Molecular Cloning and Multifunctional Characterization of Host Defense Peptides from the Bullfrog Harderian Gland with Special Reference to Catesbeianalectin

Molecular Cloning and Functional Characterization of Antimicrobial Peptides Brevinin-1ULf and Ulmin-1ULa in the Skin of the Newly Classified Ryukyu Brown Frog Rana ulma

Antimicrobial peptides (AMPs) were previously isolated from the skin of the Ryukyu brown frog Rana okinavana. However, this species has recently been reclassified as two species, i.e., Rana kobai and Rana ulma. As a result, it was determined that AMPs isolated from R. okinavana were in fact products of R. kobai, but not of R. ulma. In the present study, we collected skin samples from the species R. ulma and cloned twelve cDNAs encoding AMP precursors for the acyclic brevinin-1ULa--1ULf, the temporin-ULa-ULc, ranatuerin-2ULa, japonicin-1ULa, and a novel peptide using reverse-transcription polymerase chain reaction techniques. The deduced amino acid sequence of the novel peptide had a high similarity to those of Rana chensinensis chensinin-1CEa--1CEc, which were cloned by Zhao et al. ( 2011 ), but had a low similarity with R. chensinensis chensinin-1, which was cloned by Shang et al. ( 2009 ). To avoid confusion with these two different chensinin-1 families, we termed our peptide ulmin-1. Among these peptides, we focused on two peptides, brevinin-1ULf and ulmin-1ULa, and examined the antimicrobial and cytotoxic activity of their synthetic replicates. In broth microdilution assays, growth inhibitory activities against Staphylococcus aureus, Bacillus cereus, and Candida albicans were detected for brevinin-1ULf but not for ulmin-1ULa, whereas scanning electron microscopic observations revealed that both peptides induce morphological abnormalities in these microbes. In addition, binding activity of ulmin-1ULa to the bacterial cell wall component lipoteichoic acid was higher than that of brevinin-1ULf. In contrast, hemolytic and cytotoxic activities of brevinin-1ULf were stronger than those of ulmin-1ULa.

Bacterial toxin-inducible gene expression of cathelicidin-B1 in the chicken bursal lymphoma-derived cell line DT40: functional characterization of cathelicidin-B1

Chicken cathelicidin-B1 (chCATH-B1) is a major host defense peptide of the chicken bursa of Fabricius (BF). To investigate the mechanisms of chCATH-B1 gene expression in the BF, we focused on the DT40 cell line derived from chicken bursal lymphoma as a model for analysis. A cDNA encoding chCATH-B1 precursor was cloned from DT40 cells. The nucleotide sequence of the cDNA was identical with that of the BF chCATH-B1. A broth dilution analysis showed that the synthetic chCATH-B1 exhibited a significant defensive activity against both Escherichia coli and Staphylococcus aureus. A scanning microscopic analysis demonstrated that chCATH-B1 inhibited bacterial growth through membrane destruction with formation of blebs and spheroplasts. Limulus amoebocyte lysate assay and electromobility shift assay results revealed that chCATH-B1 bound to lipopolysaccharide (LPS) and lipoteichoic acid (LTA), which are the surface substances of the E. coli and S. aureus cell, respectively. A chemotactic assay results revealed that chCATH-B1 showed mouse-derived P-815 mastocytoma migrating activity dose-dependently but with a higher concentration, resulting in a loss of the activity. A semi-quantitative real-time RT-PCR analysis revealed that LPS stimulated chCATH-B1 gene expression in a dose-dependent manner and that the LPS-inducible chCATH-B1 gene expression was inhibited by the administration of dexamethasone. The chCATH-B1 mRNA levels in DT40 cells were also increased by the administration of bacterial LTA. The results indicate that bacterial toxins induce chCATH-B1 gene expression in the chicken BF and the peptide expressed in the organ would act against pathogenic microorganisms not only directly but also indirectly by attracting mast cells.