Chemistry: analytical and immunological testing – Biospecific ligand binding assay
Reexamination Certificate
1999-11-23
2003-11-11
Kemmerer, Elizabeth (Department: 1647)
Chemistry: analytical and immunological testing
Biospecific ligand binding assay
C436S503000, C435S007200, C435S007210, C514S085000, C514S107000, C514S183000
Reexamination Certificate
active
06645774
ABSTRACT:
BACKGROUND OF THE INVENTION
Throughout this application, various publications are referred to within parentheses. Disclosures of these publications in their entireties are hereby incorporated by reference into this application to more fully describe the state of the art to which this invention pertains. Full bibliographic citations for these publications may be found at the end of the specification, preceding the sequence listing and the claims.
Neuropeptide Y (NPY) is a member of the pancreatic polypeptide family with widespread distribution throughout the mammalian nervous system. NPY and its relatives (peptide YY or PYY, and pancreatic polypeptide or PP) elicit a broad range of physiological effects through activation of at least five G protein-coupled receptor subtypes known as Y1, Y2, Y3, Y4 (or PP), and the “atypical Y1”. The role of NPY as the most powerful stimulant of feeding behavior yet described is thought to occur primarily through activation of the hypothalamic “atypical Y1” receptor. This receptor is unique in that its classification was based solely on feeding behavior data, rather than radioligand binding data, unlike the Y1, Y2, Y3, and Y4 (or PP) receptors, each of which were described previously in both radioligand binding and functional assays.
The peptide neurotransmitter neuropeptide Y (NPY) is a 36 amino acid member of the pancreatic polypeptide family with widespread distribution throughout the mammalian nervous system. NPY is considered to be the most powerful stimulant of feeding behavior yet described (Clark et al., 1984; Levine and Morley, 1984; Stanley and Leibowitz, 1984). Direct injection into the hypothalamus of satiated rats, for example, can increase food intake up to 10-fold over a 4-hour period (Stanley et al., 1992). The role of NPY in normal and abnormal eating behavior, and the ability to interfere with NPY-dependent pathways as a means to appetite and weight control, are areas of great interest in pharmacological and pharmaceutical research (Sahu and Kalra, 1993; Dryden et al., 1994). Any credible means of studying or controlling NPY-dependent feeding behavior, however, must necessarily be highly specific as NPY can act through at least 5 pharmacologically defined receptor subtypes to elicit a wide variety of physiological functions (Dumont et al., 1992). It is therefore vital that knowledge of the molecular biology and structural diversity of the individual receptor subtypes be understood as part of a rational drug design approach to develop subtype selective compounds. A brief review of NPY receptor pharmacology is summarized below and also in Table 1.
TABLE 1
Pharmacologically defined receptors for NPY and related pancreatic
polypeptides. Rank orders of affinity for key peptides (NPY, PYY, PP,
[Leu
31
,Pro
34
]NPY, NPY
2-36
, and NPY
13-36
) are based on previously
reported binding and functional data (Schwartz et al., 1990; Wahlestedt
et al., 1991; Dumont et al., 1992; Wahlestedt and Reis, 1993). Data for
the Y2 receptor were disclosed in PCT International Application Ser. No.
No. PCT/US95/014691 filed February 3, 1995, International Publication
No. WO 95/21245, published August 10, 1995 the foregoing contents of
which are hereby incorporated by reference. Data for the Y4 receptor
were disclosed in PCT International Application Ser. No.
PCT/US94/14436 filed December 28, 1994, International Publication No.
WC 95/17906, published August 10, 1995 the contents of which are
hereby incorporated by reference. Missing peptides in the series
reflect a lack of published information. Table 1 reflects current
information obtained with cloned human Y1, Y2, Y4, and Y5 receptors.
