Cloning and expression of a rat neuromedin K receptor cDNA

Functional cDNA clones for rat neuromedin K receptor were isolated from a rat brain cDNA library by cross-hybridization with the bovine substance K receptor cDNA. Injection of the mRNA synthesized in vitro from the cloned cDNA into Xenopus oocytes elicited electrophysiological responses to tachykinins, with the most potent sensitivity being to neuromedin K. Ligand-binding displacement in membranes of mammalian COS cells transfected with the cDNA indicated the rank order of affinity of the receptor to tachykinins: neuromedin K greater than substance K greater than substance P. The hybridization analysis showed that the neuromedin K receptor mRNA is expressed in both the brain and the peripheral tissues at different levels. The rat neuromedin K receptor consists of 452 amino acid residues and belongs to the family of G protein-coupled receptors, which are though to have seven transmembrane domains. The sequence comparison of the rat neuromedin K, substance P, and substance K receptors revealed that these receptors are highly conserved in the seven transmembrane domains and the cytoplasmic sides of the receptors. They also show some structural characteristics, including the common presence of histidine residues in transmembrane segments V and VI and the difference in the numbers and distributions of serine and threonine residues as possible phosphorylation sites in the cytoplasmic regions. This paper thus presents the first comprehensive analysis of the molecular nature of the multiple peptide receptors that exhibit similar but pharmacologically distinguishable activities.     

Molecular characterization of rat substance K receptor and its mRNAs

The nucleotide sequence and the amino acid sequence for rat substance K receptor were deduced by molecular cloning and sequence analysis of its cDNAs. The rat substance K receptor consists of 390 amino acid residues and belongs to the family of G protein-coupled receptors. The comparison of the amino acid sequences of the rat and bovine substance K receptors indicated that they are highly homologous in the regions covering seven putative transmembrane domains, and this similarity is particularly remarkable in the transmembrane segments III and VII and their surrounding regions. RNA blot hybridization analysis showed that the rat substance K receptor is encoded by two species of mRNAs which differ in the lengths of the extreme 5' sequence of the 5'-untranslated regions. This analysis also indicated that the substance K receptor mRNAs are expressed in the gastrointestinal tract. Interestingly, no appreciable substance K receptor mRNAs were detected in poly(A)+ RNAs isolated from the brain and spinal cord, even though these tissues are known to not only contain substance K but also express the mRNA encoding the substance K precursor.     

Molecular cloning of the murine substance K and substance P receptor genes.

The peptides substance K and substance P evoke a variety of biological responses via distinct, guanosine-nucleotide-binding-regulatory-protein-coupled receptors. We have screened a murine genomic cosmid library using oligonucleotide probes and have isolated, cloned and characterized the substance K receptor and the substance P receptor genes. The coding portion of the substance K receptor gene consists of five exons distributed over 13 kbp. The substance P receptor gene is considerably larger than that of substance K (more than 30 kbp), however, the boundaries of the four exons that have been characterized in the substance P receptor gene correspond exactly to the homologous exons in the substance K receptor gene. To verify the identity of the isolated genes, we have cloned the corresponding cDNA by means of the polymerase chain reaction and we have expressed these cDNA species in Xenopus laevis oocytes. The ligand binding characteristics determined in this system pharmacologically confirm the identity of the two receptors. The deduced amino acid sequence of the mouse substance K receptor is 94% identical to the rat sequence and 85% identical to the bovine and human sequences. The mouse substance P receptor amino acid sequence is 99% identical to the rat sequence. The cloning of the murine substance K and substance P receptor genes should contribute substantially to the generation of in vivo models for the detailed analysis of the functional significance of these receptors.     

Cloning and sequencing of human FSH receptor cDNA.

We have isolated and sequenced a cDNA encoding the follicle stimulating hormone (FSH) receptor. The deduced amino acid sequence (678 residues) containing seven putative transmembrane segments which displays sequence similarity to G protein-coupled receptors. The receptor consists of 359 residue extracellular domain which contains four N-linked glycosylation sites. While the protein is 89% identical overall with the previously cloned rat FSH receptor, the most highly conserved regions are the putative transmembrane segments (95% similarity).     

The primary structure and gene organization of human substance P and neuromedin K receptors.

