Characterization of β‐defensin prepropeptide mRNA from chicken and turkey bone marrow

Abstract

Four avian beta-defension prepropeptide cDNA sequences [gallinacins: Gal 1 (synonym CHP 1, chicken heterophil peptide 1), and Gal 2; turkey heterophil peptides: THP 1 and THP 2] were amplified from chicken or turkey bone marrow mRNA samples, respectively. Partial chicken beta-defensin cDNA sequences were obtained using degenerate primers based on chicken peptide sequences (Gal 1/CHP 1 and Gal 2). The complete cDNA sequences of the chicken beta-defensins were then determined by designing specific intrapeptidal primers, from the newly acquired sequence, and pairing one primer with a specific poly A primer tail sequence (3' end) and the other primer with an adapter primer in a 5' rapid amplification of cDNA ends (RACE) reaction. The two, turkey beta-defensins were amplified from turkey marrow using primers designed from chicken beta-defensin preproregions. The complete amino acid sequences for the prepropeptides were deduced for all four avian beta-defensins. Previously, only partial mature peptide sequences for the turkey beta-defensins and complete mature peptide sequences for the chicken beta-defensins were known. All sequences obtained translated accurately to complete and partial amino acid sequences reported for beta-defensins purified from chicken and turkey heterophil granules except for one additional amino acid for Gal 1/CHP 1. The four deduced beta-defensin proregions lack the long, negatively charged propiece reported in classical defensin proregions. These regions are thought to stabilize and inactivate the positively charged mature peptide and target the propeptide to the storage granule. Instead, these beta-defensin proregions are shorter and similar to storage granule-free beta-defensins proregions reported for bovine tracheal antimicrobial peptide (TAP) and lingual antimicrobial peptide (LAP). These are the first prepropeptide beta-defensins from leukocyte granules to be completely characterized.

Gallinacin-3, an Inducible Epithelial β-Defensin in the Chicken

“…While defensins are often very prominent in granulocytes, they are not ubiquitous, since the neutrophils of mice (6), pigs (19), and horses (5) lack any defensins at all. Although avian ␤-defensins have been observed in bone marrow cells (4,7,15,16), neither their induction during infection nor their expression in epithelial cells has been reported until now.…”

“…␣-Defensins are remarkably abundant in human, rabbit, and rat neutrophils (20), but only ␤-defensins (at least 13 different isoforms) appear in the neutrophils of cattle (33). ␤-Defensins also occur in the polymorphonucleated granulocytes (heterophils) of chickens and turkeys (4,7,15,16). While defensins are often very prominent in granulocytes, they are not ubiquitous, since the neutrophils of mice (6), pigs (19), and horses (5) lack any defensins at all.…”

Induction of Cationic Chicken Liver-Expressed Antimicrobial Peptide 2 in Response to Salmonella enterica Infection

“…Cells and tissues synthesizing antimicrobial peptides are generally those exposed to microbial pathogens. In the chicken, four ␤-defensins have been identified in heterophils (5,8), and a fifth defensin-like antimicrobial peptide, gallinacin 3, is expressed in a number of avian tissues (28). To date, however, no cationic antimicrobial peptides have been identified in the chicken small intestine.…”

“…This is especially important, as birds are universally recognized as a major reservoir of human enteropathogens but are themselves often asymptomatic. To date, four antimicrobial peptides, termed gallinacin 1 and 2 and turkey heterophil peptides 1 and 2, have been characterized from avian heterophils (5,8). All are homologous to ␤-defensins and show activity against Salmonella enteritidis and Campylobacter jejuni.…”

The avian immune genome – a glass half-full or half-empty?

“…Comparison of the mammalian and chicken TLR repertoires ed in classical mammalian defensins, which is thought to inactivate the positively-charged mature sequence allowing their storage in granules. Its absence in chicken defensins suggested that the chicken uses some other mechanism to neutralize the positive charges of the gallinacins whilst they are stored in granules (Brockus et al, 1998). In 2001, an epithelial ␤ -defensin named gallinacin 3, expressed in epithelial organs such as the lungs, bursa and intestine, was also characterised (Zhao et al, 2001).…”