Signal transduction elements

Ionized calcium (Ca2+) is the most common signal transduction element in cells [66], Excitable cells, like neurons, contain voltage-dependent Ca2+ channels, which enable these cells to drastically increase cytosolic calcium levels. Rapid fluctuations in presynaptic... 

Calculation of Conformational Free Energies for a Model of a Bilobal Enzyme Protein kinases catalyze the transfer of phosphate from adenosine triphosphate (ATP) to protein substrates and are regulatory elements of most known pathways of signal transduction. 

R Genes Cis Elements, Trans-factors and Signal Transduction Systems in the Lens, Joram Piatigorksy and Peggy S. Zelen-ka, National Eye Institute, National Institutes of Health, Maryland. Subject Index. 

Noradrenaline acts on three types of receptor. The ai receptors mediate the main excitatory effects of noradrenaline upon wake-active neurons in the dorsal raphe, basal forebrain, and elsewhere (Vandermaelen Aghajanian, 1983 Nicoll, 1988 Fort et al., 1995 Brown et al., 2002). The a2 receptors mediate inhibitory effects of noradrenaline, e.g. on noradrenaline neurons themselves and on cholinergic brainstem neurons (Williams et al., 1985 Williams Reiner, 1993). The (3-receptors modulate neurons in a more subtle fashion, increasing excitability via blockade of afterhyperpolarizations in hippocampal and cortical neurons (Haas Konnerth, 1983). Activation of (3-receptors also promotes synaptic plasticity via activation of the cyclic-AMP-dependent kinase (PKA) and cyclic AMP response element binding protein (CREB) signal transduction pathway (Stanton Sarvey, 1987 Cirelli et al., 1996). 

Some cytokine receptors can directly initiate signal transduction upon binding of ligand. In other cases additional elements are involved. For many receptors, the exact intracellular events triggered upon ligand binding remain to be elucidated. However, the molecular details of signal transduction pathways for others (e.g. the interferons) are now understood... 

All interferon-stimulated genes are characterized by the presence of an associated interferon-stimulated response element (ISRE). Signal transduction culminates in the binding of specific regulatory factors to the ISRE, which stimulates RNA polymerase Il-mediated transcription of the interferon-sensitive genes. The induced gene products then mediate the antiviral, immunomodulatory and other effects characteristically induced by interferons. 

The essential elements of the signal transduction pathway elicited by IFN-y are even more straightforward. IFN-y binding to the type II receptor induces receptor dimerization with consequent activation of JAK1 and JAK2. The JAKs phosphorylate the receptor and subsequently the associated STATla. STATla is then released and forms a homodimer that translocates to the... 

All GTP binding proteins in signal transduction share a common structural element - the Ras-like domain which is responsible for the specific complexation of guanosine diphosphate and -triphosphate and which contains catalytic residues that promote GTP-hydrolysis. 

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