The major mechanism whereby cAMP acts as a second messenger of peptide and protein hormones is via the stimulation of the cAMP-dependent protein kinase. A wide variety of mammalian tissues contain a low molecular weight protein that inhibits the cAMP-dependent protein kinase. Inhibition occurs by direct interaction with the catalytic subunit derived from the holoenzyme by cAMP-mediated dissociation. This inhibitor protein has been of particular use in the characterization of the protein kinase but its potential physiological function and role has yet to be established. Circumstantial evidence in favor of a specific function in cAMP action is its presence in non-stimulated tissues (muscle, brain) at a level sufficient to block approximately 20% of the protein kinase and its high affinity for the catalytic subunit (Kd equals 5 nM). We propose to continue to probe the function of the inhibitor by the following approaches: (1) The multiple size and/or shape conformers and the multiple charge isomers will be examined by chemical, physiochemical and immunological procedures in order to evaluate their relationships. (2) The mechanism of inhibition of the catalytic subunit by the inhibitor will be evaluated by kinetic, chemical and physiochemical probes and by comparison with the inhibition of the catalytic subunit by an inhibitor peptide derived by staphylococcal digestion of the inhibitor, and by synthetic peptide adducts containing both the -Arg-Arg-dipeptidyl recognition sequence and an adenine moiety. (3) We will evaluate conditions (hormonal, metabolic) that may modulate the level of inhibitor in cardiac and skeletal muscle. The hormonally-stimulated phosphorylation of phosphorylase kinase, glycogen synthase, membrane and contractile proteins will be determined in perfused heart and isolated diaphragm as a function of the level of inhibitor within tissues in order to establish whether or not a correlation exists, between the level of inhibitor and cAMP-mediated phosphorylation.

Agency
National Institute of Health (NIH)
Institute
National Institute of Arthritis, Diabetes, Digestive and Kidney Diseases (NIADDK)
Type
Research Project (R01)
Project #
5R01AM021019-08
Application #
3151339
Study Section
Biochemistry Study Section (BIO)
Project Start
1977-09-01
Project End
1986-08-31
Budget Start
1985-05-01
Budget End
1986-08-31
Support Year
8
Fiscal Year
1985
Total Cost
Indirect Cost
Name
University of California Davis
Department
Type
Schools of Medicine
DUNS #
094878337
City
Davis
State
CA
Country
United States
Zip Code
95618
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Thomas, J; Van Patten, S M; Howard, P et al. (1991) Expression in Escherichia coli and characterization of the heat-stable inhibitor of the cAMP-dependent protein kinase. J Biol Chem 266:10906-11
Glass, D B; Cheng, H C; Mende-Mueller, L et al. (1989) Primary structural determinants essential for potent inhibition of cAMP-dependent protein kinase by inhibitory peptides corresponding to the active portion of the heat-stable inhibitor protein. J Biol Chem 264:8802-10
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Glass, D B; Lundquist, L J; Katz, B M et al. (1989) Protein kinase inhibitor-(6-22)-amide peptide analogs with standard and nonstandard amino acid substitutions for phenylalanine 10. Inhibition of cAMP-dependent protein kinase. J Biol Chem 264:14579-84
Fletcher, W H; Byus, C V; Walsh, D A (1987) Receptor-mediated action without receptor occupancy: a function for cell-cell communication in ovarian follicles. Adv Exp Med Biol 219:299-323
Reed, J; Kinzel, V; Cheng, H C et al. (1987) Circular dichroic investigations of secondary structure in synthetic peptide inhibitors of cAMP-dependent protein kinase: a model for inhibitory potential. Biochemistry 26:7641-7
Van Patten, S M; Heisermann, G J; Cheng, H C et al. (1987) Tyrosine kinase catalyzed phosphorylation and inactivation of the inhibitor protein of the cAMP-dependent protein kinase. J Biol Chem 262:3398-403
Glass, D B; Cheng, H C; Kemp, B E et al. (1986) Differential and common recognition of the catalytic sites of the cGMP-dependent and cAMP-dependent protein kinases by inhibitory peptides derived from the heat-stable inhibitor protein. J Biol Chem 261:12166-71

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