Diversity and activation of rhesus Paneth cell α‐defensins

Abstract

Paneth cells (PCs) occur in small intestinal crypts from which they secrete α‐defensins at high levels. To investigate rhesus macaque enteric α‐defensin (REDs) diversity, ileal mucosal protein and mRNAs were characterized. Analyses of ileum α‐defensin cDNA and gene sequences identified 20 distinct RED cDNAs and 7 RED genes not represented in the cDNA population. Certain deduced RED proteins coded by abundant mRNAs have mutations at canonical α‐defensin structural features. α‐Defensin proteins isolated from ileum occur predominantly as proREDs with negligible processed REDs detected by acid‐urea PAGE and MALDI‐TOF MS. In vitro, purified natural and recombinant proREDs were activated by trypsin to yield structurally intact, mature RED peptides. Because mature RED peptides are lacking from ileal PCs and mouse PC α‐defensins persist in colonic lumen (J. Biol. Chem. 284: 27848–27856, 2009), colonic luminal contents were assayed for evidence of post‐secretory proRED processing. Mature, intact RED peptides were evident in large bowel lumen, far downstream from their small intestinal site of secretion, and they were identified as α‐defensins by Edman sequencing. The processed state of α‐defensins in rhesus PCs resembles that in human PCs and differs from the mouse PCs, where activated, mature α‐defensins are abundant in PC dense core granules. Supported by NIH grants AI059346 and DK044632.