title: p38 MAPK α and β isoforms differentially regulate plasma membrane localization of MRP2.
abstract: In hepatocytes, cAMP both activates p38 mitogen-activated protein kinase (MAPK) and increases the amount of multidrug resistance-associated protein-2 (MRP2) in the plasma membrane (PM-MRP2). Paradoxically, taurolithocholate (TLC) activates p38 MAPK but decreases PM-MRP2 in hepatocytes. These opposing effects of cAMP and TLC could be mediated via different p38 MAPK isoforms (α and β) that are activated differentially by upstream kinases (MKK3, MKK4, and MKK6). Thus we tested the hypothesis that p38α MAPK and p38β MAPK mediate increases and decreases in PM-MRP2 by cAMP and TLC, respectively. Studies were conducted in hepatocytes isolated from C57BL/6 wild-type (WT) and MKK3-knockout (MKK3(-/-)) mice and in a hepatoma cell line (HuH7) that overexpresses sodium-taurocholate cotransporting polypeptide (NTCP) (HuH-NTCP). Cyclic AMP activated MKK3, p38 MAPK, and p38α MAPK and increased PM-MRP2 in WT hepatocytes, but failed to activate p38α MAPK or increase PM-MRP2 in MKK3(-/-) hepatocytes. In contrast to cAMP, TLC activated total p38 MAPK but decreased PM-MRP2, and did not activate MKK3 or p38α MAPK in WT hepatocytes. In MKK3(-/-) hepatocytes, TLC still decreased PM-MRP2 and activated p38 MAPK, indicating that these effects are not MKK3-dependent. Additionally, TLC activated MKK6 in MKK3(-/-) hepatocytes, and small interfering RNA knockdown of p38β MAPK abrogated TLC-mediated decreases in PM-MRP2 in HuH-NTCP cells. Taken together, these results suggest that p38α MAPK facilitates plasma membrane insertion of MRP2 by cAMP, whereas p38β MAPK mediates retrieval of PM-MRP2 by TLC.
authors.affiliation: Department of Biomedical Sciences, Cummings School of Veterinary Medicine at Tufts University, North Grafton, Massachusetts; and.
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Schonhoff
authors.affiliation: Department of Biomedical Sciences, Cummings School of Veterinary Medicine at Tufts University, North Grafton, Massachusetts; and.
authors.forename: Se Won
authors.initials: SW
authors.lastname: Park
authors.affiliation: Department of Clinical Sciences, Cummings School of Veterinary Medicine at Tufts University, North Grafton, Massachusetts.
authors.forename: Cynthia R L
authors.initials: CR
authors.lastname: Webster
authors.affiliation: Department of Biomedical Sciences, Cummings School of Veterinary Medicine at Tufts University, North Grafton, Massachusetts; and Sawkat.Anwer@tufts.edu.
authors.forename: M Sawkat
authors.initials: MS
authors.lastname: Anwer
mesh_terms: D000818:Animals; D002460:Cell Line; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism*; D002478:Cells, Cultured; D002756:Cholagogues and Choleretics / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D022781:Hepatocytes / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D048371:MAP Kinase Kinase 3 / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D000089762:Multidrug Resistance-Associated Protein 2; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000378:metabolism*; D021381:Protein Transport; D013658:Taurolithocholic Acid / Q000494:pharmacology; D048051:p38 Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*
chemical_list: D002756:Cholagogues and Choleretics; D000242:Cyclic AMP; D007527:Isoenzymes; D048371:MAP Kinase Kinase 3; D000089762:Multidrug Resistance-Associated Protein 2; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D013658:Taurolithocholic Acid; D048051:p38 Mitogen-Activated Protein Kinases; C000715087:ABCC2 protein, human; C482531:Map2k3 protein, mouse
keywords: MKK3 knockout mice; cAMP; p38 MAPK isoforms; taurolithocholate