Biomedical subjects

E Clauser

Publications and source records attributed to E Clauser.

At least 37 records · Page 2Linked to original sources

PubMed1997

The C-terminal third intracellular loop of the rat AT1A angiotensin receptor plays a key role in G protein coupling specificity and transduction of the mitogenic signal.

To identify the role(s) of the third intracellular loop of the angiotensin II (AngII) type 1A (AT1A) receptor in G protein coupling specificity and receptor activation, several chimerae were constructed and characterized. The cDNA sequence encoding the C-terminal segment of the third intracellular loop of the AT1A receptor (residues 234-240) was replaced with the homologous regions of the alpha1B adrenergic (alpha1B-AR), the beta2 adrenergic (beta2-AR), and the AngII type 2 (AT2) receptors. These chimeric receptors were stably expressed in Chinese hamster ovary cells, and their pharmacological and functional properties were characterized, including AngII-induced inositol phosphate and cyclic AMP (cAMP) productions, [3H]thymidine incorporation into DNA, and internalization. The affinities of these chimeric receptors for [Sar1]AngII, [Sar1,Ile8]AngII, and losartan were essentially normal; however, the affinity of these mutants was increased by a factor of 10-40 for the AT2-specific ligand CGP42112A. The functional properties of the alpha1B-AR chimera were essentially identical to those of the wild type AT1A receptor. On the other hand, replacement with the beta2-AR segment produced a partial reduction of the inositol phosphate production, a measurable AngII-induced cAMP accumulation, a reduced internalization, and a total impairment to transduce the mitogenic effect of AngII. The AT2 chimera presented a normal internalization, but was inactive in all the other functional tests. In conclusion, the distal segment of the third intracellular loop of the rat AT1A receptor plays a pivotal role in coupling selectivity and receptor signaling via G protein(s) as well as in the activation of the specific signaling pathways involved in the mitogenic actions of AngII.

Amino Acid Sequence↗

PubMed1997

Cleavage site mutants of the subtype B insulin receptor are uncleaved and fully functional.

The insulin receptor (IR) is a membrane-bound glycoprotein composed of alpha and beta subunits derived from a common precursor. This processing is observed for both subtypes A and B of the IR and its physiological importance is poorly understood. In order to investigate the functional consequences of the absence of IR precursor cleavage, using site-directed mutagenesis of the hIRB cDNA, we have produced two mutants replacing the sequence Arg-Lys-Arg-Arg by either His-Lys-His-Arg or Arg-Lys-Arg-Ser. These two mutants, stably expressed in CHO, were structurally and functionally characterized in comparison to the wild-type human IR. These mutations result in the production of uncleaved receptors which are expressed normally at the cell surface. These receptors bind insulin with a normal affinity and activate the tyrosine-kinase resulting in normal phosphorylation of the receptors. These uncleaved receptors can mediate both the metabolic and mitogenic effects of insulin. These results provide evidence for a fully functional uncleaved insulin receptor of the B subtype (exon 11 + ) in contrast to the uncleaved A subtype (exon 11 -) described in the literature, which shows a reduced affinity for insulin and cannot therefore correctly transduce the insulin signal.

Amino Acid Sequence↗

PubMed1997

V3 vasopressin receptor and corticotropic phenotype in pituitary and nonpituitary tumors.

Pituitary corticotropic cells express a specific vasopressin receptor, called V1b or V3, through which vasopressin stimulates corticotropin secretion. We recently cloned a cDNA coding for this receptor and showed that it belongs to the G protein-coupled receptor family. V3 mRNA is readily detected by RT-PCR in normal human pituitaries and corticotropic pituitary adenomas but not in PRL or GH-secreting adenomas, thus demonstrating that, like POMC itself and the CRH receptor, V3 is a marker of the corticotropic phenotype. Nuclease protection experiments suggest that V3 is overexpressed in some corticotropic adenomas, and thus may play a role in tumor development by activating the phospholipase C-signalling pathway. In addition analysis of its expression in nonpituitary neuroendocrine tumors showed a striking association with carcinoids of the lung responsible for the ectopic ACTH syndrome.

Adrenocorticotropic Hormone↗

PubMed1997

Somatic mutations of the angiotensin II (AT1) receptor gene are not present in aldosterone-producing adenoma.

