title: Concanavalin A-induced translocation of part of the GTP-binding activity from the membrane to the cytosol in murine thymocytes.
abstract: Concanavalin A (Con A) stimulation resulted in the rapid redistribution of part of the GTP-binding activity from the membrane to the cytosol in murine thymocytes. This change in GTP-binding activity was dependent on the Con A concentration. To investigate the relationship between this redistribution and phospholipase C (PLC) activity, the effect of GTP gamma S on the cytosol PLC activity was also examined, and it was found that GTP gamma S enhanced the phosphatidylinositol 4,5-bisphosphate (PIP2) hydrolysis activity in the cytosol of Con A-stimulated thymocytes more than in that of unstimulated thymocytes. This enhancement by GTP gamma S was also dependent on the Con A concentration. The results suggest that in murine thymocytes, the GTP-binding protein (G-protein) involved in the regulation of PLC activity may be translocated from the membrane to the cytosol upon Con A stimulation. Besides, the dose dependence curve for the change in the GTP gamma S-binding activity was similar to that for inositol phosphates formation in Con A-stimulated thymocytes, suggesting that the translocation of the G-protein is closely related to PLC activation. Furthermore, the effects of cytosol fractions containing the 38-43 and 23-28 kDa GTP-binding subunits of G-proteins on the PIP2 hydrolysis activity of partially purified PLC were examined. The fraction containing the 23-28 kDa subunit evidently enhanced the PLC activity but that containing the 38-43 kDa subunit enhanced the activity to a much lower extent. Moreover, the 23-28 kDa subunit fraction of Con A-stimulated thymocytes was more effective as to enhancement of the PLC activity than that of unstimulated thymocytes.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D003208:Concanavalin A / Q000494:pharmacology*; D003600:Cytosol / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000378:metabolism*; D007295:Inositol Phosphates / Q000096:biosynthesis; D051379:Mice; D008861:Microsomes / Q000032:analysis; D010740:Phospholipases / Q000032:analysis; D011506:Proteins / Q000032:analysis; D013950:Thymus Gland / Q000166:cytology / Q000187:drug effects*
chemical_list: D007295:Inositol Phosphates; D011506:Proteins; D003208:Concanavalin A; D010740:Phospholipases; D019204:GTP-Binding Proteins