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Epitope mapping of monoclonal antibodies specific for the 190-kDa multidrug resistance protein (MRP)
D R Hipfner1, M Gao, G Scheffer
1Department of Pathology, Queen's University, Kingston, Ontario, Canada.
Abstract:
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.
Insights
Monoclonal antibodies (MAbs) MRPr1 and MRPm6 target specific regions of the multidrug resistance-associated protein (MRP). These antibodies demonstrate high specificity for detecting MRP, crucial for cancer drug resistance research.
Area of Science:
- Biochemistry
- Molecular Biology
- Cancer Research
Background:
- Multidrug resistance-associated protein (MRP) is linked to cancer drug resistance.
- Monoclonal antibodies (MAbs) are used to study MRP, but their specificity is questioned due to related transporters.
- Identifying specific epitopes is vital for accurate MRP detection.
Purpose of the Study:
- To map the epitopes of MAbs MRPr1 and MRPm6.
- To assess the specificity of these MAbs against related ATP-binding cassette (ABC) transporters.
Main Methods:
- Epitope mapping of MAbs MRPr1 and MRPm6 using peptide sequences.
- Sequence alignment of mapped epitopes with homologous regions in related mammalian ABC proteins.
Main Results:
- MAb MRPr1 epitope mapped to decapeptide 238GSDLWSLNKE247 (intracellular loop).
- MAb MRPm6 epitope mapped to decapeptide 1511PSDLLQQRGL1520 (near C-terminus).
- Epitope sequences showed poor conservation among related ABC transporters, except for murine mrp.
Conclusions:
- MAbs MRPr1 and MRPm6, along with QCRL-1, are specific probes for distinct MRP regions.
- These specific MAbs are valuable tools for investigating MRP in biological samples.