G protein-coupled receptors

DEFINITION:

G protein-linked (or coupled) receptors mediate the cellular responses to an enormous diversity of signaling molecules, including hormones, neurotransmitters, and local mediators, which are as varied in structure as they are in function: the list includes proteins and small peptides, as well as amino acid and fatty acid derivatives.

Despite the chemical and functional diversity of the signaling molecules that bind to them, all of the G protein-linked receptors whose amino acid sequences are known from DNA sequencing studies have a similar structure and are almost certainly evolutionarily related. They consist of a single polypeptide chain that threads back and forth across the lipid bilayer seven times.

The members of this receptor family have conserved not only their amino acid sequence but also their functional relationship to G proteins by means of which they broadcast into the interior of the cell the message that an extracellular ligand is present.

GPCR

DEFINITION:

G-protein-coupled receptor.

mediated

DEFINITION:

Accomplished by the aid of an intervening medium.

binding

DEFINITION:

1. Wrapping with a binder or bandage.

2. Forming a weak, reversible chemical bond, e.g., antigen to antibody or hormone to receptor.

affinity

DEFINITION:

1. A special attraction for a specific element, organ, or structure.

2. Chemical affinity.

3. In immunology, a thermodynamic expression of the strength of interaction between a single antigen-binding site and a single antigenic determinant (and thus of the stereochemical compatibility between them), most accurately applied to interactions among simple, uniform antigenic determinants such as haptens. Expressed as the association constant (K liters mole^-1), which, owing to the heterogeneity of affinities in a population of antibody molecules of a given specificity, actually represents an average value (mean intrinsic association constant).

phosphorylated

DEFINITION:

See phosphorylation.

GPCR

DEFINITION:

G-protein-coupled receptor.

internalized

DEFINITION:

Describing the mental process whereby certain attributes, attitudes, or standards of others are unconsciously taken as one's own.

receptor

DEFINITION:

1. A molecular structure within a cell or on the surface characterized by (1) selective binding of a specific substance and (2) a specific physiologic effect that accompanies the binding, e.g., membrane receptors for peptide hormones, neurotransmitters, antigens, complement fragments, and immunoglobulins and nuclear receptors for steroid hormones.

2. A sensory nerve terminal that responds to stimuli of various kinds; classified in various ways including by the type of stimulus and by the location in the body.

V2 receptor - The structure to which the antidiuretic hormone, arginine vasopressin binds.

plasma membrane

DEFINITION:

The structure enveloping a cell, enclosing the cytoplasm, and forming a selective permeability barrier; it consists of lipids, proteins, and some carbohydrates, the lipids thought to form a bilayer in which integral proteins are embedded to varying degrees.

vasopressin receptor

DEFINITION:

A molecular structure to which the hormone, vasopressin, binds. See also receptor .

mutation

DEFINITION:

1. A change in form, quality, or some other characteristic.

2. In genetics, a permanent transmissible change in the genetic material, usually in a single gene.

frameshift mutation - A mutation resulting from an addition or subtraction that is not an exact multiple of 3 base pairs in a coding sequence. From the point of mutation onwards, base triplets (codons) are read out of phase; the reading frame of the gene is changed, and a completely different set of amino acids is made into protein.

loss-of-function mutation - Impairment of the function of a gene caused by mutation.

missense mutation - A mutation that changes a codon so that it codes for a different amino acid.

nonsense mutation - A mutation in which one of the three terminator codons in the mRNA (UAG, amber; UAA, ochre; UGA, umber or opal), used to signal the end of a polypeptide, appears in the middle of a genetic message, causes premature termination of transcription, and releases incomplete, generally nonfunctional polypeptides from the ribosome.

point mutation - A mutation resulting from a change in a single base pair in the DNA molecule, caused by the substitution of one nucleotide for another.

receptor

DEFINITION:

1. A molecular structure within a cell or on the surface characterized by (1) selective binding of a specific substance and (2) a specific physiologic effect that accompanies the binding, e.g., membrane receptors for peptide hormones, neurotransmitters, antigens, complement fragments, and immunoglobulins and nuclear receptors for steroid hormones.

2. A sensory nerve terminal that responds to stimuli of various kinds; classified in various ways including by the type of stimulus and by the location in the body.

V2 receptor - The structure to which the antidiuretic hormone, arginine vasopressin binds.

phosphorylated

DEFINITION:

See phosphorylation.

sequestered

DEFINITION:

1. Detached or separated abnormally (i.e., a small portion from the whole).

2. Isolated, e.g., a constituent of a chemical system by chelation or other means.

intracellular vesicles

DEFINITION:

Vesicles within a cell.

agonist

DEFINITION:

1. In anatomy, a prime mover.

2. In pharmacology, a drug that has affinity for and stimulateS physiologic activity at cell receptors normally stimulated by naturally occurring substances.

receptor

DEFINITION:

1. A molecular structure within a cell or on the surface characterized by (1) selective binding of a specific substance and (2) a specific physiologic effect that accompanies the binding, e.g., membrane receptors for peptide hormones, neurotransmitters, antigens, complement fragments, and immunoglobulins and nuclear receptors for steroid hormones.

2. A sensory nerve terminal that responds to stimuli of various kinds; classified in various ways including by the type of stimulus and by the location in the body.

V2 receptor - The structure to which the antidiuretic hormone, arginine vasopressin binds.

promote

DEFINITION:

1. To advance in station, rank, or honor.

2. To contribute to the growth or prosperity of; further.

3. Launch.

affinity

DEFINITION:

1. A special attraction for a specific element, organ, or structure.

2. Chemical affinity.

3. In immunology, a thermodynamic expression of the strength of interaction between a single antigen-binding site and a single antigenic determinant (and thus of the stereochemical compatibility between them), most accurately applied to interactions among simple, uniform antigenic determinants such as haptens. Expressed as the association constant (K liters mole^-1), which, owing to the heterogeneity of affinities in a population of antibody molecules of a given specificity, actually represents an average value (mean intrinsic association constant).

receptor

DEFINITION:

1. A molecular structure within a cell or on the surface characterized by (1) selective binding of a specific substance and (2) a specific physiologic effect that accompanies the binding, e.g., membrane receptors for peptide hormones, neurotransmitters, antigens, complement fragments, and immunoglobulins and nuclear receptors for steroid hormones.

2. A sensory nerve terminal that responds to stimuli of various kinds; classified in various ways including by the type of stimulus and by the location in the body.

V2 receptor - The structure to which the antidiuretic hormone, arginine vasopressin binds.

plasma membrane

DEFINITION:

The structure enveloping a cell, enclosing the cytoplasm, and forming a selective permeability barrier; it consists of lipids, proteins, and some carbohydrates, the lipids thought to form a bilayer in which integral proteins are embedded to varying degrees.

localization

DEFINITION:

1. The determination of the site or place of any process or lesion.
2. Restriction to a circumscribed or limited area.
3. Prelocalization.

etiology

DEFINITION:

The study or theory of the factors that cause disease and the method of their introduction to the host; the causes or origin of a disease or disorder.

pharmacological

DEFINITION:

Pertaining to pharmacology or to the properties and reactions of drugs.

therapeutically

DEFINITION:

1. Pertaining to therapeutics or to therapy.
2. Having a curative characteristic.

permission

DEFINITION:

Formal consent; authorization.