Cytokine inhibition: control of receptor appetite

Article Abstract:

Cytokines are regulatory proteins which are involved in many aspects of the body's immune response. This family or group of proteins includes cytokines that are produced by and affect many cells of the immune system, as well as other cells. Interleukin-1 (IL-1) is a cytokine involved in the body's response to infection, tissue injury, inflammation, and autoimmunity. The gene for the cellular receptor for one of the cytokines, known as interleukin-1, has recently been isolated and characterized. An antagonist has also been found which binds with the IL-1 receptor, and therefore inhibits IL-1 function. Substances that inhibit IL-1 activity have been identified from a number of sources including the urine and serum of patients who have had a high fever, and from monocytes (a type of white blood cell that produces IL-1) that are malignant or have been infected with a disease-causing virus. The activities of the IL-1 receptor antagonist (IRAP) include the inhibition of the binding of certain white blood cells to endothelial cells (cells that line the blood vessels) and the proliferation of thymocytes (lymphocytes of the thymus gland); these activities have been observed in the test tube. In the body, IRAP suppresses the release of corticosterone (a hormone produced by the adrenal gland), but does not inhibit the infiltration of neutrophils (a type of white blood cell) in an inflammatory response. IRAP selectively binds with certain cells and tissues; this indicates that there is more than one type of receptor for IL-1. Thus, there may be separate mechanisms for controlling the many activities of IL-1. An understanding of this is important before IL-1 antagonists such as IRAP can be used as therapeutic agents for various inflammatory diseases. (Consumer Summary produced by Reliance Medical Information, Inc.)

Interleukins, Growth factor receptors, Interleukin-1

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Receptor kinships revealed

Article Abstract:

Inositol 1,4,5-triphosphate - InsP(sub.3) - is a substance with important role in cell metabolism. Scientists have discovered that it acts as a messenger in certain biochemical processes occurring within body cells. Under specific conditions InsP(sub.3) is released into the fluid inside the cell and it is then either metabolized further or it communicates with receptors involved in release of calcium within the cell. Receptors are specialized sites that attract and bind to specific substances; when the two materials bind, certain biochemical processes may be initiated. A protein that binds to InsP(sub.3) has been isolated from brain tissue. Analysis of the structure and characteristics of this InsP(sub.3)-binding protein suggests that the same molecule influences both binding of InsP(sub.3) and release of calcium from the cell structure called the endoplasmic reticulum, a network of membranes responsible for manufacture of proteins and fats. The receptor that binds InsP(sub.3) is strikingly similar in structure to another type of receptor called the ryanodine receptor, involved in calcium metabolism within skeletal muscle. The similarity of the two receptors was a major discovery in cell metabolism research.

Calcium metabolism, Cell metabolism, Inositol

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A new pattern for helix-turn-helix recognition revealed by the PU.1 ETS-domain-DNA complex

Article Abstract:

The ETS domain of the PU.1 transcription factor bound to DNA contains four conserved amino acids that are essential for DNA recognition and binding. The DNA recognition site consists of two arginine residues in the major groove, one lysine residue in the wing, and one lysine in the turn of the helix-turn-helix motif. The crystal structure of the PU.1 ETS domain-DNA complex is similar to the alpha + beta (winged) helix-turn-helix proteins. The PU.1 ETS domain complexes with a ten-base-pair region of duplex DNA to form a curve of eight degrees.

DNA binding proteins

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