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At least 19 recordsLinked to original sources

PubMed2001

Participation of mammalian defensins and cathelicidins in anti-microbial immunity: receptors and activities of human defensins and cathelicidin (LL-37).

Defensins and cathelicidins are the two major families of mammalian anti-microbial proteins. They contribute to host, innate, anti-microbial defense by disrupting the integrity of the bacterial cell membrane. However, several members of the mammalian anti-microbial proteins including defensins and cathelicidins have been shown recently to have chemotactic effects on host cells. Human neutrophil alpha-defensins are chemotactic for resting, naïve CD45RA/CD4 T cells, CD8 T cells, and immature dendritic cells. Human beta-defensins are also chemotactic for immature dendritic cells but induce the migration of memory CD45RO/CD4 T cells. In contrast, cathelicidin/LL-37 is chemotactic for neutrophils, monocytes, and T cells but not for dendritic cells. Thus, these anti-microbial peptides have distinct, host-target cell spectra. The chemotactic activities of human beta-defensins and cathelicidin/LL-37 are mediated by human CC chemokine receptor 6 and formyl peptide receptor-like 1, respectively. The capacities of defensins and cathelicidins to mobilize various types of phagocytic leukocytes, immature dendritic cells, and lymphocytes, together with their other effects such as stimulating IL-8 production and mast cell degranulation, provide evidence for their participation in alerting, mobilizing, and amplifying innate and adaptive anti-microbial immunity of the host.

Animals↗

PubMed2005

Expression of an additional cathelicidin antimicrobial peptide protects against bacterial skin infection.

Cathelicidin antimicrobial peptides are effectors of innate immune defense in mammals. Humans and mice have only one cathelicidin gene, whereas domesticated mammals such as the pig, cow, and horse have multiple cathelicidin genes. We hypothesized that the evolution of multiple cathelicidin genes provides these animals with enhanced resistance to infection. To test this, we investigated the effects of the addition of cathelicidins by combining synthetic cathelicidin peptides in vitro, by producing human keratinocytes that overexpress cathelicidins in culture, or by producing transgenic mice that constitutively overexpress cathelicidins in vivo. The porcine cathelicidin peptide PR-39 acted additively with human cathelicidin LL-37 to kill group A Streptococcus (GAS). Lentiviral delivery of PR-39 enhanced killing of GAS by human keratinocytes. Finally, transgenic mice expressing PR-39 under the influence of a K14 promoter showed increased resistance to GAS skin infection (50% smaller necrotic ulcers and 60% fewer surviving bacteria). Similarly constructed transgenic mice designed to overexpress their native cathelicidin did not show increased resistance. These findings demonstrate that targeted gene transfer of a xenobiotic cathelicidin confers resistance against infection and suggests the benefit of duplication and divergence in the evolution of antimicrobial peptides.

Animals↗

PubMed2006

Heterogeneous expression of human cathelicidin hCAP18/LL-37 in inflammatory bowel diseases.

BACKGROUND: Inflammatory bowel diseases (IBDs) are characterized by a breakdown of colon epithelial barrier function. Antimicrobial peptides like cathelicidins are molecules of the innate immune system located at epithelial surfaces. Cathelicidins influence microbial growth and inflammation and may play a role in IBD. In this study, the expression of human cathelicidin hCAP18/LL-37 was investigated in the intestinal mucosa from patients suffering from ulcerative colitis or Crohn's disease. METHODS: Biopsy material from colon and ileal mucosa of a total of 89 patients (34 with Crohn's disease, 27 with ulcerative colitis, 28 control patients) was evaluated for cathelicidin expression by real-time reverse-transcriptase polymerase chain reaction and immunohistochemistry. Colon epithelial cells were stimulated in vitro with various cytokines to evaluate mechanisms that influence cathelicidin production. RESULTS: Cathelicidin expression was significantly increased in inflamed and non-inflamed colon mucosa from ulcerative colitis patients compared to non-inflamed control mucosa. In patients with Crohn's disease cathelicidin expression was not changed in inflamed or non-inflamed colon or ileal mucosa independent of NOD2 status. Biopsies evaluated by immunohistochemistry showed epithelial cathelicidin expression in the upper crypt that was diffuse in controls and only basal in IBD patients. Inflammation mediators, alone or in combination with the known cathelicidin inducer butyrate, had no effect on cathelicidin expression in cultured colon cells. CONCLUSIONS: In IBD the colonic expression of human cathelicidin is altered: cathelicidin expression is increased in inflamed and non-inflamed mucosa in patients suffering from ulcerative colitis but not in Crohn's disease. This deficiency may further compromise the antimicrobial barrier in Crohn's disease.

