Higgins G C, Foster J L, Postlethwaite A E
Department of Pediatrics, University of Tennessee, Memphis.
J Exp Med. 1994 Aug 1;180(2):607-14. doi: 10.1084/jem.180.2.607.
Human interleukin 1 beta (IL-1 beta) is synthesized as an inactive precursor that is cleaved by IL-1 converting enzyme (ICE) between Asp116 and Ala117 to form COOH-terminal mature IL-1 beta and NH2-terminal IL-1 beta propeptide. Little is known about the fate of the NH2-terminal cleavage product. In this study, human recombinant (hr)IL-1 beta propeptide (amino acids 2-116) was produced and used to prepare specific antibodies which do not recognize mature human IL-1 beta. These anti-propeptide antibodies were used for immunoprecipitation of biosynthetically labeled proteins from lipopolysaccharide-stimulated human monocytes. Analysis of immunoprecipitates by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and fluorography revealed that these antibodies recognize precursor IL-1 beta and two unique proteins: one migrating at 17.5 kD and one at 14 kD. The larger of these two proteins has a migration nearly identical to that of the recombinant IL-1 beta propeptide, and most likely represents naturally derived propeptide. The protein migrating at 14 kD may result from a second cleavage by ICE, between Asp27 and Gly28. These proteins accumulate intracellularly and extracellularly during pulse-chase experiments, and therefore represent stable products of precursor IL-1 beta cleavage.
人白细胞介素1β（IL-1β）最初是以无活性前体的形式合成的，该前体在天冬氨酸116和丙氨酸117之间被IL-1转换酶（ICE）切割，形成COOH末端的成熟IL-1β和NH2末端的IL-1β前肽。关于NH2末端切割产物的去向知之甚少。在本研究中，制备了人重组（hr）IL-1β前肽（氨基酸2 - 116）并用于制备不识别成熟人IL-1β的特异性抗体。这些抗前肽抗体用于从脂多糖刺激的人单核细胞中免疫沉淀生物合成标记的蛋白质。通过十二烷基硫酸钠 - 聚丙烯酰胺凝胶电泳和荧光自显影分析免疫沉淀产物，结果显示这些抗体识别前体IL-1β和两种独特的蛋白质：一种迁移率为17.5 kD，另一种为14 kD。这两种蛋白质中较大的一种迁移率与重组IL-1β前肽几乎相同，很可能代表天然来源的前肽。迁移率为14 kD的蛋白质可能是ICE在天冬氨酸27和甘氨酸28之间进行第二次切割的结果。在脉冲追踪实验中，这些蛋白质在细胞内和细胞外都会积累，因此代表前体IL-1β切割后的稳定产物。
