Receptors function

There are three advantages to study molecular recognition on surfaces and interfaces (monolayers, films, membranes or soHds) (175) (/) rigid receptor sites can be designed (2) the synthetic chemistry may be simplified (J) the surface can be attached to transducers which makes analysis easier and may transform the molecular recognition interface to a chemical sensor. And, which is also a typical fact, this kind of molecular recognition involves outside directed interaction sites, ie, exo-receptor function (9) (see Fig. 5b). 

Oxytocin and Vasopressin Receptors. The actions of oxytocin and vasopressin are mediated through their interactions with receptors. Different receptor types as well as different second messenger responses help explain their diverse activities in spite of the hormones stmctural similarities. Thus oxytocin has at least one separate receptor and vasopressin has been shown to have two principal receptor types, and V2. Subclasses of these receptors have been demonstrated, and species differences further compHcate experimental analysis. It is apparent that both oxytocin and receptors function through the GP/1 phosphoHpase C complex (75), while the V2 receptors activate cycHc AMP (76). 

CP 55940 (79) and nabilone (80) are synthetic ligands for the cannabiaoid receptor. However, the identification of the eicosanoid, anandamide (81), as an endogenous cannabimimetic has provided an important tool to study cannabiaoid receptor function. 

Sleep and its modulation by N- and N,0-heterocyclic drugs that affect y-aminobutyric acid (GABA) receptor function 99AG(E)2852. 

FIGURE 1.4 Increasing levels of protein structure. A protein has a given amino acid sequence to make peptide chains. These adopt a 3D structure according to the free energy of the system. Receptor function can change with changes in tertiary or quaternary structure. 

The operational model allows simulation of cellular response from receptor activation. In some cases, there may be cooperative effects in the stimulus-response cascades translating activation of receptor to tissue response. This can cause the resulting concentration-response curve to have a Hill coefficient different from unity. In general, there is a standard method for doing this namely, reexpressing the receptor occupancy and/or activation expression (defined by the particular molecular model of receptor function) in terms of the operational model with Hill coefficient not equal to unity. The operational model utilizes the concentration of response-producing receptor as the substrate for a Michaelis-Menten type of reaction, given as... 

Equation 7.6 defines the allosteric noncompetitive antagonism of receptor function and predicts insurmountable effects on agonist maximal response (i.e., as [A] oo) the expression for maximal response is... 

Sole effects on affinity (with no change in receptor function) result in surmountable antagonism. 

Allosteric modulators that block receptor function produce insurmountable antagonism. In addition, modulators that block function also can alter (increase or decrease) affinity. 

Cytokine receptors are a group of structurally related receptors, which couple to the JAK-STAT pathway. Cytokine receptors function as homodimers or heterooligomers. They are divided into two main subclasses, class I, which contains receptors for a variety of hematopoietic growth factors and interleukins and class II, which contains receptors for interferons and interleukins 10, 20/24 and 22. 

These findings were unexpected because previous studies had demonstrated that the y2 subunit is required for potentiation of GABAa receptor function by low concentrations of ethanol [2]. The y2 subunit gene is located within a definitely mapped quantitative trait locus (QTL) for acute alcohol withdrawal on mouse chromosome 11 [1]. Allelic variation was genetically... 

Barnard EA, Skolnick P, Olsen RW et al (1998) International Union of Pharmacology. XV. Subtypes of y-aminobutyric acidA receptors classification on the basis of subunit structure and receptor function. Pharmacol Rev 50 291-313... 

Glycine receptor function is modulated by alcohols and anesthetics [4]. Amino acid residue al(S267) is critical for alcohol potentiation, as mutation to small residues (Gly, Ala) enhance, and mutation to large residues (His, Cys, Tyr) diminish the ethanol effect. Glycine recqrtor modulation by Zn2+ involves structural determinants located within the large N-terminal domain. Additional glycinergic modulators include neuroactive steroids and the anthelmintic, ivermectin, which activates glycine receptors by a novel, strychnine-insensitive mechanism. 

Activation of the tyrosine kinase activity of the INSR is essential for the receptor function. The tyrosine kinase domain of the INSR is localized in the... 

Antagonists selective for kainate receptors are not available yet. The non-NMDA receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) blocks AMPA as well as kainate receptors. Nevertheless, compounds like GYKI53655, which acts as a noncompetitive antagonist of AMPA receptors and completely blocks AMPA receptor function at certain concentrations at which no antagonistic effect on kainate receptors is discernible, has been used to demonstrate the kainate receptor-mediated currents in neurons. 

Melanocortins. Figure 1 Shows the melanocortin receptors, function and naturally occurring peptide sequences that activate them. 

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