P-glycoprotein epitope mapping. II. The murine monoclonal antibody MM6.15 to human multidrug-resistant cells binds with three distinct loops in the MDR1-P-glycoprotein extracellular domain

Conception of circular economy obstacles in context of supply chain: a case of rubber industry

Purpose

Adopting the circular economy (CE) notion in the supply chain perspective is necessary for the sustainability viewpoint. However, such practices are deficient, especially in developing countries like India, because of several obstacles. The purpose of this study was to create an approach for circular supply chain management (CSCM) adaption in Indian rubber industries by identifying and evaluating its associated obstacles.

Design/methodology/approach

A hybrid approach of analytic hierarchy process (AHP) and the grey-based ELECTRE method had been employed in this research to obtain the mutual rankings of the identified obstacles based on their impressions on the CSCM prosperity criteria through a case study and involving diverse expert's opinions.

Findings

Presented study's findings illustrate that “Lack of consumer knowledge and consciousness towards environmental sustainability” was found to be the top-ranked obstacle followed by “Unwillingness towards supply chain re-structuring”.

Research limitations/implications

The obstacles' prioritized rankings could help leaders to create sequential strategies for adapting a resilient CSCM structure by systematically eliminating these obstacles. Moreover, the pinpointed critical obstacles could be investigated further in separate studies and generate future studies' scope.

Originality/value

During the extensive literature survey, it had been found that the CSCM practices are in the fledgling stage in the developing country's context. Moreover, studies related to CSCM adaption in rubber-based manufacturing industries were much lacking. Presented work is peculiar, aiming to accelerate the CSCM adaption in the industrial rubber sector in developing countries like India.

Identification by phage display of the linear continuous MRPr1 epitope in the multidrug resistance-associated protein (MRP1)

In order to study the structure of the multidrug resistance-associated protein (MRP1), which is one of the most important members of the ATP-binding cassette (ABC) protein family acting as drug-efflux systems, we have developed an epitope mapping-based strategy. By means of the mAb MRPr1, we have immunoselected clones from two distinct random peptide libraries displayed on phages and have identified several peptide sequences mimicking the internal conformation of this 190 kDa multidrug transporter protein. Phage clones able to block the immunolabeling of the MRPr1 antibody to MRP1-overexpressing multidrug resistance (MDR) H69/AR cells were isolated and, after sequencing the corresponding inserts, their amino acid sequence was compared to that of MRP1. This analysis led to the identification of the consensus sequence L.SLNWED, corresponding to the MRP1 segment LWSLNKED (residues 241-248). This MRP1 sequence is partially overlapping with the MRPr1 epitope GSDLWSLNKE (residues 238-247) previously mapped using peptide scanning techniques. These results demonstrate the high reliability of phage display technology to study not only the topography of complex integral membrane proteins such as MRP1, but also to help identify critical residues participating in the formation of the epitope structure.

Epitope mapping of the monoclonal antibody MM12.10 to external MDR1 P-glycoprotein domain by synthetic peptide scanning and phage display technologies

Epitope mapping of MDR1-P-glycoprotein using specific monoclonal antibodies (mAbs) may help in delineating P-glycoprotein topology and hence in elucidating the relationship between its structural organization and drug-efflux pump function. In this work, by using synthetic peptide scanning and phage display technologies, the binding sites of the mAb MM12.10, a novel antibody to intact human multidrug resistant (MDR) cells, were studied. The results we obtained confirm that two regions localized on the predicted fourth and sixth loops are indeed external and that MDR1 peptides covering the inner domain of the current 12 transmembrane segment (TMs) model of P-glycoprotein could form part of the MM12.10 epitope.

Characterization and epitope mapping of several new anti-P-glycoprotein monoclonal antibodies

Monoclonal antibodies (MAbs) were raised against partially purified Class I P-glycoprotein from multidrug-resistant Chinese hamster ovary CHRB30 cells. Fifteen stable monoclonal hybridoma cell lines were established, and the secreted antibodies were classified into 8 groups on the basis of banding pattern on immunoblots of P-glycoprotein digested with cyanogen bromide or partially digested with proteases. One representative of each group was tested further for several activities. Six of the 8 recognized human P-glycoprotein in the multidrug-resistant SKVLBI cell line. None of the antibodies recognized P-glycoprotein in unfixed cells, suggesting that all recognize cytoplasmic epitopes or extracellular epitopes not accessible in native P-glycoprotein. All 8 antibodies were able to immunoprecipitate P-glycoprotein from non-denaturing detergent solution. The linear epitopes of the antibodies were mapped to 11-27 amino acids. Two of the antibodies had epitopes in the linker region, 3 in the N-terminal nucleotide binding domain, 2 in the C-terminal nucleotide binding domain and 1 in the predicted cytoplasmic loop between predicted transmembrane helices 8 and 9. These antibodies, with known epitopes, could have uses for P-glycoprotein detection, structure/function studies, purification and quantitation.

Topology of MDR1-P-glycoprotein as indicated by epitope mapping of monoclonal antibodies to human MDR cells

The MDR1-P-glycoprotein binding sites of three different murine monoclonal antibodies (MM4.17, MM6.15 and MC57), directed towards living, intact human multidrug-resistant cells were investigated in order to study P-glycoprotein topology. By using synthetic peptide scanning, we demonstrated that well-defined regions localized on the predicted first, fourth and sixth extracellular loops are external. On the basis of the structure of MM6.15 epitope, which is distributed on the above three different extracellular loops (and thus is discontinuous), P-glycoprotein molecules result to be differently organized in the lipid bilayer. Moreover, the outcome of the MC57 and MM4.17 epitopes localization experiments, obtained through the use of phage-displayed peptide libraries, represent an additional challenge to the classical 12-transmembrane domain model of P-glycoprotein, since they agree with the novel topography of the molecule (10-transmembrane domain), which was recently proposed on the basis of biochemical and expression studies.

Isolation of antigenic mimics of MDR1-P-glycoprotein by phage-displayed peptide libraries

To identify an MC57 epitope which is more efficiently expressed on inactivated forms of P-glycoprotein we utilized peptide libraries displayed on filamentous phage. Using this technology, we selected specific phage clones blocking the binding of the murine monoclonal (MAb) MC57 with live human multi-drug-resistant (MDR) cells, and sequenced and analyzed their DNA. The results we obtained indicate that MAb MC57 epitope could be formed by 2 regions localized on the predicted fourth and sixth extracellular loops of the current 12-transmembrane-domain model predicted for MDR1-P-glycoprotein. Surprisingly, a third region, defined by residues 800-807 of the MDR1-P-glycoprotein sequence and postulated to be intracellular, was also identified as a putative part of the MC57 epitope. This finding adds weight to the interesting hypothesis that a P-glycoprotein structure different from the current model may exist.