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.
Publication types
-
Comparative Study
-
Research Support, Non-U.S. Gov't
MeSH terms
-
Amino Acid Sequence
-
Animals
-
Carrier Proteins / chemistry
-
Carrier Proteins / isolation & purification
-
Carrier Proteins / metabolism*
-
Cell Membrane / metabolism
-
GTP-Binding Proteins / metabolism*
-
Guanosine 5'-O-(3-Thiotriphosphate) / pharmacology
-
Humans
-
Immunoblotting
-
Kinetics
-
Leukemia, Promyelocytic, Acute
-
Membrane Proteins*
-
Molecular Sequence Data
-
Phosphatidylinositols / metabolism*
-
Phospholipid Transfer Proteins
-
Rats
-
Saccharomyces cerevisiae Proteins*
-
Sequence Homology, Amino Acid
-
Signal Transduction*
-
Tumor Cells, Cultured
-
Type C Phospholipases / chemistry
-
Type C Phospholipases / isolation & purification
-
Type C Phospholipases / metabolism*
Substances
-
Carrier Proteins
-
Membrane Proteins
-
Phosphatidylinositols
-
Phospholipid Transfer Proteins
-
SEC24 protein, S cerevisiae
-
Saccharomyces cerevisiae Proteins
-
Guanosine 5'-O-(3-Thiotriphosphate)
-
Type C Phospholipases
-
GTP-Binding Proteins