Controlled extracellular proteolysis of thrombospondins

Limited proteolysis of thrombospondins is a powerful mechanism to ensure dynamic tuning of their activities in the extracellular space. Thrombospondins are multifunctional matricellular proteins composed of multiple domains, each with a specific pattern of interactions with cell receptors, matrix components and soluble factors (growth factors, cytokines and proteases), thus with different effects on cell behavior and responses to changes in the microenvironment. Therefore, the proteolytic degradation of thrombospondins has multiple functional consequences, reflecting the local release of active fragments and isolated domains, exposure or disruption of active sequences, altered protein location, and changes in the composition and function of TSP-based pericellular interaction networks. In this review current data from the literature and databases is employed to provide an overview of cleavage of mammalian thrombospondins by different proteases. The roles of the fragments generated in specific pathological settings, with particular focus on cancer and the tumor microenvironment, are discussed.