Adult↗

PubMed2006

Cathelicidin deficiency predisposes to eczema herpeticum.

BACKGROUND: The cathelicidin family of antimicrobial peptides is an integral component of the innate immune response that exhibits activity against bacterial, fungal, and viral pathogens. Eczema herpeticum (ADEH) develops in a subset of patients with atopic dermatitis (AD) because of disseminated infection with herpes simplex virus (HSV). OBJECTIVE: This study investigated the potential role of cathelicidins in host susceptibility to HSV infection. METHODS: Glycoprotein D was measured by means of real-time RT-PCR as a marker of HSV replication in skin biopsy specimens and human keratinocyte cultures. Cathelicidin expression was evaluated in skin biopsy specimens from patients with AD (n = 10) without a history of HSV skin infection and from patients with ADEH (n = 10). RESULTS: The cathelicidin peptide LL-37 (human cathelicidin) exhibited activity against HSV in an antiviral assay, with significant killing (P < .001) within the physiologic range. The importance of cathelicidins in antiviral skin host defense was confirmed by the observation of higher levels of HSV-2 replication in cathelicidin-deficient (Cnlp-/-) mouse skin (2.6 +/- 0.5 pg HSV/pg GAPDH, P < .05) compared with that seen in skin from their wild-type counterparts (0.9 +/- 0.3). Skin from patients with ADEH exhibited significantly (P < .05) lower levels of cathelicidin protein expression than skin from patients with AD. We also found a significant inverse correlation between cathelicidin expression and serum IgE levels (r2 = 0.46, P < .05) in patients with AD and patients with ADEH. CONCLUSION: This study demonstrates that the cathelicidin peptide LL-37 possesses antiviral activity against HSV and demonstrates the importance of variable skin expression of cathelicidins in controlling susceptibility to ADEH. Additionally, serum IgE levels might be a surrogate marker for innate immune function and serve as a biomarker for which patients with AD are susceptible to ADEH. CLINICAL IMPLICATIONS: A deficiency of LL-37 might render patients with AD susceptible to ADEH. Therefore increasing production of skin LL-37 might prevent herpes infection in patients with AD.

Adult↗

PubMed2006

Sodium butyrate up-regulates cathelicidin gene expression via activator protein-1 and histone acetylation at the promoter region in a human lung epithelial cell line, EBC-1.

The antimicrobial protein cathelicidin is considered to play an important role in the defense mechanisms against bacterial infection. Recent studies show that sodium butyrate induces cathelicidin gene expression in human colonic, gastric and hepatic cells. However, little is known about the precise regulatory mechanisms underlying sodium butyrate-induced cathelicidin gene expression. In this study, we examined the regulatory mechanisms involved in sodium butyrate-induced cathelicidin gene expression using a human lung epithelial cell line, EBC-1. Our results indicate that sodium butyrate induces both cathelicidin mRNA and protein expression. Moreover, deletion or mutation of a putative activator protein-1 (AP-1) binding site in the cathelicidin gene promoter abrogated the response to sodium butyrate stimulation. Three different mitogen-activated protein (MAP) kinase inhibitors suppressed sodium butyrate-induced transactivation of the cathelicidin promoter. Electrophoretic mobility shift assays (EMSA) showed that nuclear extracts prepared from sodium butyrate-stimulated EBC-1 cells generated specific binding to probe including a putative AP-1 binding site in the cathelicidin gene promoter. Furthermore, chromatin immunoprecipitation (ChIP) assays demonstrated that sodium butyrate augmented histone acetylation of the cathelicidin promoter in EBC-1 cells. Therefore, these results indicate that AP-1 and histone acetylation of the cathelicidin promoter play a critical role in the regulation of inducible cathelicidin gene expression in EBC-1 cells stimulated with sodium butyrate.

