Corsi D, Paiardini M, Crinelli R, Bucchini A, Magnani M
G. Fornaini Institute of Biological Chemistry, University of Urbino, Italy.
Eur J Biochem. 1999 May;261(3):775-83. doi: 10.1046/j.1432-1327.1999.00336.x.
Mammalian red blood cell alpha-spectrin is ubiquitinated in vitro and in vivo [Corsi, D., Galluzzi, L., Crinelli, R., Magnani, M. (1995) J. Biol. Chem. 270, 8928-8935]. This process shows a cell age-dependent decrease, with senescent red blood cells having approximately one third of the amount of ubiquitinated alpha-spectrin found in young cells. In-vitro ubiquitination of alpha-spectrin was dependent on the source of the red cell membranes (those from older cells are less susceptible to ubiquitination than those from younger cells), on the source of ubiquitin-conjugating enzymes (those from older cells catalyze the process at a reduced rate compared to those from younger cells) and on the ubiquitin isopeptidase activity (which decreases during red cell ageing). However, once alpha-spectrin has been extracted from the membranes of young or old red blood cells, it is susceptible to ubiquitination to a similar extent regardless of source. This suggests that it is the membrane architecture, and not spectrin itself, that is responsible for the age-dependent decline in ubiquitination. Furthermore, spectrin oligomers, tetramers and dimers are also equally susceptible to ubiquitination. As spectrin ubiquitination occurs on domains alphaIII and alphaV of alpha-spectrin, and domain alphaV contains the nucleation site for the association of the alpha- and beta-spectrin chains, alterations in ubiquitination during red cell ageing could affect the stability and deformability of the erythrocyte membrane.
哺乳动物红细胞α-血影蛋白在体内外均会发生泛素化[科尔西，D.，加卢齐，L.，克里内利，R.，马尼亚尼，M.（1995年）《生物化学杂志》270卷，8928 - 8935页]。这一过程呈现出细胞年龄依赖性下降，衰老红细胞中泛素化α-血影蛋白的量约为年轻细胞中的三分之一。α-血影蛋白的体外泛素化取决于红细胞膜的来源（来自较老细胞的膜比来自较年轻细胞的膜更不易被泛素化）、泛素结合酶的来源（来自较老细胞的酶催化该过程的速率低于来自较年轻细胞的酶）以及泛素异肽酶活性（在红细胞衰老过程中会降低）。然而，一旦从年轻或衰老红细胞的膜中提取出α-血影蛋白，无论其来源如何，它被泛素化的程度都相似。这表明导致泛素化年龄依赖性下降的是膜结构，而非血影蛋白本身。此外，血影蛋白寡聚体、四聚体和二聚体对泛素化的敏感性也相同。由于血影蛋白泛素化发生在α-血影蛋白的αIII和αV结构域，且αV结构域包含α-血影蛋白链与β-血影蛋白链结合的成核位点，红细胞衰老过程中泛素化的改变可能会影响红细胞膜的稳定性和可变形性。
