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Originally published as MBC in Press, 10.1091/mbc.E07-12-1208 on February 6, 2008

Vol. 19, Issue 4, 1663-1669, April 2008

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Diffusion Coefficient of Fluorescent Phosphatidylinositol 4,5-bisphosphate in the Plasma Membrane of Cells

Urszula Golebiewska, Marian Nyako, William Woturski, Irina Zaitseva, and Stuart McLaughlin

Department of Physiology and Biophysics, Health Science Center, Stony Brook University, Stony Brook, NY 11794-8661

Submitted December 6, 2007; Revised January 10, 2008; Accepted January 24, 2008
Monitoring Editor: Tom U. Martin

InCytes from MBC

Phosphatidylinositol 4,5-bisphosphate (PIP2) controls a surprisingly large number of processes in cells. Thus, many investigators have suggested that there might be different pools of PIP2 on the inner leaflet of the plasma membrane. If a significant fraction of PIP2 is bound electrostatically to unstructured clusters of basic residues on membrane proteins, the PIP2 diffusion constant, D, should be reduced. We microinjected micelles of Bodipy TMR-PIP2 into cells, and we measured D on the inner leaflet of fibroblasts and epithelial cells by using fluorescence correlation spectroscopy. The average ± SD value from all cell types was D = 0.8 ± 0.2 µm2/s (n = 218; 25°C). This is threefold lower than the D in blebs formed on Rat1 cells, D = 2.5 ± 0.8 µm2/s (n = 26). It is also significantly lower than the D in the outer leaflet or in giant unilamellar vesicles and the diffusion coefficient for other lipids on the inner leaflet of these cell membranes. The simplest interpretation is that approximately two thirds of the PIP2 on inner leaflet of these plasma membranes is bound reversibly.


This was published online ahead of print in MBC in Press (http://www.molbiolcell.org/cgi/doi/10.1091/mbc.E07-12-1208) on February 6, 2008.

Address correspondence to: Stuart McLaughlin (stuart.mclaughlin{at}stonybrook.edu).

Abbreviations used: FCS, fluorescence correlation spectroscopy; GUV, giant unilamellar vesicle; MARCKS, myristoylated alanine rich C kinase substrate.


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The Pleckstrin Homology Domain of the Arf6-specific Exchange Factor EFA6 Localizes to the Plasma Membrane by Interacting with Phosphatidylinositol 4,5-Bisphosphate and F-actin
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