Siva A C, Raval-Fernandes S, Stephen A G, LaFemina M J, Scheper R J, Kickhoefer V A, Rome L H
Department of Biological Chemistry, University of California at Los Angeles, School of Medicine, Los Angeles, CA 90095, USA.
Int J Cancer. 2001 Apr 15;92(2):195-202. doi: 10.1002/1097-0215(200102)9999:9999<::aid-ijc1168>3.0.co;2-7.
Vaults are ribonucleoprotein complexes comprised of the 100 kDa major vault protein (MVP), the 2 high m.w. vault proteins p193 (VPARP) and p240 (TEP1) and an untranslated small RNA (vRNA). Increased levels of MVP, vault-associated vRNA and vaults have been linked directly to non-P-glycoprotein-mediated multidrug resistance (MDR). To further characterize the putative role of vaults in MDR, expression levels of all of the vault proteins were examined in various MDR cell lines. Subcellular fractionation of vault particles revealed that all 3 vault proteins are increased in MDR cells compared to the parental, drug-sensitive cells. Furthermore, protein analysis of subcellular fractions of the drug-sensitive, MVP-transfected AC16 cancer cell line indicated that vault levels are increased, in this stable line. Since TEP1 is shared by both vaults and the telomerase complex, TEP1 protein (and vault) levels were compared with telomerase activity in a variety of cell lines, including various MDR lines. Our studies demonstrate that while vault levels may be a good predictor of drug resistance, their up-regulation alone is not sufficient to confer the drug-resistant phenotype. This implies a requirement of an additional factor(s) for vault-mediated MDR.
穹窿体是一种核糖核蛋白复合体，由100 kDa的主要穹窿体蛋白（MVP）、两种高分子量的穹窿体蛋白p193（VPARP）和p240（TEP1）以及一种非翻译小RNA（vRNA）组成。MVP、与穹窿体相关的vRNA以及穹窿体水平的升高已直接与非P-糖蛋白介导的多药耐药性（MDR）相关联。为了进一步阐明穹窿体在MDR中的假定作用，我们检测了多种MDR细胞系中所有穹窿体蛋白的表达水平。对穹窿体颗粒进行亚细胞分级分离显示，与亲代药物敏感细胞相比，MDR细胞中所有三种穹窿体蛋白的水平均升高。此外，对药物敏感的、转染了MVP的AC16癌细胞系的亚细胞组分进行蛋白质分析表明，在这个稳定细胞系中穹窿体水平升高。由于TEP1同时存在于穹窿体和端粒酶复合体中，因此我们在包括多种MDR细胞系在内的多种细胞系中比较了TEP1蛋白（以及穹窿体）水平和端粒酶活性。我们的研究表明，虽然穹窿体水平可能是耐药性的一个良好预测指标，但仅其上调不足以赋予耐药表型。这意味着穹窿体介导的MDR还需要其他因素。
