A novel orphan G protein-coupled receptor primarily expressed in the brain is localized on human chromosomal band 2q21.

A human hippocampus cDNA library was screened with a probe obtained from degenerate RT-PCR aimed at P2Y-homologous sequences. A positive clone, designated hip4, was identified containing an open reading frame of 1,020 bp that had been previously detected in a published genomic clone called R12. Subsequent screening of a human fetal brain cDNA library yielded a splice variant with a 1,104-bp open reading frame, which was named fb1. Both variants display the seven-transmembrane topology that is typical for G protein-coupled receptors. Probing a human multitissue northern blot revealed two brain-specific transcripts of 2.3 and 6.3 kb, respectively. Northern blot analyses with specific fragments confirmed that the two transcripts are generated by alternative polyadenylation yielding two different 3' untranslated regions. A genomic clone from the corresponding gene was isolated and mapped to human chromosomal band 2q21 by fluorescence in situ hybridization.

Adenine dinucleotides: a novel class of signalling molecules.

1. Adenine dinucleotides (Ap3A, Ap4A, Ap5A, Ap6A) are stored in secretory granules of thrombocytes, chromaffin cells and neuronal cells. After release into the extracellular space, the dinucleotides exhibit divergent biological effects on a variety of target cells and organs. The dinucleotides are metabolized by soluble enzymes in the blood plasma as well as by membrane-bound ectoenzymes of endothelial cells, smooth muscle cells, and other cell types. 2. The enzymatic cleavage of the dinucleotides plays a dual role for their biological function: (a) termination of the signal; and (b) generation of purinergically active products such as ATP, ADP and finally adenosine. In contrast to ATP the dinucleotides are long-lived purine nucleotides in the blood. 3. The potential role of the dinucleotides as signalling molecules has been demonstrated in several systems. The adenosine polyphosphates have autocrine function for thrombocytes. Ap3A at low concentration reversibly activates isolated platelets. The mechanism of activation has been elucidated by showing a continuous cleavage of Ap3A, leading to the formation of ADP which is a known agonist of the P2T receptor on thrombocytes. Ap4A and other dinucleotides act as antagonists and inhibit platelet activation. 4. The vasotone of perfused isolated arteries as well as of resistance vessels in the beating heart is differentially influenced by adenine dinucleotides. While Ap3A and Ap4A exhibit relaxing effects at micromolar concentrations, Ap5A and Ap6A elicit vasoconstriction in these vessels. 5. In rat kidney mesangial cells adenine dinucleotides efficiently promote growth. Stimulation of DNA synthesis by various growth factors is enhanced synergistically. ApnA significantly increase the expression of the early growth response gene Egr-1. 6. The specificity and, in some tissues, the uniqueness of effects evoked by dinucleotides may be mediated by genuine dinucleotide receptors (P4) or by specialized P2 receptors (P2D).

Two distinct outer membrane serotype subcomplexes of Neisseria meningitidis serogroup A.

A 350-kilodalton serotype outer membrane complex containing the class 1, 3, and 4 outer membrane proteins was isolated from serogroup A Neisseria meningitidis. Partial denaturation yielded two serotype subcomplexes containing the class 3 and 1 proteins (85 kilodaltons) and the class 3 and 4 proteins (94 kilodaltons), respectively.