Cysteine residues in the organic anion transporter mOAT1.
Mouse organic anion transporter 1 (mOAT1) belongs to a family of organic anion transporters, which play critical roles in the body disposition of clinically important drugs, including anti-HIV therapeutics, anti-tumour drugs, antibiotics, anti-hypertensives and anti-inflammatories. mOAT1-mediated transport of organic anion PAH ( p -aminohippurate) in HeLa cells was inhibited by the cysteine-modifying reagent PCMBS (p-chloromercuribenzenesulphonate). Therefore the role of cysteine residues in the function of mOAT1 was examined by site-directed mutagenesis. All 13 cysteine residues in mOAT1 were replaced by alanine, singly or in combination. Single replacement of these residues had no significant effect on mOAT1-mediated PAH transport, indicating that no individual cysteine residue is necessary for function. Multiple replacements at a C-terminal region (C335/379/427/434A; Cys(335/379/427/434)-->Ala) resulted in a substantial decrease in transport activity. A simultaneous replacement of all 13 cysteine residues (C-less) led to a complete loss of transport function. The decreased or lack of transport activity of the mutants C335/379/427/434A and C-less was due to the impaired trafficking of the mutant transporters to the cell surface. These results suggest that although cysteine residues are not required for function in mOAT1, their presence appears to be important for the targeting of the transporter to the plasma membrane. We also showed that, although all cysteine mutants of mOAT1 were sensitive to the inhibition by PCMBS, C49A was less sensitive than the wild-type mOAT1, suggesting that the modification of Cys49 may play a role in the inhibition of mOAT1 by PCMBS.
Tanaka
Kunihiko
K
Department of Pharmaceutical Science, Rutgers, The State University of New Jersey, 160 Frelinghuysen Road, Piscataway, NJ 08854, USA.
Zhou
Fanfan
F
Kuze
Kogo
K
You
Guofeng
G
D002731:4-Chloromercuribenzenesulfonate / Q000494:pharmacology; D019943:Amino Acid Substitution; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D003545:Cysteine / Q000737:chemistry*; D006367:HeLa Cells / Q000378:metabolism; D006801:Humans; D008658:Inactivation, Metabolic; D007668:Kidney; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism; D051379:Mice; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D027362:Organic Anion Transport Protein 1; D027361:Organic Anion Transporters / Q000737:chemistry* / Q000378:metabolism; D017433:Protein Structure, Secondary; D021381:Protein Transport; D011993:Recombinant Fusion Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D013329:Structure-Activity Relationship; D010130:p-Aminohippuric Acid / Q000378:metabolism
D008565:Membrane Proteins; D027362:Organic Anion Transport Protein 1; D027361:Organic Anion Transporters; D011993:Recombinant Fusion Proteins; C105033:Slc22a6 protein, mouse; D002731:4-Chloromercuribenzenesulfonate; D003545:Cysteine; D010130:p-Aminohippuric Acid