An essential role for phosphatidylinositol transfer protein in phospholipase C-mediated inositol lipid signaling.
basic_science · Level V
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Abstract
Transmembrane signaling by the phospholipase C-beta (PLC-beta) pathway is known to require at least three components: the receptor, the G protein, and the PLC. Recent studies have indicated that if the cytosol is allowed to leak out of HL60 cells, then G protein-stimulated PLC activity is greatly diminished, indicating an essential role for a cytosolic component(s). We now report the complete purification of one component based on its ability to reconstitute GTP gamma S-mediated PLC activity and identify it as the phosphatidylinositol transfer protein (PI-TP). Based on the in vitro effects of PI-TP, we surmise that it is involved in transporting PI from intracellular compartments for conversion to PI bisphosphate (PIP2) prior to hydrolysis by PLC-beta 2/PLC-beta 3, the endogenous PLC isoforms present in these cells.
Medical subject headings
- Carrier Proteins
- GTP-Binding Proteins
- Membrane Proteins
- Phosphatidylinositols
- Saccharomyces cerevisiae Proteins
- Signal Transduction
- Type C Phospholipases