| gamma aminobutyric acid receptor | <physiology> Ligand gated chloride ion channel forming receptor opened by gamma aminobutyric acid. Two distinct types: A and B. A receptor: One of a family of neurotransmitter receptors with fast intrinsic ion channels that includes the glycine receptor and the nicotinic acetylcholine receptor. Distinct from another major receptor family, the muscarininc acetylcholine receptor and rhodopsin, with no intrinsic ion channel. The A receptor is specifically blocked by bicuculline. It consists of two pairs of protein chains forming an A2B2 complex, the A chains bind benzodiazepine and the B chains bind GABA. The 4 subunits are thought to form a tight group with the chloride channel in the middle. There is considerable similarity between the amino acid sequences of the receptor subunits and those of the nicotinic acetylcholine receptor suggesting that both receptors are derived from some evolutionary ancestor. See: amino acid receptor superfamily. B receptor: Brain receptor (80 kD) for the inhibitory neurotransmitter gamma amino butyric acid. Differs from the A receptor both in agonist specificity (baclofen is a specific agonist) and its effects on cells. It modulates intracellular calcium levels through a Go mediated effect on N type calcium channels and also lowers intracellular cAMP levels by an effect on adenylyl cyclase, thereby reducing the secretion of catecholamines. (05 Jan 1998) |
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| GAP-1 receptor tyrosine kinase | <enzyme> Similar to rasGTPase-activating proteins; inhibits signaling activity of let-60; amino acid sequence given in first source Registry number: EC 2.7.1.- Synonym: gap-1 gene product, gap-1 protein (26 Jun 1999) |
| gene rearrangement, beta-chain T-cell antigen receptor | Ordered rearrangement of T-cell variable gene regions coding for the beta-chain of antigen receptors. (12 Dec 1998) |
| gene rearrangement, delta-chain T-cell antigen receptor | Ordered rearrangement of T-cell variable gene regions coding for the delta-chain of antigen receptors. (12 Dec 1998) |
| gene rearrangement, gamma-chain T-cell antigen receptor | Ordered rearrangement of T-cell variable gene regions coding for the gamma-chain of antigen receptors. (12 Dec 1998) |
| genes, T-cell receptor | DNA sequences, in cells of the t-lymphocyte lineage, that code for T-cell receptors. The tcr genes are formed by somatic rearrangement (see gene rearrangement, t-lymphocyte and its children) of germline gene segments, and resemble ig genes in their mechanisms of diversity generation and expression. (12 Dec 1998) |
| genes, T-cell receptor beta | DNA sequences encoding the beta chain of the T-cell receptor. The genomic organization of the tcr beta genes is essentially the same in all species and is similar to the organization of ig genes. (12 Dec 1998) |
| genes, T-cell receptor delta | DNA sequences encoding the delta chain of the T-cell receptor. The delta-chain locus is located entirely within the alpha-chain locus. (12 Dec 1998) |
| genes, T-cell receptor gamma | DNA sequences encoding the gamma chain of the T-cell receptor. The human gamma-chain locus is organised similarly to the tcr beta-chain locus. (12 Dec 1998) |
| receptor | 1. A molecular structure within a cell or on the surface characterised by selective binding of a specific substance and a specific physiologic effect that accompanies the binding, for example, cell surface receptors for peptide hormones, neurotransmitters, antigens, complement fragments and immunoglobulins and cytoplasmic receptors for steroid hormones. 2. A sensory nerve terminal that responds to stimuli of various kinds. (18 Nov 1997) |
| receptor aggregation | Chemically stimulated aggregation of cell surface receptors, which potentiates the action of the effector cell. (12 Dec 1998) |
| receptor agonist | A substance that mimics a specificneurotransmitter, is able to attach to that neurotransmitter's receptor and thereby produces the same action that theneurotransmitter usually produces. Drugs are often designed as receptor agonists to treat a variety of diseases and disorders whenthe original chemical substance is missing or depleted. (22 May 1997) |
| receptor-CD3 complex, antigen, T-cell | Molecule composed of the non-covalent association of the T-cell antigen receptor (receptors, antigen, T-cell) with the CD3 complex (antigens, CD3). This association is required for the surface expression and function of both components. The molecule consists of up to seven chains: either the alpha/beta or gamma/delta chains of the T-cell receptor, and four or five chains in the CD3 complex. (12 Dec 1998) |
| receptor, chemokine | A molecule that receives a chemokine and acts as a dock for a chemokine. Several chemokine receptors are essential co-receptors for HIV. (12 Dec 1998) |
| receptor downregulation | A phenomenon observed in many cells: following stimulation with a ligand the number of receptors for that ligand on the cell surface diminishes because internalisation exceeds replenishment. Often used very loosely, thus destroying the utility of the term. (18 Nov 1997) |