ATP-dependent inositide phosphorylation required for Ca(2+)-activated secretion

Nature. 1995 Mar 9;374(6518):173-7. doi: 10.1038/374173a0.


Regulated fusion of secretory granules with the plasma membrane in secretory cells requires ATP, Ca2+ and cytosolic as well as membrane proteins. ATP-dependent steps in Ca(2+)-activated secretion from PC12 cells require three cytosolic PEP proteins (priming in exocytosis proteins, PEP1-3), the identity of which will provide insights into the required ATP-using reactions. PEP3 was recently identified as phosphatidylinositol transfer protein (PtdInsTP), and here we report that PEP1 consists of the type I phosphatidylinositol-4-phosphate 5-kinase (PtdInsP5K). The roles of PEP3/PtdInsTP and PEP1/PtdInsP5K in sequential phosphoinositide recruitment and phosphorylation explains their synergistic activity in ATP-dependent priming. Moreover, inhibition of Ca(2+)-activated secretion by PtdIns(4,5)P2-specific antibodies and phospholipase C implies that 5-phosphorylated inositides play a novel, necessary role in the regulated secretory pathway. The results indicate that lipid kinase-mediated phosphorylation is an important basis for ATP use in the exocytotic pathway.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adenosine Triphosphate / metabolism*
  • Animals
  • Calcium / metabolism*
  • Carrier Proteins / metabolism*
  • Cattle
  • Cytosol / metabolism
  • Exocytosis*
  • Membrane Proteins*
  • Norepinephrine / metabolism
  • PC12 Cells
  • Phosphatidylinositols / metabolism*
  • Phospholipid Transfer Proteins
  • Phosphorylation
  • Phosphotransferases (Alcohol Group Acceptor) / antagonists & inhibitors
  • Phosphotransferases (Alcohol Group Acceptor) / metabolism*
  • Rats
  • Type C Phospholipases / metabolism


  • Carrier Proteins
  • Membrane Proteins
  • Phosphatidylinositols
  • Phospholipid Transfer Proteins
  • Adenosine Triphosphate
  • Phosphotransferases (Alcohol Group Acceptor)
  • 1-phosphatidylinositol-4-phosphate 5-kinase
  • Type C Phospholipases
  • Calcium
  • Norepinephrine