Platelet Receptors

Platelet receptors are how platelets interact with their environment in order to function. They enable signals to pass to the platelet interior and change functional aspects of the platelet exterior. Major receptors (described in detail in other chapters) have well-established ligands and functions, but there are a large number of minor receptors whose roles and ligands are only starting to be identified. Some of the receptors are always present on the plasma membrane, but others are on granule membranes and are only exposed following exocytosis. While their major roles are in hemostasis, a growing number of "minor" receptors are involved in other platelet activities such as immunity or in regulating physiological functions. Some receptors can be downregulated by shape change or by induced proteolytic activity. Since platelets lack a nucleus, they are dependent on their receptors and exocytosis to react to new situations.