Recep-
Affinity (pK
1
ot pEC
50
)
tor
11 to 10
10 to 9
9 to 8
8 to 7
7 to 6
<6
Y1
NPY
NPY
2-36
NPY
13-36
PP
PYY
[Leu
31
,
Pro
34
]
NPY
Y2
PYY
NPY
13-36
[Leu
31
,
NPY
Pro
34
]
NPY
2-
NPY
36
PP
Y3
NPY
[Pro
34]
NPY
13-36
PYY
NPY
PP
Y4
PP
PYY
NPY
2-
NPY
13-36
[Leu
31
,
36
Pro
34
]-
NPY
NPY
Y5 or
PYY
NPY
13-36
atyp-
NPY
D-
ical Y1
NPY
2-36
Trp
32
(feed-
[Leu
31
,
NPY
ing)
Pro
34
]
NPY
NPY Receptor Pharmacology
NPY receptor pharmacology has historically been based on structure/activity relationships within the pancreatic polypeptide family. The entire family includes the namesake pancreatic polypeptide (PP), synthesized primarily by endocrine cells in the pancreas; peptide YY (PYY), synthesized primarily by endocrine cells in the gut; and NPY, synthesized primarily in neurons (Michel, 1991; Dumont et al., 1992; Wahlestedt and Reis, 1993). All pancreatic polypeptide family members share a compact structure involving a “PP-fold” and a conserved C-terminal hexapeptide ending in Tyr
36
(or Y
36
in the single letter code). The striking conservation of Y
36
has prompted the reference to the pancreatic polypeptides' receptors as “Y-type” receptors (Wahlestedt et al., 1987), all of which are proposed to function as seven transmembrane-spanning G protein-coupled receptors (Dumont et al., 1992).
The Y1 receptor recognizes NPY≧PYY>>PP (Grundemar et al., 1992). The receptor requires both the N- and the C-terminal regions of the peptides for optimal recognition. Exchange of Gln
34
in NPY or PYY with the analogous residue from PP (Pro
34
), however, is well-tolerated. The Y1 receptor has been cloned from a variety of species including human, rat and mouse (Larhammar et al, 1992; Herzog et al, 1992; Eva et al, 1990; Eva et al, 1992). The Y2 receptor recognizes PYY~NPY>>PP and is relatively tolerant of N-terminal deletion (Grundemar et al., 1992). The receptor has a strict requirement for structure in the C-terminus (Arg
33
-Gln
34
-Arg
35
-Tyr
36
-NH
2
); exchange of Gln
34
with Pro
34
, as in PP, is not well tolerated. The Y2 receptor has recently been cloned. The Y3 receptor is characterized by a strong preference for NPY over PYY and PP (Wahlestedt et al., 1991) [Pro
34
]NPY is reasonably well tolerated even though PP, which also contains Pro
34
, does not bind well to the Y3 receptor. The Y3 receptor (Y3) has not yet been cloned. The Y4 receptor binds PP>PYY>NPY. Like the Y1, the Y4 requires both the N- and the C-terminal regions of the peptides for optimal recognition. The “atypical Y1” or “feeding” receptor was defined exclusively by injection of several pancreatic polypeptide analogs into the paraventricular nucleus of the rat hypothalamus which stimulated feeding behavior with the following rank order: NPY
2-36
≧NPY~PYY~[Leu
31
,Pro
34
]NPY>NPY
13-36
(Kalra et al., 1991; Stanley et al., 1992). The profile is similar to that of a Y1-like receptor except for the anomalous ability of NPY
2-36
to stimulate food intake with potency equivalent or better than that of NPY. A subsequent report in
J. Med. Chem
. by Balasubramaniam et al. (1994) showed that feeding can be regulated by [D-Trp
32
]NPY. While this peptide was presented as an NPY antagonist, the published data at least in part support a stimulatory effect of [D-Trp
32
]NPY on feeding. [D-Trp
32
]NPY thereby represents another diagnostic tool for receptor identification. In contrast to other NPY receptor subtypes, the “feeding” receptor has never been characterized for peptide binding affinity in radioligand binding assays and the fact that a single receptor could be responsible for the feeding response has been impossible to validate in the absence of an isolated receptor protein; the possibility exists, for example, that the feeding response could be a composite profile of Y1 and Y2 subtypes.
This invention now reports the isolation by expression cloning of a novel Y-type receptor from a rat hypothalamic cDNA library, along with its pharmacological characterization, in situ localization, and human homolog. The data provided link this newly-cloned receptor subtype, from now on referred to as the Y5 subtype, to the “atypical Y1” feeding response. This discovery therefore provides a novel approach, through the use of heterologous expression systems, to develop a subtype selective
Branchek Theresa
Gerald Christophe P. G.
Walker Mary W.
Weinshank Richard L.
Cooper & Dunham LLP
Kemmerer Elizabeth
Synaptic Pharmaceutical Corporation
Wegert Sandra
White John P.
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