Receptors cell surface

The macrophage cell surface as a crucial interface studded with receptors Unks antibody dependent molecular immune recognition triggering a broad spectrum of cellular responses including phagocytosis, cytolysis, release of lysosomal enzymes and mediators such as prostaglandin Ej, and release of reactive oxygen metaboUtes. 

Membrane receptors contain single, fourfold, sevenfold, and 24-fold membrane-spanning domains. 

Characteristic for all partners of the single membrane-spanning receptors, which are stimulated by transformation growth factors, is the fact that endocytosis usually takes place after the Ugand binds to the receptor. 

Phorbol esters were observed to reduce the rate of acetylcholine receptor synthesis in cultured chick myotubes (Miskin et al. 1978). These findings were confirmed by Bursztajn et al. (1988) and by Klarsfeld et al. (1989), who, in addition, demonstrated that phorbol esters enhance receptor ex- 

Computer analysis of [ I]iodocyanopindolol competition studies using the relatively selective pi-adrenoceptor antagonist, ICI 89406, and the P2-selective antagonist, ICI 118551, on rabbit arterial blood mononuclear leucocyte plasmalemmal preparations favoured a two-site model indicating that both Pi- and Pj-adrenoceptor subtypes were present in approximately equal numbers (Tenner jr. et al. 1989). 

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P-Endorphin. A peptide corresponding to the 31 C-terminal amino acids of P-LPH was first discovered in camel pituitary tissue (10). This substance is P-endorphin, which exerts a potent analgesic effect by binding to cell surface receptors in the central nervous system. The sequence of P-endorphin is well conserved across species for the first 25 N-terminal amino acids. Opiates derived from plant sources, eg, heroin, morphine, opium, etc, exert their actions by interacting with the P-endorphin receptor. On a molar basis, this peptide has approximately five times the potency of morphine. Both P-endorphin and ACTH ate cosecreted from the pituitary gland. Whereas the physiologic importance of P-endorphin release into the systemic circulation is not certain, this molecule clearly has been shown to be an important neurotransmitter within the central nervous system. Endorphin has been invaluable as a research tool, but has not been clinically useful due to the avadabihty of plant-derived opiates. 

Food vitamin B 2 appears to bind to a saUvary transport protein referred to as the R-protein, R-binder, or haptocorrin. In the stomach, R-protein and the intrinsic factor competitively bind the vitamin. Release from the R-protein occurs in the small intestine by the action of pancreatic proteases, leading to specific binding to the intrinsic factor. The resultant complex is transported to the ileum where it is bound to a cell surface receptor and enters the intestinal cell. The vitamin is then freed from the intrinsic factor and bound to transcobalamin II in the enterocyte. The resulting complex enters the portal circulation. 

Tissue Uptake and Storage. Cell surface receptors take up the transcobalamin II—cobalamin complex, which is internalized into endosomes. The complex is dissociated and the transcobalamin II released. The mechanism by which cobalamin leaves the endosome is uncertain. 

Many cell-surface receptors contain immunoglobulin-like domains. 

Limbird, L. E. (1995). Cell surface receptors A short course on theory and methods. Martinns Nihjoff, Boston. 

Heldin, C. H. (1995). Dimerization of cell surface receptors in signal transduction. Cell 80 213-223. 

Downregnlation, the reduction in the number of biological targets (e.g., cell surface receptors, enzymes) usually... 

VEGF-Trap is a protein-based product candidate designed to bind all forms of VEGF and the related P1GF, and prevents their interaction with cell surface receptors. VEGF Trap is being pursued in phase II... 

The steroid hormone 1,25-dihydroxy vitamin D3 (calcitriol) slowly increases both intestinal calcium absorption and bone resorption, and is also stimulated through low calcium levels. In contrast, calcitonin rapidly inhibits osteoclast activity and thus decreases serum calcium levels. Calcitonin is secreted by the clear cells of the thyroid and inhibits osteoclast activity by increasing the intracellular cyclic AMP content via binding to a specific cell surface receptor, thus causing a contraction of the resorbing cell membrane. The biological relevance of calcitonin in human calcium homeostasis is not well established. 