Angiotensin II stimulates aldosterone secretion from the adrenal zona glomerulosa and mediates most of its biological effects via G protein-coupled type 1 angiotensin II receptors (AT1). A number of G protein-coupled receptors are constitutively activated as a result of somatic mutations in the gene encoding the protein. It is, therefore, possible that primary hyperaldosteronism caused by an aldosterone-producing adenoma (APA) may be the result of constitutive activation of the AT1 receptor. The 1.1-kilobase coding region (exon 5) of the AT1 receptor gene was analyzed in APA and normal adrenal tissue for the presence of mutations using single stranded conformational polymorphism and sequencing techniques. In 17 APAs, no functional mutations were found that could account for the observed pathophysiology. However, three silent polymorphisms were detected in regions encoding the second extracellular loop, the intracellular arm preceding the COOH terminal, and the 3'-untranslated region. In conclusion, somatic mutations in the coding region of the AT1 receptor gene do not appear to play a role in primary hyperaldosteronism caused by an APA.

Adenoma↗

PubMed1996

The natural mutation Y248C of human angiotensinogen leads to abnormal glycosylation and altered immunological recognition of the protein.

Common molecular variants of the angiotensinogen gene have been associated with human hypertension. The rare Tyr to Cys change at residue 248 of mature angiotensinogen was identified in one pedigree. Heterozygous individuals (Y248C) had a 40% decrease in plasma angiotensinogen concentration and a 35% reduction of the angiotensin I production rate. Recombinant wild-type (Tyr-248) and mutant (Cys-248) proteins were stably expressed in Chinese hamster ovary cells. Angiotensinogen monoclonal antibodies revealed marked differences in the epitope recognition of the mutant protein and allowed the demonstration of its presence in plasma of Y248C individuals. Similar kinetic constants of angiotensin I production with human renin were observed for both proteins. Western blot analysis showed similar heterogeneities; however, a 3-kDa increase in molecular mass for the Cys-248 protein was observed after immunopurification. Metabolic labeling of the intracellular Cys-248 protein showed a 61-kDa band in addition to the 55.5- and 58-kDa bands observed for the Tyr-248 protein, with all bands being sensitive to endoglycosidase H. In addition, pulse-chase studies revealed a slower intracellular processing for the Cys-248 protein. In conclusion, the Cys-248 mutation alters the structure, glycosylation, and secretion of angiotensinogen in Chinese hamster ovary cells and is accompanied by a decrease in plasma angiotensinogen concentration in Y248C individuals.

Amino Acid Sequence↗

PubMed1996

The pituitary V3 vasopressin receptor and the corticotroph phenotype in ectopic ACTH syndrome.

Ectopic ACTH secretion occurs in highly differentiated and rather indolent tumors like bronchial carcinoids or, in contrast, in various types of aggressive and poorly differentiated neuroendocrine tumors. We explored this phenomenon using the recently cloned human pituitary V3 vasopressin receptor as an alternate molecular marker of the corticotroph phenotype. Expression of V3 receptor, corticotrophin releasing hormone (CRH) receptor, and proopiomelanocortin (POMC) genes was examined in tumors of pituitary and nonpituitary origin. A comparative RT-PCR approach revealed signals for both V3 receptor and CHR receptor mRNAs in 17 of 18 ACTH-secreting pituitary adenomas, and 6 of 6 normal pituitaries; in six growth hormone- or prolactin-secreting adenomas, a very faint V3 receptor signal was observed in three cases, and CRH receptor signal was undetected in all. Six of eight bronchial carcinoids responsible for the ectopic ACTH syndrome had both POMC and V3 receptor signals as high as those in ACTH-secreting pituitary adenomas; in contrast, no POMC signal and only a very faint V3 receptor signal were detected in six of eight nonsecreting bronchial carcinoids. Northern blot analysis showed V3 receptor mRNA of identical size in ACTH-secreting bronchial carcinoids and pituitary tumors. Other types of nonpituitary tumors responsible for ectopic ACTH syndrome presented much lower levels of both POMC and V3 receptor gene expression than those found in ACTH-secreting bronchial carcinoids. In contrast with the V3 receptor, CRH receptor mRNA was detected in the majority of neuroendocrine tumors irrespective of their POMC status. These results show that expression of the V3 receptor gene participates in the corticotroph phenotype. Its striking association with ACTH-secreting bronchial carcinoids defines a subset of nonpituitary tumors in which ectopic POMC gene expression is but one aspect of a wider process of corticotroph cell differentiation, and opens new possibilities of pharmacological investigations and even manipulations of this peculiar ACTH hypersecretory syndrome.