The gene organization and amino acid sequences of human substance P and neuromedin K receptors (SPR and NKR, respectively) are reported on the basis of molecular cloning and sequence determination of genomic DNA containing the respective receptor gene. The human SPR and NKR genes, unlike many other genes for G-protein-coupled receptors, (G protein, guanyl-nucleotide-binding-regulatory protein), contain introns which interrupt the protein-coding regions into 5 exons. The human SPR and NKR genes extend over 60 kb and 45 kb, respectively and are considerably larger than the human substance K receptor (SKR) gene consisting of 12 kb. All 4 introns, however, are located at equivalent positions of the three tachykinin receptor genes, suggesting that they evolved from a common ancestral gene. Human SPR and NKR consist of 407 and 465 amino acid residues, respectively, each possessing structural features characteristic of the members of G-protein-coupled receptors. The human and rat receptors show a common tendency of distinctly segmented sequence conservation and divergence among the three receptors, and the observed sequence conservation and divergence would contribute to the emergence of similar but distinct properties of the three receptors. Furthermore, the amino acid sequences and the gene sizes are more closely related between SPR and NKR than between SKR and NKR, suggesting that the SPR gene evolved from the primordial NKR gene after a gene duplication to form the NKR and SKR genes.     

Cloning and sequencing of human LH/hCG receptor cDNA

We have isolated and sequenced a cDNA encoding the human luteinizing hormone--choriogonadotropin (LH/hCG) receptor. The deduced amino acid sequence (699 residues) containing seven putative transmembrane segments displays sequence similarity to G protein-coupled receptors. The receptor consists of 335 residue extracellular domain which contains six N-linked glycosylation sites. While the protein is 85 and 87% identical overall with the previously cloned rat and porcine LH/hCG receptor respectively, the most highly conserved regions are the putative transmembrane segments (91 and 94% similarity, respectively).     

Cloning of a cDNA encoding a novel putative G-protein-coupled receptor expressed in specific rat brain regions.

A cDNA clone encoding a novel putative G-protein-coupled receptor was isolated from a rat brain cDNA library using a PCR-amplified cDNA fragment as a hybridization probe. The 3,615-bp-long nucleotide sequence predicts a single open reading frame of 1,173 bp coding for 391 amino acids, giving a calculated molecular weight of 42.75 kD. The amino acid sequence shares features common to many other receptors, including the seven membrane-spanning hydrophobic regions and putative asparagine-linked glycosylation and phosphorylation sites. Northern blot analysis reveals that a corresponding approximately 3.7-kb mRNA is expressed in specific brain regions such as hypothalamus, cortex, hippocampus, and thalamus but not in other organs analyzed. Although the ligand for this receptor has not yet been identified, it shares some similarities with the vascular type-1 angiotensin II receptor, the vasoactive intestinal peptide (VIP) receptor, and the chemotactic receptors for human C5a anaphylatoxin and the formyl peptide fMet-Leu-Phe.     

Cloning and expression of the rat prolactin receptor, a member of the growth hormone/prolactin receptor gene family

The primary structure of the rat liver prolactin receptor has been deduced from a single complementary DNA clone. The sequence begins with a putative 19 amino acid signal peptide followed by the 291 amino acid receptor that includes a single 24 amino acid transmembrane segment. In spite of the fact that the prolactin receptor has a much shorter cytoplasmic region than the growth hormone receptor, there is strong localized sequence identity between these two receptors in both the extracellular and cytoplasmic domains, suggesting that the two receptors originated from a common ancestor.     

Leukemia inhibitory factor receptor is structurally related to the IL-6 signal transducer, gp130.

Leukemia inhibitory factor (LIF) is a cytokine with a broad range of activities that in many cases parallel those of interleukin-6 (IL-6) although LIF and IL-6 appear to be structurally unrelated. A cDNA clone encoding the human LIF receptor was isolated by expression screening of a human placental cDNA library. The LIF receptor is related to the gp130 'signal-transducing' component of the IL-6 receptor and to the G-CSF receptor, with the transmembrane and cytoplasmic regions of the LIF receptor and gp130 being most closely related. This relationship suggests a common signal transduction pathway for the two receptors and may help to explain similar biological effects of the two ligands. Murine cDNAs encoding soluble LIF receptors were isolated by cross-hybridization and share 70% amino acid sequence identity to the human sequence.     

A rat beta-interferon-induced mRNA: sequence characterization.

Polymerase chain reaction amplification of a cDNA derived from rat aortic smooth muscle cells, using sequences from conserved regions of the intramembrane domains of adrenergic receptors as primers, yielded the clone, rat8. This clone possesses a high degree of sequence similarity to a series of human interferon (IFN)-inducible genes. The rat8 sequence is 70% similar to that derived from the human alpha-IFN-induced gene, 9-27; there is 66% similarity between the deduced amino acid sequences encoded by the rat and the human genes. The rat homologue hybridizes with many bands in Southern analysis of rat DNA, suggesting that it is a member of a large multigene family.     

