Cells in the body communicate by releasing chemicals that travel to other cells and direct their behavior. These chemicals control vital processes, ranging from brain function to heart pumping to sexual reproduction. In work extending over 35 years, Professor Robert Lefkowitz showed us how chemical messengers are received and interpreted by target cells. The key is a family of proteins called G-protein coupled receptors (GPCRs) embedded in the surface membranes of receiving cells. GPCRs are distinguished from other receptors because they crisscross the membrane seven times, thereby giving rise to the alternate name of 7-transmembrane receptors. The GPCRs were theoretical concepts in the early 1970’s when Lefkowitz began the painstaking process of isolating a receptor and determining its structure. A milestone was reached in 1986 when Lefkowitz and collaborators at Merck Sharp and Dohme Research Laboratories isolated the gene encoding one receptor and used it to elucidate the protein’s primary structure. With this information as a starting point, Lefkowitz and others soon found that the genome encodes hundreds of related receptors, each specific for a different chemical messenger. Lefkowitz’s work up to this day continues to contribute to our understanding of the properties of these receptors. He demonstrated that receptors are not always active.
After they transmit their signals the receptors are silenced by a feedback mechanism that prevents over-stimulation. In elucidating feedback silencing, Lefkowitz discovered novel proteins that not only silence receptors, but also play diverse roles in physiology, controlling processes that include cell growth and differentiation. Although many scientists contributed to solving the signaling problem, Lefkowitz led the way throughout. As a result of his work, pharmaceutical companies now understand the mechanism whereby many of their classic drugs control pathologic processes. Examples include β-blockers (such as propronolol) for high blood pressure and congestive heart failure, H2 antagonists (such as cimetidine) for peptic ulcers, H1 antagonists (such as chlorpheniramine) for allergy, and dopamine antagonists (such as clozapine) for schizophrenia. This knowledge now permits companies to search for even more powerful drugs that target a wide variety of G-protein coupled receptors, thereby treating a wide assortment of diseases.