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. Author manuscript; available in PMC: 2023 Aug 1.
Published in final edited form as: Arterioscler Thromb Vasc Biol. 2022 Jun 2;42(8):931–941. doi: 10.1161/ATVBAHA.122.317164

Figure 2. Platelet FXIII-A activation and externalization.

Figure 2.

In unstimulated platelets, FXIII-A exists in the cytoplasm in a diffuse distribution. After platelet activation, increased intracellular Ca2+ nonproteolytically activates FXIII-A to FXIII-A° which crosslinks cytoskeletal proteins and contributes to cytoskeletal rearrangement and platelet conformational change. After stimulation by strong dual agonists (convulxin + thrombin), two populations of FXIII-A-exposing platelets are formed: spread platelets with FXIII-A in a diffuse distribution, and ballooned procoagulant (phosphatidylserine-exposing) platelets with FXIII-A on a protruding “cap”. FXIII-A is also exposed on extracellular vesicles (EVs).