A non-internalized non-desensitized truncated at1a receptor
transduces an amplified angiotensin ii signal.
Conchon, Sophie, Nicolas Peltier, Pierre Corvol, and Eric Clauser.
Institut National de la Sante et de la Recherche Medicale Unite 36
- College de France - 3 rue d'Ulm 75005 Paris - France.
APStracts 4:0234E, 1997.
The structural determinants of the rat angiotensin (Ang) II AT1A
receptor involved in receptor internalization, desensitization and
activation were investigated by producing 6 mutants which had
progessively larger deletions of the cytoplasmic tail (-13, -19, -24,
-31, -46 and -56 residues respectively). After stable transfection of
the cDNAs into CHO cells, all mutants, except the most truncated,
exhibit normal [Sar1]AngII affinities (Kd = 0.19 to 0.70nM) as
compared to the wild-type (WT) receptor (Kd = 0.62nM) and are able to
activate a Gq/11 protein and a phospholipase C as measured by the
AngII-induced inositol phosphate (IP) turnover in the different
clones.
However, one of these mutants, 329 (deletion of 31 residues), exhibits
a peculiar phenotype. This mutant shows a reduced ligand-induced
internalization as measured by the acid washing procedure (only 32%
of receptors are internalized versus 83% for the WT). Moreover, the
329 mutant is less desensitized by a pretreatment with either AngII
(15% desensitization of the AngII-stimulated IP turnover versus 60%
for the WT receptor) or the phorbol ester PMA (no desensitization
versus 29% for the WT receptor). These functional modifications of
the 329 mutant are associated with the transduction of an amplified
signal as demonstrated on both IP turnover and an integrated
physiological effect of AngII. Taken together, these data indicate
that the sequence 329SLSTKMS335 of the rat AT1A receptor is involved
in both receptor internalization and desensitization. This is the
first demonstration that a desensitization and internalization
defective AT1A receptor mutant is also hyper-reactive and mediates
augmented cellular responses.
Received 24 January 1997; accepted in final form 17 October 1997.
APS Manuscript Number E40-7.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 29 October 1997