and hydrogen sulfide; or secrete various exotoxins, such as community-acquired respiratory distress syndrome toxin, and hemolysins; and express various pathogenic enzymes, all of which have potent toxic effects on host cells. Furthermore, some inherent components of mycoplasmas, such as lipids, membrane lipoproteins, and even mycoplasma-generated superantigens, can exert a significant pathogenic impact on the host cells or the immune system. In this review, we describe the proposed virulence factors in the toolkit of notorious mycoplasmas to better understand the pathogenic features of these bacteria, along with their pathogenic mechanisms.

Mycobacterium tuberculosis glyceraldehyde-3-phosphate dehydrogenase plays a dual role-As an adhesin and as a receptor for plasmin(ogen)

The spread of infection is directly determined by the ability of a pathogen to invade and infect host tissues. The process involves adherence due to host-pathogen interactions and traversal into deeper tissues. Mycobacterium tuberculosis (Mtb) primarily infects the lung but is unique in its ability to infect almost any other organ of the human host including immune privileged sites such as the central nervous system (CNS). The extreme invasiveness of this bacterium is not fully understood. In the current study, we report that cell surface Mtb glyceraldehyde-3-phosphate dehydrogenase (GAPDH) functions as a virulence factor by multiple mechanisms. Firstly, it serves as a dual receptor for both plasminogen (Plg) and plasmin (Plm). CRISPRi-mediated silencing of this essential enzyme confirmed its role in the recruitment of Plg/Plm. Our studies further demonstrate that soluble GAPDH can re-associate on Mtb bacilli to promote plasmin(ogen) recruitment. The direct association of plasmin(ogen) via cell surface GAPDH or by the re-association of soluble GAPDH enhanced bacterial adherence to and traversal across lung epithelial cells. Furthermore, the association of GAPDH with host extracellular matrix (ECM) proteins coupled with its ability to recruit plasmin(ogen) may endow cells with the ability of directed proteolytic activity vital for tissue invasion.

Optimized GAPDH-truncated immunogen of Streptococcus equi elicits an enhanced immune response and provides effective protection in a mouse model

Strangles is an acute and frequently diagnosed infectious disease caused by Streptococcus equi subsp. equi. Infection with this pathogen can cause grave losses to the equine industry. The present work investigates glyceraldehyde-3-phosphate dehydrogenase (GAPDH), an important surface-localized virulence factor of S. equi, to determine whether it could be developed into an efficacious and suitable subunit vaccine against strangles. Two different recombinant fragments of S. equi GAPDH, namely, GAPDH-L and GAPDH-S, were constructed and expressed. Further, the antigenicity and immunogenicity of these two recombinant proteins were compared and evaluated in a mouse model. Our results revealed that immune responses were efficiently induced by the proteins in immunized mice. Remarkably, higher survival rates and significantly lower bacterial loads in the lung, liver, kidney, and spleen were observed in the GAPDH-S group compared with the GAPDH-L group after challenge with S. equi. High levels of specific antibodies, elevated antibody titers, and increased proportions of CD8 + T cells further indicated that GAPDH-S elicited better humoral and cellular immune responses than GAPDH-L. Furthermore, the induction of TCR, TLR-2, TLR-3, and TLR-4 significantly increased in the GAPDH-S group compared with those in the GAPDH-L and negative control groups. In summary, our results indicate that the optimized recombinant protein GAPDH-S is a promising candidate construct that may be further developed into a multivalent subunit vaccine for strangles.

Partial catalytic Cys oxidation of human GAPDH to Cys-sulfonic acid

Background: n-Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) catalyses the NAD ⁺-dependent oxidative phosphorylation of n-glyceraldehyde-3-phosphate to 1,3-diphospho-n-glycerate and its reverse reaction in glycolysis and gluconeogenesis.

Methods: Four distinct crystal structures of human n-Glyceraldehyde-3-phosphate dehydrogenase ( HsGAPDH) have been determined from protein purified from the supernatant of HEK293F human epithelial kidney cells.