Acetylation↗

PubMed2003

Expression of a cathelicidin antimicrobial peptide is augmented in cholesteatoma.

OBJECTIVES/HYPOTHESIS: Antimicrobial peptides are active defense components of innate immunity. Their importance was confirmed at epithelial surfaces as immediate barrier effectors in preventing infection. Cathelicidins are peptide antibiotics that are receiving increasing attention. Several studies have shown that overexpression of cathelicidin results in augmented protection against bacterial infection and prevention of local infection and systemic invasion of microbes. The goal of the study was to investigate whether cathelicidin is upregulated in cholesteatoma epithelium compared with normal skin. STUDY DESIGN: Twenty patients from a prospective study of cholesteatoma tissues and normal skins were enrolled in the study. The specimens were divided into two portions. One portion was used for subsequent RNA studies; the other was used for immunohistochemical staining. METHODS: Reverse transcriptase-polymerase chain reaction was used to assess the expression levels of cathelicidin messenger RNA (mRNA) both in cholesteatoma and in normal skin. Presumptive concentration of cathelicidin mRNA and beta2-microglobulin mRNA was evaluated. Ratio of beta2-microglobulin to cathelicidin was analyzed in each group. The expressions of cathelicidin in cholesteatoma and normal skin epithelium were investigated by an immunohistochemical technique. RESULTS: Cathelicidin mRNA in cholesteatoma epithelium was increased 5.5-fold compared with normal skin of the ear canal. In cholesteatoma epithelium, cathelicidin was located in all the layers, but in the normal skin it was expressed only in the granular and prickle cell layers. CONCLUSIONS: Cathelicidin is augmented in cholesteatoma epithelium, and the data in the present study are in agreement with the hypothesis that cathelicidin is likely to act as a key component in the first line of defense at the surface epithelium.

Anti-Bacterial Agents↗

PubMed2003

Expression of cathelicidin in human salivary glands.

BACKGROUND: Salivary secretions play a critical role in maintaining oral health via innate host defense mechanisms and secretion of secretory IgA. One of the antimicrobial peptides, LL-37, is the only cathelicidin protein that has yet been identified in humans. Cathelicidins are a family of peptides thought to provide an innate defensive barrier against a variety of potential microbial pathogens. OBJECTIVES: To examine the expression of cathelicidin in human salivary glands and to investigate up-regulation of cathelicidin in inflammatory conditions. DESIGN: Reverse transcriptase-polymerase chain reaction and immunohistochemical staining were performed on 20 salivary gland tissues, 10 from normal salivary glands and 10 from glands with chronic sialadenitis. RESULTS: Cathelicidin messenger RNA transcripts were detected in the tissues from the normal salivary glands and the glands with chronic sialadenitis. The level of cathelicidin messenger RNA in glands with chronic sialadenitis was significantly increased compared with that in normal salivary glands. Cathelicidin protein was expressed in the glandular epithelium of the normal salivary glands and the glands with chronic sialadenitis. CONCLUSION: The results indicate that cathelicidin might play an important role in innate host defense of human salivary glands.

Antimicrobial Cationic Peptides↗

PubMed2000

Synergistic actions of antibacterial neutrophil defensins and cathelicidins.

