Claudia G. Wiedemann

Vesicular transport: Sticky fingers grab a lipid

Within the past ten years, inositol lipids have increasingly been implicated in membrane-transport processes. Three studies now show what connects one inositol lipid — phosphatidylinositol-3-phosphate, PtdIns(3)P — to endocytosis. It turns out that a protein called the early endosomal autoantigen EEA1 contains a domain called FYVE that can bind, specifically and directly, to PtdIns(P)3. Whats more, EEA1 can also bind to Rab5, a protein involved in endocytosis.

The Role of Phosphatidylinositol Transfer Proteins (PITPs) in Intracellular Signalling

Phosphatidylinositol transfer protein (PITP) has been identified as a key player in numerous signalling pathways relying on phosphatidylinositol (PI) metabolites. Although its cellular function is most likely linked to its PI/phosphatidylcholine (PC) transfer activity-an in vitro activity shared by all known PITPs-this feature cannot explain all findings from studies with PITP. Here, we review evidence suggesting that one of the main functions of PITP in cellular signalling is to present PI to lipid kinases for localized production of phosphatidylinositol (4,5)-bisphosphate (PIP(2)), either to be used as a signalling molecule (for example, in exocytosis) or as a substrate (for example, by phospholipases).