Summary of the results.

The proteasome inhibitor MG-132 down-regulates (−) the ubiquitin-proteasome pathway (UPP). AMPK-activator AICAR and proteasome inhibitor MG-132 co-treatment activates (+) the autophagy. UPP inhibition significantly increases (+) SQSTM1/p62 protein levels, while autophagy induction during UPP inhibition robustly decreases (−) SQSTM1/p62 protein levels. Since SQSTM1/p62 localizes to aggregates, the decreasing of SQSTM1/p62 reveals its autophagy clearance. In addition, proteasome inhibition significantly increases ELAVL1/HuR protein levels by itself and during the autophagy induction (+). Proteasome inhibition induces a positive regulation of SQSTM1/p62 expression that occurs also at post-transcriptional level via ELAVL1/HuR protein (+). Activated autophagy is able to completely abolish the MG-132-induced protein aggregation (−), which, in turn improves the cell vitality. Ubiquitin is also found in intracellular aggregates in ARPE-19 cells as well as from drusens. In contrast, SQSTM1/p62 is found only in the intracellular aggregates in ARPE-19 cells, but not in drusens. However, SQSTM1/p62 levels were high in macular area of RPE cells revealing impaired autophagy. What is the relation between drusen and intracellular aggregates remains still unknown. Red lines with minus symbol represent inhibiting and decreasing events in ARPE-19 cells. Black lines and plus symbol represent activating and increasing events in the ARPE-19 cell. Zero (0) and dark blue line indicate neutral effects in the ARPE-19 cell. UPP: ubiquitin-proteasome pathway.

蛋白酶体抑制剂（proteasome inhibitor）MG-132可下调（−）泛素-蛋白酶体通路（ubiquitin-proteasome pathway，UPP）。AMPK（AMP-activated protein kinase）激活剂AICAR与蛋白酶体抑制剂MG-132联合处理可激活（+）自噬（autophagy）。UPP抑制可显著升高（+）SQSTM1/p62蛋白水平，而在UPP抑制期间诱导自噬则可显著降低（−）SQSTM1/p62蛋白水平。由于SQSTM1/p62定位于蛋白质聚集体，SQSTM1/p62水平的降低提示其通过自噬途径被清除。此外，单独使用蛋白酶体抑制剂以及在自噬诱导过程中，均可升高（+）ELAVL1/HuR蛋白水平。蛋白酶体抑制剂对SQSTM1/p62表达的正向调控，还可通过ELAVL1/HuR蛋白在转录后水平实现（+）。激活的自噬可完全逆转MG-132诱导的蛋白质聚集（−），进而改善细胞活力。泛素同样存在于ARPE-19细胞（ARPE-19 cells）的胞内聚集体以及玻璃膜疣（drusens）中。与之相反，SQSTM1/p62仅存在于ARPE-19细胞的胞内聚集体内，而非玻璃膜疣中。不过，在视网膜色素上皮细胞（retinal pigment epithelium, RPE）的黄斑区域，SQSTM1/p62水平较高，提示自噬功能受损。目前玻璃膜疣与胞内聚集体之间的关联仍未明确。带有负号的红色线条代表ARPE-19细胞中的抑制与降低事件；黑色带正号的线条代表ARPE-19细胞中的激活与升高事件；零值（0）与深蓝色线条则代表ARPE-19细胞中的中性效应。UPP：泛素-蛋白酶体通路