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Information about Cell Surface Receptor

For other uses, see Receptor.


In biochemistry, a receptor is a protein on the cell membrane or within the cytoplasm or cell nucleus that binds to a specific molecule (a ligand), such as a neurotransmitter, hormone, or other substance, and initiates the cellular response to the ligand. Ligand-induced changes in the behavior of receptor proteins result in physiological changes that constitute the biological actions of the ligands.

Binding and activation

Ligand binding to a receptor is an equilibrium process: Ligands bind to an empty receptor and they dissociate from it (according to the law of mass action):

(the brackets stand for concentrations)


A measure of how well a certain molecule fits into a given receptor is the binding affinity which is measured as the dissociation constant Kd (good fit means high affinity and a low Kd). The activation of the second messenger cascade and the final biological response is achieved only when at a certain time point a significant number of receptors are activated by bound ligands.

Agonists versus antagonists

Not every ligand that binds to a receptor it also activates the receptor. The following classes of ligands exist:
  • (Full) agonists are able to activate the receptor and result in a maximal biological response. Most natural ligands are full agonists
  • Partial agonists are not able to activate the receptor maximally, resulting in a partial biological response compared to a full agonist.
  • Antagonists bind to the receptor but do not activate it. This results in a receptor blockade that inhibits the binding of agonists.
  • Inverse agonists are antagonists that are able to further reduce the receptor activation by decreasing its basal activity

Overview

The shapes and actions of receptors are newly investigated by the X-ray crystallography and computer modelling. This increases the current understanding of drug action at binding sites on the receptors.
Enlarge picture
Transmembrane receptor:E=extracellular space; I=intracellular space; P=plasma membrane
Receptors exist in different types, dependent on their ligand and function:

Peripheral membrane protein receptors

Transmembrane receptors

Main article: Transmembrane receptor

Metabotropic receptors

Main article: Metabotropic receptor

G protein-coupled receptors

Main article: G protein-coupled receptor
These receptors are also known as seven transmembrane receptors or 7TM receptors.

Receptor tyrosine kinases

These receptors detect ligands and propagate signals via the tyrosine kinase of their intracellular domains. This family of receptors includes;

Guanylyl cyclase receptors

Ionotropic receptors

The entire repertoire of human plasma membrane receptors is listed at the Human Plasma Membrane Receptome ([1]

Intracellular receptors

Transcription factors

Various

Role in Genetic Disorders

Many genetic disorders involve hereditary defects in receptor genes. Often, it is hard to determine whether the receptor is nonfunctional or the hormone is produced at decreased level; this gives rise to the "pseudo-hypo-" group of endocrine disorders, where there appears to be a decreased hormonal level while in fact it is the receptor that is not responding sufficiently to the hormone.

Receptor Regulation

Cells can increase (upregulate) or decrease (downregulate) the number of receptors to a given hormone or neurotransmitter to alter its sensitivity to this molecule. This is a locally acting feedback mechanism.

Receptor desensitization

Ligand-bound desensitation of receptors was first characterized by Katz and Thesleff in the nicotine acetylcholine receptor[1][2] Prolonged or repeat exposure to a stimulus often results in decreased responsiveness of that receptor for a stimulus. Receptor desensitization results in altered affinity for the ligand.[1]

May be accomplished by
  • Receptor phosphorylation.[3]
    • Uncoupling of receptor effector molecules.
    • Receptor sequestration (internalization).[3]

    See also

    References

    1. ^ Y. Sun, R. Olson, M. Horning, N. Armstrong, M. Mayer and E. Gouaux. (2002) Mechanism of glutamate receptor desensitization Nature 417, 245-253
    2. ^ S. Pitchford, J.W. Day, A. Gordon and D. Mochly-Rosen. (1992) Acetylcholine receptor desensitization is Regulate by activation-induced extracellular adenosine accumulation. The Journal of Neuroscience, 1.311): 4540-4544.
    3. ^ G. Boulay, L. Chrbtien, D.E. Richard, AND
G. Guillemettes. (1994) Short-Term Desensitization of the Angiotensin II Receptor of Bovine Adrenal Glomerulosa Cells Corresponds to a Shift from a High to a Low Affinity State. Endocrinology Vol. 135. No. 5 2130-2136

External links

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Cell physiology: cell signaling
Key conceptsLigand - Cell signaling networks - Signal transduction - Apoptosis - Second messenger system (Ca2+ signaling, Lipid signaling)
ProcessesParacrine - Autocrine - Juxtacrine - Neurotransmitters - Endocrine (Neuroendocrine)
Types of proteinsReceptor (Transmembrane, Intracellular) - Transcription factor (General, Preinitiation complex, TFIID, TFIIH) - Adaptor protein
Receptor may refer to:
  • Sensory receptor, in physiology, any structure which, on receiving environmental stimuli, produces an informative nerve impulse
  • Receptor (biochemistry), in biochemistry, a protein molecule that receives and responds to a neurotransmitter, hormone,

