c-Fos reorganizes phospholipids at the interface

GRACIELA ADRIANA BORIOLI

Bariloche

Congreso; Reunión Anual de la Sociedad Argentina de Biofísica; 2003

SAB

The transcription factor c-Fos has been studied from novel viewpoints not related to nuclear transcription in recent years. It has been demonstrated that it activates phospholipid biosynthesis both in vivo and in vitro through a citoplasmic activity associated with endoplasmic reticulum (1, 2), and that it has surface activity and interacts differentially with phospholipids, especially phosphatidyl inositoldiphosphate (PIP₂), in monolayers (3). Furthermore, it modulates phospholipase A₂, sphingomyelinase and phospholipase C activity on lipid monolayers in a fienly tuned way depending on surface lateral pressure (4). Our studies, aimed at elucidating the mechanism by which c-Fos could play a role in phospholipid metabolism, anlayse the compressional behavior of lipid-protein film mixtures seen by surface lateral pressure and surface potential monitoring, epifluorescence microscopy and Brewster angle microscopy. We find that c-Fos affects intermolecular packing, depending on the phospholipid. Mixed films of the protein with either PIP₂ or dilauroylphosphatidylcholine are non ideal, respectively condensed or expanded, and show domain segregation. The contribution to deviation from ideality of each component in the mixture clearly depends on packing. Our results support the idea that c-Fos could participate as a signal transducer in membrane function.