title: Inactivation of the glutamine/amino acid transporter ASCT2 by 1,2,3-dithiazoles: proteoliposomes as a tool to gain insights in the molecular mechanism of action and of antitumor activity.
abstract: The ASCT2 transport system catalyses a sodium-dependent antiport of glutamine and other neutral amino acids which is involved in amino acid metabolism. A library of 1,2,3-dithiazoles was designed, synthesized and evaluated as inhibitors of the glutamine/amino acid ASCT2 transporter in the model system of proteoliposomes reconstituted with the rat liver transporter. Fifteen of the tested compounds at concentration of 20μM or below, inhibited more than 50% the glutamine/glutamine antiport catalysed by the reconstituted transporter. These good inhibitors bear a phenyl ring with electron withdrawing substituents. The inhibition was reversed by 1,4-dithioerythritol indicating that the effect was likely owed to the formation of mixed sulfides with the protein's Cys residue(s). A dose-response analysis of the most active compounds gave IC(50) values in the range of 3-30μM. Kinetic inhibition studies indicated a non-competitive inhibition, presumably because of a potential covalent interaction of the dithiazoles with cysteine thiol groups that are not located at the substrate binding site. Indeed, computational studies using a homology structural model of ASCT2 transporter, suggested as possible binding targets, Cys-207 or Cys-210, that belong to the CXXC motif of the protein.
authors.affiliation: Dipartimento di Biologia Cellulare Università della Calabria, via P. Bucci 4 c, 87036 Arcavacata di Rende (CS), Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Oppedisano
authors.forename: Marco
authors.initials: M
authors.lastname: Catto
authors.forename: Panayiotis A
authors.initials: PA
authors.lastname: Koutentis
authors.forename: Orazio
authors.initials: O
authors.lastname: Nicolotti
authors.forename: Lorena
authors.initials: L
authors.lastname: Pochini
authors.forename: Maria
authors.initials: M
authors.lastname: Koyioni
authors.forename: Antonellina
authors.initials: A
authors.lastname: Introcaso
authors.forename: Sophia S
authors.initials: SS
authors.lastname: Michaelidou
authors.forename: Angelo
authors.initials: A
authors.lastname: Carotti
authors.forename: Cesare
authors.initials: C
authors.lastname: Indiveri
mesh_terms: D026962:Amino Acid Transport System ASC / Q000037:antagonists & inhibitors* / Q000096:biosynthesis; D026905:Amino Acid Transport Systems / Q000378:metabolism; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D001665:Binding Sites; D003198:Computer Simulation; D003545:Cysteine / Q000737:chemistry; D004305:Dose-Response Relationship, Drug; D005973:Glutamine / Q000378:metabolism; D007700:Kinetics; D015778:Minor Histocompatibility Antigens; D009369:Neoplasms / Q000378:metabolism; D011510:Proteolipids; D051381:Rats; D013329:Structure-Activity Relationship; D013844:Thiazoles / Q000138:chemical synthesis / Q000494:pharmacology*
chemical_list: D026962:Amino Acid Transport System ASC; D026905:Amino Acid Transport Systems; D000970:Antineoplastic Agents; D015778:Minor Histocompatibility Antigens; D011510:Proteolipids; C498849:Slc1a5 protein, rat; D013844:Thiazoles; C020485:proteoliposomes; D005973:Glutamine; D003545:Cysteine