The role of phospholipase D in regulated exocytosis [Lipids]

October 2nd, 2015 by Rogasevskaia, T. P., Coorssen, J. R.

There are a diversity of interpretations concerning the possible roles of phospholipase D and its biologically active product phosphatidic acid in the late, Ca2+-triggered steps of regulated exocytosis. To quantitatively address functional and molecular aspects of the involvement of phospholipase D -derived phosphatidic acid in regulated exocytosis, we used an array of phospholipase D inhibitors for ex vivo and in vitro treatments of sea urchin eggs and isolated cortices and cortical vesicles, respectively, to study late steps of exocytosis, including docking/priming and fusion. The experiments with fluorescent phosphaltidylcholine reveal a low level of phospholipase D activity associated with cortical vesicles but a significantly higher activity on the plasma membrane. The effects of phospholipase D activity and its product phosphatidic acid on the Ca2+-sensitivity and rate of fusion correlate with modulatory upstream roles in docking and priming rather than to direct effects on fusion per se.