Highly Selective End-Tagged Antimicrobial Peptides Derived from PRELP

Background: Antimicrobial peptides (AMPs) are receiving increasing attention due to resistance development against conventional antibiotics. Pseudomonas aeruginosa and Staphylococcus aureus are two major pathogens involved in an array of infections such as ocular infections, cystic fibrosis, wound and post-surgery infections, and sepsis. The goal of the study was to design novel AMPs against these pathogens. Methodology and Principal Findings: Antibacterial activity was determined by radial diffusion, viable count, and minimal inhibitory concentration assays, while toxicity was evaluated by hemolysis and effects on human epithelial cells. Liposome and fluorescence studies provided mechanistic information. Protease sensitivity was evaluated after subjection to human leukocyte elastase, staphylococcal aureolysin and V8 proteinase, as well as P. aeruginosa elastase. Highly active peptides were evaluated in ex vivo skin infection models. C-terminal end-tagging by W and F amino acid residues increased antimicrobial potency of the peptide sequences GRRPRPRPRP and RRPRPRPRP, derived from proline arginine-rich and leucine-rich repeat protein (PRELP). The optimized peptides were antimicrobial against a range of Gram-positive S. aureus and Gram-negative P. aeruginosa clinical isolates, also in the presence of human plasma and blood. Simultaneously, they showed low toxicity against mammalian cells. Particularly W-tagged peptides displayed stability against P. aeruginosa elastase, and S. aureus V8 proteinase and aureolysin, and the peptide RRPRPRPRPWWWW-NH2 was effective against various "superbugs'' including vancomycin-resistant enterococci, multi-drug resistant P. aeruginosa, and methicillin-resistant S. aureus, as well as demonstrated efficiency in an ex vivo skin wound model of S. aureus and P. aeruginosa infection. Conclusions/Significance: Hydrophobic C-terminal end-tagging of the cationic sequence RRPRPRPRP generates highly selective AMPs with potent activity against multiresistant bacteria and efficiency in ex vivo wound infection models. A precise "tuning'' of toxicity and proteolytic stability may be achieved by changing tag-length and adding W-or F-amino acid tags

Expression and activity profiling of the steroidogenic enzymes of glucocorticoid biosynthesis and the fdx1 co-factors in zebrafish

The spatial and temporal expression of steroidogenic genes in zebrafish has not been fully characterized. Since zebrafish are increasingly employed in endocrine and stress research, a better characterization of steroidogenic pathways is required to target specific steps in the biosynthetic pathways in the future. Here, we have systematically defined the temporal and spatial expression of steroidogenic enzymes involved in glucocorticoid biosynthesis (cyp21a2, cyp11c1, cyp11a1, cyp11a2, cyp17a1, cyp17a2, hsd3b1, hsd3b2), as well as the mitochondrial electron-providing co-factors ferredoxin (fdx1, fdx1b) during zebrafish development. Our studies showed an early expression of all these genes during embryogenesis. In larvae, expression of cyp11a2, cyp11c1, cyp17a2, cyp21a2, hsd3b1 and fdx1b can be detected in the interrenal gland, the zebrafish counterpart of the mammalian adrenal gland, whereas the fdx1 transcript is mainly found in the digestive system. Gene expression studies using quantitative RT-PCR and whole-mount in situ hybridization in the adult zebrafish brain revealed a wide expression of these genes throughout the encephalon, including neurogenic regions. Using ultra-high-performance liquid chromatography tandem mass spectrometry, we were able to demonstrate the presence of the glucocorticoid cortisol in the adult zebrafish brain. Moreover, we demonstrate de novo biosynthesis of cortisol and the neurosteroid THDOC in the adult zebrafish brain from radiolabeled pregnenolone. Taken together, our study is a comprehensive characterization of the steroidogenic genes and the fdx co-factors facilitating glucocorticoid biosynthesis in zebrafish. Furthermore, we provide additional evidence of de novo neurosteroid biosynthesizing in the brain of adult zebrafish facilitated by enzymes involved on glucocorticoid biosynthesis. Our work provides a valuable source for establishing the zebrafish as a translational model to understand the roles of the genes of glucocorticoid biosynthesis and fdx co-factors during embryonic development, stress and in brain homeostasis and function

