title: Cell-penetrating antimicrobial peptides - prospectives for targeting intracellular infections.
abstract: OBJECTIVE
  To investigate the suitability of three antimicrobial peptides (AMPs) as cell-penetrating antimicrobial peptides.
  
  
  METHODS
  Cellular uptake of three AMPs (PK-12-KKP, SA-3 and TPk) and a cell-penetrating peptide (penetratin), all 5(6)-carboxytetramethylrhodamine-labeled, were tested in HeLa WT cells and analyzed by flow cytometry and confocal microscopy. Furthermore, the effects of the peptides on eukaryotic cell viability as well as their antimicrobial effect were tested. In addition, the disrupting ability of the peptides in the presence of bilayer membranes of different composition were analyzed.
  
  
  RESULTS
  AMP uptake relative to penetratin was ~13% (PK-12-KKP), ~66% (SA-3) and ~50% (TPk). All four peptides displayed a punctate uptake pattern in HeLa WT cells with co-localization to lysosomes and no indication that clathrin-mediated endocytosis was the predominant uptake mechanism. TPk showed the highest antibacterial activity. SA-3 exhibited selective disruption of liposomes mimicking Gram-positive and Gram-negative membranes.
  
  
  CONCLUSIONS
  PK-12-KKP is an unlikely candidate for targeting intracellular bacteria, as the eukaryotic cell-penetrating ability is poor. SA-3, affected the cellular viability to an unacceptable degree. TPk showed acceptable uptake efficiency, high antimicrobial activity and relatively low toxicity, and it is the best potential lead peptide for further development.
authors.affiliation: Department of Pharmacy, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, 2100, Copenhagen, Denmark.
authors.forename: Jesper S
authors.initials: JS
authors.lastname: Bahnsen
authors.forename: Henrik
authors.initials: H
authors.lastname: Franzyk
authors.forename: Edward J
authors.initials: EJ
authors.lastname: Sayers
authors.forename: Arwyn T
authors.initials: AT
authors.lastname: Jones
authors.forename: Hanne M
authors.initials: HM
authors.lastname: Nielsen
mesh_terms: D000595:Amino Acid Sequence; D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000493:pharmacokinetics / Q000494:pharmacology*; D023181:Antimicrobial Cationic Peptides / Q000737:chemistry / Q000493:pharmacokinetics / Q000494:pharmacology*; D001419:Bacteria / Q000187:drug effects*; D001424:Bacterial Infections / Q000188:drug therapy; D002352:Carrier Proteins / Q000737:chemistry / Q000493:pharmacokinetics / Q000494:pharmacology*; D057846:Cell-Penetrating Peptides / Q000737:chemistry / Q000493:pharmacokinetics / Q000494:pharmacology*; D004705:Endocytosis; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data
chemical_list: D000900:Anti-Bacterial Agents; D023181:Antimicrobial Cationic Peptides; D002352:Carrier Proteins; D057846:Cell-Penetrating Peptides; C414409:penetratin