Perregaux D G, Laliberte R E, Gabel C A
Department of Cancer, Immunology, and Infectious Diseases, Central Research, Pfizer Inc., Groton, Connecticut 06340, USA.
J Biol Chem. 1996 Nov 22;271(47):29830-8. doi: 10.1074/jbc.271.47.29830.
Interleukin (IL)-1beta produced by monocytes and macrophages is not released via the normal secretory apparatus, and prior to its release, this cytokine must be proteolytically processed to generate a mature biologically active species. Biochemical mechanisms that regulate these posttranslational steps are not well understood. Lipopolysaccharide (LPS) is a poor activator of IL-1 posttranslational processing despite serving as a potent inducer of IL-1 synthesis. For example, freshly isolated human monocytes treated with LPS released <30% of their newly synthesized IL-1beta as the mature 17-kDa cytokine species, and monocytes that were aged overnight in culture prior to LPS treatment released no 17-kDa cytokine. In contrast, addition of extracellular ATP promoted IL-1beta posttranslational processing from both monocyte populations. Previous studies indicated that ATP, acting via surface P2Z-type receptors, promoted major intracellular ionic changes. To explore whether these ionic changes were required for cytokine posttranslational processing, LPS-stimulated human monocytes were maintained in ionically altered media. Hypotonic conditions promoted an efficient and selective release of mature 17-kDa IL-1beta from LPS-activated monocytes in the absence of ATP. In contrast, hypertonic conditions blocked the ATP-induced posttranslational processing reactions. Both hypotonic stress- and ATP-induced processing were blocked when NaI was substituted for NaCl within the medium; substitution with NaSCN or NaNO3 also blocked the ATP response, but these salts were less inhibitory against the hypotonic stimulus. Sodium glucuronate substitution did not inhibit cytokine processing induced by either stimulus. Removal of divalent cations from the medium did not affect the ATP response, but pretreatment of monocytes with the phosphatase inhibitor okadaic acid dose-dependently suppressed ATP-induced IL-1beta posttranslational processing. A volume-induced change to the intracellular ionic environment, therefore, may represent a key element of the mechanism by which IL-1beta posttranslational processing is initiated. The strong dependence of this cytokine release mechanism on chloride anions suggests that selective anion transporters function as important components of this response.
单核细胞和巨噬细胞产生的白细胞介素（IL）-1β并非通过正常分泌途径释放，在其释放之前，这种细胞因子必须经过蛋白水解加工以产生成熟的生物活性形式。调节这些翻译后步骤的生化机制尚不清楚。脂多糖（LPS）尽管是IL-1合成的有效诱导剂，但对IL-1翻译后加工的激活作用较弱。例如，用LPS处理的新鲜分离的人单核细胞仅释放不到30%新合成的IL-1β作为成熟的17 kDa细胞因子形式，而在LPS处理前在培养中过夜老化的单核细胞则不释放17 kDa细胞因子。相反，添加细胞外ATP可促进两个单核细胞群体中IL-1β的翻译后加工。先前的研究表明，ATP通过表面P2Z型受体起作用，可促进主要的细胞内离子变化。为了探究这些离子变化是否是细胞因子翻译后加工所必需的，将LPS刺激的人单核细胞置于离子改变的培养基中。低渗条件在没有ATP的情况下促进了成熟的17 kDa IL-1β从LPS激活的单核细胞中有效且选择性地释放。相反，高渗条件阻断了ATP诱导的翻译后加工反应。当培养基中的NaCl被NaI替代时，低渗应激和ATP诱导的加工均被阻断；用NaSCN或NaNO3替代也阻断了ATP反应，但这些盐对低渗刺激的抑制作用较小。葡糖醛酸钠替代不抑制任何一种刺激诱导的细胞因子加工。从培养基中去除二价阳离子不影响ATP反应，但用磷酸酶抑制剂冈田酸预处理单核细胞可剂量依赖性地抑制ATP诱导的IL-1β翻译后加工。因此，细胞内离子环境的体积诱导变化可能是启动IL-1β翻译后加工机制的关键要素。这种细胞因子释放机制对氯离子的强烈依赖性表明，选择性阴离子转运体是该反应的重要组成部分。
