Structure-Function Analysis of Peptide Signaling in the Clostridium perfringens Agr-Like Quorum Sensing System

Abstract

.07925.x) that an 8-amino-acid, AgrD-derived peptide named 8-R upregulates CPB production by this QS system. The current study synthesized a series of small signaling peptides corresponding to sequences within the C. perfringens AgrD polypeptide to investigate the C. perfringens autoinducing peptide (AIP) structure-function relationship. When both linear and cyclic ring forms of these peptides were added to agrB null mutants of type B strain CN1795 or type C strain CN3685, the 5-amino-acid peptides, whether in a linear or ring (thiolactone or lactone) form, induced better signaling (more CPB production) than peptide 8-R for both C. perfringens strains. The 5-mer thiolactone ring peptide induced faster signaling than the 5-mer linear peptide. Strain-related variations in sensing these peptides were detected, with CN3685 sensing the synthetic peptides more strongly than CN1795. Consistent with those synthetic peptide results, Transwell coculture experiments showed that CN3685 exquisitely senses native AIP signals from other isolates (types A, B, C, and D), while CN1795 barely senses even its own AIP. Finally, a C. perfringens AgrD sequence-based peptide with a 6-amino-acid thiolactone ring interfered with CPB production by several C. perfringens strains, suggesting potential therapeutic applications. These results indicate that AIP signaling sensitivity and responsiveness vary among C. perfringens strains and suggest C. perfringens prefers a 5-mer AIP to initiate Agr signaling. IMPORTANCEClostridium perfringens possesses an Agr-like quorum sensing (QS) system that regulates virulence, sporulation, and toxin production. The current study used synthetic peptides to identify the structure-function relationship for the signaling peptide that activates this QS system. We found that a 5-mer peptide induces optimal signaling. Unlike other Agr systems, a linear version of this peptide (in addition to thiolactone and lactone versions) could induce signaling. Two C. perfringens strains were found to vary in sensitivity to these peptides. We also found that a 6-mer peptide can inhibit toxin production by some strains, suggesting therapeutic applications. In humans and livestock, Clostridium perfringens is a major cause of histotoxic infections, such as human gas gangrene, and intestinal infections, including enteritis and enterotoxemias (1, 2). The versatility of this Gram-positive anaerobic bacterium is largely attributable to its ability to produce ϳ17 different toxins (3-5). However, individual strains produce only portions of this toxin repertoire; this toxin production variability is used in a classification system that assigns C. perfringens isolates to one of five types (A to E) based upon their production of alpha (CPA), beta (CPB), epsilon (ETX), and iota toxins (4, 5). Each C. perfringens type is associated with certain diseases (1, 4).C. perfringens-induced diseases are not intoxications but rather true infections where the bacterium must grow and produce toxins in the host (1). There is only a relatively rudiment...

Structure–Activity Relationships of the Competence Stimulating Peptides (CSPs) in Streptococcus pneumoniae Reveal Motifs Critical for Intra-group and Cross-group ComD Receptor Activation

“…12 Moreover, AIP-based inhibitors of the agr QS circuitry were found to attenuate both virulence factor production in cellular assays and pathogenicity in different staphylococcal infection models. 14-16 The extensive work that has been conducted on the agr circuitry in S. aureus highlights the therapeutic potential associated with QS interception and has sparked numerous studies of QS circuits in other Gram-positive bacterial pathogens, including Staphylococcus epidermidis , 17, 18 Enterococcus faecalis , 19-21 Clostridium perfringens , 22, 23 and Streptococcus pneumoniae . 24-27 S. pneumoniae is a commensal bacterium that predominately colonizes in the nasopharynx of many humans, but is also an opportunistic pathogen that causes diverse acute and chronic infections such as pneumonia, meningitis, and bacteremia.…”

Advances in Microbiology, Infectious Diseases and Public Health

“…On the basis of the deduced amino acid sequences of AgrD, now 5-membered cyclic peptide (CLWFT) has been confirmed as an AIP Cp in C. perfringens where the thiolactone ring occurs between 1st and 5th residue (Ma et al 2015). However, this peptide has also been identified from C. perfringens strain 13 (type A) culture filtrates in our laboratory (Singh et al 2014).…”

“…The importance of this finding is highlighted by the study from Espinal et al (2000) that emphasized association between any INH resistance other than multidrug resistance and unfavorable treatment outcome. The chemical structure of AIPs is diversified into several types, such as small oligopeptides, cyclic lactone/thiolactone peptides, and bacteriocin-like peptides which includes lantibiotics (Bierbaum and Sahl 1993;Nakayama et al 2001;Novick 2003;Ma et al 2015). To synchronize the function of each cell in a community, unicellular organisms employ a quorum sensing (QS) system in which diffusible, extracellular signals control the expression of certain gene(s) (Bassler 1999).…”

“…To synchronize the function of each cell in a community, unicellular organisms employ a quorum sensing (QS) system in which diffusible, extracellular signals control the expression of certain gene(s) (Bassler 1999). Thiolactone/lactone AIPs are widely used by Firmicutes, which include some serious and/or problematic pathogens such as staphylococci, enterococci, clostridia, and listeria Nakayama et al 2001;Autret et al 2003;Ma et al 2015). The chemical structure of AIPs is diversified into several types, such as small oligopeptides, cyclic lactone/thiolactone peptides, and bacteriocin-like peptides which includes lantibiotics (Bierbaum and Sahl 1993;Nakayama et al 2001;Novick 2003;Ma et al 2015).…”

The Agr-Like Quorum Sensing System Is Required for Pathogenesis of Necrotic Enteritis Caused by Clostridium perfringens in Poultry

“…Furthermore, our in vitro results suggest several mechanisms by which Agr-like QS may influence virulence. Currently, efforts are under way to develop therapies against S. aureus infections using AIP analogues to interfere with the Agr QS system (50,51), which have the added benefit of not promoting the development of antibiotic resistance, and some progress has also been made to target the C. perfringens AIP (52). Considering that Agr-like QS is essential for the pathogenesis of NE in vivo, this system may serve as a target for developing novel interventions to prevent NE disease in chickens, as an alternative to the antibiotic therapies currently in use.…”