Intracellular messengers

Interaction of the food with the gastric mucosal layer is the normal trigger for gastric cells to release gastrin, which is then carried by the bloodstream to the parietal cells. Calcium ions and cyclic AMP act as intracellular messengers in the transfer of the signal from the receptors to the proton pumps of parietal cells where the acid is generated. 

Flubendiamide is an example of a new chemical class of insecticides that have been termed phthalic acid diamides (Nauen 2006, Copping and Duke 2007). They are related to the alkaloid ryanodine, which is extracted from Ryania species. Ryanodine affects muscles by binding to calcium channels of the sarcoplasmic reticulum. Ca + ions act as intracellular messengers, and their flux is modulated by calcium channels of this type. The toxic action of ryanodine and synthetic insecticides related to it is due to the disturbance of calcium flux. 

CATECHOLAMINE) HORMONES HAVE MEMBRANE RECEPTORS USE INTRACELLULAR MESSENGERS... 

Ionized calcium is an important regulator of a variety of cellular processes, including muscle contraction, stimulus-secretion coupling, the blood clotting cascade, enzyme activity, and membrane excitability. It is also an intracellular messenger of hormone action. 

Other ion channels are closed at rest, but may be opened by a change in membrane potential, by intracellular messengers such as Ca + ions, or by neurotransmitters. These are responsible for the active signalling properties of nerve cells and are discussed below (see Hille 1992, for a comprehensive account). A large number of ion channels have now been cloned. This chapter concerns function, rather than structure, and hence does not systematically follow the structural classification. 

Buckley, N. J. (1990). Molecular pharmacology of cloned muscarinic receptors. In Transmembrane Signalling, Intracellular Messengers and Implications for Drug Development, ed. S. R. Nahorski, pp. 11-30. Chichester John Wiley 8r Sons. 

METH-Induced Alterations in Intracellular Messenger Systems Related... 

H linked intracellular messengers. Activated H receptors are known to activate a pertussis-toxin-insensitive G protein, Gq, that stimulates phosphoinositide-specific phospholipase C (PI-PLC), with the subsequent generation of inositol 1,4,5-trisphosphate (IP3) and diacylglyc-erol (DAG). These two mediators are known to elevate intracellular Ca2+ concentrations and to activate PKC,... 

The Ca2+-calmodulin complex may also activate nitric oxide synthase (NOS), which binds to a PDZ domain of PSD-95. Activated NOS produces NO from arginine NO, in turn, activates guanylate cyclase, the enzyme that catalyzes the conversion of GTP to the intracellular messenger cGMP, which activates protein kinase G (PKG). 

How do a wide variety of neurotransmitters and hormones produce tissue- and cell-specific biological responses, if many such responses are mediated by the same intracellular messengers, cAMP and cAMP-depen-dent protein kinase Specificity is achieved at two levels at the level of tissue-specific receptors for the neurotransmitter or hormone and at the level of tissue-specific substrate proteins for the protein kinase. Only tissues that possess specific receptors will respond to a certain neurotransmitter or hormone. Moreover, since all cells contain very similar catalytic subunits of protein kinase A (see Ch. 23), the nature of the proteins that are phosphor-ylated in a given tissue depends on the types and amounts of proteins expressed in that tissue and on their accessibility to the protein kinase. 

Several key questions remain with regard to the regulation of tyrosine hydroxylase by phosphorylation. What is the precise effect of the phosphorylation of each of these serine residues on the catalytic activity of the enzyme How does the phosphorylation of multiple residues affect enzyme activity Does the phosphorylation of one residue affect the ability of the others to be phosphorylated Tyrosine hydroxylase provides a striking example as to how multiple intracellular messengers and protein kinases converge functionally through the phosphorylation of a single substrate protein. Phosphorylation of tyrosine hydroxylase by cAMP-dependent and Ca2+-dependent protein kinases and by MAPK cascades... 

Cellular signals converge at the level of protein phosphorylation pathways. Individual intracellular messenger pathways, such as cAMP, Ca2+ and MAPK pathways, are often drawn as distinct biochemical cascades that operate in parallel in the control of cell function. While this is useful for didactic purposes, it is now well established that these various pathways function as complex webs, with virtually every conceivable type of interaction seen among them. 

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