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Inflammation-inducing Factors of Mycoplasma pneumoniae.

Shimizu T - Front Microbiol (2016)

Bottom Line: Mycoplasma pneumoniae, which causes mycoplasmal pneumonia in human, mainly causes pneumonia in children, although it occasionally causes disease in infants and geriatrics.Lipoproteins induce inflammatory responses through Toll-like receptors (TLR) 2.TLR4 and autophagy are involved in this TLR2-independent inflammation.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Veterinary Public Health, Joint Faculty of Veterinary Medicine, Yamaguchi University Yamaguchi, Japan.

ABSTRACT
Mycoplasma pneumoniae, which causes mycoplasmal pneumonia in human, mainly causes pneumonia in children, although it occasionally causes disease in infants and geriatrics. Some pathogenic factors produced by M. pneumoniae, such as hydrogen peroxide and Community-Acquired Respiratory Distress Syndrome (CARDS) toxin have been well studied. However, these factors alone cannot explain this predilection. The low incidence rate of mycoplasmal pneumonia in infants and geriatrics implies that the strong inflammatory responses induced by M. pneumoniae coordinate with the pathogenic factors to induce pneumonia. However, M. pneumoniae lacks a cell wall and does not possess an inflammation-inducing endotoxin, such as lipopolysaccharide (LPS). In M. pneumoniae, lipoproteins were identified as an inflammation-inducing factor. Lipoproteins induce inflammatory responses through Toll-like receptors (TLR) 2. Because Mycoplasma species lack a cell wall and lipoproteins anchored in the membrane are exposed, lipoproteins and TLR2 have been thought to be important for the pathogenesis of M. pneumoniae. However, recent reports suggest that M. pneumoniae also induces inflammatory responses also in a TLR2-independent manner. TLR4 and autophagy are involved in this TLR2-independent inflammation. In addition, the CARDS toxin or M. pneumoniae cytadherence induces inflammatory responses through an intracellular receptor protein complex called the inflammasome. In this review, the inflammation-inducing factors of M. pneumoniae are summarized.

No MeSH data available.


Related in: MedlinePlus

Biosynthesis of bacterial lipoproteins. (1) Lgt transfers a diacylglyceryl moiety from a phospholipid to the sulfhydryl group of the cysteine located after the lipobox sequence. (2) Lsp cleaves the signal peptide at the N-terminus of the cysteine. (3) Lnt transfers an acyl chain derived from phospholipid to the amino group of the cysteine.
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Figure 1: Biosynthesis of bacterial lipoproteins. (1) Lgt transfers a diacylglyceryl moiety from a phospholipid to the sulfhydryl group of the cysteine located after the lipobox sequence. (2) Lsp cleaves the signal peptide at the N-terminus of the cysteine. (3) Lnt transfers an acyl chain derived from phospholipid to the amino group of the cysteine.

Mentions: Lipoproteins were discovered in 1969 by Braun et al. (Braun, 1975). Lipoproteins are hydrophilic membrane proteins characterized by a conserved N-terminal lipid-modified cysteine residue. Lipoproteins contain S-glyceryl cysteine modified with three fatty acids (N-acyl-S-diacylglyceryl cysteine) at their N-terminal. This triacylated structure is also called Braun’s lipoprotein. Braun’s Lipoproteins are synthesized by the following three steps (Figure 1): (1) Transfer of the diacylglyceryl moiety from a membrane phospholipid to a cysteine residue of a protein through the recognition of the lipobox (L-[A/S/T]-[G/A]-C) by prolipoprotein diacylglyceryl transferase (Lgt); (2) Digestion of the signal sequence at the amino-terminal side of the cysteine by prolipoprotein signal peptidase (Lsp); and (3) Linkage of an acyl chain to the amino group of the amino-terminal cysteine (N-acylation) by prolipoprotein N-acyl-transferase (Lnt). Because genes orthologous to Lnt gene are not found in some bacterial species (Firmicutes and and Tenericutes), including Mycoplasma species, lipoproteins from these bacterial species have been assumed to be of the diacylated form (Nakayama et al., 2012).


