Surface Expression of the Netrin Receptor UNC5H1 Is Regulated through a Protein Kinase C-Interacting Protein/Protein Kinase-Dependent Mechanism

Bile salts influence signaling and metabolic pathways. In hepatocytes, the sodium taurocholate cotransporting polypeptide (Ntcp) is a major determinant of intracellular bile salt levels. Short-term downregulation of Ntcp is not well characterized to date. FLAG and enhanced green fluorescent protein (EGFP) tags were cloned to the extra- and intracellular termini of Ntcp. Endocytosis of Ntcp in transfected HepG2 cells was visualized by fluorescence of EGFP, and membrane surface expression of Ntcp was quantified by flow cytometry with fluorochrome-labeled FLAG antibodies. Activation of protein kinase C (PKC) by phorbolester or thymeleatoxin an activator of Ca2+-dependent conventional PKCs (cPKCs), induced endocytosis of Ntcp, whereas the Na+-K+-ATPase remained in the plasma membrane. The PKC inhibitor BIM I and the cPKC-selective inhibitor Gö6976 abolished PMA-induced endocytosis. Because of this internalization, cell surface expression of Ntcp was reduced by 36 ± 7%, bile salt uptake was decreased by 25%, and taurolithocholate sulfate-induced cell toxicity was prevented. In conclusion, Ca2+-dependent PKCs induce vesicular retrieval of Ntcp, thereby reducing bile salt uptake. This mechanism may protect hepatocytes from toxic intracellular bile salt concentrations.

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Mammalian Homologue of the Caenorhabditis elegans UNC-76 Protein Involved in Axonal Outgrowth Is a Protein Kinase C ζ–interacting Protein

The Journal of Cell Biology ◽

10.1083/jcb.144.3.403 ◽

1999 ◽

Vol 144 (3) ◽

pp. 403-411 ◽

Cited By ~ 62

Author(s):

Shun'ichi Kuroda ◽

Noritaka Nakagawa ◽

Chiharu Tokunaga ◽

Kenji Tatematsu ◽

Katsuyuki Tanizawa

Keyword(s):

Plasma Membrane ◽

Protein Kinase C ◽

Caenorhabditis Elegans ◽

Protein Kinase ◽

Rat Brain ◽

Axonal Outgrowth ◽

Yeast Two Hybrid ◽

Interacting Protein ◽

Kinase C ◽

Two Hybrid

By the yeast two-hybrid screening of a rat brain cDNA library with the regulatory domain of protein kinase C ζ (PKCζ) as a bait, we have cloned a gene coding for a novel PKCζ-interacting protein homologous to the Caenorhabditis elegans UNC-76 protein involved in axonal outgrowth and fasciculation. The protein designated FEZ1 (fasciculation and elongation protein zeta-1) consisting of 393 amino acid residues shows a high Asp/Glu content and contains several regions predicted to form amphipathic helices. Northern blot analysis has revealed that FEZ1 mRNA is abundantly expressed in adult rat brain and throughout the developmental stages of mouse embryo. By the yeast two-hybrid assay with various deletion mutants of PKC, FEZ1 was shown to interact with the NH2-terminal variable region (V1) of PKCζ and weakly with that of PKCε. In the COS-7 cells coexpressing FEZ1 and PKCζ, FEZ1 was present mainly in the plasma membrane, associating with PKCζ and being phosphorylated. These results indicate that FEZ1 is a novel substrate of PKCζ. When the constitutively active mutant of PKCζ was used, FEZ1 was found in the cytoplasm of COS-7 cells. Upon treatment of the cells with a PKC inhibitor, staurosporin, FEZ1 was translocated from the cytoplasm to the plasma membrane, suggesting that the cytoplasmic translocation of FEZ1 is directly regulated by the PKCζ activity. Although expression of FEZ1 alone had no effect on PC12 cells, coexpression of FEZ1 and constitutively active PKCζ stimulated the neuronal differentiation of PC12 cells. Combined with the recent finding that a human FEZ1 protein is able to complement the function of UNC-76 necessary for normal axonal bundling and elongation within axon bundles in the nematode, these results suggest that FEZ1 plays a crucial role in the axon guidance machinery in mammals by interacting with PKCζ.

