Chong H, Vodovotz Y, Cox G W, Barcellos-Hoff M H
Life Sciences Division, Lawrence Berkeley National Laboratory, University of California, Berkeley 94720, USA.
J Cell Physiol. 1999 Mar;178(3):275-83. doi: 10.1002/(SICI)1097-4652(199903)178:3<275::AID-JCP1>3.0.CO;2-Q.
Transforming growth factor-beta1 (TGF-beta) is secreted in a latent form consisting of mature TGF-beta noncovalently associated with its amino-terminal propeptide, which is called latency associated peptide (LAP). Biological activity depends upon the release of TGF-beta from the latent complex following extracellular activation, which appears to be the key regulatory mechanism controlling TGF-beta action. We have identified two events associated with latent TGF-beta (LTGF-beta) activation in vivo: increased immunoreactivity of certain antibodies that specifically detect TGF-beta concomitant with decreased immunoreactivity of antibodies to LAP. Macrophages stimulated in vitro with interferon-gamma and lipopolysaccharide reportedly activate LTGF-beta via cell membrane-bound protease activity. We show through dual immunostaining of paraformaldehyde-fixed macrophages that such physiological TGF-beta activation is accompanied by a loss of LAP immunoreactivity with concomitant revelation of TGF-beta epitopes. The induction of TGF-beta immunoreactivity colocalized with immunoreactive betaglycan/RIII in activated macrophages, suggesting that LTGF-beta activation occurs on the cell surface. Confocal microscopy of metabolically active macrophages incubated with antibodies to TGF-beta and betaglycan/RIII prior to fixation supported the localization of activation to the cell surface. The ability to specifically detect and localize LTGF-beta activation provides an important tool for studies of its regulation.
转化生长因子-β1（TGF-β）以潜伏形式分泌，由成熟的TGF-β与其氨基末端前肽非共价结合组成，该前肽称为潜伏相关肽（LAP）。生物学活性取决于细胞外激活后潜伏复合物中TGF-β的释放，这似乎是控制TGF-β作用的关键调节机制。我们已经确定了体内与潜伏性TGF-β（LTGF-β）激活相关的两个事件：某些特异性检测TGF-β的抗体免疫反应性增加，同时LAP抗体的免疫反应性降低。据报道，用γ干扰素和脂多糖体外刺激巨噬细胞可通过细胞膜结合蛋白酶活性激活LTGF-β。我们通过对多聚甲醛固定的巨噬细胞进行双重免疫染色表明，这种生理性TGF-β激活伴随着LAP免疫反应性的丧失，同时TGF-β表位得以暴露。在活化的巨噬细胞中，TGF-β免疫反应性的诱导与免疫反应性β聚糖/RIII共定位，表明LTGF-β激活发生在细胞表面。在用TGF-β和β聚糖/RIII抗体孵育后固定的代谢活跃巨噬细胞的共聚焦显微镜检查支持了激活定位在细胞表面。特异性检测和定位LTGF-β激活的能力为其调节研究提供了重要工具。
