Thrombospondins: Multifunctional regulators of cell interactions

dThrombospondins are secreted, multidomain macromolecules that act as regul ators of cell interactions in vertebrates. Gene knockout mice constructed f or two members of this family demonstrate roles in the organization and hom eostasis of multiple tissues, with particularly significant activities in t he regulation of angiogenesis. This review discusses the functions of throm bospondins with regard to their cellular mechanisms of action and highlight s recent advances in understanding how multifactorial molecular interaction s, at the cell surface and within extracellular matrix, produce cell-type-s pecific effects on cell behavior and the organization of matrix and tissues .