Powell Saul R, Wang Ping, Divald Andras, Teichberg Saul, Haridas Viraga, McCloskey Thomas W, Davies Kelvin J A, Katzeff Harvey
Department of Medicine, Long Island Jewish Medical Center Campus of the Albert Einstein College of Medicine, 270-05 76th Avenue, New Hyde Park, NY 11042, USA.
Free Radic Biol Med. 2005 Apr 15;38(8):1093-101. doi: 10.1016/j.freeradbiomed.2005.01.003.
Cellular senescence may be accompanied by accumulation of large aggregates of oxidized proteins, also known as lipofuscin. The hypothesis that cellular accumulation of lipofuscin-like materials (LIP) results in cell death as a result of proteasome inhibition was examined. Rat neonatal cardiomyocytes were incubated with synthetic LIP for up to 48 h. This was accompanied by increases in cellular autofluorescence (207% by 48 h; p < 0.05) and electron microscopic evidence of internalization of LIP particles. LIP incubation resulted in loss of viability (-46% by 48 h; p < 0.05) through apoptotic cell death. Although 20S-proteasome activity was increased by 74% after 6 h, both 20S- and 26S-proteasome activities were decreased after 48 h of incubation (-54% (p < 0.05) and -50%, respectively), accompanied by large increases in ubiquitinated proteins. Several proteasome-regulated proapoptotic proteins, including c-Jun (2.9-fold; p < 0.05), Bax (1.8-fold; p < 0.05), and p27(kip1) (3.2-fold; p < 0.05), were observed to be increased by 48 h. Observation of ubiquitinated homologues of Bax and p27(kip1) suggested that part of the increase was due to decreased proteasomal degradation of these proteins. The results of this study are consistent with the conclusion that accumulation of LIP results in inhibition of the proteasome, which initiates an apoptotic cascade as a result of dysregulation of several proapoptotic proteins.
细胞衰老可能伴随着氧化蛋白大聚集体的积累，氧化蛋白大聚集体也被称为脂褐素。本研究检验了如下假说：类脂褐素样物质（LIP）在细胞内的积累会因蛋白酶体抑制而导致细胞死亡。将大鼠新生心肌细胞与合成LIP一起孵育长达48小时。这伴随着细胞自发荧光的增加（48小时时增加207%；p<0.05）以及LIP颗粒内化的电子显微镜证据。LIP孵育导致细胞活力丧失（48小时时降低46%；p<0.05），通过凋亡性细胞死亡实现。虽然孵育6小时后20S蛋白酶体活性增加了74%，但孵育48小时后20S和26S蛋白酶体活性均降低（分别降低54%（p<0.05）和50%），同时泛素化蛋白大幅增加。观察到几种蛋白酶体调节的促凋亡蛋白，包括c-Jun（增加2.9倍；p<0.05）、Bax（增加1.8倍；p<0.05）和p27(kip1)（增加3.2倍；p<0.05）在48小时时增加。对Bax和p27(kip1)泛素化同源物的观察表明，部分增加是由于这些蛋白的蛋白酶体降解减少所致。本研究结果与以下结论一致：LIP的积累导致蛋白酶体抑制，进而由于几种促凋亡蛋白的失调引发凋亡级联反应。
