title: The beta-adrenergic receptor system in human glioma-derived cell lines: the mode of phosphodiesterase induction and the macromolecules phosphorylated by cyclic AMP-dependent protein kinase.
abstract: beta-Adrenergic receptors and the activities of adenylate cyclase, phosphodiesterase and protein kinase were examined in two human glioma cell lines, U 251 and LM, as well as in rat C6 glioma. [3H]Dihydroalprenolol binding to beta-adrenergic receptors was specific, saturable and of high affinity in each cell line. The dissociation constant (Kd) and maximal binding (Bmax) extrapolated from Scatchard curves were Kd = 17.4 +/- 3.2 nM and Bmax = 1110 +/- 197 fmol/mg protein for the U-251 cells; Kd = 14.4 +/- 2.2 nM and Bmax = 655 +/- 105 fmol/mg protein for the LM cells; and Kd = 5.6 +/- 1.1 nM and Bmax = 454 +/- 80 fmol/mg protein for the C6 glioma cells. L-Isoproterenol stimulated cyclic AMP formation in all 3 cell lines. beta-Adrenergic agonists also increased calcium-dependent and calcium non-dependent phosphodiesterase activity in these tumor cells. Cytosolic protein kinase in the 3 cell lines phosphorylated exogenous histone as a substrate. The phosphorylation was enhanced by cyclic AMP. Cytosolic protein kinase also phosphorylated endogenous cytosolic macromolecules. The phosphorylated proteins had molecular weights of 30,000, 51,000 and 90,000 in the two human glioma cell lines. The present results indicate that human glioma cell lines have functional beta-adrenergic receptors linked to adenylate cyclase. These beta-receptors can also regulate phosphodiesterase activity and cyclic AMP in human glioma cells can activate protein kinase and induce the phosphorylation of specific proteins.
mesh_terms: D015105:3',5'-Cyclic-AMP Phosphodiesterases / Q000096:biosynthesis*; D000262:Adenylyl Cyclases / Q000378:metabolism*; D000818:Animals; D002460:Cell Line; D000242:Cyclic AMP / Q000378:metabolism; D003600:Cytosol / Q000201:enzymology; D004082:Dihydroalprenolol / Q000378:metabolism; D004790:Enzyme Induction; D005910:Glioma / Q000378:metabolism*; D006801:Humans; D007545:Isoproterenol / Q000494:pharmacology; D007700:Kinetics; D010750:Phosphoproteins / Q000302:isolation & purification; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism*; D051381:Rats; D011943:Receptors, Adrenergic, beta / Q000187:drug effects / Q000378:metabolism*
chemical_list: D010750:Phosphoproteins; D011943:Receptors, Adrenergic, beta; D004082:Dihydroalprenolol; D000242:Cyclic AMP; D011494:Protein Kinases; D015105:3',5'-Cyclic-AMP Phosphodiesterases; D000262:Adenylyl Cyclases; D007545:Isoproterenol