Trends in Neurosciences
Y-receptor subtypes—how many more?
Section snippets
Cloned receptor subtypes
The use of various cloning techniques has resulted in the identification of five receptors to date (Y1, Y2, Y4, Y5 and y6, see Table 1). Sequence analyses of the cloned receptors reveal a substantial divergence in primary sequence between the receptor subtypes (see Fig. 1). The human Y1 subtype shares closest amino acid identity with the Y4 subtype (42%) and the non-active, human form of the y6 subtype (51%) (Table 2). Interestingly, homology to the Y5 and Y2 subtypes decreases to values as low
The Y3 subtype
A receptor recognized by NPY, but not PYY, has been proposed. This receptor, Y3, was first localized to the adrenal medulla where it inhibited the release of catecholamines[46]. The Y3 receptor has also been observed in cardiac membranes47, 48and in the brainstem, for example nucleus tractus solitarii (NTS)[49]. Recently, a thorough characterization of the Y3 receptor in rat brainstem was carried out with various porcine NPY/PYY chimeras and other ligands[50]. Results indicated that positions
Variations in the pharmacological characterization of receptors
The choice of binding assay, for example binding of radioligand to membranes or whole cells, can result in different agonist and antagonist affinities. Furthermore, the type of radioligand and the species origin of the peptides used in an assay can have a major influence on the pharmacological profile of a particular Y-receptor. Species origin probably has minor effects for conserved peptides like NPY or PYY. However, major alterations may be observed for the less conserved PP. The use of
References (64)
Regul. Pept.
(1996)Genomics
(1995)J. Biol. Chem.
(1992)J. Biol. Chem.
(1995)FEBS Lett.
(1990)FEBS Lett.
(1992)J. Biol. Chem.
(1995)Biochim. Biophys. Acta
(1995)J. Biol. Chem.
(1993)Genomics
(1996)