Novel Phenol-soluble Modulin Derivatives in Community-associated Methicillin-resistant Staphylococcus aureus Identified through Imaging Mass Spectrometry

Gonzalez, David J.; Okumura, Cheryl; Hollands, Andrew; Kersten, Roland D.; Akong-Moore, Kathryn; Pence, Morgan A.; Malone, Cheryl L.; Derieux, Jaclyn; Moore, Bradley S.; Horswill, Alexander R.; Dixon, Jack E.; Dorrestein, Pieter C.; Nizet, Victor

doi:10.1074/jbc.m112.349860

Cited by 62 publications

(64 citation statements)

References 31 publications

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“…The phenol-soluble modulins (PSMs) of S. aureus have been shown to have many characteristics, including the ability to recruit leukocytes, lyse erythrocytes and neutrophils, act as antimicrobial peptides, modulate biofilm development, and exhibit surfactant-like properties (19)(20)(21)(22)(23)(24)(25)(26)(27)(28). PSMs are small peptides ranging from 22 to 44 amino acids in length that are predicted to form amphipathic helices and in some cases can form amyloid fibers to abrogate their toxic properties and stabilize biofilms (19,23).…”

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Staphlyococcus aureus Phenol-Soluble Modulins Stimulate the Release of Proinflammatory Cytokines from Keratinocytes and Are Required for Induction of Skin Inflammation

et al. 2015

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Staphylococcus aureus is a human commensal that colonizes the skin. While it is normally innocuous, it has strong associations with atopic dermatitis pathogenesis and has become the leading cause of skin and soft tissue infections in the United States. The factors that dictate the role of S. aureus in disease are still being determined. In this work, we utilized primary keratinocyte culture and an epidermal murine colonization model to investigate the role of S. aureus phenol-soluble modulins (PSMs) in proinflammatory cytokine release and inflammation induction. We demonstrated that many species of Staphylococcus are capable of causing release of interleukin 18 (IL-18) from keratinocytes and that S. aureus PSMs are necessary and sufficient to stimulate IL-18 release from keratinocytes independently of caspase 1. Further, after 7 days of epicutaneous exposure to wild-type S. aureus, but not S. aureus ⌬psm, we saw dramatic changes in gross pathology, as well as systemic release of proinflammatory cytokines. This work demonstrates the importance of PSM peptides in S. aureus-mediated inflammatory cytokine release from keratinocytes in vitro and in vivo and further implicates PSMs as important contributors to pathogenesis. Staphylococcus aureus is a human commensal that lives in the nose, skin, and throat in approximately 30% of the human population (1, 2). While S. aureus is usually harmless, it is an opportunistic pathogen that has become a leading cause of nosocomial infections in the United States (3) and can manifest as skin and soft tissue infections, infective endocarditis, osteomyelitis, and sepsis (1). Further, it has a role in exacerbation of atopic dermatitis (AD), a chronic inflammatory disease of the skin that affects up to 20% of children and up to 3% of adults (4, 5). Chronic cutaneous inflammation during AD results in increased production of extracellular matrix components that permit attachment of S. aureus (6). Subsequently, S. aureus promotes AD by stimulating a strong proinflammatory response (7). S. aureus proteins, such as hemolysin ␣ (HLA), staphylococcal protein A (SPA), and lipoteichoic acids (LTA), promote proinflammatory cytokine production from keratinocytes (7-11). However, this stimulation requires the concurrent presence of a surfactant, such as SDS (11).Keratinocytes serve as the first line of defense against cutaneous pathogens and are able to stimulate an immune response by releasing cytokines, defensins, and antimicrobial cationic peptides, such as LL-37, to fight off pathogens (12). One cytokine that is produced by keratinocytes and has a role in promoting AD is interleukin 18 (IL-18) (13,14). IL-18 is a proinflammatory cytokine that is cleaved and activated primarily by caspase 1 (15). Caspase 1 activation occurs following exposure to danger-associated molecular patterns (DAMPs) or pathogen-associated molecular patterns (PAMPs), which stimulate the activation of the inflammasome (16). Caspase 1 activation can also result in the activation of the proinflammatory cytokine IL-1␤ (17)...

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Staphlyococcus aureus Phenol-Soluble Modulins Stimulate the Release of Proinflammatory Cytokines from Keratinocytes and Are Required for Induction of Skin Inflammation

et al. 2015

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“…The second group of signals represented ribosomal proteins, which constitute Յ50% of the cellular proteins (Table 3). A third group of signals in the low molecular weight range was formed by excreted peptides, the phenol-soluble modulins (PSMs), and the delta-toxin double peak, which had already been identified (19,20). In cell extracts, PSM␣2 (m/z 2,307) and PSM␣3 (m/z 2,636) were predominant.…”

