The anti-apoptotic activity associated with phosphatidylinositol transfer protein alpha activates the MAPK and Akt/PKB pathway.
The conditioned medium (CM) from mouse NIH3T3 fibroblast cells overexpressing phosphatidylinositol transfer protein alpha (PI-TPalpha; SPIalpha cells) demonstrates an increased anti-apoptotic activity compared with CM from wild type NIH3T3 (wtNIH3T3) cells. As previously shown, the anti-apoptotic activity acts by activating a G protein-coupled receptor, most probably a cannabinoid 1 (CB1)-like receptor as the activity was blocked by both pertussis toxin and rimonabant [M. Schenning, C.M. van Tiel, D. Van Manen, J.C. Stam, B.M. Gadella, K.W. Wirtz and G.T. Snoek, Phosphatidylinositol transfer protein alpha regulates growth and apoptosis of NIH3T3 cells: involvement of a cannabinoid 1-like receptor, J. Lipid Res. 45 (2004) 1555-1564]. The CB1 receptor appears to be expressed in mouse fibroblast cells, at levels in the order SPIalpha>wtNIH3T3>SPIbeta cells (i.e. wild type cells overexpressing PI-TPbeta). Upon incubation of SPIbeta cells with the PI-TPalpha-dependent anti-apoptotic factors, both the ERK/MAP kinase and the Akt/PKB pathway are activated in a CB1 receptor dependent manner as shown by Western blotting. In addition, activation of ERK2 was also shown by EYFP-ERK2 translocation to the nucleus, as visualized by confocal laser scanning microscopy. The subsequent activation of the anti-apoptotic transcription factor NF-kappaB is in line with the increased resistance towards UV-induced apoptosis. On the other hand, receptor activation by CM from SPIalpha cells was not linked to phospholipase C activation as the YFP-labelled C2-domain of protein kinase C was not translocated to the plasma membrane of SPIbeta cells as visualized by confocal laser scanning microscopy.
Schenning
Martijn
M
Bijvoet Center, Department of Biochemistry of Lipids, Institute of Biomembranes, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands. M.Schenning@Dundee.ac.uk
Goedhart
Joachim
J
Gadella
Theodorus W J
TW
Avram
Diana
D
Wirtz
Karel W A
KW
Snoek
Gerry T
GT
D000818:Animals; D017209:Apoptosis; D002462:Cell Membrane / Q000378:metabolism; D004789:Enzyme Activation; D020935:MAP Kinase Signaling System; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism*; D016328:NF-kappa B; D041681:NIH 3T3 Cells; D049294:Phospholipid Transfer Proteins / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D043884:Receptor, Cannabinoid, CB1 / Q000378:metabolism; D010738:Type C Phospholipases / Q000378:metabolism
D016328:NF-kappa B; D049294:Phospholipid Transfer Proteins; D043884:Receptor, Cannabinoid, CB1; D051057:Proto-Oncogene Proteins c-akt; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D010738:Type C Phospholipases