Günthert A R, Sträter J, von Reyher U, Henne C, Joos S, Koretz K, Moldenhauer G, Krammer P H, Möller P
Institute of Pathology, University of Heidelberg, Germany.
J Cell Biol. 1996 Aug;134(4):1089-96. doi: 10.1083/jcb.134.4.1089.
Ligation of CD95 (APO-1/Fas) cell surface receptors induces death in apoptosis-sensitive cells. Induction of apoptosis in adherent gamma interferon-stimulated HT-29 and COLO 205 colon carcinoma cells by cross-linking CD95 with anti-APO-1 monoclonal antibody resulted in detachment of the cells from hyaluronate starting about 1 h after antibody exposure. Loss of adhesion was paralleled by a substantial reduction of the multifunctional cell surface adhesion molecule CD44. As evidenced by cycloheximide treatment, this effect was not caused by impaired protein synthesis. Depletion of surface CD44 was also not due to membrane blebbing, since cytochalasin B failed to inhibit ascension from hyaluronate. Instead, ELISA and time kinetics showed increasing amounts of soluble CD44 in the supernatant of CD95-triggered cells. SDS-PAGE revealed that soluble CD44 had an apparent molecular mass of about 20 kD less than CD44 immunoprecipitated from intact cells. Thus, CD95-triggering induced shedding of CD44. Shedding is a novel mechanism operative in early steps of CD95-mediated apoptosis. Shedding surface molecules like CD44 might contribute to the active disintegration of dying epithelial cells in vivo.
CD95（APO-1/Fas）细胞表面受体的结扎可诱导凋亡敏感细胞死亡。通过用抗APO-1单克隆抗体交联CD95，在贴壁的γ干扰素刺激的HT-29和COLO 205结肠癌细胞中诱导凋亡，导致细胞在抗体暴露后约1小时开始从透明质酸盐上脱离。细胞黏附丧失的同时，多功能细胞表面黏附分子CD44也大幅减少。环己酰亚胺处理表明，这种效应不是由蛋白质合成受损引起的。表面CD44的减少也不是由于膜泡形成，因为细胞松弛素B未能抑制细胞从透明质酸盐上脱离。相反，ELISA和时间动力学显示，CD95触发的细胞上清液中可溶性CD44的量增加。SDS-PAGE显示，可溶性CD44的表观分子量比从完整细胞中免疫沉淀的CD44小约20 kD。因此，CD95触发诱导了CD44的脱落。脱落是CD95介导的凋亡早期阶段起作用的一种新机制。像CD44这样的表面分子脱落可能有助于体内死亡上皮细胞的主动解体。
