The distribution of polyphosphoinositides in lipid films

Fluorescence microscopy of Langmuir films is used to determine the effect of polyphosphoinositides (PPIs) on the structure of phosphatidylcholine-containing monolayers. Dramatic alterations in the texture of these films occur as the fraction of PPI in the film is altered. These changes depend on the ionic strength of the underlying subphase and can be accounted for by considering the electrostatic interactions among PPIs. Surface adsorption of a fluorescent peptide derivative based on the PPI binding site of the protein gelsolin co-localizes with PPI-rich domains. Localization of polyphosphoinositides in domains within the inner leaflet of the plasma membrane is proposed to be a key element in some aspects of intracellular signaling, and these data have implications for explaining the cause of restructuring of such domains.