Responses to activation

AMPK can also be activated by a Ca2+-mediated pathway involving phosphorylation at Thr-172 by the Ca2+/calmodulin-dependent protein kinase, CaMKK 3. CaMKKa and CaMKK 3 were discovered as the upstream kinase for the calmodulin-dependent protein kinases-1 and -IV they both activate AMPK in a Ca2+/ calmodulin-dependent manner in cell-free assays, although CaMKK 3 appears to much more active against AMPK in intact cells. Expression of CaMKKa and CaMKK(3 primarily occurs in neural tissues, but CaMKKp is also expressed in some other cell types. Thus, the Ca2+-mediated pathway for AMPK activation has now been shown to occur in response to depolarization in rat neuronal tissue, in response to thrombin (acting via a Gq-coupled receptor) in endothelial cells, and in response to activation of the T cell receptor in T cells. 

There are several major classes of Ca channels (1) receptor-operated Ca channels in plasma membranes (2) ligand-gated Ca " channels in intracellular membranes and (3) voltage-dependent Ca channels that are usually found in plasma membranes or the invaginations of the plasma membrane that are known as transverse tubule membranes. Receptor-dependent or receptor-operated Ca channels (ROCCs) are primarily opened in response to activation of their associated receptors and, by definition, exhibit a certain amount of selectivity for Ca " over other cations. Several potentially different types of ROCCs have been characterized including ATP-sensitive channels in smooth muscle [1], mitogen and IP3-sensitive... 

Srivastava, S. P., Kumar, K. U., and Kaufman, R. J. (1998). Phosphorylation of eukaryotic translation initiation factor 2 mediates apoptosis in response to activation of the double-stranded RNA-dependent protein kinase. J. Biol. Chem. 273, 2416—2423. 

IL-2, also known as T-cell growth factor, represents the most studied member of the interleukin family. It was the first T-cell growth factor to be identified and it plays a central role in the immune response. It is produced exclusively by T-lymphocytes (especially T-helper cells), in response to activation by antigen and mitogens. 

CNS development are employed for the same purpose in the PNS. PNS microglia-like cells, like microglia in the CNS, are bone-marrow-derived and have a similar repertoire of responses to activation [2], Both oligodendroglia and Schwann cells speed axonal action potential propagation by assembling and maintaining myelin. Capillary endothelial cells linked by tight junctions restrict entry of polar molecules into the PNS, as into the CNS [3],... 

Fig. 4. Ras (in the GTP state) activates a variety of effectors each with different functions and cellular pathways. Only five out of more than ten putative effectors are shown. The signal cascades following effector triggering are schematically shown which lead to one of the possible cellular responses to activated Ras. Due to their high sequence homology, Rap, R-Ras, and TC21 may also interact with the Ras effectors. Scheme according to [55]...

Smooth muscles not only alter their tension in response to changes in the frequency of action potential discharge, but also in response to activation of various receptors... 

In contrast to the metabotropic effects described for presynaptic kainate receptors in CA1 (90,94), the effects of kainate in CA3 appear to be mediated by direct depolarization of the presynaptic terminals. The kainate-induced facilitation is not sensitive to antagonists of other receptors (e.g., GABAb), and can be mimicked by elevating the extracellular potassium concentration (77,100). It has been proposed that the facilitation is owing to increased calcium influx that is induced by modest depolarization of the terminals by kainate receptors, whereas a strong depolarization, in response to activation of a larger receptor population, causes the sodium channels to inactivate and thereby depresses transmission (77,84,88,100-102). 

D2. Daynes, R. A., and Araneo, B. A., Programming of lymphocyte response to activation extrinsic factors. Chem. Immunol. 54, 21-43 (1992). 

B cells are produced by the bone marrow. In response to activation of CD4+ T helper cells (see below), B cells proliferate and produce antibodies. (The term CD stands for cluster of differentiation. They are proteins coating cell surfaces. Altogether, there are more than 160 different types of CDs.) The antibodies produced by B cells circulate in the bloodstream and bind to antigens. Once bound, other cells are in turn activated to destroy the antigens. 

Luo, X., Budihardjo, L, Zou, H., Slaughter, C., and Wang, X., 1998, Bid, a Bcl-2 interacting protein, mediates cythochrome c release from mitochondria in response to activation of cell surface death receptors. Cell 94 481-490. 

This division into classes is also supported by a comparison of their specificities toward peptide substrates [15,18,19], their interaction with substrate-analogue inhibitors [20], their response to active site metal substitutions [21,22], and their mode of attack of triple helical collagens [23] (French, M.F., Bhown, A. and Van Wart, H.E., unpublished data). 

Responses to activation of the parasympathetic system. Parasympathetic nerves regulate processes connected with energy assimilation (food intake, digestion, absorption) and storage. These processes operate when the body is at rest, allowing a decreased tidal volume (increased bronchomotor tone) and decreased cardiac activity. Secretion of saliva and intestinal fluids promotes the digestion of foodstuffs transport of intestinal contents is speeded up because of enhanced peristaltic activity and lowered tone of sphincteric muscles. To empty the urinary bladder (micturition), wall tension is increased by detrusor activation with a concurrent relaxation of sphincter tonus. 

This complex, cardiostimulatory and vasodilating action is expressed by a significant increase of cardiac ontput and stroke volnme. In response to activation of j32-adrenorecep-tors, bronchodilation also increases. Isoproterenol is used in bronchospasms, asthma, cardiac block, and shock. Synonyms of isoproterenol are protemol, isoprenaline, isadrine, norisodrine, novodrin, and others. 

The rate decay time constant is independent of cation form of the zeolite in the ethene system (Figure 4) although the alkylation activity of the three forms is considerably different (Figure 2). This indicates that the active site within the zeolite (at least for deactivation) is the same for all three cation forms as expected from our current picture of active sites for acid-catalyzed reactions in these zeolites (8, 18, 19). The three catalysts should have different numbers of active sites because of their individual response to activation at 823°K, but these sites should be similar thus M2 should be independent of cation form, Mi should depend on it. 

Koleske, J., and R. A. Young, An RNA polymerase II holoen-zyme responsive to activators. Nature 368 466-469, 1994. 

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