OBJECTIVE: Activated neutrophils extracellularly release antibacterial defensins and cathelicidins from the granules. In this study, to elucidate the interactions between defensins and cathelicidins in the extracellular environment, we evaluated the individual and synergistic actions of defensins and cathelicidins in the presence of physiological concentration of NaCl (150 mM). MATERIALS AND METHODS: Antibacterial activities against Escherichia coli and Staphylococcus aureus were assessed using human and guinea pig defensins and cathelicidins. Furthermore, the effect of defensins and cathelicidins on membrane permeabilization was examined using E. coli ML-35p, as a target organism. RESULTS: In the absence of NaCl, human defensin (HNP-1) and guinea pig defensins (GNCPs) exhibited the antibacterial activities in a dose-dependent manner (0.1-10 microg/ml); however, their activities were completely lost in the presence of 150 mM NaCl. In contrast, the antibacterial activities of human cathelicidin (CAP18/LL-37) and guinea pig cathelicidin (CAP11) were resistant to NaCl. Interestingly, HNP-1 and GNCPs synergized with CAP18/LL-37 and CAP11 to enhance the antibacterial activities against E. coli and S. aureus in the presence of 150 mM NaCl (p<0.05). Similarly, HNP-1 and GNCPs were synergistic with CAP18/LL-37 and CAP11 to potentiate the outer and inner membrane permeabilization of E. coli ML-35p (p<0.05). CONCLUSIONS: Together these observations indicate that when extracellularly released from neutrophils, defensins cannot function as antibacterial molecules by themselves, but can synergistically work with cathelicidins to exert the antibacterial activity in the extracellular milieu by augmenting the membrane permeabilization of target cells.

Animals↗

PubMed2005

Anti-fungal activity of cathelicidins and their potential role in Candida albicans skin infection.

Cathelicidins have broad anti-microbial capacity and are important for host defense against skin infections by some bacterial and viral pathogens. This study investigated the activity of cathelicidins against Candida albicans. The human cathelicidin LL-37, and mouse cathelicidin mCRAMP, killed C. albicans, but this fungicidal activity was dependent on culture conditions. Evaluation of the fungal membrane by fluorescent dye penetration after incubation with cathelicidins correlated membrane permeabilization and inhibition of fungal growth. Anti-fungal assays carried out in an ionic environment that mimicked human sweat and with the processed forms of cathelicidin such as are present in sweat found that the cleavage of LL-37 to forms such as RK-31 conferred additional activity against C. albicans. C. albicans also induced an increase in the expression of cathelicidin in mouse skin, but this induction did not confer systemic or subcutaneous resistance as mCRAMP-deficient mice were not more susceptible to C. albicans in blood-killing assays or in an intradermal infection model. Therefore, cathelicidins appear active against C. albicans, but may be most effective as a superficial barrier to infection.

Animals↗

PubMed2006

Two cathelicidin genes are present in both rainbow trout (Oncorhynchus mykiss) and atlantic salmon (Salmo salar).

Further to the previous finding of the rainbow trout rtCATH_1 gene, this paper describes three more cathelicidin genes found in salmonids: two in Atlantic salmon, named asCATH_1 and asCATH_2, and one in rainbow trout, named rtCATH_2. All the three new salmonid cathelicidin genes share the common characteristics of mammalian cathelicidin genes, such as consisting of four exons and possessing a highly conserved preproregion and four invariant cysteines clustered in the C-terminal region of the cathelin-like domain. The asCATH_1 gene is homologous to the rainbow trout rtCATH_1 gene, in that it possesses three repeat motifs of TGGGGGTGGC in exon IV and two cysteine residues in the predicted mature peptide, while the asCATH_2 gene and rtCATH_2 gene are homologues of each other, with 96% nucleotide identity. Salmonid cathelicidins possess the same elastase-sensitive residue, threonine, as hagfish cathelicidins and the rabbit CAP18 molecule. The cleavage site of the four salmonid cathelicidins is within a conserved amino acid motif of QKIRTRR, which is at the beginning of the sequence encoded by exon IV. Two 36-residue peptides corresponding to the core part of rtCATH_1 and rtCATH_2 were chemically synthesized and shown to exhibit potent antimicrobial activity. rtCATH_2 was expressed constitutively in gill, head kidney, intestine, skin and spleen, while the expression of rtCATH_1 was inducible in gill, head kidney, and spleen after bacterial challenge. Four cathelicidin genes have now been characterized in salmonids and two were identified in hagfish, confirming that cathelicidin genes evolved early and are likely present in all vertebrates.

