Seglen P O, Gordon P B, Grinde B, Solheim A, Kovács A L, Poli A
Acta Biol Med Ger. 1981;40(10-11):1587-98.
On the basis of experiments using amino acids and various inhibitors (lysosomotropic amines, leupeptin, chymostatin, vanadate, vinblastine, anoxia, methylaminopurines), five different modes of endogenous protein degradation in isolated rat hepatocytes can be distinguished. The two non-lysosomal (amine-resistant) mechanisms preferentially degrade relatively labile (short-lived) proteins: one of these mechanisms is energy-dependent and chymostatin-sensitive, the other is not. Of the three lysosomal (amine-sensitive) mechanisms, one--quantitatively minor--is amino acid-resistant and preferentially degrades labile proteins. The two amino acid-sensitive mechanisms each seen account for about one-half of the degradation of relatively stable (long-lived) proteins; one of them is suppressed by leucine and apparently corresponds to the formation of electron microscopically visible autophagosomes; the other may represent a different type of autophagy, inhibited by asparagine and glutamine. A new class of inhibitors, the purine derivatives (methylated 6-aminopurines, and 6-mercaptopurines) appear to specifically suppress autophagic/lysosomal protein degradation, and may help to further elucidate the mechanisms of autophagy.
基于使用氨基酸和各种抑制剂（溶酶体促效胺、亮抑蛋白酶肽、抑糜蛋白酶素、钒酸盐、长春花碱、缺氧、甲基氨基嘌呤）进行的实验，可以区分分离的大鼠肝细胞中内源性蛋白质降解的五种不同模式。两种非溶酶体（抗胺）机制优先降解相对不稳定（寿命短）的蛋白质：其中一种机制依赖能量且对抑糜蛋白酶素敏感，另一种则不敏感。在三种溶酶体（胺敏感）机制中，一种——在数量上较少——对氨基酸有抗性且优先降解不稳定蛋白质。两种对氨基酸敏感的机制各自约占相对稳定（寿命长）蛋白质降解的一半；其中一种被亮氨酸抑制，显然与电子显微镜下可见的自噬体形成相对应；另一种可能代表不同类型的自噬，被天冬酰胺和谷氨酰胺抑制。一类新的抑制剂，嘌呤衍生物（甲基化6-氨基嘌呤和6-巯基嘌呤）似乎能特异性抑制自噬/溶酶体蛋白降解，并可能有助于进一步阐明自噬机制。
