Clofibrate-induced relocation of phosphatidylcholine transfer protein to mitochondria in endothelial cells.
The phosphatidylcholine transfer protein (PC-TP) is a specific transporter of phosphatidylcholine (PC) between membranes. To get more insight into its physiological function, we have studied the localization of PC-TP by microinjection of fluorescently labeled PC-TP in foetal bovine heart endothelial (FBHE) cells and by expression of an enhanced yellow fluorescent protein-PC-TP fusion protein in FBHE cells, human umbilical vein endothelial cells, and HepG2 cells. Analysis by confocal laser scanning microscopy showed that PC-TP was evenly distributed throughout the cytosol with an apparently elevated level in nuclei. By measuring the fluorescence recovery after bleaching it was established that PC-TP is highly mobile throughout the cell, with its transport into the nucleus being hindered by the nuclear envelope. Given the proposed function of PC-TP in lipid metabolism, we have tested a number of compounds (phorbol ester, bombesin, A23187, thrombin, dibutyryl cyclic AMP, oleate, clofibrate, platelet-derived growth factor, epidermal growth factor, and hydrogen peroxide) for their ability to affect intracellular PC-TP distribution. Only clofibrate (100 microM) was found to have an effect, with PC-TP moving to mitochondria within 5 min of stimulation. This relocation did not occur with PC-TP(S110A), lacking the putative protein kinase C (PKC)-dependent phosphorylation site, and was restricted to the primary endothelial cells. Relocation did not occur in HepG2 cells, possibly due to the fact that clofibrate does not induce PKC activation in these cells.
de Brouwer
A P M
AP
Department of Biochemistry of Lipids, Institute of Biomembranes, Padualaan 8, Utrecht, 3584 CH, The Netherlands. a.p.m.debrouwer@chem.uu.nl
Westerman
J
J
Kleinnijenhuis
A
A
Bevers
L E
LE
Roelofsen
B
B
Wirtz
K W A
KW
D000727:Androgen-Binding Protein; D000818:Animals; D001665:Binding Sites / Q000235:genetics; D002352:Carrier Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D002417:Cattle; D002994:Clofibrate / Q000494:pharmacology*; D004727:Endothelium / Q000166:cytology* / Q000378:metabolism / Q000648:ultrastructure; D005456:Fluorescent Dyes; D006801:Humans; D008845:Microinjections; D008928:Mitochondria / Q000378:metabolism*; D009206:Myocardium / Q000166:cytology; D049488:Phosphatidylethanolamine Binding Protein; D049294:Phospholipid Transfer Proteins; D010766:Phosphorylation; D017354:Point Mutation; D021381:Protein Transport / Q000187:drug effects; D014407:Tumor Cells, Cultured; D014471:Umbilical Veins / Q000166:cytology
D000727:Androgen-Binding Protein; D002352:Carrier Proteins; D005456:Fluorescent Dyes; C511482:PEBP1 protein, human; D049488:Phosphatidylethanolamine Binding Protein; D049294:Phospholipid Transfer Proteins; D002994:Clofibrate