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Free keywords:
Calcium; Membrane structure; Plasma membrane; Protein-lipid interaction; SNARE proteins; PI(4; 5)P-2; Clustering; Membrane domains; Syntaxin 1
Abstract:
Phosphatidylinositiol 4,5-bisphosphate (PI(4,5)P2) is a minor component of total plasma membrane lipids, yet it has a substantial role in 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 super-resolution STED microscopy, Foerster resonance energy transfer (FRET) and atomic force microscopy (AFM) we show that calcium ions act as the charge bridges that specifically and reversibly connect multiple syntaxin 1/PI(4,5)P2 complexes into larger mesoscale domains. This transient reorganization of the plasma membrane by physiological calcium concentrations is likely to be important for caaclium-regulated secretion.
