Robert Lefkowitz is the James B. Duke Professor of Medicine, and Investigator of the Howard Hughes Medical Institute at Duke University Medical Center, Durham, North Carolina, USA. His work has contributed in a major way to our understanding of how cells in our body communicate with other cells and how they respond to chemicals, hormones and drugs.

The human body is made up of many different types of tissues and many different kinds of cells. To coordinate body functions, cells signal to other cells in the same organ and in different organs by releasing chemical messengers that travel through the bloodstream. These chemicals control vital processes, ranging from brain function to heart beat to sexual reproduction. In work extending over 35 years, Robert Lefkowitz showed us how chemical messengers are received and interpreted by the cells they target. The key is a family of proteins, called G-protein coupled receptors (GPCRs) embedded in the surface membranes of receiving cells. These receptors 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 of these receptors 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, which are the most important targets of currently used therapeutic drugs. 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 how many of their classic drugs control pathologic processes. Examples include β-blockers (such as propranolol) for high blood pressure and heart failure, H₂ antagonists such as (cimetidine) for peptic ulcers, H₁ antagonists ("antihistamines" 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. As a result there is no field or subspecialty of medical practice which has not been touched by his discoveries.