A phosphatidylinositol 3-kinase and phosphatidylinositol transfer protein act synergistically in formation of constitutive transport vesicles from the trans-Golgi network.
Current evidence suggests that phosphatidylinositol (PI) kinases and phosphatidylinositol transfer protein (PITP) are involved in driving vesicular traffic from yeast and mammalian trans-Golgi network (TGN). We have tested the interaction between these cytosolic proteins in an assay that measures the formation of constitutive transport vesicles from the TGN in a hepatocyte cell-free system. This reaction is dependent on a novel PI 3-kinase, and we now report that, under conditions of limiting cytosol, purified PI 3-kinase and PITP functionally cooperate to drive exocytic vesicle formation. This synergy was observed with both yeast and mammalian PITPs, and it also extended to the formation of PI 3-phosphate. These collective findings indicate that the PI 3-kinase and PITP synergize to form a pool of PI 3-phosphate that is essential for formation of exocytic vesicles from the hepatocyte TGN.
Jones
S M
SM
Department of Cellular and Structural Biology, University of Colorado School of Medicine, Denver, Colorado 80262, USA.
Alb
J G
JG
Phillips
S E
SE
Bankaitis
V A
VA
Howell
K E
KE
D000818:Animals; D001692:Biological Transport; D002352:Carrier Proteins / Q000378:metabolism*; D005089:Exocytosis; D006056:Golgi Apparatus / Q000378:metabolism*; D008099:Liver / Q000378:metabolism / Q000648:ultrastructure; D008565:Membrane Proteins; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D010716:Phosphatidylinositols / Q000378:metabolism*; D049294:Phospholipid Transfer Proteins; D051381:Rats; D029701:Saccharomyces cerevisiae Proteins; D013379:Substrate Specificity
D002352:Carrier Proteins; D008565:Membrane Proteins; D010716:Phosphatidylinositols; D049294:Phospholipid Transfer Proteins; C118289:SEC24 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D019869:Phosphatidylinositol 3-Kinases