| Autor: |
Moon, H-E., Cavalli, A., Bahia, D.S., Hoffmann, M., Massotte, D., Milligan, G. |
| Předmět: |
|
| Zdroj: |
Journal of Neurochemistry; Mar2001, Vol. 76 Issue 6, p1805-1813, 9p, 2 Charts, 10 Graphs |
| Abstrakt: |
To assess the relative capacity of the human δ opioid receptor to activate closely related G proteins, fusion proteins were constructed in which the α-subunits of either G[sub i1] or G[sub o1], containing point mutations to render them insensitive to the actions of pertussis toxin, were linked in-frame with the C-terminus of the receptor. Following transient and stable expression in HEK 293 cells, both constructs bound the antagonist [[sup 3]H]naltrindole with high affinity. d-ala[sup 2],d-leu[sup 5] Enkephalin effectively inhibited forskolin-stimulated adenylyl cyclase activity in intact cells in a concentration-dependent, but pertussis toxin-insensitive, manner. The high-affinity GTPase activity of both constructs was also stimulated by d-ala[sup 2],d-leu[sup 5] enkephalin with similar potency. However, enzyme kinetic analysis of agonist stimulation of GTPase activity demonstrated that the GTP turnover number produced in response to d-ala[sup 2],d-leu[sup 5] enkephalin was more than three times greater for G[sub i1]α than for G[sub o1]α. As the effect of agonist in both cases was to increase V[sub max] without increasing the observed K[sub m] for GTP, this is consistent with receptor promoting greater guanine nucleotide exchange, and thus activation, of G[sub i1]α compared with G[sub o1]α. An equivalent fusion protein between the human µ opioid receptor-1 and G[sub i1]α produced a similar d-ala[sup 2],d-leu[sup 5] enkephalin-induced GTP turnover number as the δ opioid receptor-G[sub i1]α fusion construct, consistent with agonist occupation of these two opioid receptor subtypes being equally efficiently coupled to activation of G[sub i1]α. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
|
Plný text