Caveolae are invaginations of the plasma membrane. They contain the protein caveolin and are rich in certain phospholipids. Similar to coated pits, they bud off internally forming endocytic vesicles. Caveolae play an important role in the internalization of certain cell surface receptors. 

A process in which a substance gains entry into a cell. Endocytic mechanisms are crucial for a variety of cellular functions such as the uptake of nutrients, regulation of cell surface expression of receptors, maintenance of cell polarity, and more. Receptor-mediated endocytosis via clathrin-coated pits is the most studied endocytic process, which is important for regulation of the time and magnitude of signals generated by a variety of cell-surface receptors. 

Muscarinic acetylcholine receptors (mAChRs) form a class of cell surface receptors that are activated upon binding of the neurotransmitter, acetylcholine. Structurally and functionally, mAChRs are prototypical members of the superfamily of G protein-coupled receptors. Following acetylcholine binding, the activated mAChRs interact with distinct classes of heterotrimeric G proteins resulting in the activation or inhibition of distinct downstream signaling cascades. 

The neurotransmitter acetylcholine (ACh) exerts its diverse pharmacological actions via binding to and subsequent activation of two general classes of cell surface receptors, the nicotinic and the mAChRs. These two classes of ACh receptors have distinct structural and functional properties. The nicotinic receptors,... 

The role of NFAT in the immune system is not restricted to T cells. NFAT proteins are also expressed in other cells of the immune system, such as B cells, NK cells, and mast cells, where they have been shown to regulate the expression of cytokines, cell surface receptors, and immunoglobulins [4, 5]. 

A purinoceptor is a cell surface receptor for the purinergic nucleotides ATP and ADP and for the purine nucleotide, adenosine. 

Receptor for advanced glycation end products (RAGE) is a member of the immunoglobulin-like cell surface receptor superfamily inter-acting with several SI00 proteins. 

Hofmann MA, Drury S, Fu C et al (1999) RAGE mediates a novel proinflammatory axis a central cell surface receptor for SlOO/calgranulin polypeptides. Cell 97 889-901... 

Figure 2. Mechanism of PDH. The three different subunits of the PDH complex in the mitochondrial matrix (E, pyruvate decarboxylase E2, dihydrolipoamide acyltrans-ferase Ej, dihydrolipoamide dehydrogenase) catalyze the oxidative decarboxylation of pyruvate to acetyl-CoA and CO2. E, decarboxylates pyruvate and transfers the acetyl-group to lipoamide. Lipoamide is linked to the group of a lysine residue to E2 to form a flexible chain which rotates between the active sites of E, E2, and E3. E2 then transfers the acetyl-group from lipoamide to CoASH leaving the lipoamide in the reduced form. This in turn is oxidized by E3, which is an NAD-dependent (low potential) flavoprotein, completing the catalytic cycle. PDH activity is controlled in two ways by product inhibition by NADH and acetyl-CoA formed from pyruvate (or by P-oxidation), and by inactivation by phosphorylation of Ej by a specific ATP-de-pendent protein kinase associated with the complex, or activation by dephosphorylation by a specific phosphoprotein phosphatase. The phosphatase is activated by increases in the concentration of Ca in the matrix. The combination of insulin with its cell surface receptor activates PDH by activating the phosphatase by an unknown mechanism.

G Protein Families. Cell responses to the binding of stimulatory ligands (L) to cell-surface receptors (R) proceed through a multistep... 

Real-time spectroscopic methods can be used to measure the binding, dissociation, and internalization of fluorescent ligands with cell-surface receptors on cells and membranes. The time resolution available in these methods is sufficient to permit a detailed analysis of complex processes involved in cell activation, particularly receptor-G protein dynamics. A description of the kinetics and thermodynamics of these processes will contribute to our understanding of the basis of stimulus potency and efficacy. 

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