Results: X-ray crystallography and mass-spectrometry indicate that the catalytic cysteine of the protein ( HsGAPDH Cys152) is partially oxidised to cysteine S-sulfonic acid. The average occupancy for the Cys152-S-sulfonic acid modification over the 20 crystallographically independent copies of HsGAPDH across three of the crystal forms obtained is 0.31±0.17.

Conclusions: The modification induces no significant structural changes on the tetrameric enzyme, and only makes aspecific contacts to surface residues in the active site, in keeping with the hypothesis that the oxidising conditions of the secreted mammalian cell expression system result in HsGAPDH catalytic cysteine S-sulfonic acid modification and irreversible inactivation of the enzyme.

Partial catalytic Cys oxidation of human GAPDH

Background: n-Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) catalyses the reversible NAD+-dependent oxidative phosphorylation of n-glyceraldehyde-3-phosphate to 1,3-diphospho-n-glycerate in both glycolysis and gluconeogenesis.Methods: Four distinct crystal structures of human n-Glyceraldehyde-3-phosphate dehydrogenase (HsGAPDH) have been determined from protein purified from the supernatant of HEK293F human epithelial kidney cells.Results: X-ray crystallography and mass-spectrometry indicate that the catalytic cysteine of the protein (HsGAPDH Cys152) is partially oxidised to cysteine S-sulfonic acid. The average occupancy for the Cys152-S-sulfonic acid modification over the 20 crystallographically independent copies ofHsGAPDH across three of the crystal forms obtained is 0.31±0.17.Conclusions: The modification induces no significant structural changes on the tetrameric enzyme, and only makes aspecific contacts to surface residues in the active site, in keeping with the hypothesis that the oxidising conditions of the secreted mammalian cell expression system result inHsGAPDH catalytic cysteine S-sulfonic acid modification and irreversible inactivation of the enzyme.

Cell surface processing of the P1 adhesin of Mycoplasma pneumoniae identifies novel domains that bind host molecules

Mycoplasma pneumoniae is a genome reduced pathogen and causative agent of community acquired pneumonia. The major cellular adhesin, P1, localises to the tip of the attachment organelle forming a complex with P40 and P90, two cleavage fragments derived by processing Mpn142, and other molecules with adhesive and mobility functions. LC-MS/MS analysis of M. pneumoniae M129 proteins derived from whole cell lysates and eluents from affinity matrices coupled with chemically diverse host molecules identified 22 proteoforms of P1. Terminomics was used to characterise 17 cleavage events many of which were independently verified by the identification of semi-tryptic peptides in our proteome studies and by immunoblotting. One cleavage event released ¹⁵⁹⁷TSAAKPGAPRPPVPPKPGAPKPPVQPPKKPA¹⁶²⁷ from the C-terminus of P1 and this peptide was shown to bind to a range of host molecules. A smaller synthetic peptide comprising the C-terminal 15 amino acids, ¹⁶¹³PGAPKPPVQPPKKPA¹⁶²⁷, selectively bound cytoskeletal intermediate filament proteins cytokeratin 7, cytokeratin 8, cytokeratin 18, and vimentin from a native A549 cell lysate. Collectively, our data suggests that ectodomain shedding occurs on the surface of M. pneumoniae where it may alter the functional diversity of P1, Mpn142 and other surface proteins such as elongation factor Tu via a mechanism similar to that described in Mycoplasma hyopneumoniae.

Diverse Localization and Protein Binding Abilities of Glyceraldehyde-3-Phosphate Dehydrogenase in Pathogenic Bacteria: The Key to its Multifunctionality?

Bacterial proteins exhibiting two or more unrelated functions, referred to as moonlighting proteins, are suggested to contribute to full virulence manifestation in pathogens. An expanding number of published studies have revealed the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH) to be a multitasking protein with virulence impact in a number of pathogenic bacteria. This protein can be detected on the bacterial surface or outside the bacterial cell, where it interacts with host proteins. In this way, GAPDH is able to modulate various pathogenic processes. Moreover, it has been shown to be involved in non-enzymatic processes inside the bacterial cell. In this mini review, we summarize main findings concerning the multiple localization and protein interactions of GAPDH derived from bacterial pathogens of humans. We also briefly discuss problems associated with using GAPDH as a vaccine antigen and endeavor to inspire further research to fill gaps in the existing knowledge.