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Activation of protein kinase C delays apoptosis of nerve growth factor-deprived rat sympathetic neurons through a Ca2+-influx dependent mechanism

Neuroscience Letters ◽

10.1016/s0304-3940(01)02193-0 ◽

2001 ◽

Vol 313 (1-2) ◽

pp. 9-12 ◽

Cited By ~ 5

Author(s):

Shuuitsu Tanaka ◽

Tatsuro Koike

Keyword(s):

Protein Kinase C ◽

Nerve Growth Factor ◽

Growth Factor ◽

Protein Kinase ◽

Sympathetic Neurons ◽

Nerve Growth ◽

Kinase C ◽

Dependent Mechanism

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MAC-1 mediates adherence of human monocytes to endothelium via a protein kinase C dependent mechanism

Biochimica et Biophysica Acta (BBA) - Molecular Cell Research ◽

10.1016/0167-4889(90)90072-l ◽

1990 ◽

Vol 1052 (1) ◽

pp. 166-172 ◽

Cited By ~ 18

Author(s):

Ann-Marie Gladwin ◽

David G. Hassall ◽

John F. Martin ◽

Robert F.G. Booth

Keyword(s):

Protein Kinase C ◽

Protein Kinase ◽

Human Monocytes ◽

Kinase C ◽

Dependent Mechanism

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Insulin generates free radicals in human fibroblasts ex vivo by a protein kinase C-dependent mechanism, which is inhibited by pravastatin

Free Radical Biology and Medicine ◽

10.1016/j.freeradbiomed.2006.04.015 ◽

2006 ◽

Vol 41 (3) ◽

pp. 473-483 ◽

Cited By ~ 16

Author(s):

G CEOLOTTO ◽

I PAPPARELLA ◽

L LENZINI ◽

M SARTORI ◽

M MAZZONI ◽

...

Keyword(s):

Protein Kinase C ◽

Free Radicals ◽

Protein Kinase ◽

Ex Vivo ◽

Human Fibroblasts ◽

Kinase C ◽

Dependent Mechanism

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The activation-induced decrease in the platelet surface expression of the glycoprotein Ib-IX complex is reversible

Blood ◽

10.1182/blood.v83.12.3562.3562 ◽

1994 ◽

Vol 83 (12) ◽

pp. 3562-3573 ◽

Cited By ~ 56

Author(s):

AD Michelson ◽

SE Benoit ◽

MH Kroll ◽

JM Li ◽

MJ Rohrer ◽

...

Keyword(s):

Protein Kinase C ◽

Protein Kinase ◽

Light Chain ◽

Myosin Light Chain Kinase ◽

Myosin Light Chain ◽

Surface Expression ◽

Platelet Surface ◽

Kinase C ◽

Von Willebrand ◽

Willebrand Factor

Abstract Thrombin decreases the platelet surface expression of the glycoprotein (GP) Ib-IX complex. To determine whether this effect is reversible, flow cytometric studies were performed with GPIb-IX-specific monoclonal antibodies. In both whole blood and washed platelet systems, incubation of platelets with thrombin or a combination of adenosine diphosphate and epinephrine resulted in a maximal decrease of the platelet surface expression of GPIb-IX within 5 minutes, after which there was a time- dependent return of the platelet surface GPIb-IX complex, which was maximal by 60 minutes. Exposure of the same platelets to additional exogenous thrombin resulted in a second decrease in platelet surface GPIb-IX, followed by a second reconstitution of platelet surface GPIb- IX. Throughout these experiments there was no measurable release from the platelets of glycocalicin (a proteolytic fragment of GPIb). Experiments in which platelets were preincubated with a biotinylated GPIb-specific MoAb showed that the GPIb molecules that returned to the platelet surface were the same molecules that had been translocated to the intraplatelet pool. The GPIb molecules that returned to the platelet surface were functionally competent to bind von Willebrand factor, as determined by ristocetin-induced platelet agglutination and ristocetin-induced binding of exogenous von Willebrand factor. Inhibitors of protein kinase C and myosin light-chain kinase enhanced the reexpression of platelet surface GPIb. In summary, the activation- induced decrease in the platelet surface expression of the GPIb-IX complex is reversible. Inactivation of protein kinase C and myosin light-chain kinase are important mechanisms in the reexpression of the platelet surface GPIb-IX complex.

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