Responses of the silkworm tyramine receptor to 2-phenylethylamines and 5-phenyloxazoles.
Tyramine (TA), a biogenic amine, attenuates intracellular cAMP production by acting on its receptor in insects. Several non-biogenic amines were examined for their actions on native and heterologously expressed silkworm TA receptors. 5-(4-Hydroxyphenyl)oxazole, which showed an attenuating effect on cAMP production in silkworm-head membranes, did not attenuate forskolin-stimulated cAMP production in HEK-293 cells expressing the silkworm TA receptor, although the compound bound to the cloned receptor. 2-Phenylethylamines (2-PEAs), which showed positive and negative effects on cAMP production in silkworm-head membranes, inhibited [3H]TA binding to the cloned TA receptor. 2-Chloro-2-(4-chlorophenyl)ethylamine was the most potent inhibitor of [3H]TA binding among the 2-PEAs tested, with an IC50 of 30.4 nM. This compound acted as an antagonist and abolished TA-attenuation of forskolin-stimulated cAMP production in the cloned TA receptor. The discrepancy in the effects of the non-biogenic amines on the native and cloned TA receptors remains to be further examined. A newly synthesized 2-PEA, 2-chloro-2-(4-hydroxyphenyl)ethylamine, attenuated forskolin-stimulated cAMP production in the cloned TA receptor, indicating that the para-hydroxy group is important for the agonist action.
Department of Life Science and Biotechnology, Faculty of Life and Environmental Science, Shimane University, Matsue, Shimane, Japan.
Hiroto
H
Ohta
Md Anwar Arfien
MA
Khan
Idumi
I
Nagai
Natsuko
N
Umemoto
Tomohiro
T
Hamasaki
Yoshihisa
Y
Ozoe
D000818:Animals; D012831:Bombyx / Q000378:metabolism*; D002460:Cell Line; D005576:Colforsin; D000242:Cyclic AMP / Q000378:metabolism*; D006801:Humans; D020128:Inhibitory Concentration 50; D010063:Ovum / Q000378:metabolism*; D010080:Oxazoles / Q000494:pharmacology*; D010627:Phenethylamines / Q000494:pharmacology*; D017982:Receptors, Biogenic Amine / Q000037:antagonists & inhibitors* / Q000378:metabolism; D014316:Tritium; D014439:Tyramine / Q000378:metabolism*
D010080:Oxazoles; D010627:Phenethylamines; D017982:Receptors, Biogenic Amine; C066175:tyramine receptor; D014316:Tritium; D005576:Colforsin; C029261:phenethylamine; D000242:Cyclic AMP; D014439:Tyramine