Phosphorylation and redistribution of the phosphatidylinositol-transfer protein in phorbol 12-myristate 13-acetate- and bombesin-stimulated Swiss mouse 3T3 fibroblasts.
By immunofluorescence microscopy it was shown that the phosphatidylinositol-transfer protein (PI-TP) becomes associated with the Golgi membranes when confluent (quiescent) Swiss mouse 3T3 fibroblast cells are stimulated with phorbol 12-myristate 13-acetate (PMA) and bombesin. Dibutyryl cyclic AMP or dexamethasone had no effect on the intracellular redistribution of PI-TP. In exponentially growing cells and in serum-starved (semi-quiescent) cells, PI-TP is already associated with Golgi structures. Stimulation of semi-quiescent cells by PMA resulted in a rapid redistribution of PI-TP. A similar yet slower response was observed after stimulation with bombesin. Stimulation of semi-quiescent 3T3 cells by PMA significantly increased the phosphorylation of PI-TP, as shown by immunoprecipitation of PI-TP from pre-labelled cells. No significant increase in phosphorylation of PI-TP was observed after stimulation of these cells by bombesin. Purified PI-TP was shown to be a substrate for protein kinase C in vitro. The possibility that the phosphorylation of PI-TP after activation of protein kinase C is involved in the observed redistribution of PI-TP is discussed.
Center for Biomembranes and Lipid Enzymology, University of Utrecht, The Netherlands.
G T
GT
Snoek
J
J
Westerman
F S
FS
Wouters
K W
KW
Wirtz
D016475:3T3 Cells / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D000818:Animals; D001839:Bombesin / Q000494:pharmacology*; D003994:Bucladesine / Q000494:pharmacology; D002352:Carrier Proteins / Q000378:metabolism*; D003907:Dexamethasone / Q000494:pharmacology; D005455:Fluorescent Antibody Technique; D006056:Golgi Apparatus / Q000378:metabolism; D007163:Immunosorbent Techniques; D008565:Membrane Proteins; D051379:Mice; D008856:Microscopy, Fluorescence; D049294:Phospholipid Transfer Proteins; D010766:Phosphorylation; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D002352:Carrier Proteins; D008565:Membrane Proteins; D049294:Phospholipid Transfer Proteins; D003994:Bucladesine; D003907:Dexamethasone; D013755:Tetradecanoylphorbol Acetate; D001839:Bombesin