You have recently cloned a cDNA from RNA isolated from human brain
tissue. The cDNA may encode a putative adrenergic receptor, based on its
putative DNA and amino acid sequence homologies to known adrenergic receptors.
You can assume it will be a new member of the beta adrenergic receptor family,
called beta5. You are also given a drug X100 which has potent action (EC50=1 x
10-11nM) in vivo similar to beta adrenergic agonists, but which does NOT bind
any of the known alpha or beta receptors. You may assume an active,
radiolabelled form of X100 ([¹²⁵I]-X100) is available.

The following questions #1-11 refer to what experiments you would
perform to characterize and confirm that this cDNA clone codes for beta5, a new
member of the adrenergic receptor family which binds all the same agonists and
antagonists as the beta2 receptor subtype, and uniquely binds the drug X100.
You stably express this cDNA in a cytomegalovirus-promoted expression plasmid
in Chinese Hamster Ovary cells (CHO cells) after selection with antibiotic, but
unfortunately, you can detect NOdetectable specific binding to [¹²⁵I]-X100!
You need to determine why
you can not detect binding, and what you must do to successfully express this
receptor in cultured cells and to determine its potential as a drug target for
human therapies. Since you can not detect
specific binding, what would be your reasons for doing each of the
following?

1. transfect the expression plasmid into other cell types,
including monkey COS cells and human embryonic kidney cells (HEK cells)? Explain your answer.