The finding in the last two years of different proteins presenting structural homology with platelet thrombospondin (TSP-1) has permitted to establish the existence of a set of related genes referred to as thrombospondin family. While much work remains to be done concerning the characterization of the newly described members of the family, careful studies carried out on TSP-1 have been implicating this high molecular weight molecule (420-450 kDa) in a variety of aspects of cellular physiology. 2. The present text discusses the implications of the matrix-bound and fluid TSP-1 forms for cell adhesion and protease activity generation. Their relationships with growth factors in matrices are also discussed.
