CLONING AND PHARMACOLOGICAL CHARACTERIZATION OF HUMAN ALPHA-1-ADRENERGIC RECEPTORS - SEQUENCE CORRECTIONS AND DIRECT COMPARISON WITH OTHER SPECIES HOMOLOGS

We have cloned cDNAs encoding three human alpha-1 adrenergic receptor (AR) subtypes and characterized pharmacological properties of the expr essed receptor protein. A number of significant sequence corrections h ave been identified and compared with previously published data, at bo th nucleotide and amino acid levels; the most major differences occur for the human alpha-1(a/d)AR. Pharmacological characterization was per formed simultaneously using six cloned alpha-1AR subtypes (human and r at alpha-1(a/d), human and hamster alpha-1(b), human and bovine alpha- 1(c)) stably expressed in rat-1 fibroblasts at approximately equal rec eptor concentrations (1-2 pmol/mg of total protein). In general, human alpha-1AR subtypes have similar pharmacology compared to their rat, h amster and bovine homologs, although a few minor species differences i mportant for alpha-1AR classification are noted. In addition, much low er inactivation (approximate to 20%) by the alkylating agent chloroeth ylclonidine is noted in this study compared to previous reports for bo th human and bovine alpha-1(c)AR membrane preparations. All six alpha- 1 AR subtypes couple to phosphoinositide hydrolysis in a pertussis tox in-insensitive manner, including the cloned human alpha-1(a/d)AR which had not been expressed previously. In spite of significant sequence d ifferences between human alpha-1ARs and their other species counterpar ts, previously established ligand selectivity remains fairly comparabl e. In summary, these data represent the first side-by-side comparison of pharmacological properties between species homologs of alpha-1AR su btypes and should facilitate the development of alpha-1AR subtype sele ctive drugs for clinical use.