Ca2+-dependent cross-linking processes in human platelets

Isaac Cohen*, Tova Glaser, Arthur Veis, Joyce Bruner-Lorand

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

43 Scopus citations


When platelet cytoplasmic Ca2+ is increased by the ionophore A23187 in the presence of the protease inhibitor leupeptin, there is the coincident appearance of a cross-linked polymer and the partial disappearance of monomeric protein and glycoprotein units. In the absence of leupeptin only 30% of the polymer was formed. The disappearance of monomeric protein bands, as detected by sodium dodecyl sulfate polyacrylamide gel electrophoresis, is prevented by histamine, which as a pseudodonor amine is a known inhibitor of transglutaminase-catalyzed cross-linking. [14C]Histamine, at a tracer concentration, is incorporated into the polymer as well as into myosin, glycoproteins IIB and III, actin and tropomyosin. The lose of monomeric protein bands is mostly due to their conversion into polymers. Control measurements show that leupeptin effectively inhibited platelet Ca2+-dependent proteases. The cross-linking processes bringing about the observed increase in polymer formation are thus the result of a Ca2+-dependent platelet transglutaminase activity. The latter is located in the platelet cytosol and has been identified as platelet factor XIII on the basis of its specific cross-linking of fibrin. Platelet factor XIII, upon activation, may function physiologically to couple membrane proteins to cytoplasmic structural proteins. Thus, a new concept is proposed for the stabilization of platelet membranes and platelets as they form the hemostatic plug.

Original languageEnglish (US)
Pages (from-to)137-147
Number of pages11
JournalBBA - General Subjects
Issue number2
StatePublished - Aug 17 1981


  • (Human platelet)
  • Ca dependence
  • Cross-linking
  • Factor XIII

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Molecular Biology

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