Cells Cell surface receptors, drug

The main drug targets are enzymes, intracellular receptors, and extracellular (cell surface) receptors. Drugs are normally designed to interact with these entities either as agonists or antagonists to achieve control over the disease pathway. 

Limbird, L. E., Cell Surface Receptors A Short Course on Theory and Methods, 2nd ed., Nijhoff, Boston, 1996. Pratt, W. B. and Taylor, P., Principles of Drug Action, Churchill Livingstone, New York, 1990 (see, in particular, Chapters 1 and 2). 

G-protein coupled receptor family comprises most well-known cell surface receptors including the major drug targets, as previously stated. Early PAL results have been reviewed in several papers, and book chapters. For opiate, NMDA, sigma, benzodiazepine, GABA, acetyl choline, and adrenerg, serotonine receptors see [52,59,60], and for purinerg, histamine, and dopamine receptors see [61]. 

As human enzymes and cell surface receptors are chiral, the two enantiomers of a racemic drug may be absorbed, activated, or degraded in very different ways, both in vivo and in vitro. The two enantiomers may have unequal degrees... 

Reviewed in Christopoulos, A. Allosteric binding sites on cell-surface receptors novel targets for drug discovery. Nat. Rev. Drug Discov. 2002, 1, 198-210. 

Finally, continuous exposure of certain receptors to their macromolecular ligands can lead to rapid downregulation of cell surface receptors, especially if receptor recycling within the cells is incomplete. Fortunately, expression of many receptors, for example for certain cytokines, growth hormones and adhesion factors, can be extensively upregulated in the disease process and this can result in disease-induced drug-targeting. 

Many of the drugs used in the treatment of hypertension and cardiovascular disease are designed to interfere with the action of cell-surface receptors that couple to heterotrimeric G proteins. 

Fig. I. Endocytic pathways used by cells to internalize soluble macromolecules [25] fluid-phase pinocytosis (1), adsorptive pinocytosis (2), and receptor-mediated endocytosis (pinocytosis) (6). Each of these processes involves a formation of a sealed vesicle formed from the plasma membrane which encloses part of the extracellular medium. The internalization of a polymer-drug conjugate (P-D), and targeted polymer-drug conjugate ( => —P-D) is shown. Other abbreviations — = cell surface receptor/antigen 1 = clathrin molecule X = lysosomal enzyme. Fluid-phase pinocytosis (1) and adsorptive pinocytosis (2) are nonspecific processes which direct the macromolecule into the lysosomal compartment of the cell. Once P-D is internalized, whether by (1) or (2), the resulting endosome (3) is ultimately fused with a primary lysosome (4) forming a secondary lysosome (5). In the latter compartment P-D is in contact with several types of lysosomal enzymes. The membrane of (5) is impermeable to macromolecules. Consequently, the structure of P-D may be designed in such...

Rihova, B. Targeting of drugs to cell surface receptors. Crit. Rev. Biotechnol. 17 149-169, 1997. 

There are two major categories of desensitization of responses mediated by G protein coupled receptors. Homologous desensitization refers to loss of responsiveness exclusively of the receptors that have been exposed to repeated or sustained activation by a drug. Heterologous desensitization refers to loss of responsiveness of some cell surface receptors that have not been directly activated by the drug in question. 

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