ACTH Syndrome, Ectopic↗

PubMed1996

Structure, sequence, expression, and chromosomal localization of the human V1a vasopressin receptor gene.

We recently reported the structure and functional expression of a human V1a vasopressin receptor (V1aR) cDNA isolated from human liver cDNA libraries. To understand further the expression and regulation of the V1aR, we now describe the genomic characteristics, tissue expression, chromosomal localization, and regional mapping of the human V1aR gene, AVPR1A. Tissue distribution of the human V1aR mRNA explored by Northern blot analysis of various human tissues or organs revealed the presence of a 5.5-kb mRNA transcript expressed in the liver and to a lesser degree in the heart, the kidney, and skeletal muscle. Screening of human genomic libraries revealed that the human AVPR1A gene is included entirely within a 6.4-kb EcoRI fragment and comprises two coding exons separated by a 2.2-kb intron located before the corresponding seventh transmembrane domain of the receptor sequence. The first exon also contains 2 kb of 5'-untranslated region, and the second exon includes 1 kb of 3'-untranslated region. 5'-RACE analysis of human liver mRNA by PCR localized the V1aR mRNA transcription start site 1973 bp upstream of the translation initiation site. Specific oligonucleotides derived from the intron sequence were used as primers in polymerase chain reaction (PCR) analysis of human/rodent somatic cell hybrids. AVPR1A was localized by PCR analysis of a somatic cell hybrid panel to chromosome 12. Fluorescence in situ hybridization using a yeast artificial chromosome physically mapped AVPR1A to region 12q14-q15.

Animals↗

PubMed1996

Polar residues in the transmembrane domains of the type 1 angiotensin II receptor are required for binding and coupling. Reconstitution of the binding site by co-expression of two deficient mutants.

Type 1 angiotensin receptors (AT1) are G-protein coupled receptors, mediating the physiological actions of the vasoactive peptide angiotensin II. In this study, the roles of 7 amino acids of the rat AT1A receptor in ligand binding and signaling were investigated by performing functional assays of individual receptor mutants expressed in COS and Chinese hamster ovary cells. Substitutions of polar residues in the third transmembrane domain with Ala indicate that Ser105, Ser107, and Ser109 are not essential for maintenance of the angiotensin II binding site. Replacement of Asn111 or Ser115 does not alter the binding affinity for peptidic analogs, but modifies the ability of the receptor to interact with AT1 (DuP753)- or AT2 (CGP42112A)-specific ligands. These 2 residues are probably involved in determining the binding specificity for these analogs. The absence of G-protein coupling to the Ser115 mutant suggests that this residue, in addition to previously identified residues, Asp74 and Tyr292, participates in the receptor activation mechanism. Finally, Lys102 (third helix) and Lys199 (fifth helix) mutants do not bind angiotensin II or different analogs. Co-expression of these two deficient receptors permitted the restoration of a normal binding site. This effect was not due to homologous recombination of the cDNAs but to protein trans-complementation.

Amino Acid Sequence↗

PubMed1996

Mechanisms of ANG II-induced mitogenic responses: role of 12-lipoxygenase and biphasic MAP kinase.

The potential mechanisms of angiotensin II (ANG II)-induced mitogenesis were studied in a Chinese hamster ovary fibroblast cell line overexpressing the rat vascular type 1a ANG II receptor (CHO-AT1a). ANG II had potent mitogenic effects in these CHO-AT1a cells, leading to a sustained increase in cell number as well as a dose-dependent increase in DNA synthesis. ANG II treatment also induced a biphasic elevation of mitogen-activated protein (MAP) kinase activity of both p42MAPK and p44MAPK with a rapid early peak at 5 min (2- to 6-fold) followed by a second sustained increase that reached a peak at 3 h (1.5- to 3-fold). We have previously shown that the 12-lipoxygenase (12-LO) pathway of arachidonate metabolism plays a key role in ANG II-induced growth of vascular smooth muscle and adrenal cells. In the present study, ANG II (10(-7) M) increased the formation of the 12-LO product, 12-hydroxyeicosatetraenoic acid (12-HETE). ANG II-induced DNA synthesis was inhibited by a specific LO inhibitor, cinnamyl-3,4-dihydroxy-alpha-cyanocinnamate (CDC, 10 microM). In contrast, a cyclooxygenase blocker of arachidonate metabolism such as ibuprofen had no effect on ANG II-induced DNA synthesis. ANG II-induced DNA synthesis was also partially (32%) blocked by pertussis toxin (PTX). CDC and PTX also selectively blocked only the late (3 h) peak of ANG II-induced MAP kinase activity, suggesting that the late sustained peak of MAP kinase activity may be linked to the mitogenic effect of ANG II. Direct addition of 12-HETE (10(-7) M) led to a sustained increase in cell number similar to the effect of ANG II. 12-HETE also caused an increase in MAP kinase activity, and 12-HETE effects were blocked by PTX. These results suggest that ANG II-induced mitogenic response is associated with sustained MAP kinase activation and that LO activation may play a key role in this process.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗

