Mu-Opiod receptor splice variant polypeptides
The present invention encompasses novel splice variant forms of the mu-opioid receptor-1 (MOR-1) and the polynucleotide sequences encoding the MOR-1 splice variants. The invention further encompasses methods of screening for compositions regulating the MOR-1 splice variant activities and the development of therapeutic modalities directed to regulating activity. Regulation of the MOR-1 splice variant activities may impact the physiologic process of analgesia.
1. An isolated human MOR-1P splice variant polypeptide that consists essentially of the amino acid residues having the sequence of SEQ ID NO 40.
2. An isolated human MOR-1O splice variant polypeptide that consists essentially of the amino acid residues having the sequence of SEQ ID NO 39.
3. A method of screening compositions for opioid activity comprising the steps of: a) obtaining a control cell that does not express an MOR-1 splice variant polypeptide; b) obtaining a test cell that is the same as the control cell except that it expresses an MOR-1 splice variant polypeptide of claim 1 or 2 ; c) contacting the control cell and test cell with an amount of an opioid sufficient to exert a physiologic effect; d) separately measuring the physiologic effect of the composition on the control cell and test cell; and e) comparing the physiologic effect wherein the physiologic effect is a change in the level of neuroendocrine hormones of the composition to the physiologic effect of the opioid, where determination of a physiologic effect of the composition is expressed relative to that of the opioid.
4. The method according to claim 3 , where the composition is selected from the group consisting of synthetic combinatorial libraries of small molecule ligands, eukaryotic whole cell lysates or extracts, or media conditioned by cultured eukaryotic cells.
5. The method according to claim 3 , where the opioid is selected from the group consisting of morphine, methadone, etorphine, levorphanol, fentanyl, sufentanil, [D-Ala2,MePhe4,Gly(ol)5]enkephalin, pentazocine, ethylketocyclazocine, bremazocine, spiradoline, [D-Ser2,Leu5]enkephalin-Thr6, Met-enkephalin, Leu-enkephalin, (3-endorphin, dynorphin A, dynorphin B, or a-neoendorphin.
6. The method according to claim 3 , where the hormone is selected from the group consisting of prolactin, growth hormone, gonadotropin-releasing hormone, adrenocorticotropin, corticotropin-releasing factor, luteinizing hormone, follicle stimulating hormone, testosterone or cortisol.
7. A method of screening compositions for opioid binding activity comprising the steps of: a) obtaining a control polypeptide that is not an MOR-1 splice variant polypeptide; b) obtaining a test polypeptide that is an MOR-1 splice variant polypeptide of claim 1 or 2 ; c) contacting a composition with the control polypeptide and the test polypeptide; d) contacting the test polypeptide with an amount of an opioid sufficient to measurably bind the test polypeptide; e) measuring the binding of the composition and the opioid; and f) comparing test polypeptide binding of the composition to that of the opioid, where determination of binding of the composition is expressed relative to that of the opioid.
8. The method according to claim 7 where the composition is selected from the group consisting of synthetic combinatorial libraries of small molecule ligands, eukaryotic whole cell lysates or extracts, or media conditioned by cultured eukaryotic cells.