Kickhoefer V A, Rajavel K S, Scheffer G L, Dalton W S, Scheper R J, Rome L H
Department of Biological Chemistry and the Jonsson Comprehensive Cancer Center, University of California, School of Medicine, Los Angeles, California 90095-1737, USA.
J Biol Chem. 1998 Apr 10;273(15):8971-4. doi: 10.1074/jbc.273.15.8971.
Vaults are 13-MDa ribonucleoprotein particles composed largely of a 104-kDa protein, termed major vault protein or MVP, and a small vault RNA, vRNA. While MVP levels have been found to increase up to 15-fold in non-P-glycoprotein multidrug-resistant cell lines, the levels of vault particles have not been investigated. As both the function of vault particles and the mechanism of drug resistance in non-P-glycoprotein cells are unknown, we decided to determine whether vault synthesis was coupled to MDR. By cloning the human gene for vRNA and careful quantitation of the MVP and vRNA levels in MDR cells, we find that vRNA is in considerable excess to MVP. Sedimentation measurements of vault particles in multidrug resistance cells have indeed revealed up to a 15-fold increase in vault synthesis, coupled with a comparable shift of associated vRNA, demonstrating that vault formation is limited by expression of MVP or the minor vault proteins. The observation that vault synthesis is linked directly to multidrug resistance supports a direct role for vaults in drug resistance.
穹窿体是13兆道尔顿的核糖核蛋白颗粒，主要由一种104千道尔顿的蛋白质（称为主要穹窿体蛋白或MVP）和一种小穹窿体RNA（vRNA）组成。虽然已发现在非P-糖蛋白多药耐药细胞系中MVP水平可增加至15倍，但穹窿体颗粒的水平尚未得到研究。由于穹窿体颗粒的功能和非P-糖蛋白细胞中的耐药机制均未知，我们决定确定穹窿体的合成是否与多药耐药相关。通过克隆vRNA的人类基因并仔细定量多药耐药细胞中的MVP和vRNA水平，我们发现vRNA相对于MVP有相当大的过量。对多药耐药细胞中穹窿体颗粒的沉降测量确实显示穹窿体合成增加了15倍，同时相关vRNA也有类似的变化，表明穹窿体的形成受MVP或次要穹窿体蛋白表达的限制。穹窿体合成与多药耐药直接相关这一观察结果支持了穹窿体在耐药性中起直接作用。
