The cellular fate of mutant rhodopsin: quality control, degradation and aggresome formation.
The cellular fate of mutant rhodopsin: quality control, degradation and aggresome formation.
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发表时间：
2002-07
影响因子：
4
通讯作者：
R. S. Saliba;Peter M. G. Munro;P. Luthert;M. Cheetham
中科院分区：
文献类型：
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作者：
R. S. Saliba;Peter M. G. Munro;P. Luthert;M. Cheetham
色素视紫红质的突变是常染色体显性视网膜色素变性的主要原因。视紫红质中的大多数突变导致蛋白质的错误折叠。通过对COS-7细胞中P23 H和K296 E突变体视蛋白加工的详细研究，我们已经表明突变体蛋白质并不像以前认为的那样在高尔基体中积累，而是形成具有侵略者的许多特征的聚集体。聚集体靠近中心体形成，导致高尔基体分散。此外，这些聚集体是泛素化的，募集细胞伴侣并破坏中间丝网络。突变体视蛋白表达可以破坏正常视蛋白的加工，因为共转染揭示了野生型蛋白被募集到突变体视蛋白聚集体中。突变体视蛋白的降解依赖于蛋白酶体机制。与DeltaF 508-CFTR的情况不同，蛋白酶体抑制不会导致攻击体形成的显著增加，但会增加蛋白质在ER内的保留，这表明蛋白酶体是突变蛋白质有效逆易位所必需的。用衣霉素抑制N-连接的糖基化导致突变体蛋白选择性保留在ER内，并增加突变体视蛋白的稳态水平。然而，糖基化对野生型视蛋白在培养细胞中的生物发生和靶向没有影响。这表明N-连接的糖基化是突变蛋白的ER相关降解所需的，但对于视蛋白折叠的质量控制不是必需的。向培养基中加入9-顺式-视黄醛增加了可溶并到达质膜的P23 H的量，但不增加K296 E的量。这些数据表明，视紫红质常染色体显性视网膜色素变性与许多其他神经退行性疾病相似，其中细胞内蛋白质聚集体的形成是疾病发病机制的核心，并且它们表明了疾病显性的机制。
Mutations in the photopigment rhodopsin are the major cause of autosomal dominant retinitis pigmentosa. The majority of mutations in rhodopsin lead to misfolding of the protein. Through the detailed examination of P23H and K296E mutant opsin processing in COS-7 cells, we have shown that the mutant protein does not accumulate in the Golgi, as previously thought, instead it forms aggregates that have many of the characteristic features of an aggresome. The aggregates form close to the centrosome and lead to the dispersal of the Golgi apparatus. Furthermore, these aggregates are ubiquitinated, recruit cellular chaperones and disrupt the intermediate filament network. Mutant opsin expression can disrupt the processing of normal opsin, as co-transfection revealed that the wild-type protein is recruited to mutant opsin aggregates. The degradation of mutant opsin is dependent on the proteasome machinery. Unlike the situation with DeltaF508-CFTR, proteasome inhibition does not lead to a marked increase in aggresome formation but increases the retention of the protein within the ER, suggesting that the proteasome is required for the efficient retrotranslocation of the mutant protein. Inhibition of N-linked glycosylation with tunicamycin leads to the selective retention of the mutant protein within the ER and increases the steady state level of mutant opsin. Glycosylation, however, has no influence on the biogenesis and targeting of wild-type opsin in cultured cells. This demonstrates that N-linked glycosylation is required for ER-associated degradation of the mutant protein but is not essential for the quality control of opsin folding. The addition of 9-cis-retinal to the media increased the amount of P23H, but not K296E, that was soluble and reached the plasma membrane. These data show that rhodopsin autosomal dominant retinitis pigmentosa is similar to many other neurodegenerative diseases in which the formation of intracellular protein aggregates is central to disease pathogenesis, and they suggest a mechanism for disease dominance.