title: Caveolin-1--a novel interacting partner of organic cation/carnitine transporter (Octn2): effect of protein kinase C on this interaction in rat astrocytes.
abstract: OCTN2--the Organic Cation Transporter Novel family member 2 (SLC22A5) is known to be a xenobiotic/drug transporter. It transports as well carnitine--a compound necessary for oxidation of fatty acids and mutations of its gene cause primary carnitine deficiency. Octn2 regulation by protein kinase C (PKC) was studied in rat astrocytes--cells in which β-oxidation takes place in the brain. Activation of PKC with phorbol ester stimulated L-carnitine transport and increased cell surface presence of the transporter, although no PKC-specific phosphorylation of Octn2 could be detected. PKC activation resulted in an augmented Octn2 presence in cholesterol/sphingolipid-rich microdomains of plasma membrane (rafts) and increased co-precipitation of Octn2 with raft-proteins, caveolin-1 and flotillin-1. Deletion of potential caveolin-1 binding motifs pointed to amino acids 14-22 and 447-454 as the caveolin-1 binding sites within Octn2 sequence. A direct interaction of Octn2 with caveolin-1 in astrocytes upon PKC activation was detected by proximity ligation assay, while such an interaction was excluded in case of flotillin-1. Functioning of a multi-protein complex regulated by PKC has been postulated in rOctn2 trafficking to the cell surface, a process which could be important both under physiological conditions, when carnitine facilitates fatty acids catabolism and controls free Coenzyme A pool as well as in pathology, when transport of several drugs can induce secondary carnitine deficiency.
authors.affiliation: Department of Molecular and Cellular Neurobiology, Nencki Institute of Experimental Biology, Warsaw, Poland.
authors.forename: Magdalena
authors.initials: M
authors.lastname: Czeredys
authors.affiliation: Department of Molecular and Cellular Neurobiology, Nencki Institute of Experimental Biology, Warsaw, Poland.
authors.forename: Łukasz
authors.initials: Ł
authors.lastname: Samluk
authors.affiliation: Department of Molecular and Cellular Neurobiology, Nencki Institute of Experimental Biology, Warsaw, Poland.
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Michalec
authors.affiliation: Department of Molecular and Cellular Neurobiology, Nencki Institute of Experimental Biology, Warsaw, Poland.
authors.forename: Karolina
authors.initials: K
authors.lastname: Tułodziecka
authors.affiliation: Laboratory of Bioinformatics and Protein Engineering, International Institute of Molecular and Cell Biology, Warsaw, Poland ; Department of Biochemistry, Nencki Institute of Experimental Biology, Warsaw, Poland.
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Skowronek
authors.affiliation: Department of Molecular and Cellular Neurobiology, Nencki Institute of Experimental Biology, Warsaw, Poland.
authors.forename: Katarzyna A
authors.initials: KA
authors.lastname: Nałęcz
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism / Q000648:ultrastructure; D001692:Biological Transport / Q000187:drug effects; D002331:Carnitine / Q000378:metabolism; D051242:Caveolin 1 / Q000737:chemistry / Q000378:metabolism*; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D057809:HEK293 Cells; D006801:Humans; D047468:Immunoprecipitation; D021962:Membrane Microdomains / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D027701:Organic Cation Transport Proteins / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D011485:Protein Binding / Q000187:drug effects; D011493:Protein Kinase C / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D051381:Rats; D015203:Reproducibility of Results; D000074058:Solute Carrier Family 22 Member 5; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D051242:Caveolin 1; D008565:Membrane Proteins; D027701:Organic Cation Transport Proteins; C115441:Slc22a5 protein, rat; D000074058:Solute Carrier Family 22 Member 5; C106354:flotillins; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate; D002331:Carnitine