Coding block and 5 ' leader cistron polymorphisms of the beta(2)-adrenergic receptor

The gene encoding the beta(2)-adrenergic receptor (beta(2)AR) is highly pol ymorphic in the human population. Common polymorphisms in the receptor codi ng block (amino acids 16 and 27) affect agonist-promoted downregulation. An other common polymorphism in the 5' leader cistron of the beta(2)AR gene al so regulates receptor expression, but does so through a mechanism that is i ndependent of agonist exposure. None of these polymorphisms appears to be c ausative factor for asthma. However, data from several studies now indicate that the asthmatic phenotype and therapeutic response may be modified by t he different polymorphic variants. This modifying effect is not likely due to a single dominant polymorphic locus, but rather the result of interactio n among multiple polymorphic loci that regulate receptor expression through different mechanisms.