MOLECULAR CHARACTERIZATION OF A DUAL ENDOTHELIN-1 ANGIOTENSIN-II RECEPTOR

Background: The molecular recognition theory (MRT) provides a conceptu al framework that could explain the evolution of intermolecular and in tramolecular interaction of peptides and proteins. As such, it predict s that binding sites of peptide hormones, and its receptor binding sit es were originally encoded by and evolved from complementary strands o f genomic DNA. Materials and Methods: On the basis of principles under lying the MRT, we screened a rat brain complementary DNA library using an AngII followed by an endothelin-1 (ET-1) antisense oligonucleotide probe, expecting to isolate potential cognate receptors. Results: An identical cDNA clone was isolated independently from both the AngII an d ET-1 oligonucleotide screenings. structural analysis revealed a rece ptor polypeptide containing a single predicted transmembrane region wi th distinct ET-1 and AngII putative binding domains. Functional analys is demonstrated ET-1- and AngII-specific binding as well as ET-1- and AngII- induced coupling to a Ca2+ mobilizing transduction system. Amin o acid substitutions within the predicted ET-1 binding domain oblitera te ET-1 binding while preserving AngII binding, thus defining the stru ctural determinants of ET-1 binding within the dual ET-1/AngII recepto r, as well as corroborating the dual nature of the receptor.Conclusion s: Elucidation of the dual ET-1/AngII receptor provides further molecu lar genetic evidence in support of the molecular recognition theory an d identifies for the first time a molecular link between the ET-1 and AngII hormonal systems that could underlie observed similar physiologi cal responses elicited by ET-1 and AngII in different organ systems. T he prominent expression of the ET-I/AngII receptor mRNA in brain and h eart tissues suggests an important role in cardiovascular function in normal and pathophysiological states.