Brandt E, Petersen F, Flad H D
Forschungsinstitut Borstel, Department of Immunology and Cell Biology, Germany.
Mol Immunol. 1993 Aug;30(11):979-91. doi: 10.1016/0161-5890(93)90123-s.
The human neutrophil-activating peptide 2 (NAP-2) belongs to the so-called beta-thromboglobulin/interleukin 8-family of chemotactic and reparative host defense cytokines. NAP-2 represents one of several N-terminally truncated cleavage products that originate from platelet-derived precursor molecules through proteolytic processing. Among these homologous isoforms that are comprised as beta-thromboglobulin antigen (beta-TG Ag), NAP-2 is recognized as the major component, having the highest potential for the activation of polymorphonuclear neutrophils (PMN). We now present evidence that there exists a second molecular form of NAP-2 with even higher biological activity. This novel isoform was detected in concentrates of culture supernatants from peripheral blood mononuclear cells, and could be separated from authentic NAP-2 by several steps of column chromatography. It had an N-terminus identical to that of NAP-2 but was biochemically different as indicated by its slightly lower molecular weight and a higher isoelectric point. To examine our hypothesis that the polypeptide represented a C-terminally truncated variant of NAP-2, we prepared synthetic peptides that were used for the induction and characterization of two rabbit antibody fractions, directed against different and defined epitopes within the C-terminal alpha-helix of the NAP-2 molecule. Comparison of reactivity patterns of these antibodies in Western blots as well as in a NAP-2 biological assay (PMN degranulation assay) confirmed that the variant NAP-2 was truncated at its C-terminus by at least one and by maximally three residues. The specific activity of the truncated polypeptide was estimated to be about four-fold higher than that of authentic NAP-2, as determined in the PMN degranulation assay. Thus, proteolytic modification at the C-terminus appears to play a role in the regulation of NAP-2-biological activity.
人中性粒细胞激活肽2（NAP - 2）属于趋化性和修复性宿主防御细胞因子的所谓β - 血小板球蛋白/白细胞介素8家族。NAP - 2是通过蛋白水解加工从血小板衍生的前体分子产生的几种N端截短的裂解产物之一。在这些作为β - 血小板球蛋白抗原（β - TG Ag）组成的同源异构体中，NAP - 2被认为是主要成分，具有激活多形核中性粒细胞（PMN）的最高潜力。我们现在提供证据表明存在第二种具有更高生物活性的NAP - 2分子形式。这种新型异构体在外周血单核细胞培养上清液浓缩物中被检测到，并可通过几步柱色谱与天然NAP - 2分离。它的N端与NAP - 2相同，但生化性质不同，表现为分子量略低和等电点较高。为了检验我们的假设，即该多肽代表NAP - 2的C端截短变体，我们制备了合成肽，用于诱导和表征两种兔抗体组分，它们针对NAP - 2分子C端α - 螺旋内不同且明确的表位。这些抗体在蛋白质免疫印迹以及NAP - 2生物学测定（PMN脱颗粒测定）中的反应模式比较证实，变体NAP - 2在其C端截短了至少一个且最多三个残基。如在PMN脱颗粒测定中所确定的，截短多肽的比活性估计比天然NAP - 2高约四倍。因此，C端的蛋白水解修饰似乎在NAP - 2生物活性的调节中起作用。
