Structural aspects and biological properties of the cathelicidin PMAP‐36

Abstract

A large number of gene encoded host defence peptides (HDPs) has been described over the past two decades (many are collected in the AMSDb database at http:// www.bbcm.units.it/tossi/antimic.html), and it has become quite clear that they are used as a defence mechanism throughout the living world [1][2][3][4]. Microorganisms use them to antagonize competitors [5,6], plants and insects as the major effector molecules to prevent and combat microbial infections [7,8], while mammals use them to control commensal microorganisms and as a first line of defence against invading pathogens [9][10][11].Several families of HDPs contribute to host defence in mammals. Among them, a prominent role is played by the cysteine-rich a-and b-defensins [10] and by several other linear peptides belonging to the cathelicidins. This family includes a large and quite diverse group of HDPs, all deriving from propeptides with a wellconserved N-terminal proregion [11] among which the a-and b-defensins and cathelicidins play a prominent role. Mammalian HDPs can have both a direct antimicrobial activity and ⁄ or act as immunomodulatory molecules for cellular components of innate and adaptive immune responses. In the former case, they are thought to function principally at the level of bacterial membranes, to which they are drawn by their cationic nature, and into which they can insert by preformed or assumed amphipathic structures. These are based on PMAP-36 is a cathelicidin-derived host defence peptide originally deduced by a transcript from pig bone marrow RNA. The expression of the propeptide in leukocytes, and the structure, antimicrobial activity, and mechanism of action of the mature peptide were investigated. The proform is stored as a dimeric precursor of 38 kDa formed by a dimerization site at its C-terminal cysteine residue; it is likely that the mature peptide is dimeric when released. Monomeric and dimeric forms of PMAP-36 were chemically synthesized and their activity compared. Both forms assumed an amphipathic a-helical conformation and exhibited a potent and rapid microbicidal activity against a wide spectrum of microorganisms, mediated by their ability to permeabilize the microbial membranes rapidly. A shortened fragment localized the helical region to the N terminus, but showed a significantly lower potency and slower permeabilization kinetics, indicating an important role of the nonhelical C-terminal hydrophobic portion of this molecule. Dimerization modulated the effectiveness of the peptide in terms of killing and permeabilization kinetics, and reduced medium dependence. It allows the molecule to achieve an impressive charge density (+28 in 70 residues), although the significance of this feature with respect to biological activity has yet to be determined. Abbreviations

Determination of the Antibacterial and Lipopolysaccharide-Neutralizing Regions of Guinea Pig Neutrophil Cathelicidin Peptide CAP11

“…2, the dimeric (native) form of CAP11 exhibited almost the same antibacterial and LPS-neutralizing activities as the S-pyridylethylated monomer. Consistent with our findings, Scocchi et al reported that the monomeric and dimeric forms of PMAP36 have the same antimicrobial activity against various microbes (31). These results suggest that the dimerization or disulfide bonding of the ␣-helical cathelicidin peptides has no effect on their biological activities.…”

“…1). Most cathelicidin peptides have a monomeric structure, except CAP11 and PMAP36 (the 36-residue C-terminal region of pig myeloid antibacterial peptide), a recently characterized cathelicidin (31). Thus, we evaluated the effect of dimerization or the presence of a disulfide bond on antibacterial and LPS-neutralizing activity.…”

Porcine Cathelicidins Efficiently Complex and Deliver Nucleic Acids to Plasmacytoid Dendritic Cells and Can Thereby Mediate Bacteria-Induced IFN-α Responses

“…The ability of killing or inhibiting the growth of XL1-Blue E. coli was investigated for the scrambled peptide and PMAP-36 using adapted protocols (8,26). All inoculums were harvested in midlog phase growth of XL1-Blue E. coli, and the CFU/ml was calculated with the OD 600 value (0.3-0.6) from a previous known standard curve.…”

“…The porcine cathelicidin family includes the prophenin-1 and -2, proline-arginine-rich 39-aa peptide (PR-39), disulfide-bridged cysteine-rich protegrins (PG-1 to PG-5), and a-helical porcine myeloid antimicrobial peptides (PMAP-23, PMAP-36, and PMAP-37) (3). Antimicrobial activity has been well characterized for PR-39 (4,5), PMAP-23 (6, 7), PMAP-36 (8), and PG-1 (9,10). It was also shown that PR-39 displays chemotactic activity in neutrophils (11).…”

Different effect of doxycycline and enrofloxacin on cathelicidin-3 mRNA expression in chickens with or without probiotics supplementation

“…The liver levels of cathelicidin-1 were low and those of the cathelicidin-2 were higher (Lynn et al, 2004;van Dijk et al, 2005). Their activity against Gram-positive and Gramnegative microorganisms and also against pathogenic fungi and nematodes has been demonstrated (Scocchi et al, 2005). In addition to these properties, cathelicidins possess immunomodulatory activity, such as chemotaxis, binding and inactivation of toxins (Agerberth et al, 2000;Scott et al, 2002).…”