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Why are most drug receptors located in cell membranes?

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Gleevec; imatinib — drug Docking of the anticancer drug Gleevec (imatinib) in the abl domain of the bcr-abl tyrosine kinase. Abnormalities in bcr-abl stimulate the continuous proliferation of bone marrow stem cells, causing an increase in myelogenous cells (granulocytes and macrophages) in the body and leading to chronic myelogenous leukemia (CML).

Most receptors are incorporated into the cell membrane with their binding regions facing the exterior of the cell. This specific positioning is advantageous because it provides endogenous chemical messengers, such as hormones or neurotransmitters, with freer access to the cell without requiring them to penetrate the membrane.12

By situating these protein molecules on the surface, the cell can efficiently recognize and respond to signaling molecules that are unable to cross the lipid bilayer. Once a drug binds to these membrane-bound receptors, it can initiate physiological changes through various mechanisms, such as controlling ion channels or triggering intracellular signaling cascades via second messengers. In contrast, receptors for certain substances like steroid hormones are located inside the cell, meaning they are only accessible to molecules capable of crossing the membrane.12