Amino Acid Sequence↗

PubMed2005

Keratinocyte production of cathelicidin provides direct activity against bacterial skin pathogens.

Immune defense at an interface with the external environment reflects the functions of physical and chemical barriers provided by epithelial and immune cells. Resident epithelial cells, such as keratinocytes, produce numerous peptides with direct antimicrobial activity but also provide a physical barrier against invading pathogens and signal the recruitment of circulating immune cells, such as neutrophils. Antimicrobial peptides such as cathelicidin are produced constitutively by neutrophils and are inducible in keratinocytes in response to infection. The multiplicity of antimicrobial peptides and their cellular sources has resulted in an incomplete understanding of the role of cathelicidin production by epithelial cells in cutaneous immune defense. Therefore, this study sought to evaluate keratinocyte antimicrobial activity and the potential contribution of keratinocyte cathelicidin to host protection against two leading human skin pathogens. Wild-type mice and those with a targeted deletion of the cathelicidin gene, Cnlp, were rendered neutropenic prior to cutaneous infection. Interestingly, Cnlp-deficient mice remained more susceptible to group A streptococcus infection than mice with Cnlp intact, suggesting the involvement of epithelial cell-derived cathelicidin in host immune defense. Keratinocytes were then isolated in culture and found to inhibit the growth of Staphylococcus aureus, an effect that was partially dependent on their ability to synthesize and activate cathelicidin. Further, lentivirus-mediated delivery of activated human cathelicidin enhanced keratinocyte antimicrobial activity. Combined, these data illustrate the potential contribution of keratinocyte cathelicidin to the innate immune defense of skin against bacterial pathogens and highlight the need to consider epithelial antimicrobial function in the diagnosis and therapy of skin infection.

Animals↗

PubMed2005

Expression of cathelicidin in recurrent throat infection.

BACKGROUND: Epithelial cells can be called the first line of a defense barrier to microorganisms by the innate immune system. The antimicrobial peptides are the major participants of this system. Cathelicidins are a family of peptides thought to provide an innate defensive barrier against a variety of potential microbial pathogens. OBJECTIVES: To evaluate the expression of the cathelicidin in recurrent throat infection. PATIENTS AND METHODS: Reverse transcriptase-polymerase chain reaction (RT-PCR) and immunohistochemical staining were performed for 10 palatine tonsil tissues with hypertrophy and 10 palatine tonsil tissues with recurrent throat infection. RESULTS: Cathelicidin mRNA transcripts were detected in recurrent throat infection. The expression levels of cathelicidin mRNA in recurrent throat infection was significantly higher compared with those in hypertrophic tonsils. Cathelicidin protein was localized on the tonsillar surface epithelium and inflammatory cells in the tonsillar crypt of recurrent throat infection patients. CONCLUSION: These results suggest that cathelicidin is one of antimicrobial peptides in the human palatine tonsils, and that cathelicidin may also play an important role in innate host defense of human tonsils.

Adolescent↗

PubMed2005

Identification and functional characterization of three chicken cathelicidins with potent antimicrobial activity.

Cathelicidins comprise a family of antimicrobial peptides sharing a highly conserved cathelin domain. Here we report that the entire chicken genome encodes three cathelicidins, namely fowlicidin-1 to -3, which are densely clustered within a 7.5-kb distance at the proximal end of chromosome 2p. Each fowlicidin gene adopts a fourexon, three-intron structure, typical for a mammalian cathelicidin. Phylogenetic analysis revealed that fowlicidins and a group of distantly related mammalian cathelicidins known as neutrophilic granule proteins are likely to originate from a common ancestral gene prior to the separation of birds from mammals, whereas other classic mammalian cathelicidins may have been duplicated from the primordial gene for neutrophilic granule proteins after mammals and birds are diverged. Similar to ovine cathelicidin SMAP-29, putatively mature fowlicidins displayed potent and salt-independent activities against a range of Gram-negative and Gram-positive bacteria, including antibiotic-resistant strains, with minimum inhibitory concentrations in the range of 0.4-2.0 microm for most strains. Fowlicidin-1 and -2 also showed cytotoxicity, with 50% killing of mammalian erythrocytes or epithelial cells in the range of 6-40 microm. In addition, two fowlicidins demonstrated a strong positive cooperativity in binding lipopolysaccharide (LPS), resulting in nearly complete blockage of LPS-mediated proinflammatory gene expression in RAW264.7 cells. Taken together, fowlicidin-1 and -2 are clearly among the most potent cathelicidins that have been reported. Their broad spectrum and salt-insensitive antibacterial activities, coupled with their potent LPS-neutralizing activity, make fowlicidins excellent candidates for novel antimicrobial and anti-sepsis agents.

