Prodefensins are matrix proteins of specific granules in human neutrophils

Abstract

Defensins are potent antimicrobial and proinflammatory peptides. The human neutrophil defensins human neutrophil peptide (HNP)-1-3 are synthesized as 94 amino acide (aa) preproHNPs, which are converted to 75 aa proHNPs by cotranslational removal of a 19 aa endoplasmic reticulum signal peptide. At the promyelocytic stage of myelopoiesis, proHNPs are further proteolytically modified and accumulate in azurophil granules as 29-30 aa HNPs. In contrast, proHNPs produced by more mature myeloid cells are not subjected to proteolytic cleavage and undergo a high degree of constitutive exocytosis. The proHNPs are devoid of antimicrobial potential, and the significance of their secretion is unknown. To investigate whether mature neutrophils contain proHNPs, we developed antibodies against proHNP-1 by DNA immunization of rabbits. In addition, antibodies against the 45 aa proHNP pro-piece were raised by conventional immunization procedures. These antibodies allowed detection of proHNPs in homogenates of peripheral blood neutrophils. The proHNPs were isolated by affinity chromatography, and their identity was confirmed by mass spectrometry and N-terminal aa sequence analysis. Finally, the neutrophil proHNPs were identified as novel matrix proteins of specific granules by subcellular fractionation experiments, release studies, and immunoelectron microscopy. Thus, human neutrophils not only store large amounts of mature defensins in azurophil granules but also contain a more easily mobilized reservoir of unprocessed prodefensins in specific granules.

Neutrophil α-Defensins Cause Lung Injury by Disrupting the Capillary–Epithelial Barrier

“…Myeloid-specific expression of HNPs was confirmed by Northern blot, Western blots, and immunohistochemistry of peripheral and bone marrow PMNs. Def 1/1 PMNs express mature HNP-1 and HNP-2 and two higher molecular weight bands, consistent with preproHNP and proHNP found in myeloid progenitors (55,56). HNP-1 was expressed at approximately 10% of the total concentration of mature a-defensins in human PMN, a finding that might underestimate their contribution to ALI, but enabled us to study the mechanism of action, which might have been precluded by more intense release.…”

Young, adult, and old rats have similar changes in mRNA expression of many skeletal genes after fracture despite delayed healing with age

“…5A-D) for both red cells 53,54 and white cells. 55,56 The younger rats recovered normal levels of hematopoietic gene expression faster than did the older rats. To minimize damage to the marrow, 57,58 the intramedullary rod had been placed without reaming.…”

Immunomodulatory activity of acidic polysaccharides isolated from Tanacetum vulgare L.

“…Neutrophil granules contain a multitude of antimicrobial and potentially cytotoxic substances that are delivered to the phagosome or to the exterior of the cell following degranulation [42]. MPO is a key enzyme released into the phagosome or the extracellular space upon neutrophil activation, and plays an important role in microbicidal activity by catalyzing the formation of various ROS that can attack microorganisms [43]. Thus, the ability to stimulate neutrophil MPO release could represent an important immunomodulatory property of Tansy polysaccharides.…”