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Characterization of Duplicate Delta Opioid receptors from zebrafish
Author(s) -
Rodriguez Raquel Emilia,
GonzalezNunez Veronica
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.5.a425-d
Subject(s) - diprenorphine , receptor , enkephalin , opioid , dynorphin , zebrafish , opioid receptor , proenkephalin , agonist , biology , chemistry , microbiology and biotechnology , opioid peptide , biochemistry , gene
zfDOR1 and zfDOR2 are two duplicate opioid receptors isolated from zebrafish. These receptors present similar homology to the mammalian delta opioid receptor (65 and 66%, respectively), and the encoded polypeptides show 72% identity among them. When expressed in HEK293 cells both receptors bound the non‐selective antagonist [3H]‐diprenorphine with high affinity (zfDOR1: KD = 3.4±0.6nM and a receptor density of Bmax= 4405±475 fmol/mg protein, ZFdor2: KD = 3.42±0.38nM and a Bmax of 6231±335 fmol/mg protein. We have also studied the effect of Met‐enkephalin‐Gly‐Tyr (MEGY), an opioid heptapeptide encoded in the zebrafish proenkephalin that binds to opioid sites from brain homogenates. While zfDOR1 presents one single binding site for [3H]‐MEGY (KD= 4.03±0.38nM), the experimental data from zfDOR2 fit better to the two‐site binding model (KD1= 0.79±0.18nM and KD2= 30.18±10.22nM). In competition binding assays using [3H]‐MEGY the Ki values found for zfDOR2 were always lower than those obtained for zfDOR1, except for dynorphin A. Our results prove the existence of two functional duplicate genes of the delta opioid receptor in the teleost zebrafish.