Cooperativity of phosphatidylinositol transfer protein and phospholipase D in secretory vesicle formation from the TGN--phosphoinositides as a common denominator?

Phosphatidylinositol transfer protein (PITP) and phospholipase D (PLD) stimulate the formation of constitutive secretory vesicles (CSVs) and immature secretory granules (ISGs) from the trans-Golgi network (TGN) in a cell-free system. The stimulatory effects of PITP and PLD are additive. Stimulation by either PITP or PLD is blocked by geneticin, a member of the aminoglycoside antibiotics known to bind to phosphoinositides. Since the PLD we used is insensitive to geneticin, our results suggest that phosphoinositides promote secretory vesicle formation as downstream effectors of both PITP and PLD, possibly via the recruitment of proteins mediating membrane budding and fission.