Discovery of new human β-defensins using a genomics-based approach

Abstract

Epithelial b-defensins are broad-spectrum cationic antimicrobial peptides that also act as chemokines for adaptive immune cells. In the human genome, all known defensin genes cluster to a ,1 Mb region of chromosome 8p22-p23. To identify new defensin genes, the DNA sequence from a contig of large-insert genomic clones from the region containing human b-defensin-2 (HBD-2) was analyzed for the presence of defensin genes. This sequence survey identi®ed a novel b-defensin, termed HBD-3. The HBD-3 gene contains two exons, is located 13 kb upstream from the HBD-2 gene, and it is transcribed in the same direction. A partial HBD-3 cDNA clone was ampli®ed from cDNA derived from IL-1b induced fetal lung tissue. The cDNA sequence encodes for a 67 amino acid peptide that is ,43% identical to HBD-2 and shares the b-defensin six cysteine motif. By PCR analysis of two commercial cDNA panels, HBD-3 expression was detected in adult heart, skeletal muscle, placenta and in fetal thymus. From RT-PCR experiments, HBD-3 expression was observed in skin, esophagus, gingival keratinocytes, placenta and trachea. Furthermore, in fetal lung explants and gingival keratinocytes, HBD-3 mRNA expression was induced by IL-1b. Additional sequence analysis identi®ed the HE2 (human epididymis secretory protein) gene 17 kb upstream from the HBD-3 gene. One splice variant of this gene (HE2b1) encodes a b-defensin consensus cysteine motif, suggesting it represents a defensin gene product. HE2b1 mRNA expression was detected in gingival keratinocytes and bronchial epithelia using RT-PCR analysis. The discovery of these novel b-defensin genes may allow further understanding of the role of defensins in host immunity at mucosal surfaces. q

Signal Transduction and Nuclear Responses in Staphylococcus aureus- Induced Expression of Human β-Defensin 3 in Skin Keratinocytes

“…3C). The additive inhibition of hBD-3 transcripts with the use of p38 and NF-B inhibitors was unexpected since the hBD-3 promoter region has no discernible NF-B binding sites (22). Using the Matinspector software program of Genomatix Suite, we also were unable to detect NF-B motifs.…”

“…The signaling mechanisms involved in the upregulation of hBD-3 in skin epithelia upon contact with microorganisms, including S. aureus, are incompletely understood. The hBD-3 gene promoter has no discernible NF-B binding elements but does contain transcriptional binding motifs for activator protein 1 (AP-1), interferon gamma interferon (IFN-␥) response elements, and NF-IL-6 response elements (22). IFN-␥ is a potent inducer of hBD-3 in most epithelial cells, including keratinocytes.…”

Antimicrobial peptides and pregnancy

“…Production of HBD1 is generally constitutive, whereas HBD2 and HBD3 tend to be upregulated by a variety of inflammatory stimuli including bacteria, bacterial products, and inflammatory cytokines (Lai & Gallo 2009). The 5 0 -flanking region of the HBD2 gene contains NFKB, C/EBP, and AP-1 binding sites (Tsutsumi-Ishii & Nagaoka 2002), whereas the region of the HBD3 gene has C/EBP and AP-1 sites (Jia et al 2001), suggesting that these elements are important in HBD expression. In vivo, HBD2 and HBD3 tend to be found in epithelia in association with infection and inflammation, whereas HBD1 is often intrinsically present in healthy tissues (Lai & Gallo 2009).…”

Isoleucine, an Essential Amino Acid, Induces the Expression of Human <i>β</i> Defensin 2 through the Activation of the G-Protein Coupled Receptor-ERK Pathway in the Intestinal Epithelia

“…The alterations in α-defensin have since been considered to be associated with the etiology of various intestinal disorders such as cystic fibrosis [4] and Crohn's disease (CD) [5]. Conversely, β-defensin (HBD) is produced by the epithelial cells particularly in the bronchus and colon, which includes 6 isotypes, HBD1 -6 [6][7][8][9][10]. While HBD1 is constitutively expressed, HBD2 and 3 are inducible defensins.…”