Signal Cascades in Regulation of Glycogenolysis
Glycogen Phosphorylase was the first enzyme recognized some thirty years ago to be regulated by phosphorylation/dephosphorylation. Over the years many fundamental observations allowed to formulate cascades by which extracellular signals could be coupled to the physiological response — glycogenolysis (1). Before trying to analyze this “glycogenolytic cascade” on the basis of accumulated physiological and biochemical data it seems worthwhile to summarize some general principles inherent in intracellular signal pathways. Extracellular agonists like hormones or neurotransmitters are pleiotropic, however, they provoke a cell specific physiological response. As an initiating event agonists combine with specific receptors on the cell surface. Plasma membrane-localized signaling systems, transmit and amplify the signal; they release intracellularly a second messenger. All known second messengers again are pleiotropic and potentially can influence simultaneously more than one process. An advantage of this pleiotropism is the possibility to coordinate cellular processes e.g. cell motility with energy metabolism or, for example, to prevent futile cycling by shutting down glycogen synthesis when glycogenolysis is activated. In analogy to the extracellular event second messengers interact with specific receptors; their saturation constitutes the corresponding intracellular signal.
KeywordsGlycogen Phosphorylase cAMP Dependent Protein Kinase Dependent Protein Kinase Nucleotide Binding Domain Frog Skeletal Muscle
Unable to display preview. Download preview PDF.
- (1).Fischer, E.H., this volume. Plenum Publ. Corp., pp. (1987).Google Scholar
- (4).Malencik, D.A. and Fischer, E.H., Calcium and Cell Function (Cheung, W.Y., ed.). Vol. III, 161–188 (1982).Google Scholar
- (8).Cohen, P., Current Top. Cell. Regul. 14, 117–196 (1978).Google Scholar
- (11).Crabb, J.W. and Heilmeyer, L.M.G., Jr. J. Biol. Chem. 259. 6346–6350 (1984).Google Scholar
- Sotiroudis, T.G., Crabb, J.W. and Heilmeyer, L.M.G., Jr., unpublished.Google Scholar
- Meyer, H. E. and Heilmeyer, L.M.G., Jr., unpublished.Google Scholar
- (20).Heilmeyer, L.M.G., Jr., Jahnke, U., Kilimann, M.W., Kohse, K.P. and Sperling, J.E., Cold Spring Harbor Conferences on Cell Proliferation. Vol. 8, 321–329 (1981).Google Scholar
- (21).Gulyaeva, N.B., Vulfson, P.L. and Severin, E.S., Biokhimiya 43. 373–381 (1977).Google Scholar
- (22).Fischer, E.H., Alaba, J.O., Brautigan, D.L., Kerrick, W.G.D., Malencik, D.A., Moeschler, H.J., Picton, C. and Pocinwong, S., in: Versatility of Proteins. (C.H. Li, ed.), Academic Press, New York, 133–145 (1978).Google Scholar
- (24).Chan, K.F.J, and Graves, D.J., J. Biol Chem. 257, 5948–5955 (1981).Google Scholar
- (27).Sudhakar Babu, Y., Sack, J.S., Greenhough, T.J., Bugg, C.E., Means, A.R. and Cook, W.J., Naure 315 37–40 (1985).Google Scholar