Requirement of membrane-proximal amino acids in the carboxyl-terminal tail for expression of the rat AT1a angiotensin receptor.

A series of deletion mutants was created to analyze the function of the membrane-proximal region of the cytoplasmic tail of the rat type 1a (AT1a) angiotensin receptor. In transiently transfected COS-7 cells, the truncated mutant receptors showed a progressive decrease in surface expression, with no major change in binding affinity for the peptide antagonist, [Sar1,Ile8]angiotensin II. In parallel with the decrease in receptor expression, a progressive decrease in angiotensin II-induced inositol phosphate responses was observed. Alanine substitutions in the region 307-311 identified the highly conserved phenylalanine309 and adjacent lysine residues as significant determinants of AT1a receptor expression.