PubMed1996

Angiotensin II receptors: protein and gene structures, expression and potential pathological involvements.

Two distinct types of cell-surface angiotensin II receptors (AT1 and AT2) have been defined pharmacologically and cDNAs encoding each type have been identified by expression cloning. These pharmacological studies showed the AT1 receptors to mediate all the known functions of angiotensin II in regulating salt and fluid homeostasis. Further complexity in the angiotensin II receptor system was revealed when homology cloning showed the existence of two AT1 subtypes in rodents and in situ hybridization and reverse transcription-polymerase chain reaction analyses showed their level of expression to be regulated differently in different tissues: AT1A is the principal receptor in the vessels, brain, kidney, lung, liver, adrenal gland and fetal pituitary, while AT1B predominates in the adult pituitary and is only expressed in specific regions of the adrenal gland (zona glomerulosa) and kidney (glomeruli). Expression of AT1A appears to be induced by angiotensin II in vascular smooth-muscle cells but is inhibited in the adrenal gland. Preliminary analysis of the AT1 promoters is also suggestive of a high degree of complexity in their regulation. Investigation of a potential role for altered AT1 receptor function has commenced at a genetic level in several diseases of the cardiovascular system. No mutations affecting the coding sequence have been identified in Conn adenoma and no linkage has been demonstrated with human hypertension by sib-pair analysis. None the less, certain polymorphisms that do not alter the protein structure have been found to be associated with hypertension and to occur at an increased frequency in conjunction with specific polymorphisms in the ACE gene in individuals at increased risk for myocardial infarction. Further characterization of the regions of the AT1 gene that regulate its expression are therefore needed. The physiological importance of the AT2 gene product still remains a matter of debate.

Amino Acid Sequence↗

PubMed1995

Two sequences flanking the major autophosphorylation site of the insulin receptor are essential for tyrosine kinase activation.

The tyrosine kinase domain of the human insulin receptor (IR) contains several short amino acid motifs which are strictly conserved in all protein kinases and two sequence motifs which are specific to the tyrosine kinases (AAR or RAA and P(I)/VK/RWT/M). In the serine/threonine kinases these motifs are replaced by the sequences KPE and GT/SXXY/PX respectively. In the present work, the tyrosine kinase-specific sequences of the IR (1134AAR1136 and 1172PVRWM1176) were replaced using site-directed mutagenesis by sequences which confer a serine kinase specificity on the receptor. Five different IR mutants were expressed in Chinese hamster ovary (CHO) or COS cells and their structural and functional properties compared with those of the wild-type recombinant human IR. These mutants are processed normally and bind insulin with normal affinities. None of the mutants containing a putative serine kinase-specific sequence display detectable autophosphorylation or tyrosine kinase activity in response to insulin, either in vitro or in vivo. These mutants were also unable to phosphorylate serine/threonine kinase substrates after insulin stimulation. Unexpectedly, they showed impaired ATP binding, as studied by an original technique consisting of cross-linking adenosine 5'-([35S]thio)triphosphate to partially purified receptors. Finally, none of the studied mutants transmit the insulin signal necessary to stimulate either DNA or glycogen synthesis. These data provide evidence for the importance of these conserved sequences in the kinase domain for both receptor activation and kinase activity. Furthermore, they demonstrate that the exchange of sequences specific to the catalytic domain of tyrosine kinases for those specific to the serine/threonine kinases is not sufficient to confer serine/threonine specificity on the insulin receptor.

Adenosine Triphosphate↗

PubMed1995

Lipid signal transduction pathways in angiotensin II type 1 receptor-transfected fibroblasts.

