Protein kinase C-theta is specifically localized on centrosomes and kinetochores in mitotic cells.
In this study we provide evidence that the protein kinase C (PKC)-straight theta isoenzyme is recruited on to the mitotic spindle in dividing murine erythroleukaemia (MEL) cells and associates specifically with centrosome and kinetochore structures. None of the other PKC isoenzymes (-alpha, -delta, -epsilon, -mu and -zeta) expressed by MEL cells shows this localization on the mitotic spindle. An identical subcellular distribution of PKC-straight theta is also observed in dividing murine P3 myeloma cells and human LAN-5 neuroblastoma cells, indicating that this PKC isoenzyme interacts with the mitotic apparatus in mammalian cells. In phorbol-ester-treated non-growing MEL cells, a rapid change in the intracellular distribution of PKC-straight theta occurs. Under these conditions, PKC-straight theta is translocated from the nuclear to the cytosolic cell compartment, an event that is accompanied by phosphorylation of the PKC-straight theta molecule and is followed by its down-regulation. The recovery of cell growth capacity results in the concomitant reappearance of PKC-straight theta. Furthermore, when MEL cells acquire the differentiated non-growing phenotype, the level of PKC-straight theta is reduced to less than 5%, suggesting that this PKC isoenzyme is no longer required. We propose that, unlike other members of the PKC family, PKC-straight theta may play a role in cell proliferation.
Passalacqua
M
M
Institute of Biological Chemistry, University of Genoa, Viale Benedetto XV, 1-16132 Genoa, Italy.
Patrone
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M
Sparatore
B
B
Melloni
E
E
Pontremoli
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S
D000818:Animals; D018797:Cell Cycle Proteins / Q000378:metabolism; D002455:Cell Division; D018385:Centrosome / Q000201:enzymology*; D015536:Down-Regulation; D007527:Isoenzymes / Q000378:metabolism*; D018386:Kinetochores / Q000201:enzymology*; D051379:Mice; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism*; D000074121:Protein Kinase C-theta; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D018797:Cell Cycle Proteins; D007527:Isoenzymes; C076233:PRKCQ protein, human; C489593:Prkcq protein, mouse; D011493:Protein Kinase C; D000074121:Protein Kinase C-theta; D013755:Tetradecanoylphorbol Acetate