According to Abedon (2012), receptor proteins are intracellular proteins, or protein fractions, that have a high specific affinity for binding a known stimulus to cellular activity. Receptor proteins may be located at cell surfaces or within the interior of cells. They may detect hormones or instead keep track of what otherwise is going on in cell’s environment. They may be enzymes or serve to relay the occurrence of signal reception in other ways such as by opening up ion channels.
Receptor proteins are often targets for drug action. These drugs either stimulate the receptors upon binding or, instead, block the binding of receptor to normal signals. There are four principle protein targets with which drugs can interact: enzymes, membrane carriers, ion channels and receptors. An article by Riding (2004), was concerned with the receptor and describes the dynamics of drug–receptor interaction, agonists, antagonists, partial agonists and inverse agonists, efficacy and potency.
Proteins that respond to steroid hormones are cytoplasmic receptor proteins. Ligand activated receptors may enter the cell nucleus where they modulate gene expressions. Many receptors for hormones and neurotransmission are trans-membrane proteins. However, receptors within cell membranes may be peripheral or trans-membrane proteins. Acting through various secondary pathways involving ion channels, enzymes such as adenylyl (adenylate) cyclases, and phospolipases, or PDZ domains, metabotropic receptors are coupled to G proteins.
Ion tropic receptors are ligand-activated ion channels that permit entry of ions when the central pore is open. According to Hofmeyer (2009), receptor protein tyrosine phosphatases control many aspects of nervous system development. At the Drosophila neuromuscular junction, regulation of synapse growth and maturation by the RPTP LAR depends on catalytic phosphatase activity and on the extracellular ligands syndecan and dally-like.
Abedon, Stephen T. “Receptor Protein.” Http://www.archaealviruses.org/abedon/. N.p., 2012. Web. 11 Oct. 2012. . Edmund. “Drugs and Receptors.” Http://www.oxfordjournals.org. N.p., n.d. Web. 11 Oct. 2012. . Hofmeyer, Kerstin, and Jessica E. Treisman. “The Receptor Protein.” Http://www.pnas.org. N.p., 30 Sept. 2009. Web. 11 Oct. 2012. .