Ligands for Surface Receptors

Abstract

In Chap. 29, “Agonists and Antagonists of Membrane-Bound Receptors,” receptors were discussed that allow a signal transmission from outside the cell to its interior. Numerous processes in the cell are initiated by these systems that alter the cell’s state. In addition to this type of information exchange, a cell must also have other ways to remain constantly in contact with its environment. To accomplish this task, they have many other surface receptors. For example, the cell’s integrin receptor not only can accept signals from outside, it can also transmit signals into the environment. If a cell moves, for example in a blood vessel or in tissue, it must remain in constant communication with the environment during the translocation. In this way, leukocytes find their way to sites of infection as part of immune response to pathogens. For this, they receive signals from the environment through their surfaces by using special surface receptors. In viral disease, a virus attempts to adhere to a host cell and finally to penetrate the cell. The recognition of endogenous cell-surface receptors or special adhesion molecules initially occurs before the target cell under attack can be reprogrammed in the invasion process. After viral maturation and reproduction, the new virus must be budded and released from the infected host cell (exocytosis). Proteins that are exposed to the surface also regulate this process. Drugs can be used to intervene in both processes: the attack by and release of viruses. Our immune system uses specific surface proteins to distinguish between diseased and healthy cells. Influencing these processes leads to immune stimulation. The structure and function of the above-mentioned surface receptors shall be discussed in this chapter. How specific ligands can suppress or reprogram the actual tasks of these surface receptors to lead to a successful therapeutic concept shall be explained.