Dual role of calmodulin in excitable cells.
Consideration of the enzymatic reactions governing calcium channel phosphorylation and dephosphorylation leads one to deduce that there exist separate groups of enzymes, membrane-bound and cytoplasmic that are activated by a common mediator, calmodulin (CaM), whose time-dependent appearance (via diffusion) at both locales is controlled by both intracellular calcium levels and electrostatic interaction with the membrane. In brief, the change in the sign and extent of the electrical charge borne by the modulator in the presence of calcium (Ca) brings about the electrostatic attraction that enables the transport of [Ca-CaM] to the membrane. This translocation of Ca-CaM makes possible a sequential activation of cellular enzymes whose locations differ. The sequence, both spatial and temporal, of the activation of various cellular enzymes by Ca-CaM appears to be a control network shared in common by excitable cells containing a stimulus-response pathway mediated by second messengers.
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Department of Chemical and Biochemical Engineering, Rutgers, State University of New Jersey, Piscataway 08855-0909.
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D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D015220:Calcium Channels / Q000502:physiology*; D002147:Calmodulin / Q000502:physiology*; D003198:Computer Simulation; D000242:Cyclic AMP / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D008564:Membrane Potentials / Q000502:physiology; D008954:Models, Biological; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism; D010766:Phosphorylation; D012849:Sinoatrial Node / Q000502:physiology
D015220:Calcium Channels; D002147:Calmodulin; D000242:Cyclic AMP; D010727:Phosphoric Diester Hydrolases; D000262:Adenylyl Cyclases