Purification, cloning, and expression of the prolactin receptor

The rat liver prolactin receptor has been purified to homogeneity, and partial amino acid sequences have been obtained. The structure of the receptor has been deduced from a single complementary DNA clone. The mature protein of 291 amino acids has a relatively long extracellular region, a single transmembrane segment, and a short (57 amino acids) cytoplasmic domain. With the rat cDNA used as a probe, the prolactin receptor in rabbit mammary gland and human hepatoma cells has also been isolated. These tissues contain a second, longer form of the receptor (592 and 598 amino acids, respectively). Both the short and long forms of the prolactin receptor show regions of strong sequence identity with the human and rabbit growth hormone receptors, suggesting that the prolactin and growth hormone receptors originate from a common ancestor.     

A cDNA presumptively coding for the alpha subunit of the receptor with high affinity for immunoglobulin E

Rat mast cells and a neoplastic analogue such as rat basophilic leukemia (RBL) cells have receptors that have exceptionally high affinity for immunoglobulin E (IgE). When aggregated, these receptors induce cellular degranulation. The alpha chain of the receptor contains the binding site for IgE; the function(s) of the noncovalently associated beta and gamma chains is (are) still undefined. Using a cDNA library constructed from the mRNA of RBL cells, we have isolated a cDNA clone whose sequence predicts a putative 23-residue signal peptide, followed by a sequence that accurately predicts the amino acid composition, the peptide molecular weight, and six peptide sequences (encompassing 59 residues or 26% of the total number) determined for the alpha chain by direct analysis. These findings provide strong evidence that the cDNA codes for the alpha chain, even though expression has not been unambiguously achieved. The sequence suggests that the alpha chain contains a 180-residue extracellular portion with two homologous domains of approximately 35 residues, a 20-residue transmembrane segment containing an aspartic acid, and a 27-residue cytoplasmic portion containing 9 basic amino acids. The sequence shows no homology with the low-affinity receptor for IgE from lymphocytes but over 30% homology with an Fc gamma receptor.     

Molecular cloning and sequencing of a cDNA encoding a human alpha 1A adrenergic receptor.

DNA from a rat hippocampus cDNA library and sets of highly degenerate oligonucleotide primers directed toward conserved regions of previously cloned G-protein receptors were used in the polymerase chain reaction to selectively amplify and clone new members of this gene family. A human hippocampus cDNA library was screened with a 610 base pair fragment generated by PCR and a cDNA clone, H318/3, was isolated. The deduced amino acid sequence of this clone encoded a protein of 501 amino acids that showed strong sequence homology to previously cloned G-protein receptors. Nucleotide sequence analysis revealed clone H318/3 was 78% homologous to a rat alpha 1A adrenergic receptor with homology being 95% when comparisons were made in the region that lies between the first to the seventh transmembrane domains. Based on this high degree of sequence homology, we conclude that clone H318/3 represents a cDNA for a human alpha 1A adrenergic receptor.     

Molecular cloning and sequence analysis of cDNA encoding delta 4-3-ketosteroid 5 beta-reductase of rat liver.

A cDNA clone encoding delta 4-3-ketosteroid 5 beta-reductase was isolated from rat liver cDNA libraries using antibodies specific for the enzyme and oligonucleotides as probes. The cDNA contained 981-base pair open reading frame encoding 327 amino acid residues (Mr 37,376) and an unusually long 3'-untranslated region rich in AT sequence in the total length of 3189 base pairs. The predicted amino acid sequence contains the sequences similar to the putative NADPH- and steroid-binding regions.     

Structure and functional expression of a cloned Xenopus thyroid hormone receptor.

A clone corresponding to a thyroid hormone receptor was isolated from a Xenopus laevis cDNA library prepared from folliculated oocytes. The cDNA encodes a protein of 418 amino acid residues with a domain structure, including a putative DNA binding region with two zinc fingers, similar to other members of the v-erbA-related superfamily of receptors. The encoded protein resembles the TR alpha 1-type receptor of the rat. When expressed in COS cells the protein product binds triiodothyronine with a Kd of 0.12 nM. The receptor mediates thyroid-hormone-inducible expression of a reporter gene which includes a thyroid hormone response element in its upstream region.     

