Schematic representation of translocation of fibrin to lipid rafts. On platelet activation, fibrin(ogen) binds to integrin α_IIbβ₃. In the presence of FXIII, the α_IIbβ₃-finbrin(ogen) complex translocates to SM-rich rafts. FXIIIa crosslinks fibrin fibrils to each other and covalently links fibrin to α_IIbβ₃ and possibly other, as yet unidentified, receptors. Concurrently, translocation of cFXIII to the lipid raft–associated actin cytoskeleton would promote crosslinking of receptor cytoplasmic domains to the cytoskeleton. Together, FXIII-dependent crosslinking would cement extracellular fibrin cables to the intracellular platelet cytosolic motors to promote clot retraction.