Tracheal cytotoxin (TCT) is a 921

dalton Dalton may refer to: Science * Dalton (crater), a lunar crater * Dalton (program), chemistry software * Dalton (unit) (Da), the atomic mass unit * John Dalton, chemist, physicist and meteorologist Entertainment * Dalton (Buffyverse), minor cha ...

glycopeptide Glycopeptides are peptides that contain carbohydrate moieties (glycans) covalently attached to the side chains of the amino acid residues that constitute the peptide. Over the past few decades it has been recognised that glycans on cell surfac ...

released by ''

Bordetella pertussis ''Bordetella pertussis'' is a Gram-negative, aerobic, pathogenic, encapsulated coccobacillus of the genus ''Bordetella'', and the causative agent of pertussis or whooping cough. Like '' B. bronchiseptica'', ''B. pertussis'' is motile and expres ...

'', ''

Vibrio fischeri ''Aliivibrio fischeri'' (also called ''Vibrio fischeri'') is a Gram-negative, rod-shaped bacterium found globally in marine environments. This species has bioluminescent properties, and is found predominantly in symbiosis with various marine anim ...

'' (as a symbiosis chemical), and ''

Neisseria gonorrhoeae ''Neisseria gonorrhoeae'', also known as ''gonococcus'' (singular), or ''gonococci'' (plural), is a species of Gram-negative diplococci bacteria isolated by Albert Ludwig Sigesmund Neisser, Albert Neisser in 1879. It causes the sexually transmit ...

'' (among other peptidoglycan-derived cytotoxins it produces). It is a soluble piece of

peptidoglycan Peptidoglycan or murein is a unique large macromolecule, a polysaccharide, consisting of sugars and amino acids that forms a mesh-like peptidoglycan layer outside the plasma membrane, the rigid cell wall (murein sacculus) characteristic of most ...

(PGN) found in the

cell wall A cell wall is a structural layer surrounding some types of cells, just outside the cell membrane. It can be tough, flexible, and sometimes rigid. It provides the cell with both structural support and protection, and also acts as a filtering mech ...

of all

gram-negative Gram-negative bacteria are bacteria that do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. They are characterized by their cell envelopes, which are composed of a thin peptidoglycan cell wall ...

bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...

, but only some bacteria species release TCT due to inability to recycle this piece of anhydromuropeptide.

History

In 1980, it was discovered that ''B. pertussis'' could attach to hamster

tracheal The trachea, also known as the windpipe, is a cartilaginous tube that connects the larynx to the bronchi of the lungs, allowing the passage of air, and so is present in almost all air-breathing animals with lungs. The trachea extends from the la ...

epithelial Epithelium or epithelial tissue is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. It is a thin, continuous, protective layer of compactly packed cells with a little intercellula ...

(HTE)

cell Cell most often refers to: * Cell (biology), the functional basic unit of life Cell may also refer to: Locations * Monastic cell, a small room, hut, or cave in which a religious recluse lives, alternatively the small precursor of a monastery w ...

s, and also, that the

supernatant In an aqueous solution, precipitation is the process of transforming a dissolved substance into an insoluble solid from a super-saturated solution. The solid formed is called the precipitate. In case of an inorganic chemical reaction leading ...

from the cultured

bacterium Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...

could disrupt the

cell cycle The cell cycle, or cell-division cycle, is the series of events that take place in a cell that cause it to divide into two daughter cells. These events include the duplication of its DNA (DNA replication) and some of its organelles, and subs ...

of uninfected

s. This prompted the scientists W. E. Goldman, D. G. Klapper, and J. B. Baseman to isolate and characterize a novel substance from ''B. pertussis''

. The novel

disaccharide A disaccharide (also called a double sugar or ''biose'') is the sugar formed when two monosaccharides are joined by glycosidic linkage. Like monosaccharides, disaccharides are simple sugars soluble in water. Three common examples are sucrose, lact ...

tetrapeptide A tetrapeptide is a peptide, classified as an oligopeptide, since it only consists of four amino acids joined by peptide bonds. Many tetrapeptides are pharmacologically active, often showing affinity and specificity for a variety of receptors in p ...

that they had purified showed

toxicity Toxicity is the degree to which a chemical substance or a particular mixture of substances can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a subst ...

for HTE cells and

ring cultures. Subsequently, they named the newly sequestered molecule

cytotoxin Cytotoxicity is the quality of being toxic to cells. Examples of toxic agents are an immune cell or some types of venom, e.g. from the puff adder (''Bitis arietans'') or brown recluse spider (''Loxosceles reclusa''). Cell physiology Treating cells ...

