| receptors, polymeric immunoglobulin | Specialised fc receptors (receptors, fc) for polymeric immunoglobulins, which mediate transcytosis of polymeric IgA and IgM into external secretions. They are found on the surfaces of epithelial cells and hepatocytes. After binding to IgA, the receptor-ligand complex undergoes endocytosis, transport by vesicle, and secretion into the lumen by exocytosis. Before release, the part of the receptor (secretory component) that is bound to IgA is proteolytically cleaved from its transmembrane tail. (12 Dec 1998) |
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| receptors, presynaptic | Neurotransmitter receptors located on or near presynaptic terminals or varicosities. Presynaptic receptors which bind transmitter molecules released by the terminal itself are termed autoreceptors. (12 Dec 1998) |
| receptors, progesterone | Specific proteins found in or on cells of progesterone target tissues that specifically combine with progesterone. The cytosol progesterone-receptor complex then associates with the nucleic acids to initiate protein synthesis. There are two kinds of progesterone receptors, a and b. Both are induced by oestrogen and have short half-lives. (12 Dec 1998) |
| receptors, prolactin | Labile proteins on or in prolactin-sensitive cells that bind prolactin initiating the cells' physiological response to that hormone. Mammary casein synthesis is one of the responses. The receptors are also found in placenta, liver, testes, kidneys, ovaries, and other organs and bind and respond to certain other hormones and their analogs and antagonists. This receptor is related to the growth hormone receptor. (12 Dec 1998) |
| receptors, prostaglandin | Cell surface receptors that bind prostaglandins with high affinity and trigger intracellular changes which influence the behaviour of cells. Prostaglandin receptor subtypes have been tentatively named according to their relative affinities for the endogenous prostaglandins. They include those which prefer prostaglandin d2 (dp receptors), prostaglandin e2 (ep1, ep2, and ep3 receptors), prostaglandin f2-alpha (fp receptors), and prostacyclin (ip receptors). (12 Dec 1998) |
| receptors, prostaglandin e | Cell surface receptors which bind prostaglandins with a high affinity and trigger intracellular changes which influence the behaviour of cells. Prostaglandin e receptors prefer prostaglandin e2 to other endogenous prostaglandins. They are subdivided into ep1, ep2, and ep3 types based on their effects and their pharmacology. (12 Dec 1998) |
| receptors, purinergic | Cell surface proteins that bind purines with high affinity and trigger intracellular changes which influence the behaviour of cells. The best characterised classes of purinergic receptors in mammals are the p1 receptors, which prefer adenosine, and the p2 receptors, which prefer ATP or ADP. (12 Dec 1998) |
| receptors, purinergic p1 | A class of cell surface receptors that prefers adenosine to other endogenous purines. Purinergic p1 receptors are widespread in the body including the cardiovascular, respiratory, immune, and nervous systems. There are at least two pharmacologically distinguishable types (a1 and a2, or ri and ra). The methylxanthines, e.g., caffeine, bind to these receptors, but also have other unrelated effects. (12 Dec 1998) |
| receptors, purinergic p2 | A class of cell surface receptors for purines that prefer ATP or ADP over adenosine. P2 purinergic receptors are widespread in the periphery and in the central and peripheral nervous system. Subtypes have been proposed, usually designated p2 x, y, z, and t. P2x receptors may mediate fast synaptic transmission by ATP. The ADP-preferring p2t receptors in platelets stimulate aggregation. (12 Dec 1998) |
| receptors, retinoic acid | Proteins in the nucleus or cytoplasm that specifically bind retinoic acid or retinol and trigger changes in the behaviour of cells. Retinoic acid receptors, like steroid receptors, are ligand-activated transcription regulators. Several types have been recognised. (12 Dec 1998) |
| receptors, sensory | Specialised neurons or parts of neurons which transduce sensory information and relay it centrally. Included are receptors for stimuli outside the body (exteroceptors) as well as receptors for stimuli from within the body itself (interoceptors and proprioceptors). Sensory receptors may include accessory structures which condition (e.g., filter) the input received by the receptor neurons themselves. (12 Dec 1998) |
| receptors, serotonin | Cell-surface proteins that bind serotonin and trigger intracellular changes which influence the behaviour of cells. Several types of serotonin receptors have been recognised which differ in their pharmacology, molecular biology, and mode of action. (12 Dec 1998) |
| receptors, sigma | A class of cell surface receptors recognised by its pharmacological profile. Sigma receptors were originally considered to be opioid receptors because they bind certain synthetic opioids. However they also interact with a variety of other psychoactive drugs, and their endogenous ligand is not known (although they can react to certain endogenous steroids). Sigma receptors are found in the immune, endocrine, and nervous systems, and in some peripheral tissues. (12 Dec 1998) |
| receptors, somatomedin | Cell surface receptors that bind somatomedins and trigger intracellular changes which influence the behaviour of cells. Studies have disclosed two types of receptors for this family of peptide hormones. The type I receptor is homologous to the insulin receptor and has tyrosine kinase activity. The type II receptor is identical to the mannose-6-phosphate receptor which is important in trafficking of lysosomal enzymes. (12 Dec 1998) |
| receptors, somatostatin | Cell surface proteins that bind somatostatin and trigger intracellular changes which influence the behaviour of cells. Somatostatin is a hypothalamic hormone, a pancreatic hormone, and a central and peripheral neurotransmitter. Activated somatostatin receptors on pituitary cells inhibit the release of growth hormone; those on endocrine and gastrointestinal cells regulate the absorption and utilization of nutrients; and those on neurons mediate somatostatin's role as a neurotransmitter. (12 Dec 1998) |