title: Nostocyclopeptide-M1: a potent, nontoxic inhibitor of the hepatocyte drug transporters OATP1B3 and OATP1B1.
abstract: We have isolated a novel cyanobacterial cyclic peptide (nostocyclopeptide M1; Ncp-M1) that blocks the hepatotoxic action of microcystin (MC) and nodularin (Nod). We show here that Ncp-M1 is nontoxic to primary hepatocytes in long-term culture. Ncp-M1 does not affect any known intracellular targets or pathways involved in MC action, like protein phosphatases, CaM-KII, or ROS-dependent cell death effectors. In support of this conclusion Ncp-M1 had no protective effect when microinjected into cells. Rather, the antitoxin effect was solely due to blocked hepatocyte uptake of MC and Nod. The hepatic uptake of MC and Nod is mainly via the closely related organic anion transporters OATP1B1 and OATP1B3, which also mediate hepatic transport of endogenous metabolites and hormones as well as drugs. OATP1B3 is also expressed in some aggressive cancers, where it confers apoptosis resistance. We show that Ncp-M1 inhibits transport through OATP1B3 and OATP1B1 expressed in HEK293 cells. The Ncp-M1 molecule has several nonproteinogenic amino acids and an imino bond, which hamper its synthesis. Moreover, a cyclic all L-amino acid heptapeptide analogue of Ncp-M1 also inhibits the OATP1B1/1B3 transporters, and with higher OATP1B3 preference than Ncp-M1 itself. The nontoxic Ncp-M1 and its synthetic cyclic peptide analogues thus provide new tools to probe the role of OATB1B1/1B3 mediated drug and metabolite transport in liver and cancer cells. They can also serve as scaffolds to design new, exopeptidase resistant OATP1B3-specific modulators.
authors.affiliation: Department of Biomedicine, University of Bergen, Jonas Lies vei 91, 5009 Bergen, Norway.
authors.forename: Lars
authors.initials: L
authors.lastname: Herfindal
authors.forename: Lene
authors.initials: L
authors.lastname: Myhren
authors.forename: Rune
authors.initials: R
authors.lastname: Kleppe
authors.forename: Camilla
authors.initials: C
authors.lastname: Krakstad
authors.forename: Frode
authors.initials: F
authors.lastname: Selheim
authors.forename: Jouni
authors.initials: J
authors.lastname: Jokela
authors.forename: Kaarina
authors.initials: K
authors.lastname: Sivonen
authors.forename: Stein O
authors.initials: SO
authors.lastname: Døskeland
mesh_terms: D000818:Animals; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2 / Q000378:metabolism; D057809:HEK293 Cells; D022781:Hepatocytes / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D027381:Liver-Specific Organic Anion Transporter 1; D052998:Microcystins / Q000494:pharmacology; D027361:Organic Anion Transporters / Q000037:antagonists & inhibitors* / Q000378:metabolism; D029362:Organic Anion Transporters, Sodium-Independent / Q000037:antagonists & inhibitors* / Q000378:metabolism; D010456:Peptides, Cyclic / Q000494:pharmacology*; D010766:Phosphorylation / Q000187:drug effects; D051381:Rats; D000074542:Solute Carrier Organic Anion Transporter Family Member 1B3
chemical_list: D027381:Liver-Specific Organic Anion Transporter 1; D052998:Microcystins; D027361:Organic Anion Transporters; D029362:Organic Anion Transporters, Sodium-Independent; D010456:Peptides, Cyclic; C503999:SLCO1B1 protein, human; C421209:SLCO1B3 protein, human; D000074542:Solute Carrier Organic Anion Transporter Family Member 1B3; C560265:nostocyclopeptide M1, Nostoc; C063998:nodularin; C078588:microcystin; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2