Clofibrate-Induced Relocation of Phosphatidylcholine Transfer Protein to Mitochondria in Endothelial Cells

• Published in: Experimental cell research 2002-03, Vol.274 (1), p.100-111
• Main Authors: de Brouwer, A.P.M., Westerman, J., Kleinnijenhuis, A., Bevers, L.E., Roelofsen, B., Wirtz, K.W.A.
• Format: Article
• Language: English
• Subjects: Androgen-Binding Protein; Animals; Binding Sites - genetics; Carrier Proteins - drug effects; Carrier Proteins - genetics; Carrier Proteins - metabolism; Cattle; clofibrate; Clofibrate - pharmacology; endothelial cells; Endothelium - cytology; Endothelium - metabolism; Endothelium - ultrastructure; FBHE cells; Fluorescent Dyes; HepG2 cells; Humans; HUVEC; Microinjections; mitochondria; Mitochondria - metabolism; Myocardium - cytology; peroxisome proliferators; phosphatidylcholine transfer protein; Phosphatidylethanolamine Binding Protein; Phospholipid Transfer Proteins; Phosphorylation; Point Mutation; PPARα; Protein Transport - drug effects; subcellular localization; Tumor Cells, Cultured; Umbilical Veins - cytology
• ISSN: 0014-4827; 1090-2422
• DOI: 10.1006/excr.2001.5460

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 μM) 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.