Mammalian thrombospondins (TSPs) are a group of large, secreted, calcium-binding glycoproteins of complex spatial structure that mediate a wide range of intercellular activities and participate in cell-matrix interactions. This family includes five proteins, divided into two subfamilies, that possess different roles and tissue expression. TSPs have complex roles in mediating cellular processes. Apoptotic cell and phagocyte interactions show a dynamic structure with expanding complexity. However, a vast majority of the consequences of these interactions can be mediated by a single protein. One of these signaling molecules is TSP-1, which binds to a wide variety of integrin and nonintegrin cell surface receptors and mediates both engulfment and immune modulation. This mechanism is not only important in homeostasis but may also be a major mechanism for inflammation downregulation and in avoiding autoimmunity.
© 2010 New York Academy of Sciences.