Biochemical effects of retinoic acid on GTP-binding Protein/Transglutaminases in HeLa cells. Stimulation of GTP-binding and transglutaminase activity, membrane association, and phosphatidylinositol lipid turnover.
Treatment of HeLa cells with retinoic acid (RA) gives rise to a marked stimulation in the incorporation of [alpha-32P]GTP into an approximately 87-kDa cytosolic protein that cross-reacts with a monoclonal antibody raised against tissue transglutaminases. In the absence of RA treatment, the transglutaminase immunoreactivity elutes from a gel filtration column with an apparent size of approximately 600 kDa (designated TGa), whereas following RA treatment, a second peak of transglutaminase immunoreactivity (designated TGb) is detected with an apparent size of approximately 150 kDa. The TGa fractions show little or no GTP-binding or GTP hydrolytic activity and very little transglutaminase activity. However, the TGb fractions show all three activities. Retinoic acid treatment also promotes the association of the GTP-binding protein/transglutaminase with membrane fractions, as detected by Western blotting and photoaffinity cross-linking with [alpha-32P]GTP. In addition, the TGb fraction shows a markedly enhanced ability (relative to TGa) to associate with membranes from control (non-RA-treated) cells. The ability of the GTP-binding protein/transglutaminase to bind to membranes is correlated with the stimulation of a membrane-associated phospholipase C activity. Thus, these findings indicate that RA treatment results in a number of changes in the biochemical properties of a GTP-binding protein/transglutaminase which strongly enhance its ability to bind GTP, associate with plasma membranes, and stimulate phosphoinositide lipid turnover.
Department of Pharmacology, Veterinary Medical Center, Cornell University, Ithaca, New York 14853, USA.
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D002462:Cell Membrane / Q000378:metabolism; D002850:Chromatography, Gel; D003600:Cytosol / Q000378:metabolism; D020558:GTP Phosphohydrolases / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000302:isolation & purification / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D007700:Kinetics; D010716:Phosphatidylinositols / Q000378:metabolism*; D011503:Transglutaminases / Q000302:isolation & purification / Q000378:metabolism*; D014212:Tretinoin / Q000494:pharmacology*; D010738:Type C Phospholipases / Q000378:metabolism
D010716:Phosphatidylinositols; D014212:Tretinoin; D006160:Guanosine Triphosphate; D011503:Transglutaminases; D010738:Type C Phospholipases; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins