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

Abstract

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 M) 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.

Interacting Proteins Dictate Function of the Minimal START Domain Phosphatidylcholine Transfer Protein/StarD2

“…Observations 6 In a nomenclature revision, Them1 and CACH have been also been renamed acyl-CoA thioesterase 11 (Acot11) and acyl-CoA thioesterase 12 (Acot12), respectively (41). here and by de Brouwer et al (40) have suggested that fluorescent PC-TP fusion proteins are present within the nucleus, which is supported by immunolocalization of the endogenous protein in HEK 293T cells. Considering that PC-TP has no apparent DNA-binding domain, we tested the possibility that it might coactivate or corepress Pax3 transcriptional activity.…”

Functional characterization of thioesterase superfamily member 1/Acyl-CoA thioesterase 11: implications for metabolic regulation

“…By contrast, PC-TP and Them2 are individually targeted to mitochondria ,where they engage in interactions. Whereas Them2 is enriched in mitochondria ( 8 ), PC-TP is enriched in cytosol but relocalizes to mitochondria in response to selective cell signaling events ( 30 ).…”

Bezafibrate stimulates canalicular localization of NBD-labeled PC in HepG2 cells by PPARα-mediated redistribution of ABCB4

“…It has been suggested that PCTP may play a role in resupplying the canalicular membrane with biliary PC during bile formation (46) and that PCTP may be regulated by PPAR␣ stimulation both transcriptionally (31) and posttranslationally (47). Moreover, coregulation of PCTP, ABCB4, and biliary PC secretion in humans (13) suggests that PCTP may play a role in bile formation.…”