Hipfner D R, Gao M, Scheffer G, Scheper R J, Deeley R G, Cole S P
Department of Pathology, Queen's University, Kingston, Ontario, Canada.
Br J Cancer. 1998 Nov;78(9):1134-40. doi: 10.1038/bjc.1998.642.
Inherent or acquired resistance to multiple natural product drugs in human tumour cells is often associated with increased expression of multidrug resistance protein (MRP), a 190-kDa integral membrane protein that belongs to the ATP-binding cassette (ABC) superfamily of transport proteins. Both clinical and experimental investigations of MRP have been facilitated by several monoclonal antibodies (MAbs) generated against intracellular epitopes of the molecule. Recently, however, several new ABC transporters that are quite closely related to MRP have been identified, raising concerns about the specificity of the MRP-reactive MAbs. In the present study, we have mapped the epitopes of MAbs MRPr1 and MRPm6 to the decapeptides 238GSDLWSLNKE247 (located in the intracellular loop between the first and second membrane-spanning domains of MRP) and 1511PSDLLQQRGL1520 (located near the carboxy terminus of MRP) respectively. Alignment of the MRPr1 and MRPm6 epitope sequences with the comparable regions in mammalian ABC proteins most closely related to MRP indicates that, with the exception of murine mrp, the sequences are poorly conserved. We conclude that MAbs MRPm6 and MRPr1, together with MAb QCRL-1, which has previously been mapped to the heptapeptide 918SSYSGDI924, remain highly specific probes for detection of different regions of the MRP molecule.
人类肿瘤细胞对多种天然产物药物的固有或获得性耐药性通常与多药耐药蛋白（MRP）的表达增加有关，MRP是一种190 kDa的整合膜蛋白，属于ATP结合盒（ABC）转运蛋白超家族。针对该分子细胞内表位产生的几种单克隆抗体（MAb）促进了对MRP的临床和实验研究。然而，最近发现了几种与MRP密切相关的新ABC转运蛋白，这引发了对MRP反应性MAb特异性的担忧。在本研究中，我们已将MAb MRPr1和MRPm6的表位分别定位到十肽238GSDLWSLNKE247（位于MRP的第一和第二跨膜结构域之间的细胞内环中）和1511PSDLLQQRGL1520（位于MRP的羧基末端附近）。将MRPr1和MRPm6表位序列与与MRP关系最密切的哺乳动物ABC蛋白中的可比区域进行比对表明，除了小鼠mrp外，这些序列的保守性很差。我们得出结论，MAb MRPm6和MRPr1，以及先前已定位到九肽918SSYSGDI9*24的MAb QCRL-1，仍然是检测MRP分子不同区域的高度特异性探针。
