Phosphatidylinositol transfer protein alpha regulates growth and apoptosis of NIH3T3 cells: involvement of a cannabinoid 1-like receptor

• Published in: Journal of lipid research 2004-08, Vol.45 (8), p.1555-1564
• Main Authors: Schenning, Martijn, van Tiel, Claudia M, Van Manen, Daniëlle, Stam, Jord C, Gadella, Barend M, Wirtz, Karel W A, Snoek, Gerry T
• Format: Article
• Language: English
• Subjects: Animals; Apoptosis - physiology; Arachidonic Acid - metabolism; Cell Division - physiology; Cell Survival; Culture Media, Conditioned; Cyclooxygenase 1; Cyclooxygenase 2; Isoenzymes - genetics; Isoenzymes - metabolism; Membrane Proteins; Mice; NIH 3T3 Cells; Phospholipid Transfer Proteins - metabolism; Prostaglandin-Endoperoxide Synthases - genetics; Prostaglandin-Endoperoxide Synthases - metabolism; Receptors, Cannabinoid - metabolism; Ultraviolet Rays
• ISSN: 0022-2275
• DOI: 10.1194/jlr.M400127-JLR200

Mouse fibroblast cells overexpressing phosphatidylinositol transfer protein alpha [PI-TPalpha; sense PI-TPalpha (SPIalpha) cells] show a significantly increased rate of proliferation and an extreme resistance toward ultraviolet- or tumor necrosis factor-alpha-induced apoptosis. The conditioned medium (CM) from SPIalpha cells or the neutral lipid extract from CM stimulated the proliferation of quiescent wild-type NIH3T3 cells. CM was also highly effective in increasing resistance toward induced apoptosis in both wild-type cells and the highly apoptosis-sensitive SPIbeta cells (i.e., wild-type cells overexpressing PI-TPbeta). CM from SPIalpha cells grown in the presence of NS398, a specific cyclooxygenase-2 (COX-2) inhibitor, expressed a diminished mitogenic and antiapoptotic activity. This strongly suggests that at least one of the bioactive factor(s) is an eicosanoid. In accordance, SPIalpha cells express enhanced levels of COX-1 and COX-2. The antiapoptotic activity of CM from SPIalpha cells tested on SPIbeta cells was inhibited by approximately 50% by pertussis toxin and suramin as well as by SR141716A, a specific antagonist of the cannabinoid 1 receptor. These inhibitors had virtually no effect on the COX-2-independent antiapoptotic activity of CM from SPIalpha cells. The latter results imply that PI-TPalpha mediates the production of a COX-2-dependent eicosanoid that activates a G-protein-coupled receptor, most probably a cannabinoid 1-like receptor.