G receptors

An assay that produces multiple biological readouts. Most commonly used in relation to the mathematical analysis of an image acquired using an automated microscope whereby analysis algorithms quantify cellular parameters (e.g., number, motility, neurite outgrowth, size, shape) and subcellular events (e.g., receptor internalization, protein translocation, protein expression nuclei shape). 

The term 1 + ( I. KL) is often referred to as the Cheng-Prusoff correction. It is clear from this analysis that the IC50 does not give a direct estimate of Kt unless [L] is very low, when IC50 tends to Kv Just as with saturation experiments, the situation will be complicated by the presence of different classes of binding sites (e.g., receptor subtypes) and by the involvement of G-proteins in agonist binding. 

Figure 1 General pathways through which molecules can actively or passively cross a monolayer of cells. (A) Endocytosis of solutes and fusion of the membrane vesicle with the opposite plasma membrane in an active process called transcytosis. (B) Similar to A, but the solute associates with the membrane via specific (e.g., receptor) or nonspecific (e.g., charge) interactions. (C) Passive diffusion between the cells through the paracellular space. (C, C") Passive diffusion (C ) through the cell membranes and cytoplasm or (C") via partitioning into and lateral diffusion within the cell membrane. (D) Active or carrier-mediated transport of an otherwise poorly membrane permeable solute into and/or out of a cellular barrier.

Some cytokine receptors are composed of a single transmembrane polypeptide (e.g. receptors for IL-8, -9 and -10). Many contain two polypeptide components (including the IL-3, -4, and -5 receptors), and a few contain three or more polypeptide components (e.g. the IL-2 receptor contains three polypeptide chains). In some instances a single cytokine may be capable of initiating signal transduction by binding two or more distinct receptors (e.g. IL-1 has two distinct receptors (types I and II), both of which are transmembrane glycoproteins). 

Gudermann, T., Nurnberg, B., and Schultz, G. Receptors and G proteins as primary components of transmembrane signal transduction. Part 1. G-protein-coupled receptors structure and function./. Mol. Med. 1995, 73, 51-63. 

Many of the proposed toxicity tests have been criticized for nonspecificity and lack of reproducibility. Concern has also been raised about their relevance for generating useful data for hazard and risk assessment purposes. The diversity of the possible modes of action (e.g., receptor binding. 

To determine binding constants between drugs and biological structures (e.g., receptors, cells, peptide fragments), proteins (e.g., enzymes), nucleic acids, and plasmids... 

Similarly, intrahippocampal injections of 8-OH-DPAT induced no change in performance levels of the rat trained to run in a radial maze (Buhot et al. 1995). However, the intrahippocampal injection of the 5-HTjg receptor agonist CP-93,129 [3-(l,2,5,6-tetrahydropyrid-4-yl] pyrrolo [3,2-6] pyrid-5-one] induced a higher frequency of reference memory errors than of working memory. It was concluded that stimulation of 5-HT,g receptors in the CAl field of the dorsal hippocampus impairs performance of rats in a spatial learning task. 

Figure 1. Schematic representations of significant biological functions displayed by host-guest complexation in homogeneous solutions or at membrane surfaces, (a) Separation (e.g., antibody-antigen complex formation), (b) Transformation (e.g., enzymatic reaction), (c) Translocation (e.g., carrier- or channel-mediated transport), (d) Transduction (e.g., receptor-mediated transmembrane signaling).

Collaborative signaling integrin-mediated cell adhesion modulates signal transduction by other receptors (e.g., receptor tyrosine kinases). 

Carpenter G. Receptor tyrosine kinase substrates Src homology domains and signal transduction. 

Blasberg, R. G. Receptor binding radiotracers personal history of the past 20 years. Nucl. Med. Biol. 2001, 23(5), 573-583. 

Sakatsume M, Igarashi K-I, Winestock KD, Garotta G, Larner AC, Finbloom DS. The Jak Kinases differentially associate with the a and b (accessory factor) chains of the interferon-g receptor to form a functional receptor unit capable of activating ST AT transcription factors. J Biol Chem 1995 270 17528-17534. 

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