(TCT).

Structure

TCT is a soluble piece of

(PGN) found in the

of all

. Like all PGNs, TCT is composed of a disaccharide and a peptide chain. The IUPAC name for TCT is N-acetylglucosaminyl-1,6-anhydro-N-acetylmuramyl-(L)-alanyl-γ-(D)-glutamyl-mesodiaminopimelyl-(D)-alanine. It is classified as a DAP (

diaminopimelic acid Diaminopimelic acid (DAP) is an amino acid, representing an epsilon-carboxy derivative of lysine. DAP is a characteristic of certain cell walls of some bacteria. DAP is often found in the peptide linkages of NAM-NAG chains that make up the ce ...

)-type PGN due to the third amino group within the chain being a diaminopimelyl peptide. TCT within Cell Wall

The DAP residue is responsible for directly bonding to the

D-alanine Alanine (symbol Ala or A), or α-alanine, is an α-amino acid that is used in the biosynthesis of proteins. It contains an amine group and a carboxylic acid group, both attached to the central carbon atom which also carries a methyl group side c ...

peptide Peptides (, ) are short chains of amino acids linked by peptide bonds. Long chains of amino acids are called proteins. Chains of fewer than twenty amino acids are called oligopeptides, and include dipeptides, tripeptides, and tetrapeptides. A ...

of another PGN molecule, thus aiding TCT's attachment within the

The DAP portion of TCT also implies importance in cytopathogenicity as analogs lacking DAP show a significant reduction in

Mechanism of pathogenesis

Most

Gram-negative Gram-negative bacteria are bacteria that do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. They are characterized by their cell envelopes, which are composed of a thin peptidoglycan cell wall ...

keep TCT within the

by using a PGN-transporter

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...

known as AmpG. However, ''B. pertussis'' is not capable of recycling PGNs via AmpG and thus, TCT escapes into the surrounding environment. Also, TCT appears to be constitutively expressed by ''B. pertussis''. The first murine-model studies using TCT involved treatment of

hamster Hamsters are rodents (order Rodentia) belonging to the subfamily Cricetinae, which contains 19 species classified in seven genera.Fox, Sue. 2006. ''Hamsters''. T.F.H. Publications Inc. They have become established as popular small pets. The b ...

cells. These experiments alluded to TCT's role in ciliostasis and cellular extrusion of ciliated hamster cells. Also, HTE cells had a markedly reduced level of DNA synthesis post-treatment with TCT. TCTonEpithelialCells

While previous studies using murine models reported evidence of TCT causing ciliostasis, in

vitro Vitro is the largest glass producer in Mexico and one of the world's largest organizations in the glass industry. Founded in 1909 in Monterrey, Mexico, this corporation has 30 subsidiaries in Mexico, United States, Brazil, Colombia, Bolivia, Cost ...

studies using human

cells have shown that TCT does not affect ciliary beat frequency of living cells, but instead causes damage and eventual extrusion of ciliated cells. In

gonorrhea Gonorrhea, colloquially known as the clap, is a sexually transmitted infection (STI) caused by the bacterium '' Neisseria gonorrhoeae''. Infection may involve the genitals, mouth, or rectum. Infected men may experience pain or burning with ...

infections, vaginal ciliated epithelial cells have also displayed the same cytopathogenic effects due to TCT recognition. The extensive damage to ciliated epithelial tissue caused by TCT results in major disruption to the ciliary escalator; an important asset of the host's non-specific defenses. This disruption hinders the host's ability to remove mucous and foreign microbes from the epithelial tissue. Paroxysmal cough, e.g.

whooping cough Whooping cough, also known as pertussis or the 100-day cough, is a highly contagious bacterial disease. Initial symptoms are usually similar to those of the common cold with a runny nose, fever, and mild cough, but these are followed by two or ...

