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.
Singh
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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