Multiple Roles of Charged Amino Acids in Cytoplasmic Loop 7 for Expression and Function of the Multidrug and Organic Anion Transporter MRP1 (ABCC1)

Abstract

Multidrug resistance protein MRP1 mediates the ATP-dependent efflux of many chemotherapeutic agents and organic anions. MRP1 has two nucleotide binding sites (NBSs) and three membrane spanning domains (MSDs) containing 17 transmembrane helices linked by extracellular and cytoplasmic loops (CL). Homology models suggest that CL7 (amino acids 1141-

Molecular Basis for Reduced Estrone Sulfate Transport and Altered Modulator Sensitivity of Transmembrane Helix (TM) 6 and TM17 Mutants of Multidrug Resistance Protein 1 (ABCC1)

“…Site-directed mutagenesis and vesicular transport assays have been used extensively to identify particular domains or amino acids involved in the substrate selectivity and transport mechanism of MRP1 (Ren et al, 2002;Conseil et al, 2006Conseil et al, , 2009Deeley and Cole, 2006;Chang 2007). Evidence gathered to date supports a model in which each substrate of MRP1 establishes its own distinct and often mutually exclusive interactions with amino acids in at least one substrate binding pocket of the transporter.…”

“…In this way, a number of amino acids important for the stable plasma membrane expression of MRP1, or for its overall activity, have been identified (Haimeur et al, 2002Ren et al, 2002;Koike et al, 2004;Situ et al, 2004;Conseil et al, 2006Conseil et al, , 2009Deeley and Cole, 2006;Chang 2007). Amino acids important for the substrate specificity of MRP1 have also been identified, two of which are Lys 332 , located in TM6 in the second MSD, and Trp 1246 , located in TM17 in the third MSD (Fig.…”

Multidrug Resistance Protein 1 (MRP1, ABCC1), a “Multitasking” ATP-binding Cassette (ABC) Transporter

“…For example, Ala substitution of several charged amino acids in MSD1-CL5 and MSD2-CL7 causes misfolding of MRP1 resulting in reduced levels of the transporter at the plasma membrane (55)(56)(57)(58). Although both CL5 and CL7 are important, MSD1-CL5 and its bonding interactions with NBD2 appear to play a more pivotal role in the proper folding and membrane trafficking and function of MRP1 than do the domain-domain interactions involving MSD2-CL7 (56).…”

Expression and Function of Human MRP1 (ABCC1) Is Dependent on Amino Acids in Cytoplasmic Loop 5 and Its Interface with Nucleotide Binding Domain 2

“…1A). Thus, mutation of the adjacent Tyr residues at positions 1189 and 1190 decreases MRP1 transport activity, especially with respect to the transport of the tripeptide antioxidant glutathione (21 (22,23). Homology models of the nucleotide-bound core structure of human MRP1 predict that a stretch of amino acids parallel to the membrane at the bottom of CL7 of MSD2 is in close proximity to the first NBD (NBD1), whereas the analogous region in CL5 of MSD1 is in contact with the second NBD (NBD2) (Fig.…”