Journal of Biological Chemistry
Calcium promotes the formation of syntaxin 1 mesoscale domains through phosphatidylinositol 4, 5-bisphosphate
Milovanovic, D., Platen, M., Junius, M., Diederichsen, U., Schaap, I. A., Honigmann, A., ... & Van Den Bogaart, G.
calcium, membrane structure, plasma membrane, protein-lipid interaction, SNARE proteins, PI(4,5)P2, clustering, membrane domains, syntaxin 1
Phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) is a minor component of total plasma membrane lipids, but it has a substantial role in the regulation of many cellular functions, including exo- and endocytosis. Recently, it was shown that PI(4,5)P2 and syntaxin 1, a SNARE protein that catalyzes regulated exocytosis, form domains in the plasma membrane that constitute recognition sites for vesicle docking. Also, calcium was shown to promote syntaxin 1 clustering in the plasma membrane, but the molecular mechanism was unknown. Here, using a combination of superresolution stimulated emission depletion microscopy, FRET, and atomic force microscopy, we show that Ca2+ acts as a charge bridge that specifically and reversibly connects multiple syntaxin 1/PI(4,5)P2 complexes into larger mesoscale domains. This transient reorganization of the plasma membrane by physiological Ca2+ concentrations is likely to be important for Ca2+-regulated secretion.