[Principles of transmembranous signal transduction in the action of hormones and neurotransmitters].
In the membranous signal transduction process, hormone-binding to receptors causes receptor interaction with signal-transducing components; these components transfer the stimulus to effector systems, which generate intracellular signals. Several guanine nucleotide-binding proteins (N- or G-proteins) have been identified as membranous signal-transducing components. Two N-proteins are involved in the hormonal regulation of adenylate cyclase activity, one of which being stimulatory (Ns), the other one being inhibitory (Ni). Ns, Ni and a third N-protein, No, whose function is unknown, occur ubiquitously. On the other hand, transducin, an N-protein, which functionally couples light-activated rhodopsin to a cGMP phosphodiesterase, is specific for the retina. In addition to their established role as transducers regulating adenylate cyclase and retinal cGMP phosphodiesterase, N-proteins proteins may be involved in two mechanisms by which the cytoplasmic calcium concentration is elevated, i.e. hormonal stimulation of a phospholipase C catalyzing phosphatidyl-inositol 4,5-diphosphate hydrolysis (Pi response) and hormone-induced opening of receptor-operated calcium channels; the membrane-bound forms of cAMP phosphodiesterase and guanylate cyclase, stimulated by insulin and atrial natriuretic factor, respectively, are also likely to be regulated via N-proteins. Guanine nucleotide-binding proteins appear to play a universal role in transmembranous signalling processes, controlling effector systems (i.e. enzymes and ion channels) that regulate cytoplasmic concentrations of intracellular messengers such as cyclic AMP, cyclic GMP and calcium.
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D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism; D006152:Cyclic GMP / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000378:metabolism; D006728:Hormones / Q000502:physiology*; D006801:Humans; D008564:Membrane Potentials; D018377:Neurotransmitter Agents / Q000502:physiology*; D010455:Peptides / Q000502:physiology; D011956:Receptors, Cell Surface / Q000187:drug effects / Q000502:physiology; D017981:Receptors, Neurotransmitter / Q000187:drug effects / Q000502:physiology
D006728:Hormones; D018377:Neurotransmitter Agents; D010455:Peptides; D011956:Receptors, Cell Surface; D017981:Receptors, Neurotransmitter; D019204:GTP-Binding Proteins; D000262:Adenylyl Cyclases; D006152:Cyclic GMP; D002118:Calcium
Prinzipien der transmembranären Signalumsetzung bei der Wirkung von Hormonen und Neurotransmittern.