, is a direct symptom of said mucous build-up due to ciliated tissue damage. NOD-1 recognition and the presence of

Lipooligosaccharide Lipopolysaccharides (LPS) are large molecules consisting of a lipid and a polysaccharide that are bacterial toxins. They are composed of an O-antigen, an outer core, and an inner core all joined by a covalent bond, and are found in the outer me ...

(LOS) are two factors that modulate the effect of TCT. NOD-1 is a pattern recognition receptor that detects peptidoglycan. This receptor reacts weakly to TCT in humans, but robustly in mice. TCT is thought to work synergistically with LOS to mediate an inflammatory response, thus causing damage to ciliated epithelial cells. Notably, the human pathogens (B. pertussis and N. gonorrhea) that produce excess TCT, causing damage to cilia also both produce LOS in their outer membrane.

Effect on immune system

TCT has been classified as an

adjuvant In pharmacology, an adjuvant is a drug or other substance, or a combination of substances, that is used to increase the efficacy or potency of certain drugs. Specifically, the term can refer to: * Adjuvant therapy in cancer management * Analgesic ...

molecule because of the stimulating effects it has on the immune system. Cellular damage associated with TCT is thought to be a result of increased levels of nitric oxide (NO) secretion by mucosal cells as part of an innate defense response to extracellular

lipopolysaccharide Lipopolysaccharides (LPS) are large molecules consisting of a lipid and a polysaccharide that are bacterial toxins. They are composed of an O-antigen, an outer core, and an inner core all joined by a covalent bond, and are found in the outer m ...

(LPS) and TCT. In humans, peptidoglycan recognition proteins, e.g. PGRPIαC, appear to bind with TCT and consequently induce the Tumor Necrosis Factor Receptor (TNFR) pathway. Studies using murine macrophages have shown that TCT encourages

cytokine Cytokines are a broad and loose category of small proteins (~5–25 kDa) important in cell signaling. Cytokines are peptides and cannot cross the lipid bilayer of cells to enter the cytoplasm. Cytokines have been shown to be involved in autocrin ...

secretion, probably through the

NOD1 Nucleotide-binding oligomerization domain-containing protein 1 (NOD1) is a protein receptor that in humans is encoded by the ''NOD1'' gene. It recognizes bacterial molecules and stimulates an immune reaction . NOD1 protein contains a caspase recr ...

receptor. As a

pleiotropic Pleiotropy (from Greek , 'more', and , 'way') occurs when one gene influences two or more seemingly unrelated phenotypic traits. Such a gene that exhibits multiple phenotypic expression is called a pleiotropic gene. Mutation in a pleiotropic g ...

toxin, TCT also acts as a pyrogen and as a stimulant of

slow-wave sleep Slow-wave sleep (SWS), often referred to as deep sleep, consists of stage three of non-rapid eye movement sleep. It usually lasts between 70 and 90 minutes and takes place during the first hours of the night. Initially, SWS consisted of both St ...

. Peptidoglycan recognition protein 4 ( PGLYRP4), in mammals (mice), interacts with TCT and reduces damage from pertussis inflammation. This molecule has similar immune-eliciting properties in ''

Drosophila ''Drosophila'' () is a genus of flies, belonging to the family Drosophilidae, whose members are often called "small fruit flies" or (less frequently) pomace flies, vinegar flies, or wine flies, a reference to the characteristic of many species ...

'', where a pair of PGRPs perform the recognition.

References

{{Reflist

External links

* Ligand entry in the

Protein Data Bank The Protein Data Bank (PDB) is a database for the three-dimensional structural data of large biological molecules, such as proteins and nucleic acids. The data, typically obtained by X-ray crystallography, NMR spectroscopy, or, increasingly, cry ...

MLD
* Entry in

MetaCyc The MetaCyc database is one of the largest metabolic pathways and enzymes databases currently available. The data in the database is manually curated from the scientific literature, and covers all domains of life. MetaCyc has extensive information ...

CPD0-1080
Glycopeptides Bacterial toxins