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Peptide localization and gene structure of cryptdin 4, a differentially expressed mouse paneth cell alpha-defensin.

ABSTRACT: Paneth cells in crypts of the small intestine express antimicrobial peptides, including alpha-defensins, termed cryptdins in mice. Of the known Paneth cell alpha-defensins, the cryptdin 4 gene is unique, because it is inactive in the duodenum and expressed at maximal levels in the distal small bowel (D. Darmoul and A. J. Ouellette, Am. J. Physiol. 271:G68-G74, 1996). With a cryptdin 4-specific antibody, immunohistochemical staining of ileal Paneth cells was strong and specific for cytoplasmic granules, demonstrating that this microbicidal peptide is a secretory product of Paneth cells in the distal small intestine. Consistent with the pattern of cryptdin 4 mRNA distribution along the length of the gut, the cryptdin 4 peptide was not detected in duodenum. Structurally, the cryptdin 4 gene resembles other Paneth cell alpha-defensin genes. Its two exons, transcriptional start site, intron, splice sites, and 3' flanking sequences are characteristic of the highly conserved mouse alpha-defensin genes. However, in the region upstream of the transcriptional initiation site, the cryptdin 4 gene contains a repeated 130-bp element that is unique to this alpha-defensin gene. Every independent cryptdin 4 genomic clone examined carries the repeated element, which contains putative recognition sequences for TF-IID-EIIA, cMyc-RS-1, and IgHC.2/CuE1.1; the repeat proximal to the start of transcription replaces DNA at the corresponding position in other mouse alpha-defensin genes. We speculate that this unique duplicated element may have a cis-acting regulatory role in the positional specificity of cryptdin 4 gene expression.

SUBMITTER: Ouellette AJ

PROVIDER: S-EPMC97078 | biostudies-literature | 1999 Dec

REPOSITORIES: biostudies-literature

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Peptide localization and gene structure of cryptdin 4, a differentially expressed mouse paneth cell alpha-defensin.

Ouellette A J AJ Darmoul D D Tran D D Huttner K M KM Yuan J J Selsted M E ME

Infection and immunity 19991201 12

Paneth cells in crypts of the small intestine express antimicrobial peptides, including alpha-defensins, termed cryptdins in mice. Of the known Paneth cell alpha-defensins, the cryptdin 4 gene is unique, because it is inactive in the duodenum and expressed at maximal levels in the distal small bowel (D. Darmoul and A. J. Ouellette, Am. J. Physiol. 271:G68-G74, 1996). With a cryptdin 4-specific antibody, immunohistochemical staining of ileal Paneth cells was strong and specific for cytoplasmic gr ...[more]

PMID: 10569786

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Project description:IntroductionThe mechanism underlying radiation-induced gut microbiota dysbiosis is undefined. This study examined the effect of radiation on the intestinal Paneth cell α-defensin expression and its impact on microbiota composition and mucosal tissue injury and evaluated the radio-mitigative effect of human α-defensin 5 (HD5).MethodsAdult mice were subjected to total body irradiation, and Paneth cell α-defensin expression was evaluated by measuring α-defensin mRNA by RT-PCR and α-defensin peptide levels by mass spectrometry. Vascular-to-luminal flux of FITC-inulin was measured to evaluate intestinal mucosal permeability and endotoxemia by measuring plasma lipopolysaccharide. HD5 was administered in a liquid diet 24 hours before or after irradiation. Gut microbiota was analyzed by 16S rRNA sequencing. Intestinal epithelial junctions were analyzed by immunofluorescence confocal microscopy and mucosal inflammatory response by cytokine expression. Systemic inflammation was evaluated by measuring plasma cytokine levels.ResultsIonizing radiation reduced the Paneth cell α-defensin expression and depleted α-defensin peptides in the intestinal lumen. α-Defensin down-regulation was associated with the time-dependent alteration of gut microbiota composition, increased gut permeability, and endotoxemia. Administration of human α-defensin 5 (HD5) in the diet 24 hours before irradiation (prophylactic) significantly blocked radiation-induced gut microbiota dysbiosis, disruption of intestinal epithelial tight junction and adherens junction, mucosal barrier dysfunction, and mucosal inflammatory response. HD5, administered 24 hours after irradiation (treatment), reversed radiation-induced microbiota dysbiosis, tight junction and adherens junction disruption, and barrier dysfunction. Furthermore, HD5 treatment also prevents and reverses radiation-induced endotoxemia and systemic inflammation.ConclusionThese data demonstrate that radiation induces Paneth cell dysfunction in the intestine, and HD5 feeding prevents and mitigates radiation-induced intestinal mucosal injury, endotoxemia, and systemic inflammation.

Project description:Enteric antimicrobial peptides secreted from Paneth cells, including alpha-defensins (in mice named cryptdins), are key effector molecules of innate immunity in the small intestine. The importance of Paneth cells alpha-defensins emerged from studies of enteric bacterial infection in genetically modified mice, as well as from recent studies linking reduced levels of these alpha-defensins to Crohn's disease localized to the ileum. However, analysis of expression of Paneth cell alpha-defensins is incomplete. We therefore performed a comprehensive evaluation of the distribution of antimicrobial molecules along the mouse small intestinal tract to identify potential variations in regional expression.In conventionally reared mice, the repertoire of Paneth cell antimicrobials differs between duodenum and ileum. In contrast to the uniform expression of most Paneth cell antimicrobials, both cryptdin 4 and cryptdin-related sequences (CRS) 4C peptides were expressed at progressively increasing amounts (101- and 104-fold, respectively) comparing duodenum and ileum. In tissues other than the small intestine, expression of CRS peptides was noted in thymus and caecum. Most Paneth cell products were also produced in the small intestine of germ-free mice at levels similar to those in controls, however CRS4C and RegIIIgamma had reduced levels in the former (3- and 8-fold, respectively). No significant changes in expression levels of Paneth cell antimicrobial peptides was observed after oral challenge with either Salmonella enterica serovar typhimurium or Listeria monocytogenes, supporting current notions on the constitutive nature of this defensive system.The repertoire of antimicrobial peptides changes along the small intestinal tract, and a subset of these molecules are up-regulated upon colonization, but not in response to enteric bacterial pathogens. The changes detected upon colonization suggest that Paneth cell antimicrobial peptides may play an important role in commensal microbial homeostasis, in addition to their proposed role in protection against infection. In addition, the differential expression of CRS4C along the small intestine suggests mechanisms of regulation that are distinct from other Paneth cell derived antimicrobial peptides.

Dataset Information

Peptide localization and gene structure of cryptdin 4, a differentially expressed mouse paneth cell alpha-defensin.

Publications

Peptide localization and gene structure of cryptdin 4, a differentially expressed mouse paneth cell alpha-defensin.

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