A stable Chinese hamster ovary fibroblast line expressing the rat vascular type 1a angiotensin II (ANG II) receptor was used to study the lipid-derived signal transduction pathways elicited by type 1a ANG II receptor activation. ANG II caused a biphasic and dose-dependent increase in diacylglycerol (DAG) accumulation with an initial peak at 15 s (181 +/- 11% of control, P < 0.02) and a second sustained peak at 5-10 min (214 +/- 10% of control, P < 0.02). The late DAG peak was derived from phosphatidylcholine (PC), and the formation was blocked by ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid. ANG II also increased phosphatidic acid (PA) production nearly fourfold by 7.5 min. In the presence of ethanol, ANG II markedly increased phosphatidylethanol (PEt) formation, indicating activation of phospholipase D (PLD). ANG II was shown to increase the mass of three separate PA species, one of which apparently originated from DAG kinase action on PC-phospholipase C (PLC)-produced DAG, providing evidence for PC-PLC activity. ANG II also formed a third PA species, which originated neither from PLD nor from DAG kinase. These results demonstrate that multiple lipid signals propagated via collateral stimulation of PLC and PLD are generated by specific activation of the vascular type 1a ANG II receptor.

Angiotensin II↗

PubMed1995

Expression of angiotensin II AT2 receptor mRNA during development of rat kidney and adrenal gland.

The angiotensin II (ANG II) receptors have been pharmacologically classified into two major distinct types, designated AT1 and AT2. A high transient expression of AT2 receptors in the fetal tissues has been previously demonstrated. This study describes the cellular distribution of AT2 receptor mRNA in the developing rat kidney and adrenal gland by in situ hybridization with 35S-labeled cRNA probes. From day 12 of fetal life (F12) to day 15 postpartum (D15) AT2 mRNA was detected in the undifferentiated nephrogenic mesenchymal tissue but not in the immature and mature glomeruli and tubules of the kidney. No AT2 mRNA was observed in the kidney after D22. The adrenal gland also expressed AT2 receptor mRNA early during development from F12 but, unlike the kidney, continuously expressed the mRNA at high levels through to adulthood. The disappearance of AT2 mRNA in the kidney was synchronous with the completion of nephrogenesis and suggests that ANG II might act through this receptor as a differentiation/growth factor during nephron development. In the adrenal gland ANG II could act as a hormone and also as a differentiation/growth factor via the AT2 receptor.

Adrenal Glands↗

PubMed1995

Vasopressin-responsive adrenocortical tumor in a mild Cushing's syndrome: in vivo and in vitro studies.

We report a case of a Cushing's syndrome caused by an autonomously secreting unilateral adrenocortical tumor, characterized by a clinically and biologically mild hypercortisolemic state and an unusual response pattern to vasopressin. Laboratory tests showed normal early morning plasma cortisol and 24-h urinary cortisol excretion, but lack of nycthemeral variations and suppressed plasma ACTH. Urinary cortisol excretion was not suppressed by either the low dose or the high dose dexamethasone test. Injection of lysine vasopressin, (10 IU, im) induced a marked increase in plasma cortisol, without an elevation of plasma ACTH. Computed tomography scan revealed an adrenocortical mass of the left gland with a contralateral atrophic gland. Removal of the tumor led to complete remission of Cushing's symptoms. In vitro studies were then performed to investigate the effect of arginine vasopressin (AVP) on calcium mobilization in cultured tumor cells using a microfluorimetric technique. Application of AVP in the vicinity of the cells induced a rapid and marked increase in the intracellular calcium concentration. Preincubation of the cells with the V1 vasopressin receptor antagonist [d(CH2)5,Tyr(OMe)2]AVP totally suppressed the AVP-induced stimulation of intracellular calcium concentration. Reverse transcription followed by polymerase chain reaction of tumor ribonucleic acid with specific oligonucleotides amplified high levels of V1 receptor signal compared with normal adrenocortical ribonucleic acid. Specific oligonucleotides for the V2 or V3 receptors amplified only a faint signal. This is the first report describing a mild case of Cushing's syndrome caused by an AVP-sensitive cortisol-producing adenoma. The direct effect of AVP on cultured tumor cells was mediated through the V1 type of vasopressin receptor, similar to that previously characterized in normal human fasciculata cells, suggesting that the tumor expressed an eutopic V1 AVP receptor and exhibited overresponsiveness to AVP.

Adrenal Cortex Neoplasms↗

PubMed1995

Alternatively spliced human type 1 angiotensin II receptor mRNAs are translated at different efficiencies and encode two receptor isoforms.

