Insulin increased cAMP phosphodiesterase activity antagonizing metabolic actions of glucagon in rat hepatocytes cultured with herbimycin A.
The baseline activity of cyclic nucleotide phosphodiesterase 4 was markedly lowered by primary culture of rat hepatocytes with herbimycin A for 4 h [Eur. J. Biochem. 260 (1999) 398-408.]. We now report that insulin added to this preparation of hepatocytes, which had been completely freed of herbimycin, increased the thus lowered phosphodiesterase activity, consequently antagonizing glucagon-induced production of cAMP and activation of glycogen phosphorylase. The insulin receptor beta-subunits and alpha-tubulin were tyrosine-phosphorylated upon the addition of insulin. The phosphorylation of alpha-tubulin afforded conditions unfavorable for microtubule assembly that is responsible for phosphodiesterase inhibition. These effects of insulin observed in herbimycin-pretreated hepatocytes were not inhibited by wortmannin that actually abolished insulin-induced activation of phosphatidylinositol 3-kinase (PtdIns 3-kinase) under the same conditions. The physiological significance of the insulin action not mediated by PtdIns 3-kinase in herbimycin-pretreated hepatocytes is discussed.
Ishibashi
K
K
The Ui Laboratory, Institute of Physical and Chemical Research, Hirosawa 2-1, Wako 351-0198, Japan.
Fujioka
T
T
Ui
M
M
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D015105:3',5'-Cyclic-AMP Phosphodiesterases / Q000187:drug effects* / Q000378:metabolism; D000818:Animals; D016227:Benzoquinones; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism; D054703:Cyclic Nucleotide Phosphodiesterases, Type 4; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects; D005934:Glucagon / Q000494:pharmacology*; D022781:Hepatocytes / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology; D007328:Insulin / Q000494:pharmacology*; D047029:Lactams, Macrocyclic; D008297:Male; D008870:Microtubules / Q000187:drug effects / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D006005:Phosphorylases / Q000187:drug effects / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011809:Quinones / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D017828:Rifabutin / Q000031:analogs & derivatives; D014404:Tubulin / Q000187:drug effects / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism
D016227:Benzoquinones; D007328:Insulin; D047029:Lactams, Macrocyclic; D011809:Quinones; D014404:Tubulin; D017828:Rifabutin; D014443:Tyrosine; C020754:herbimycin; D005934:Glucagon; D000242:Cyclic AMP; D006005:Phosphorylases; D019869:Phosphatidylinositol 3-Kinases; D015105:3',5'-Cyclic-AMP Phosphodiesterases; D054703:Cyclic Nucleotide Phosphodiesterases, Type 4; D015056:1-Methyl-3-isobutylxanthine