Molecular cloning and expression of the cDNA for the alpha 1A-adrenergic receptor. The gene for which is located on human chromosome 5.

Pharmacological and molecular cloning studies have demonstrated heterogeneity of alpha 1-adrenergic receptors. We have now cloned two alpha 1-adrenergic receptors from a rat cerebral cortex cDNA library, using the hamster alpha 1B-adrenergic receptor as a probe. The deduced amino acid sequence of clone RA42 encodes a protein of 560 amino acids whose putative topology is similar to that of the family of G-protein-coupled receptors. The primary structure though most closely resembles that of an alpha 1-adrenergic receptor, having approximately 73% amino acid identity in the putative transmembrane domains with the previously isolated hamster alpha 1B receptor. Analysis of the ligand binding properties of RA42 expressed in COS-7 cells with a variety of adrenergic ligands demonstrates a unique alpha 1-adrenergic receptor pharmacology. High affinity for the antagonist WB4101 and agonists phenylephrine and methoxamine suggests that cDNA RA42 encodes the alpha 1A receptor subtype. Northern blot analysis of various rat tissues also shows the distribution expected of the alpha 1A receptor subtype with abundant expression in vas deferens followed by hippocampus, cerebral cortex, aorta, brainstem, heart and spleen. The second alpha 1-adrenergic receptor cloned represents the rat homolog of the hamster alpha 1B subtype. Expression of mRNA for this receptor is strongly detected in liver followed by heart, cerebral cortex, brain stem, kidney, lung, and spleen. This study provides definitive evidence for the existence of three alpha 1-adrenergic receptor subtypes.     

Rat testis P-450(17)alpha cDNA: the deduced amino acid sequence, expression and secondary structural configuration

A complete amino acid sequence for rat testis P-450(17)alpha was deduced from nucleotide analysis of a cDNA clone isolated from a rat Leydig cell cDNA library. This DNA clone, containing initiation and termination codons and a polyA tail, translated a polypeptide in COS-1 cells that expressed both 17 alpha-hydroxylase and 17,20 lyase activities. It exhibited significant similarity to the nucleotide and deduced amino acid sequences of the bovine and human cytochrome P-450(17)alpha, particularly with respect to the highly conserved regions and secondary structure. The P-450(17)alpha appears to be anchored to the membrane of the endoplasmic reticulum through two transmembrane regions, specifically the N terminal insertion peptide and the stop-transfer sequence. Hydropathic analysis indicates that the remainder of the C terminus is associated with the membrane through four hydrophobic clefts, including the putative steroid binding site.     

Molecular cloning and genomic organization of a novel receptor from Drosophila melanogaster structurally related to mammalian galanin receptors

We screened the Berkeley "Drosophila Genome Project" database with "electronic probes" corresponding to conserved amino acid sequences from the five known rat somatostatin receptors. This yielded alignment with a Drosophila genomic clone that contained a DNA sequence coding for a protein, having amino acid sequence identities with the rat galanin receptors. Using PCR with Drosophila cDNA as a template, and oligonucleotide probes coding for the exons of the presumed Drosophila gene, we were able to clone the cDNA for this receptor. The Drosophila receptor has most amino acid sequence identity with the three mammalian galanin receptors (37% identity with the rat galanin receptor type-1, 32% identity with type-2, and 29% identity with type-3). Less sequence identity exists with the mammalian opioid/nociceptin-orphanin FQ receptors (26% identity with the rat micro opioid receptor), and mammalian somatostatin receptors (25% identity with the rat somatostatin receptor type-2). The novel Drosophila receptor gene contains ten introns and eleven exons and is located at the distal end of the X chromosome.     

Sequence analysis of cloned cDNA for rat substance P precursor: existence of a third substance P precursor

The sequence of the mRNA for the rat substance P precursor (preprotachykinin A) has been elucidated by molecular cloning and sequence analysis. The deduced amino acid sequence of rat preprotachykinin A indicates that it contains both substance P and substance K but differs in the sequence organization from either bovine alpha- or beta-preprotachykinin A reported previously. The existence of the bovine mRNA for the third preprotachykinin A has thus been examined and evidenced by the isolation of the corresponding cDNA clone. This mRNA, named gamma-preprotachykinin A mRNA, deletes the sequence precisely corresponding to the exon 4 sequence of the preprotachykinin A gene. Thus, alternative RNA splicing in the expression of the single preprotachykinin A gene results in the generation of three different forms of the preprotachykinin A mRNAs.