Nuclear protein kinase substrates in AtT-20 cells: translocation of a 14 kDa phosphoprotein.
In this work we characterize some acidic nuclear substrates of protein kinase C (PKC) and cyclic AMP-dependent protein kinase (PKA), using intact anterior pituitary corticotrophic tumor cells (AtT-20/D16-16). It was found that, as in the cytosolic fraction, substrates for both PKC and PKA exist in the nucleus and that changes in the phosphorylation states of a few of these phosphoproteins are mediated by both kinases. One of the phosphoproteins examined, a 14 kDa phosphoprotein (pp14) described previously, exhibited a phorbol-ester induced translocation from nucleus to cytosol in pulse-chase experiments utilizing 35S-methionine labeling. These results suggest that pp14 may be involved in signal transduction in AtT-20 cells. Although its identity remains to be determined, a 14 kDa DNA-binding protein was also seen in nuclear extracts of AtT-20 cells.
Bishop
J F
JF
Experimental Therapeutics Branch, National Institute of Neurological and Communicative Disorders and Stroke, Bethesda, Maryland 20892.
Chronwall
B M
BM
Farah
J M
JM
Gehlert
D R
DR
D000818:Animals; D002460:Cell Line; D002467:Cell Nucleus / Q000201:enzymology / Q000648:ultrastructure; D004268:DNA-Binding Proteins / Q000302:isolation & purification / Q000378:metabolism*; D007700:Kinetics; D008854:Microscopy, Electron; D008970:Molecular Weight; D009687:Nuclear Proteins / Q000378:metabolism*; D010750:Phosphoproteins / Q000302:isolation & purification / Q000378:metabolism*; D010766:Phosphorylation; D010911:