Nucleic acid encoding human neurotensin subtype 2 receptor

Details Nucleic acid encoding human neurotensin subtype 2 receptor Nucleic acid encoding human neurotensin subtype 2 receptor

1998-11-25

2002-07-16

Mertz, Prema (Department: 1646)

Chemistry: molecular biology and microbiology

Micro-organism, tissue cell culture or enzyme using process...

Recombinant dna technique included in method of making a...

C435S007200, C435S320100, C435S325000, C435S455000, C530S350000, C536S023500

Reexamination Certificate

active

06420137

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to a novel human neurotensin receptor, designated HNT2R, present in two isoforms, a long isoform designated HNT2RL, and a deletion variant (short) form of the long isoform designated HNT2RS, and to nucleic acids encoding the human neurotensin receptor proteins. The invention further relates to high throughput screening assays with these receptors.
BACKGROUND OF THE INVENTION
Neurotensin and Neuromedin
Neurotensin is a neuropeptide that is found predominantly in the hypothalamus and gut. Neurotensin acts as a neurotransmitter and neuromodulator in the brain and as a hormone in the periphery. Native neurotensin [NT (1-13)] is a 13 amino acid peptide. However, the carboxyl terminal 6 amino acids of neurotensin (8-13) [NT (8-13)] and the more stable N-acetylated form [AcNT (8-13)] are sufficient to elicit fill biological activity mediated by neurotensin in most, but not all, tissues. A closely related peptide, neuromedin N, also binds to and activates neurotensin receptors, but with lower affinity than neurotensin. Neurotensin and neuromedin N are processed from the same precursor protein.
Neurotensin Physiology
An important response mediated by neurotensin is suppression of appetite, making this hormone a potential anti-obesity target. Both central and peripheral administration of neurotensin suppresses appetite in fed and fasted animals without altering water consumption or initiating a conditioned taste aversion (Stanley et al., Peptides 4:493-500, 1983; Hawkins, Physiol. and Behavior 36:1-8, 1986; Luttinger et al., Eur. J. Pharmacol. 81:499-503, 1982; Bailey and Flatt, Comp. Biochem. & Physiology, 84:451-4,1986). The active moiety of neurotensin is only 6 amino acids, making this potential target amenable to high throughput screens for the discovery of non-peptide agonists. Very little has been reported, however, on the chronic effects of neurotensin on metabolic responses in vivo.
Obesity
Obesity is a complex, multifactorial disease defined as a body mass index (BMI) of greater than 27 kg/m
2
(relative weight ≧120% of normal). Morbid obesity is defined as a BMI of 40 kg/m
2
(relative weight≧200% of normal) or greater. Many genetic and environmental factors can lead to the development of obesity, including decreased resting metabolic expenditure and hyperphagia. A significant number of obese subjects have characteristic metabolic changes associated with this disease. Many are hyperinsulinemic as well as hyperglycemic indicating an insulin-resistant state, a common characteristic of non-insulin dependent diabetes mellitus (NIDDM).
The ideal anti-obesity agent would have to accomplish several tasks for it to be successful therapeutically. Three of the most important effects mediated by effective anti-obesity agents would be to increase satiety, increase metabolic energy expenditure, and increase utilization of existing fat depots (lipolytic). Most individual medical treatments for obesity either increase metabolic energy expenditure (&bgr;
3
-agonists) or decrease appetite (dexfenfluramine). Very few drugs actually do both. In fact, many appetite suppressants cause a decrease in metabolic energy expenditure to compensate for the decreased energy intake. Thus, there is a need for a novel anti-obesity target that increases energy expenditure as well as decreases appetite.
Role of Neurotensin in Obesity
