scholarly journals The Golgi Localization of Phosphatidylinositol Transfer Protein β Requires the Protein Kinase C-dependent Phosphorylation of Serine 262 and Is Essential for Maintaining Plasma Membrane Sphingomyelin Levels

2002 ◽  
Vol 277 (25) ◽  
pp. 22447-22452 ◽  
Author(s):  
Claudia M. van Tiel ◽  
Jan Westerman ◽  
Marten A. Paasman ◽  
Martha M. Hoebens ◽  
Karel W. A. Wirtz ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Transfer Protein ◽  
Kinase C ◽  
Golgi Localization ◽  
Phosphatidylinositol Transfer Protein ◽  
Phosphatidylinositol Transfer

scholarly journals Phosphorylation and redistribution of the phosphatidylinositol-transfer protein in phorbol 12-myristate 13-acetate- and bombesin-stimulated Swiss mouse 3T3 fibroblasts

1993 ◽  
Vol 291 (2) ◽  
pp. 649-656 ◽  
Author(s):  
G T Snoek ◽  
J Westerman ◽  
F S Wouters ◽  
K W A Wirtz
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Swiss Mouse ◽  
Quiescent Cells ◽  
Transfer Protein ◽  
Kinase C ◽  
Phosphatidylinositol Transfer Protein ◽  
Phosphatidylinositol Transfer ◽  
Stimulation Of

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.

Protein kinase C(alpha) actively downregulates through caveolae-dependent traffic to an endosomal compartment

2000 ◽  
Vol 113 (14) ◽  
pp. 2575-2584
Author(s):  
C. Prevostel ◽  
V. Alice ◽  
D. Joubert ◽  
P.J. Parker
Keyword(s):  
Plasma Membrane ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Initial Step ◽  
Receptor Internalization ◽  
Similar Process ◽  
Receptor Desensitization ◽  
Kinase C ◽  
Annexin I ◽  
Pkc Alpha

Receptor desensitization occurs through receptor internalization and targeting to endosomes, a prerequisite for sorting and degradation. Such trafficking processes may not be restricted to membrane associated receptors but may also play an important role in the downregulation of cytoplasmic transducers such as protein kinase C (PKC). It is demonstrated here that acute TPA exposure induces the transport of activated PKC(alpha) from the plasma membrane to endosomes. This process requires PKC activity and catalytically competent PKC can even promote a similar process for a truncated regulatory domain PKC(α) protein. It is established that PKC(α) is targeted to the endosome compartment as an active kinase, where it colocalizes with annexin I, a substrate of PKC. Thus, PKC(alpha) downregulation shares features with plasma membrane associated receptor sorting and degradation. However, it is shown that PKC(α) delivery to the endosome compartment is not a Rab5 mediated process in contrast to the well characterised internalisation of the transferrin receptor. An alternative route for PKC(alpha) is evidenced by the finding that the cholesterol binding drugs nystatin and filipin, known to inhibit caveolae mediated trafficking, are able to block PKC(alpha) traffic and down regulation. Consistent with this, the endosomes where PKC(alpha) is found also contain caveolin. It is concluded that the initial step in desensitisation of PKC(alpha) involves active delivery to endosomes via a caveolae mediated process.

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