Amino Acid Sequence↗

PubMed2006

Expression and potential function of cathelicidin antimicrobial peptides in dermatophytosis and tinea versicolor.

OBJECTIVES: This study was designed to characterize the role of the human cathelicidin LL-37 in fungal skin infections such as dermatophytosis and tinea versicolor. METHODS: The in vitro antimicrobial activity of synthetic antimicrobial peptides including the human cathelicidin LL-37 against Malassezia furfur and several dermatophytes was determined. Immunostaining was performed to determine expression of cathelicidin in skin biopsies from patients with tinea pedis, tinea corporis and tinea versicolor. Cathelicidin peptide expression was evaluated by western blotting and mRNA expression was studied in keratinocytes exposed to M. furfur or Trichophyton rubrum. RESULTS: LL-37 inhibits the growth of fungi with an MIC of 20-30 microM for M. furfur and 12.5 microM for Trichophyton mentagrophytes and T. rubrum. LL-37 also shows fungicidal activity with a minimum fungicidal concentration (MFC) of 12.5 and 25 microM for T. mentagrophytes and T. rubrum, respectively. An increase in cathelicidin expression was observed in human skin tissue infected with fungi compared with healthy skin. Western blotting of skin scrapings demonstrated that human cathelicidin is processed from its precursor into an active peptide in both healthy and infected plantar skin. CONCLUSIONS: These findings support a hypothesis that antimicrobial peptides such as cathelicidins can play a role in skin defence against dermatophytes and M. furfur.

Adult↗

PubMed2005

Keratinocytes store the antimicrobial peptide cathelicidin in lamellar bodies.

Innate immune defense against microbial pathogens occurs by physical barriers, by recruitment of cells such as neutrophils, NK cells, and macrophages, and by secretion of molecules with antimicrobial activity. Such molecules are produced by various epithelia including skin. The importance of antimicrobial peptides has been shown in cathelicidin-deficient mice, which have increased susceptibility to skin infection by Streptococcus. Although keratinocytes increase cathelicidin expression upon injury, their role relative to neutrophil cathelicidin and their sites of peptide storage and activation have not been elucidated. Herein, it is reported that cathelicidin predominantly resides in granules of the superficial epidermis and partially localizes in lamellar bodies as determined by immunogold electron microscopy and immunoblot of lamellar bodies isolated from mice. In cultured keratinocytes, cathelicidin displays a granular distribution and partially localizes within the Golgi apparatus. Cathelicidin processing can be observed by western blot analysis in keratinocyte extracts but not in conditioned media. Further, fluorescent bacteria colocalize with cathelicidin in granules both intracellularly and at the cell surface. These observations illustrate the immune defense potential of keratinocytes acting directly through storage and processing of antimicrobial peptides.

Antimicrobial Cationic Peptides↗

PubMed2005

CMAP27, a novel chicken cathelicidin-like antimicrobial protein.