In animal models of obesity and in human obese patients, neurotensin levels are decreased when compared to lean animals and humans. Decreased hypothalamic neurotensin concentrations (up to 50%) have been observed in five different animal models of obesity: ob/ob, db/db, and CPE mice, and fa/faZucker and Corpulent rat models (Beck et al., Neuropeptides, 13:1-7, 1989; Williams et al., Metabolism 40:1112-16. 1991, Beck et al., J. Nutrition, 120:806-811, 1990). For ob/ob mice, the decreased hypothalamic neurotensin concentration precedes the onset of non-insulin-dependent diabetes. Decreased plasma neurotensin levels have also been observed in diabetic obese, but not diabetic lean, humans suggesting that insulin does not play a direct role in the regulation of neurotensin levels or signaling (Service et al., Regulatory Peptides 14:85-92, 1986). However, neurotensin may play a role in the regulation of insulin secretion, as high-affinity neurotensin binding sites are found in the pancreas. More importantly, the increase in plasma neurotensin levels observed in response to a meal is not observed in obese humans (Bloom et al., Anal. NY Acad. Sci. 400:105-114, 1982). Exogenously administered neurotensin suppresses appetite in lean, ob/ob, and db/db mice, suggesting that even though this important satiety signal is decreased in obesity, the signal transduction pathway is still fully functional in obese animal models.
In Vivo Studies
In vivo studies measuring the effects of AcNT(8-13) on modulation of appetite were conducted with several different mouse models of obesity. AcNT(8-13) i.p. was shown to promote biphasic suppression of food consumption in fasted ob/ob males. It was demonstrated that in animals pretreated with the NT2R-selective antagonist levocabastine, the levocabastine completely reversed the suppression of food intake mediated by 50 &mgr;g/kg AcNT(8-13), suggesting that an NT2R-like subtype mediates the NT response of feeding.
To determine whether blockade of the neurotensin response is a general phenomenon among antihistamines or specific to levocabastine, a second antihistamine, pyridine, was also tested. Pyridine exhibits high affinity binding to H1-histamine receptors but not to any NTR subtypes. Pyridine (1 mg/kg) did not block the AcNT(8-13)-mediated appetite suppression. These data indicate that the AcNT(8-13)-mediated blockade of appetite suppression by levocabastine is NTR-selective and not a general response to antihistamines.
Obesity is associated with decreased metabolic energy expenditure and increased metabolic efficiency. Increasing metabolic energy expenditure (thermogenesis) is a desirable characteristic of anti-obesity targets. AcNT(8-13), when administered acutely, displays many of the characteristics required for a good anti-obesity target, such as: appetite suppression—food consumption is suppressed 40-60%; lipolytic effects—elevated NEFAs and glycerol are observed in response to AcNT(8-13); and oxygen consumption is increased—thermogenesis is controlled by the activity of a family of proteins termed uncoupling protein (UCP); UCP uncouples respiration leading to generation of heat. Thus, there is a need in the art to identify neurotensin agonists, particularly agonists that are selective for the subtype 2 neurotensin receptor.
Neurotensin Receptor Subtypes
Based on the use of selective antagonists, three neurotensin receptor subtypes have been identified. These are designated NT1R, NT2R, and NT3R. Pharmacological data support the existence of a separate neuromedin N receptor. Thus, a fourth subtype with high affinity for the closely related peptide neuromedin N has also been proposed. Two of these receptor subtypes, NT1R and NT2R (termed high and low affinity NT binding sites), have been identified in rat by molecular cloning. All four subtypes are members of the G protein-coupled receptor superfamily and display many of the structural characteristics of this receptor family. G protein-coupled receptors, characterized by seven transmembrane domains, mediate many extracellular signals and are present in organisms as divergent as yeast and man.
Rat NT1R is a 424 amino acid polypeptide (Tanaka et al., Neuron 4:847-854, 1990; Vita et al., FEBS Letters 317:139-142, 1993). The quinoline pyrazole antagonist, SR48692 ({2-[1-(7-chloro-4-quinolinyl)-5-(2,6-dimethoxyphenyl)pyrazol-3-yl)carbonylamino]tricyclo (3,3,1,1,3,7)-decan-2-carboxyic acid}), displays a 20 to 100-fold selectivity for the NT1R over the NT2R subtype. The NT1R subtype appears to couple to at least three G protein-mediated pathways, namely, release of intracellular calcium, release of cGMP-depend

Affiliated with

Also associated with

Rating

Nucleic acid encoding human neurotensin subtype 2 receptor does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Nucleic acid encoding human neurotensin subtype 2 receptor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Nucleic acid encoding human neurotensin subtype 2 receptor will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2855069