The peptide hormone angiotensin II (AngII) plays a principal role in regulating blood pressure and fluid homeostasis. Most of its known effects are mediated by a guanine nucleotide-regulatory protein (G protein)-coupled receptor pharmacologically defined as the type-1 AngII receptor or AT1. Characterization of cDNA and genomic clones shows that the human AT1 gene contains five exons and encodes two receptor isoforms as a result of alternative splicing. Exon 5 contains the previously characterized open reading frame for AT1, and exons 1 to 3 are alternatively spliced upstream of it to generate several mRNA species, while transcripts containing exon 4 are of minor abundance. In an in vitro translation system, the presence of exon 1 was found to be extremely inhibitory to translation, probably because it can form a stable secondary structure at the RNA level. The alternatively spliced second exon also had a strong inhibitory effect on translation, presumably because it contains a minicistron commencing with an ATG in an optimal context for translation initiation. Exon 2 was similarly inhibitory to protein production in transfected cells, but exon 1 was found to enhance protein synthesis in this system. Transcripts containing exon 3 and 5, which comprise up to one-third of AT1 mRNAs in all tissues examined, encode a receptor with an amino-terminal extension of 32-35 amino acids. These transcripts were translated into a larger receptor isoform in vitro and produced a functional receptor with normal ligand binding and signaling properties in transfected cells.

Alternative Splicing↗

PubMed1995

[Comparative study of the structure and molecular functions of angiotensin II and vasopressin receptors].

The peptide hormones angiotensin II and vasopressin play a major role in water and electrolyte homeostasis. These peptides act on membrane bound receptors, which all belong to the large family of G protein coupled receptors. The receptors for angiotensin II are divided into 2 groups: the AT1 receptors, which are responsible for transducing the majority if not all actions of angiotensin II. The primary structure of this receptor has been identified by molecular cloning of the cDNA in many species and is represented by two isoforms (AT1A and AT1B) in rodent. This receptor is specifically coupled to a G protein of the Gq family, which activates a phospholipase C producing two second messengers involved in protein phosphorylation and calcium mobilization. The sequences or amino-acids involved in the binding site of peptidic agonists or non peptidic antagonists and in receptor activation and G protein coupling have been identified; the AT2 receptor primary sequence has also been identified, but the physiological role and the signaling mechanisms of this receptor are still unknown. The vasopressin receptors can be divided in three classes depending on their pharmacological properties, their tissular distribution and their coupling mechanisms. The primary structure of all 3 types of receptors has been elucidated. The V1a receptor is ubiquitous and transduces the vasoconstrictive effect of vasopressin by activating a phospholipase C, like the AT1 receptors; the V2 receptor is involved in water reabsorption in the kidney and is coupled to a GS protein activating an adenylyl cyclase; the V3 or V1b receptor is expressed in the pituitary, where it regulates the ACTH secretion, via the activation of a phospholipase C. These two family of G protein coupled receptors illustrate the structural and functional diversity of the receptors for peptidic hormones.

Angiotensin II↗

PubMed1995

[Insulin receptor].

The cloning of the insulin receptor not only established the primary structure of this membrane-bound glycoprotein but also offered the material necessary for the study of the molecular functions of this tyrosine-kinase receptor using molecular biology tools. This short review will summarize the actual knowledge of the structure, the functions (molecular structure of the binding site, tyrosine-kinase functions and role of autophosphorylation) and of the pathology of this receptor in extreme insulin resistances and type II diabetes.

Diabetes Mellitus, Type 1↗

PubMed1994

Cloning and characterization of the human V3 pituitary vasopressin receptor.

Arginine-vasopressin (AVP) plays a determinant role in the normal ACTH response to stress in mammals. We cloned a human cDNA coding a 424 amino acid G-protein coupled receptor structurally related to the vasopressin/oxytocin receptor family. When expressed in COS cells, this receptor binds AVP with a high affinity (Kd = 0.55 +/- 0.13 nM) and is functionally coupled to phospholipase C. Competition studies with peptidic or non peptidic AVP analogues reveal that it is pharmacologically distinct from V1a and V2 AVP receptors and therefore it is designated V3. RT-PCR analysis shows that the human V3 receptor is expressed in normal pituitary and also in kidney, but is undetectable in liver, myometrium and adrenal gland. Northern blot analysis reveals a approximately 4.8 kb messenger in human corticotropic pituitary adenomas.

Adenoma↗