title: SLC10A4 is a protease-activated transporter that transports bile acids.
abstract: SLC10A4 belongs to the sodium bile acid cotransporter family, but has no transport activity for bile acids. We performed multiple amino acid alignments and examined the relationships between the SLC10 proteins. The extracellular N-terminus of SLC10A4 was predicted to be relatively longer at the amino acid level than those of SLC10A1, SLC10A2 and SLC10A6. We examined the relationship between the N-terminus and transport activity of SLC10A4. Rat Slc10a4 is predominantly expressed in rat cholinergic neurons; therefore, TE671 cells expressing the acetylcholine receptor and acetylcholinesterase were used. After thrombin treatment, western blotting and immunofluorescence staining demonstrated that the N-terminus of SLC10A4 might be cleaved. Substrates were added to the cells, and their uptake was quantified by liquid chromatography tandem mass spectrometry. Lithocholic acid (LCA) and taurocholic acid (TCA) uptake and cell death effects of LCA were increased by thrombin treatment. After RNA interference treatment for SLC10A4, bile acid uptake was also quantified. In consequence, increases in the LCA and TCA uptake did not occur. Therefore, SLC10A4 may have low activity but becomes activated by proteases, including thrombin, following cleavage. We have demonstrated that SLC10A4 appears to be a protease-activated transporter and transports bile acids.
authors.affiliation: Laboratory of Oncology, Pharmacy Practice and Sciences, Department of Pharmacy Practice and Sciences, Graduate School of Pharmaceutical Sciences, Tohoku University, Aoba, Aramaki, Aoba-ku, Sendai 980-8578, Japan.
authors.forename: Takuya
authors.initials: T
authors.lastname: Abe
authors.forename: Yoshitomi
authors.initials: Y
authors.lastname: Kanemitu
authors.forename: Masateru
authors.initials: M
authors.lastname: Nakasone
authors.forename: Ichiro
authors.initials: I
authors.lastname: Kawahata
authors.forename: Tohru
authors.initials: T
authors.lastname: Yamakuni
authors.forename: Akira
authors.initials: A
authors.lastname: Nakajima
authors.forename: Naoto
authors.initials: N
authors.lastname: Suzuki
authors.forename: Masazumi
authors.initials: M
authors.lastname: Nishikawa
authors.forename: Takanori
authors.initials: T
authors.lastname: Hishinuma
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Tomioka
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001647:Bile Acids and Salts / Q000378:metabolism*; D002460:Cell Line; D006801:Humans; D007700:Kinetics; D008095:Lithocholic Acid / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D029363:Organic Anion Transporters, Sodium-Dependent / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010447:Peptide Hydrolases / Q000378:metabolism; D034622:RNA Interference; D051381:Rats; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D027981:Symporters / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013656:Taurocholic Acid / Q000378:metabolism; D013917:Thrombin / Q000378:metabolism
chemical_list: D001647:Bile Acids and Salts; D029363:Organic Anion Transporters, Sodium-Dependent; D027981:Symporters; C071908:sodium-bile acid cotransporter; D013656:Taurocholic Acid; D008095:Lithocholic Acid; D010447:Peptide Hydrolases; D013917:Thrombin
keywords: bile acid; mass spectrometry; thrombin; transporter