Cathelicidins, antimicrobial peptides with broad spectrum activity, have been almost exclusively found in mammals. Here, we report the cloning of a novel avian cathelicidin, chicken myeloid antimicrobial peptide 27 (CMAP27) from chicken bone marrow cells. A combined expressed sequence tag (EST) and genomic based search revealed a cathelicidin-like gene located at the terminus of chromosome 2. Reverse transcriptase-polymerase chain reaction (RT-PCR) and 5'RACE techniques resulted in a 154 amino acid prepropeptide, homologous to chicken cathelicidin 1 (51%) and most similar to alpha-helical myeloid antibacterial peptides (MAPs; 29-33%). A putative elastase cleavage site (LVQRG/RF) suggests the production of a 27 amino acid antimicrobial peptide, predicted to adopt an alpha-helical configuration followed by a hydrophobic tail. Comparative analyses between antimicrobial peptide domains showed marked similarity between CMAP27 and MAP members of the bovidae family, but not with the alpha-helical chicken cathelicidin 1. Strongest expression of CMAP27 mRNA was found in myeloid/lymphoid tissues, testis and uropygial gland. In accordance with the phylogenetic tree analysis, these findings support the theory of a common ancestral cathelicidin gene and suggest an important role for cathelicidins in chicken innate host defense.

Amino Acid Sequence↗

PubMed1996

Purification and structural characterization of bovine cathelicidins, precursors of antimicrobial peptides.

Cathelicidins are a novel family of antimicrobial peptide precursors from mammalian myeloid cells. They are characterized by a conserved N-terminal region while the C-terminal antimicrobial domain can vary considerably in both primary sequence and length. Four cathelicidins, proBac5, proBac7, prododecapeptide and proBMAP-28, have been concurrently purified from bovine neutrophils, using simple and rapid methodologies. The correlation of ES-MS data from the purified proteins with their cDNA-deduced sequences has revealed several common features of their primary sequence, such as the presence of N-terminal 5-oxoproline (pyroglutamate) residues and two disulfide bridges in a 1-2, 3-4 arrangement. The N-terminal domains of the cathelicidins present one or two Asp-Pro bonds, which are particularly acid-labile in proBac5 and proBac7, but stable in prododecapeptide. This suggests that the spatial organization around these bonds may vary in different cathelicidins, and favour hydrolysis in some cases. An unexpected feature of the prododecapeptide is that it exists as dimers formed by three possible combinations of its two isoforms. The isolation of a truncated, monomeric form of this protein, lacking the cysteine-containing antimicrobial dodecapeptide, indicates that dimerization occurs via disulfide bridge formation at the level of the C-terminal domain and that the dodecapeptide is likely released as a dimer from its precursor. Sequence-based secondary structure predictions and CD results indicate for cathelicidins a 30-50% content of extended conformation and <20% content of alpha-helical conformation, with the alpha-helical segment placed near the N-terminus. Finally, similarity searching and topology-based structure prediction underline a significant sequential and structural similarity between the conserved N-terminal domain of cathelicidins and cystatin-like domains, placing this family within the cystatin superfamily. When assayed against cathepsin L, unlike the potent cystatin inhibitors, three of the four cathelicidins show only a poor inhibitory activity (Ki = 0.6-3 microM).

Amino Acid Sequence↗

PubMed2003

Phylogeny, processing and expression of the rat cathelicidin rCRAMP: a model for innate antimicrobial peptides.

A database search identified a rat cDNA clone which phylogenetic analysis revealed to encode a cathelicidin most similar to mouse cathelicidin CRAMP. The analysis also showed that the evolutionary pattern of the cathelicidin family is lineage specific. The rat cathelicidin is called rCRAMP. Its peptide was isolated from granulocytes, and determined to be 43 amino acids long by mass spectrometry and N-terminal sequencing. Synthetic rCRAMP had antimicrobial activity. The expression of rCRAMP was investigated by reverse-transcriptase polymerase chain reaction followed by Southern hybridization and by Western blot analysis. rCRAMP was identified in granulocytes, thymus, testis, lung, mouth mucosa, tongue, oesophagus, colon, caecum and small intestine, a distribution similar to cathelicidins of mouse and human. The rat is a small laboratory animal with additional disease models available compared to the mouse. Our results open up the possibility to use the rat as a model system to study responses connected to cathelicidin expression in health and disease.

Amino Acid Sequence↗