Inflammation-inducing Factors of Mycoplasma pneumoniae.

Shimizu T - Front Microbiol (2016)

Biosynthesis of bacterial lipoproteins. (1) Lgt transfers a diacylglyceryl moiety from a phospholipid to the sulfhydryl group of the cysteine located after the lipobox sequence. (2) Lsp cleaves the signal peptide at the N-terminus of the cysteine. (3) Lnt transfers an acyl chain derived from phospholipid to the amino group of the cysteine.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4814563&req=5

Figure 1: Biosynthesis of bacterial lipoproteins. (1) Lgt transfers a diacylglyceryl moiety from a phospholipid to the sulfhydryl group of the cysteine located after the lipobox sequence. (2) Lsp cleaves the signal peptide at the N-terminus of the cysteine. (3) Lnt transfers an acyl chain derived from phospholipid to the amino group of the cysteine.
Mentions: Lipoproteins were discovered in 1969 by Braun et al. (Braun, 1975). Lipoproteins are hydrophilic membrane proteins characterized by a conserved N-terminal lipid-modified cysteine residue. Lipoproteins contain S-glyceryl cysteine modified with three fatty acids (N-acyl-S-diacylglyceryl cysteine) at their N-terminal. This triacylated structure is also called Braun’s lipoprotein. Braun’s Lipoproteins are synthesized by the following three steps (Figure 1): (1) Transfer of the diacylglyceryl moiety from a membrane phospholipid to a cysteine residue of a protein through the recognition of the lipobox (L-[A/S/T]-[G/A]-C) by prolipoprotein diacylglyceryl transferase (Lgt); (2) Digestion of the signal sequence at the amino-terminal side of the cysteine by prolipoprotein signal peptidase (Lsp); and (3) Linkage of an acyl chain to the amino group of the amino-terminal cysteine (N-acylation) by prolipoprotein N-acyl-transferase (Lnt). Because genes orthologous to Lnt gene are not found in some bacterial species (Firmicutes and and Tenericutes), including Mycoplasma species, lipoproteins from these bacterial species have been assumed to be of the diacylated form (Nakayama et al., 2012).

Bottom Line: Mycoplasma pneumoniae, which causes mycoplasmal pneumonia in human, mainly causes pneumonia in children, although it occasionally causes disease in infants and geriatrics.Lipoproteins induce inflammatory responses through Toll-like receptors (TLR) 2.TLR4 and autophagy are involved in this TLR2-independent inflammation.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Veterinary Public Health, Joint Faculty of Veterinary Medicine, Yamaguchi University Yamaguchi, Japan.

ABSTRACT
Mycoplasma pneumoniae, which causes mycoplasmal pneumonia in human, mainly causes pneumonia in children, although it occasionally causes disease in infants and geriatrics. Some pathogenic factors produced by M. pneumoniae, such as hydrogen peroxide and Community-Acquired Respiratory Distress Syndrome (CARDS) toxin have been well studied. However, these factors alone cannot explain this predilection. The low incidence rate of mycoplasmal pneumonia in infants and geriatrics implies that the strong inflammatory responses induced by M. pneumoniae coordinate with the pathogenic factors to induce pneumonia. However, M. pneumoniae lacks a cell wall and does not possess an inflammation-inducing endotoxin, such as lipopolysaccharide (LPS). In M. pneumoniae, lipoproteins were identified as an inflammation-inducing factor. Lipoproteins induce inflammatory responses through Toll-like receptors (TLR) 2. Because Mycoplasma species lack a cell wall and lipoproteins anchored in the membrane are exposed, lipoproteins and TLR2 have been thought to be important for the pathogenesis of M. pneumoniae. However, recent reports suggest that M. pneumoniae also induces inflammatory responses also in a TLR2-independent manner. TLR4 and autophagy are involved in this TLR2-independent inflammation. In addition, the CARDS toxin or M. pneumoniae cytadherence induces inflammatory responses through an intracellular receptor protein complex called the inflammasome. In this review, the inflammation-inducing factors of M. pneumoniae are summarized.

No MeSH data available.


Related in: MedlinePlus