Eg. Ponimaskin et al., 5-hydroxytryptamine 4(a) receptor expressed in Sf9 cells is palmitoylated in an agonist-dependent manner, BIOCHEM J, 353, 2001, pp. 627-634
The mouse 5-hydroxytryptamine 4(a) receptor [5-HT4(a)] was expressed with a
baculovirus system in insect cells and analysed for acylation. [H-3]Palmit
ic acid was effectively incorporated into 5-HT4(a) and label was sensitive
to the treatment with reducing agents indicating a thioester-type bond. Ana
lysis of protein-bound fatty acids revealed that 5-HT4(a) contains predomin
antly palmitic acid. Treatment of infected Sf9 (Spodoptera frugiperda) cell
s with BIMU8 {(endo-N-8-methyl-8-azabicyclo[3.2.1]oct-3-yl)-2,3-dehydro-2-o
xo-3-(prop-2-yl)- 1H-benzimid-azole-1-carboxamide), a 5-HT4 receptor-select
ive agonist, generated a dose-dependent increase in [H-3]palmitate incorpor
ation into 5HT(4(a)) with an EC50 of approx. 10 nM. The change in receptor
labelling after stimulation with agonist was receptor-specific and did not
result from general metabolic effects.. We also used both pulse labelling a
nd pulse-chase labelling to address the dynamics of 5-HT4(a) palmitoylation
. Incorporation studies revealed that the rate of palmitate incorporation w
as increased approx. 3-fold after stimulation with agonist. Results of puls
e-chase experiments show that activation with BIMU8 promoted the release of
radiolabel from 5-HT4(a), thereby reducing the levels of receptor-bound pa
lmitate to approximately one-half. Taken together. our results demonstrate
that palmitoylation of 5-HT4(a) is a reversible process and that stimulatio
n of 5-HT4(a) with agonist increases the turnover rate for receptor-bound p
almitate. This provides evidence for a regulated cycling of receptor-bound
palmitate and suggests a functional role for palmitoylation/depalmitoylatio
n in 5-hydroxytryptamine-mediated signalling.