Neurturin (NTN) is a recently identified homologue of glial-cell-line-derived neurotrophic factor (GDNF). Both factors promote the survival of a variety of neurons, and GDNF is required for the development of the enteric nervous system and kidney. GDNF signals through a receptor complex consisting of the receptor tyrosine kinase Ret and a glycosyl-phosphatidylinositol (GPI)-linked receptor termed GDNFR-alpha. Here we report the cloning of a new GPI-linked receptor termed NTNR-alpha that is homologous with GDNFR-alpha and is widely expressed in the nervous system and other tissues. By using microinjection to introduce expression plasmids into neurons, we show that coexpression of NTNR-alpha with Ret confers a survival response to neurturin but not GDNF, and that coexpression of GDNFR-alpha with Ret confers a survival response to GDNF but not neurturin. Our findings indicate that GDNF and neurturin promote neuronal survival by signalling through similar multicomponent receptors that consist of a common receptor tyrosine kinase and a member of a GPI-linked family of receptors that determines ligand specificity.

A partial cDNA encoding most of the third intracellular loop of the mouse a, d -adrenergic receptor subtype was amplified from hippocampus by reverse transcription-polymerase chain reaction (RT-PCR) using degenerate oligodeoxynucleotide primers . This DNA fragment was used as a probe to isolate an a, d -adrenergic receptor cDNA from a mouse brain cDNA library . The deduced amino acid sequence encodes a potential protein of 562 amino acids, and northern hybridization of poly(A)+ RNA isolated from mouse brain detected a single 3 .0-kb transcript . Partial cDNA fragments of the alband a, a -adrenergic receptor subtypes were also amplified from mouse brain and sequenced . Analysis of the mRNA expression by RT-PCR indicated that the a,-adrenergic receptors are widely distributed in mouse tissues . The a,d subtype is expressed in brain areas such as hippocampus, striatum, and brainstem and also in many extracerebral tissues, such as lung, liver, heart, kidney, and spleen . The a,a subtype is also expressed in many tissues, whereas the alb subtype has a more restricted expression, with high levels in striatum, brainstem, and diencephalus . Key Words : a,d -Adrenergic receptor-Mouse-cDNA cloning-Tissue distribution -a,-Adrenergic receptor subtypes . J. Neurochem . 65, 2387Neurochem . 65, -2392Neurochem . 65, (1995 .The adrenergic receptors are members of a large family of membrane proteins that are coupled to guanine nucleotide-binding proteins (G proteins) . They are currently divided into three types (a,, a2 , and ß), each having several receptor members (Lomasney et al., 1991a ;Bylund, 1992) . Radioligand binding data with the a,-adrenergic receptor agonists oxymetazoline and methoxamine and the antagonists WB4101 and phentolamine indicated the existence of two a,-adrenergic receptor subtypes in rat cerebral cortex, which were named a1A and a,B (Battaglia et al., 1983 ; Morrow and Creese, 1986;Han et al., 1987) .Several cDNAs and genes encoding a t-adrenergic receptor subtypes from various sources, and initially named a]A/alD, a,B , and a lc , have been isolated by

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The interactions of nicotinic acetylcholine receptor (nAChR) with two monoclonal antibodies (mAb370A and mAb371A) which block the agonist-induced ion flux into nicotinic acetylcholine receptor vesicles [Donnelly, D., Mihovilovic, M., Gonzalez-Ros, J. M., Ferragut, J. A., Richman, D., & Martinez-Carrion, M. (1984) Proc. Natl. Acad. Sci. U.S.A. 81, 7999] have been studied by a combination of immunochemical and spectroscopic techniques. Both mAbs are specific for the alpha-subunit of the receptor, but they recognize different epitopes. We have detected specific binding of the mAb370A to a synthetic peptide corresponding to residues alpha 187-205, a sequence known to contain the alpha-bungarotoxin binding site. By contrast, mAb371A seems to recognize an epitope which is largely silent after proteolytic digestion of the subunit. Binding of mAb370A to the receptor is inhibited by cholinergic agonist and alpha-neurotoxins but not by competitive antagonists or local anesthetics. By contrast, none of these ligands interferes with binding of mAb371A. The spectroscopic properties of the fluorescent probe ethidium have been used to investigate the effect of the mAbs on the interaction of the agonist carbamylcholine with nAChR in membranes. mAb370A, but not mAb371A, blocks both the agonist-induced increase in the fluorescence intensity of receptor-bound ethidium and the agonist-induced increase in the polarization value of the probe. In addition, measurements of ethidium binding followed by stopped-flow techniques showed that mAb370A, but not mAb371A, blocked the agonist-induced association of the probe to nAChR membranes.(ABSTRACT TRUNCATED AT 250 WORDS)

Complementary DNAs that encode two forms of the chicken y-aminobutyric acid type A (GABA,) receptor p2 subunit have been isolated. These polypeptides differ by the presence (p2L) or absence (p2S) of 17 amino acids, which contain a possible target for phosphorylation by protein kinase C, in the large intracellular loop between the third and fourth membrane-spanning domains. The extra sequence in the chicken p2L subunit is not found in previously published GABA, receptor 02-subunit sequences. Analysis of genomic DNA has revealed that the two p2-subunit mRNAs arise by alternative splicing of a novel 51 -nucleotide exon. Although the two p2-subunit transcripts appear to be present in 1 -day-old chick brain at similar steady-state levels, we have been unable to detect an mRNA for the long form of the p2 subunit in either the bovine or the rat. Because the various GABA, receptor genes are thought to have arisen by duplication of a common ancestor, our data, taken together with that on the 7 2 subunit, which occurs in two forms that arise by alternative splicing of a 24-nucleotide exon, suggest that the coding region of the primordial gene or one of its very early descendants contained 10 exons, not nine as previously thought. Key Words: Alternative splicing-7-Aminobutyric acid, receptor-cDNA cloning-Chicken p2 subunit -Evolution-Protein kinase C. J. Neurochem. 62, 10-1 6 (1 994).