Skin-Derived C-Terminal Filaggrin-2 Fragments Are Pseudomonas aeruginosa-Directed Antimicrobials Targeting Bacterial Replication

PLoS Pathog. 2015 Sep 15;11(9):e1005159. doi: 10.1371/journal.ppat.1005159. eCollection 2015 Sep.

Abstract

Soil- and waterborne bacteria such as Pseudomonas aeruginosa are constantly challenging body surfaces. Since infections of healthy skin are unexpectedly rare, we hypothesized that the outermost epidermis, the stratum corneum, and sweat glands directly control the growth of P. aeruginosa by surface-provided antimicrobials. Due to its high abundance in the upper epidermis and eccrine sweat glands, filaggrin-2 (FLG2), a water-insoluble 248 kDa S100 fused-type protein, might possess these innate effector functions. Indeed, recombinant FLG2 C-terminal protein fragments display potent antimicrobial activity against P. aeruginosa and other Pseudomonads. Moreover, upon cultivation on stratum corneum, P. aeruginosa release FLG2 C-terminus-containing FLG2 fragments from insoluble material, indicating liberation of antimicrobially active FLG2 fragments by the bacteria themselves. Analyses of the underlying antimicrobial mechanism reveal that FLG2 C-terminal fragments do not induce pore formation, as known for many other antimicrobial peptides, but membrane blebbing, suggesting an alternative mode of action. The association of the FLG2 fragment with the inner membrane of treated bacteria and its DNA-binding implicated an interference with the bacterial replication that was confirmed by in vitro and in vivo replication assays. Probably through in situ-activation by soil- and waterborne bacteria such as Pseudomonads, FLG2 interferes with the bacterial replication, terminates their growth on skin surface and thus may contributes to the skin's antimicrobial defense shield. The apparent absence of FLG2 at certain body surfaces, as in the lung or of burned skin, would explain their higher susceptibility towards Pseudomonas infections and make FLG2 C-terminal fragments and their derivatives candidates for new Pseudomonas-targeting antimicrobials.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antimicrobial Cationic Peptides / chemistry
  • Antimicrobial Cationic Peptides / genetics
  • Antimicrobial Cationic Peptides / metabolism*
  • DNA Replication*
  • DNA, Bacterial / antagonists & inhibitors*
  • DNA, Bacterial / metabolism
  • DNA-Binding Proteins / metabolism
  • Eccrine Glands / cytology
  • Eccrine Glands / metabolism
  • Electrophoretic Mobility Shift Assay
  • Epidermal Cells
  • Epidermis / metabolism
  • Filaggrin Proteins
  • Host-Pathogen Interactions*
  • Humans
  • Immunity, Innate
  • Microbial Viability
  • Peptide Fragments / genetics
  • Peptide Fragments / metabolism
  • Protein Structure, Tertiary
  • Pseudomonas Infections / immunology
  • Pseudomonas Infections / metabolism
  • Pseudomonas Infections / microbiology
  • Pseudomonas Infections / pathology
  • Pseudomonas aeruginosa / growth & development
  • Pseudomonas aeruginosa / immunology
  • Pseudomonas aeruginosa / physiology*
  • Pseudomonas aeruginosa / ultrastructure
  • Recombinant Proteins / metabolism
  • S100 Proteins / genetics
  • S100 Proteins / metabolism*
  • Skin / immunology
  • Skin / metabolism
  • Skin / microbiology*
  • Skin / pathology
  • Skin Diseases, Bacterial / immunology
  • Skin Diseases, Bacterial / metabolism
  • Skin Diseases, Bacterial / microbiology
  • Skin Diseases, Bacterial / pathology
  • Sweat / metabolism

Substances

  • Antimicrobial Cationic Peptides
  • DNA, Bacterial
  • DNA-Binding Proteins
  • FLG protein, human
  • FLG2 protein, human
  • Filaggrin Proteins
  • Peptide Fragments
  • Recombinant Proteins
  • S100 Proteins

Grants and funding

This study was supported by grants of the Deutsche Forschungsgemeinschaft DFG (http://www.dfg.de) to JMS (Schr 305/6-1 and 5-1). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.