Interaction between amphiphilic peptides and phospholipid membranes

This brief review aims at providing some illustrative examples on the interaction between amphiphilic peptides and phospholipid membranes an area of significant current interest Focusing on antimicrobial peptides factors affecting peptide-membrane interactions are addressed including effects of peptide length charge hydrophobicity secondary structure and topology Effects of membrane composition are also illustrated including effects of membrane charge nature of the polar headgroup and presence of cholesterol and other sterols Throughout novel insights on the importance of peptide adsorption density on membrane stability are emphasized as is the correlation between peptide adsorption peptide induced leakage in model liposome systems peptide-induced lysis of bacteria and bacteria killing (C) 2010 Elsevier Ltd All rights reserve

Oligotryptophan-tagged antimicrobial peptides and the role of the cationic sequence

The effects of varying the cationic sequence of oligotryptophan-tagged antimicrobial peptides were investigated in terms of peptide adsorption to model lipid membranes, liposome leakage induction, and antibacterial potency. Heptamers of lysine (K7) and arginine (R7) were lytic against Escherichia coli bacteria at low ionic strength. In parallel, both peptides adsorbed on to bilayers formed by E. coli phospholipids, and caused leakage in the corresponding liposomes. K7 was the more potent of the two peptides in causing liposome leakage, although the adsorption of this peptide on E coli membranes was lower than that of R7. The bactericidal effect, liposome lysis, and membrane adsorption were all substantially reduced at physiological ionic strength. When a tryptophan pentamer tag was linked to the C-terminal end of these peptides, substantial peptide adsorption, membrane lysis, and bacterial killing were observed also at high ionic strength, and also for a peptide of lower cationic charge density (KNKGKKN-W5). Strikingly, the order of membrane lytic potential of the cationic peptides investigated was reversed when tagged. This and other aspects of peptide behavior and adsorption, in conjunction with effects on liposomes and bacteria, suggest that tagged and untagged peptides act by different lytic mechanisms, which to some extent counterbalance each other. Thus, while the untagged peptides act by generating negative curvature strain in the phospholipid membrane, the tagged peptides cause positive curvature strain. The tagged heptamer of arginine, R7W5, was the best candidate for E coli membrane lysis at physiological salt conditions and proved to be an efficient antibacterial agent. (C) 2009 Elsevier B.V. All rights reserved

Gremlin1 preferentially binds to Bone Morphogenetic Protein-2 (BMP-2) and BMP-4 over BMP-7

Gremlin (Grem1) is a member of the DAN family of secreted bone morphogenetic protein (BMP) antagonists. Bone morphogenetic protein-7 (BMP-7) mediates protective effects during renal fibrosis associated with diabetes and other renal diseases. The pathogenic mechanism of Grem1 during diabetic nephropathy (DN) has been suggested to be binding and inhibition of BMP-7. However, the precise interactions between Grem1, BMP-7 and other BMPs have not been accurately defined. In the present study, we show the affinity of Grem1 for BMP-7 is lower than that of BMP-2 and BMP-4, using a combination of surface plasmon resonance and cell culture techniques. Using kidney proximal tubule cells and HEK (human embryonic kidney)-293 cell Smad1/5/8 phosphorylation and BMP-dependent gene expression as readouts, Grem1 consistently demonstrated a higher affinity for BMP-2&amp;gt;BMP-4&amp;gt;BMP-7. Cell-associated Grem1 did not inhibit BMP-2- or BMP-4-mediated signalling, suggesting that Grem1–BMP-2 binding occurred in solution, preventing BMP receptor activation. These data suggest that Grem1 preferentially binds to BMP-2 and this may be the dominant complex in a disease situation where levels of Grem1 and BMPs are elevated.</jats:p