title: Several adaptor proteins promote intracellular localisation of the transporter MRP4/ABCC4 in platelets and haematopoietic cells.
abstract: The multidrug resistance protein 4 (MRP4/ABCC4) has been identified as an important transporter for signalling molecules including cyclic nucleotides and several lipid mediators in platelets and may thus represent a novel target to interfere with platelet function. Besides its localisation in the plasma membrane, MRP4 has been also detected in the membrane of dense granules in resting platelets. In polarised cells it is localised at the basolateral or apical plasma membrane. To date, the mechanism of MRP4 trafficking has not been elucidated; protein interactions may regulate both the localisation and function of this transporter. We approached this issue by searching for interacting proteins by in vitro binding assays, followed by immunoblotting and mass spectrometry, and by visualising their co-localisation in platelets and haematopoietic cells. We identified the PDZ domain containing scaffold proteins ezrin-binding protein 50 (EBP50/NHERF1), postsynaptic density protein 95 (PSD95), and sorting nexin 27 (SNX27), but also the adaptor protein complex 3 subunit β3A (AP3B1) and the heat shock protein HSP90 as putative interaction partners of MRP4. The knock-down of SNX27, PSD95, and AP3B1 by siRNA in megakaryoblastic leukaemia cells led to a redistribution of MRP4 from intracellular structures to the plasma membrane. Inhibition of HSP90 led to a diminished expression and retention of MRP4 in the endoplasmic reticulum. These results indicate that MRP4 localisation and function are regulated by multiple protein interactions. Changes in the adaptor proteins can hence lead to altered localisation and function of the transporter.
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Schaletzki
authors.forename: Marie-Luise
authors.initials: ML
authors.lastname: Kromrey
authors.forename: Susanne
authors.initials: S
authors.lastname: Bröderdorf
authors.forename: Elke
authors.initials: E
authors.lastname: Hammer
authors.forename: Markus
authors.initials: M
authors.lastname: Grube
authors.forename: Paul
authors.initials: P
authors.lastname: Hagen
authors.forename: Sonja
authors.initials: S
authors.lastname: Sucic
authors.forename: Michael
authors.initials: M
authors.lastname: Freissmuth
authors.forename: Uwe
authors.initials: U
authors.lastname: Völker
authors.forename: Andreas
authors.initials: A
authors.lastname: Greinacher
authors.forename: Bernhard H
authors.initials: BH
authors.lastname: Rauch
authors.forename: Heyo K
authors.initials: HK
authors.lastname: Kroemer
authors.affiliation: Gabriele Jedlitschky PhD, Department of Pharmacology, Center of Drug Absorption and Transport (C_DAT), University Medicine Greifswald, Felix-Hausdorff-Str. 3, 17487 Greifswald, Germany, Tel.: +49 3834 8622146, Fax: +49 3834 865631, E-mail: jedlits@uni-greifswald.de.
authors.forename: Gabriele
authors.initials: G
authors.lastname: Jedlitschky
mesh_terms: D033963:Adaptor Protein Complex 3 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D033966:Adaptor Protein Complex beta Subunits / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism*; D000076122:Disks Large Homolog 4 Protein / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004285:Dogs; D057809:HEK293 Cells; D018841:HSP90 Heat-Shock Proteins / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D007947:Leukemia, Megakaryoblastic, Acute / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D018942:Macrolides / Q000494:pharmacology; D061985:Madin Darby Canine Kidney Cells; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010750:Phosphoproteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D021381:Protein Transport; D034622:RNA Interference; D017923:Sodium-Hydrogen Exchangers / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014162:Transfection
chemical_list: D033963:Adaptor Protein Complex 3; D033966:Adaptor Protein Complex beta Subunits; D000076122:Disks Large Homolog 4 Protein; D018841:HSP90 Heat-Shock Proteins; D018942:Macrolides; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D010750:Phosphoproteins; D017923:Sodium-Hydrogen Exchangers; C073492:ABCC4 protein, human; C439973:AP3B1 protein, human; C501444:DLG4 protein, human; C093376:sodium-hydrogen exchanger regulatory factor; C035359:monorden
keywords: AP3B1; HSP90; PDZ domain; Protein trafficking; delta-storage pool deficiencies