Adhesive glycoprotein that mediates cell-to-cell and cell-to-matrix interactions. Can bind to fibrinogen, fibronectin, laminin, type V collagen and integrins alpha-V/beta-1, alpha-V/beta-3 and alpha-IIb/beta-3 (By similarity). May play a role in ER stress response (By similarity). Homotrimer; disulfide-linked. Belongs to the thrombospondin family.