Substrates for adenosine 3',5'-monophosphate (cAMP)-dependent protein kinase in the rat pituitary gland

• Published in: Cellular and molecular neurobiology 1988-03, Vol.8 (1), p.71-83
• Main Authors: FURUKI, Y, YAMAMOTO, T, GUILD, S, KEBABIAN, J. W
• Format: Article
• Language: English
• Subjects: Analytical, structural and metabolic biochemistry; Animals; Biological and medical sciences; Cell-Free System; Cyclic AMP - pharmacology; Enzymes and enzyme inhibitors; Fundamental and applied biological sciences. Psychology; Phosphorylation; Pituitary Gland - metabolism; Protein Kinases - metabolism; Rats; Rats, Inbred Strains; Transferases
• ISSN: 0272-4340; 1573-6830
• DOI: 10.1007/BF00712913

1. Substrates for cAMP-dependent protein kinase were investigated in anterior, intermediate, and neural lobes of the rat pituitary gland. In a cell-free assay system, cAMP increased phosphorylation of 17 K, 33 K, and 60 K macromolecules of the anterior lobe, 17 K, 33 K, 60 K, and 80 K macromolecules of the intermediate lobe, and 60 K, 80 K, and 85 K macromolecules of the neural lobe. 2. Other nucleotides were tested in the intermediate lobe; 8 Br-cAMP mimicked cAMP, cGMP was much less effective than cAMP or 8 Br-cAMP, and 5'-AMP showed no significant effect. The purified catalytic subunit of cAMP-dependent protein kinase evoked the same phosphorylation pattern as the endogenous kinase. 3. Maximum cAMP-dependent phosphorylation occurred at between 1 and 2 min of incubation; after 20 min, phosphorylation was reduced by 80%. This suggests the presence of phosphatase activity in the intermediate lobe. 4. When tested upon dispersed intermediate lobe cells permeabilized by high-voltage electrical discharges, cAMP increased phosphorylation of the 17 K and 33 K macromolecules.