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Biochemistry is the study of the chemical processes in living organisms.[1] The word "biochemistry" comes from the Greek word βιοχημεία biochēmeia, which means "the chemistry of life.
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Proteins are large organic compounds made of amino acids arranged in a linear chain and joined together by peptide bonds between the carboxyl and amino groups of adjacent amino acid residues.
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Cytoplasm is a gelatinous, semi-transparent fluid that fills most cells. Eukaryotic cells contain a nucleus that is kept separate from the cytoplasm by a double membrane layer. The cytoplasm has three major elements; the cytosol, organelles and inclusions.
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nucleus (3) ribosome (4) vesicle (5) rough endoplasmic reticulum (ER) (6) Golgi apparatus (7) Cytoskeleton (8) smooth ER (9) mitochondria (10) vacuole (11) cytoplasm (12) lysosome (13) centrioles]]

In cell biology, the nucleus (pl.
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ligand (latin ligare = to bind) is a molecule that is able to bind to and form a complex with a biomolecule to serve a biological purpose. In a narrower sense, it is an effector molecule binding to a site on a target protein, by intermolecular forces such as ionic bonds,
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Neurotransmitters are chemicals that are used to relay, amplify and modulate signals between a neuron and another cell. According to the prevailing beliefs of the 1960s, a chemical can be classified as a neurotransmitter if it meets the following conditions:

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hormone (from Greek όρμή - "to set in motion") is a chemical messenger that carries a signal from one cell (or group of cells) to another. All multicellular organisms produce hormones (including plants - see phytohormone).
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chemical equilibrium is the state in which the chemical activities or concentrations of the reactants and products have no net change over time. Usually, this state results when the forward chemical process proceeds at the same rate as their reverse reaction.
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In chemistry, Law of Mass Action has two aspects: 1) the equilibrium aspect, concerning the composition of a reaction mixture at equilibrium and 2) the kinetic aspect concerning the rate equations for elementary reactions.
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dissociation constant is a specific type of equilibrium constant that measures the propensity of a larger object to separate (dissociate) reversibly into smaller components, as when a complex falls apart into its component molecules, or when a salt splits up into its component ions.
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In cell physiology, a secondary messenger system (also known as a second messenger system) is a method of cellular signalling where the signalling molecule does not enter the cell, but rather utilizes a cascade of events that transduces the signal into a cellular change.
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agonist is a substance that binds to a specific receptor and triggers a response in the cell. It mimics the action of an endogenous ligand (such as hormone or neurotransmitter) that binds to the same receptor.
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receptor antagonist is a drug that does not provoke a biological response itself upon binding to a receptor, but blocks or attenuates agonist-mediated responses. It may be competitive (or surmountable), i.e.
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X-ray crystallography is the science of determining the arrangement of atoms within a crystal from the manner in which a beam of X-rays is scattered from the electrons within the crystal.
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The action of drugs on the human body is called pharmacodynamics, and what the body does with the drug is called pharmacokinetics. The drugs that enter the human tend to stimulate certain receptors, ion channels, act on enzymes or transporter proteins.
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ligand (latin ligare = to bind) is a molecule that is able to bind to and form a complex with a biomolecule to serve a biological purpose. In a narrower sense, it is an effector molecule binding to a site on a target protein, by intermolecular forces such as ionic bonds,
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Peripheral membrane proteins are proteins that adhere only temporarily to the biological membrane with which they are associated. These molecules attach to integral membrane proteins, or penetrate the peripheral regions of the lipid bilayer.
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A hormone receptor is a receptor protein on the surface of a cell or in its interior that binds to a specific hormone. The hormone causes many changes to take place in the cell.
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A neurotransmitter receptor is a receptor protein on the surface of a cell that binds to a specific ligand, such as a neurotransmitter, receptor antagonist, biogenic amines, etc.
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Transmembrane receptors are integral membrane proteins, which reside and operate typically within a cell's plasma membrane, but also in the membranes of some subcellular compartments and organelles.
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lipid bilayer or bilayer lipid membrane (BLM) is a membrane or zone of a membrane composed of lipid molecules (usually phospholipids). The lipid bilayer is a critical component of all biological membranes, including cell membranes, and so is absolutely essential for all
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In biology, signal transduction refers to any process by which a cell converts one kind of signal or stimulus into another, most often involving ordered sequences of biochemical reactions inside the cell, that are carried out by enzymes, activated by second messengers resulting in
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ligand (latin ligare = to bind) is a molecule that is able to bind to and form a complex with a biomolecule to serve a biological purpose. In a narrower sense, it is an effector molecule binding to a site on a target protein, by intermolecular forces such as ionic bonds,
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metabotropic and ionotropic receptors. In contrast to the latter, metabotropic receptors do not form an ion channel pore; rather, they are indirectly linked with ion-channels on the plasma membrane of the cell through signal transduction mechanisms.
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G proteins, short for guanine nucleotide binding proteins, are a family of proteins involved in second messenger cascades. Their nomenclature originates from their ability to function as "molecular switches", alternating between an inactive guanosine diphosphate (GDP) and
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Enzymes are proteins that catalyze (i.e. accelerate) chemical reactions.[1] In enzymatic reactions, the molecules at the beginning of the process are called substrates, and the enzyme converts them into different molecules, the products.
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Ion channels are pore-forming proteins that help to establish and control the small voltage gradient across the plasma membrane of all living cells (see cell potential) by allowing the flow of ions down their electrochemical gradient.
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