Renato Gennaro

Cathelicidins: a novel protein family with a common proregion and a variable C-terminal antimicrobial domain.

A novel protein family, showing a conserved proregion and a variable C‐terminal antimicrobial domain, and named0 cathelicidin, has been identified in mammalian myeloid cells. The conserved proregion shows sequence similarity to members of the cystatin superfamily of cysteine proteinase inhibitors. Cathelicidins are stored in the cytoplasmic granules of neutrophil leukocytes and release the antimicrobial peptides upon leukocyte activation. Some of these peptides can assume an α‐helical conformation, others contain one or two disulfide bonds, still others are Pro‐ and Arg‐rich, or Trp‐rich. In addition to bacterial killing, some of these peptides exert additional functions related to host defense such as LPS‐neutralization and promotion of wound healing.

Biological Characterization of Two Novel Cathelicidin-derived Peptides and Identification of Structural Requirements for Their Antimicrobial and Cell Lytic Activities

Cathelicidins are a family of myeloid antimicrobial peptide precursors that have been identified in several mammalian species (Zanetti, M., Gennaro, R., and Romeo, D. (1995) FEBS Lett. 374, 1-5). Two novel bovine congeners have been deduced from cDNA. Their C-terminal sequences of 27 and 28 residues correspond to putative antimicrobial peptides with a cationic N-terminal region predicted to assume an amphipathic α-helical conformation followed by a hydrophobic C-terminal tail. Peptides corresponding to these sequences have been chemically synthesized and shown to exert a potent antimicrobial activity against Gram-negative and Gram-positive bacteria, including methicillin-resistant Staphylococcus aureus, and fungi. Both peptides are also cytotoxic to human erythrocytes and neutrophils, although at higher than microbicidal concentrations. The target selectivity has been improved by synthesizing truncated analogues, comprising only the 18 N-terminal residues, which show a great reduction in cytotoxic, but not in antimicrobial activity. The involvement of the C-terminal hydrophobic tail in the cytotoxic activity has been further demonstrated by inducing a major loss of activity in an analogue after replacing highly hydrophobic residues with more hydrophilic ones.

Chemical synthesis and biological activity of a novel antibacterial peptide deduced from a pig myeloid cDNA

Several myeloid precursors of antibacterial peptides have recently been shown to share homologous pre‐ and pro‐regions. Taking advantage of this homology, a novel cDNA was cloned from pig bone marrow RNA. This encodes a 166‐residue polypeptide with highly conserved pre‐ (29 residues) and pro‐ (101 residues) sequences, followed by a unique, 36‐residue C‐terminal sequence. Structure analyses of this C‐terminal region have identified a highly cationic sequence predicted to adopt an amphipathic α‐helical conformation. A peptide corresponding to this sequence was chemically synthesized and shown to arrest the growth of both Gram‐positive and Gram‐negative bacteria. At least for Escherichia coli, the activity of this peptide appears to be mediated by its ability to permeabilize the bacterial membranes.

Identification and characterization of a primary antibacterial domain in CAP18, a lipopolysaccharide binding protein from rabbit leukocytes

Secondary structure prediction studies on CAP18, a lipopolysaccharide binding protein from rabbit granulocytes, identified a highly cationic, 21‐residue sequence with the tendency to adopt an amphipathic α‐helical conformation, as observed in many antimicrobial peptides. The corresponding peptide was chemically synthesized and shown to exert a potent bacterieidal activity against both Gram‐negative and Gram‐positive bacteria, and a rapid permeabilization of the inner membrane of Escherichia coli. Five analogues were synthesized to elucidate structure/activity relationships. It was found that helix disruption virtually eliminates antibacterial activity, while the degree of amphipathicity and the presence of an aromatic residue greatly affect the kinetics of bacterial inner membrane permeabilization.

The Cathelicidin Family of Antimicrobial Peptide Precursors: A Component of the Oxygen‐Independent Defense Mechanisms of Neutrophilsa

Host protection from invading pathogens involves cellular and humoral effectors and results from the concerted action of both non-adaptive (innate) and adaptive (acquired) immunity. The latter is based on specific immunological recognition mediated by clonally distributed receptors, is a recent acquisition of the immune system, and is present only in vertebrates. The former evolved well before the development of adaptive immunity and consists of a variety of cells and molecules distributed

Neutrophil and Eosinophil Granules as Stores of “Defense” Proteins

The accumulation of phagocytic cells at the site of infection represents one of the most important defense mechanisms for protecting the host from noxious microorganisms, viruses, and parasites. The defense cells, also known as professional phagocytes, include neutrophils, eosinophils, monocytes, and a variety of macrophage phenotypes.