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Analysis of the Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrum of Staphylococcus aureus Identifies Mutations That Allow Differentiation of the Main Clonal Lineages

et al. 2013

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Staphylococcus aureus causes a wide range of hospital infections. Often, these infections involve epidemic methicillin-resistant S. aureus (MRSA) strains that are transferred by health care workers to patients. In order to detect outbreaks that are caused by epidemic strains, the clinical isolates have to be typed. Multilocus sequence typing (MLST) relies on the sequence analysis of housekeeping genes and is used to allocate the strains to sequence types (ST), which can be grouped into clonal complexes (CC). This method has provided a detailed insight into the population structure of MRSA and methicillin-susceptible S. aureus (MSSA) strains (1). Finer discrimination is achieved by pulsed-field gel electrophoresis (PFGE) and spa typing (2). All of these methods need additional experimentation.In matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS), different spectra or signatures of cell extracts (3, 4, 5, 6) or whole cells (7,8,9,10,11,12) could be identified for different strains or groups of strains. An increasing number of laboratories use MALDI-TOF MS for the identification of S. aureus. However, the differences in the signatures of the strains have not been evaluated so far, because the discriminatory threshold of the software used in clinical settings is set up to assign the isolate to a species. To this end, more subtle differences are ignored. Another reason is that, so far, MALDI-TOF MS of whole bacterial cells has been employed in a heuristic manner, and for most species, the identities of the compounds that are detected in the measurements are unknown. Thus, the spectra are not well understood, and the variations in the signatures cannot be interpreted.In principle, two spectra might differ by signal intensity, loss of a signal, or by the shift of a signal. Variations in signal intensity are probably caused by expression differences, which might be directly correlated with culture conditions and, therefore, do not give unambiguous information about a genotype of the strain. The loss of a signal is caused by the total failure to express a protein or peptide, which in turn might indicate a mutation causing a frameshift or stop codon, but might also depend on culture conditions, mutations of regulatory factors, or sample preparation. Thus, there is no clear-cut correlation between the loss of a signal and a genotype. In contrast, peak shifts (i.e., loss of a signal coupled to the appearance of a new signal, both of which are correlated to the same peptide) correspond to point mutations in the genes of the peptides detected in the analysis; the mutation leads to an amino acid exchange that alters the molecular weight of the corresponding gene product.In order to characterize the clonal lineages of S. aureus in the MALDI-TOF MS, this work was aimed at the identification of the peptides that are detected in the spectra and that show mass variations between the clonal complexes of S. aureus. To this end, we analyzed the spectra of 401 S. aureus strains, concentrating on...

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“…aureus produces multiple extracellular proteases that have been shown to modulate the levels and activities of the secreted proteome (15,21,(24)(25)(26)(27). These proteases belong to several classes, including the Aur metalloprotease, the cysteine proteases ScpA and SspB, the serine protease SspA (V8), and the serine-like proteases SplABCDEF.…”

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Identification of the Staphylococcus aureus vfrAB Operon, a Novel Virulence Factor Regulatory Locus

et al. 2014

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b During a screen of the Nebraska Transposon Mutant Library, we identified 71 mutations in the Staphylococcus aureus genome that altered hemolysis on blood agar medium. Although many of these mutations disrupted genes known to affect the production of alpha-hemolysin, two of them were associated with an apparent operon, designated vfrAB, that had not been characterized previously. Interestingly, a ⌬vfrB mutant exhibited only minor effects on the transcription of the hla gene, encoding alphahemolysin, when grown in broth, as well as on RNAIII, a posttranscriptional regulatory RNA important for alpha-hemolysin translation, suggesting that VfrB may function at the posttranscriptional level. Indeed, a ⌬vfrB mutant had increased aur and sspAB protease expression under these conditions. However, disruption of the known secreted proteases in the ⌬vfrB mutant did not restore hemolytic activity in the ⌬vfrB mutant on blood agar. Further analysis revealed that, in contrast to the minor effects of VfrB on hla transcription when strains were cultured in liquid media, the level of hla transcription was decreased 50-fold in the absence of VfrB on solid media. These results demonstrate that while VfrB represses protease expression when strains are grown in broth, hla regulation is highly responsive to factors associated with growth on solid media. Intriguingly, the ⌬vfrB mutant displayed increased pathogenesis in a model of S. aureus dermonecrosis, further highlighting the complexity of VfrB-dependent virulence regulation. The results of this study describe a phenotype associated with a class of highly conserved yet uncharacterized proteins found in Gram-positive bacteria, and they shed new light on the regulation of virulence factors necessary for S. aureus pathogenesis.

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Novel Phenol-soluble Modulin Derivatives in Community-associated Methicillin-resistant Staphylococcus aureus Identified through Imaging Mass Spectrometry

Cited by 62 publications

References 31 publications

Staphlyococcus aureus Phenol-Soluble Modulins Stimulate the Release of Proinflammatory Cytokines from Keratinocytes and Are Required for Induction of Skin Inflammation

Staphlyococcus aureus Phenol-Soluble Modulins Stimulate the Release of Proinflammatory Cytokines from Keratinocytes and Are Required for Induction of Skin Inflammation

Analysis of the Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrum of Staphylococcus aureus Identifies Mutations That Allow Differentiation of the Main Clonal Lineages

Identification of the Staphylococcus aureus vfrAB Operon, a Novel Virulence Factor Regulatory Locus

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