Identification of proline residues in the core cytoplasmic and transmembrane regions of multidrug resistance protein 1 (MRP1/ABCC1) important for transport function, substrate specificity, and nucleotide interactions.
Multidrug resistance protein 1 (MRP1/ABCC1) is an ATP-binding cassette transporter that confers resistance to drugs and mediates the transport of organic anions. MRP1 has a core structure of two membrane spanning domains (MSDs) each followed by a nucleotide binding domain. This core structure is preceded by a third MSD with five transmembrane (TM) helices, whereas MSD2 and MSD3 each contain six TM helices. We investigated the consequences of Ala substitution of 18 Pro residues in both the non-membrane and TM regions of MSD2 and MSD3 on MRP1 expression and organic anion transport function. All MRP1-Pro mutants except P1113A were expressed in human embryonic kidney cells at levels comparable with wild-type MRP1. In addition, five mutants containing substitutions of Pro residues in or proximal to the TM helices of MSD2 (TM6-Pro(343), TM8-Pro(448), TM10-Pro(557), and TM11-Pro(595)) and MSD3 (TM14-Pro(1088)) exhibited significantly reduced transport of five organic anion substrates. In contrast, mutation of Pro(1150) in the cytoplasmic loop (CL7) linking TM15 to TM16 caused a substantial increase in 17beta-estradiol-17-beta-(D-glucuronide) and methotrexate transport, whereas transport of other organic anions was reduced or unchanged. Significant substrate-specific changes in the ATP dependence of transport and binding by the P1150A mutant were also observed. Our findings demonstrate the importance of TM6, TM8, TM10, TM11, and TM14 in MRP1 transport function and suggest that CL7 may play a differential role in coupling the activity of the nucleotide binding domains to the translocation of different substrates across the membrane.
Koike
Koji
K
Cancer Research Laboratories, Botterell Hall, Queen's University, Kingston, Ontario K7L 3N6, Canada.
Conseil
Gwenaëlle
G
Leslie
Elaine M
EM
Deeley
Roger G
RG
Cole
Susan P C
SP
D000255:Adenosine Triphosphate / Q000737:chemistry; D000409:Alanine / Q000737:chemistry; D000595:Amino Acid Sequence; D000838:Anions; D001692:Biological Transport; D015152:Blotting, Northern; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D005822:Genetic Vectors; D006801:Humans; D007668:Kidney / Q000196:embryology; D007700:Kinetics; D008727:Methotrexate / Q000494:pharmacology; D018613:Microscopy, Confocal; D008969:Molecular Sequence Data; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000737:chemistry* / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D009711:Nucleotides / Q000737:chemistry; D011392:Proline / Q000737:chemistry*; D011485:Protein Binding; D021381:Protein Transport; D012269:Ribosomal Proteins; D029701:Saccharomyces cerevisiae Proteins; D013379:Substrate Specificity; D014162:Transfection; D014638:Vanadates / Q000494:pharmacology
D000255:Adenosine Triphosphate; D000409:Alanine; D000838:Anions; D008727:Methotrexate; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D009711:Nucleotides; D011392:Proline; D012269:Ribosomal Proteins; D029701:Saccharomyces cerevisiae Proteins; D014638:Vanadates; C105693:MRP10 protein, S cerevisiae; C421109:multidrug resistance-associated protein 1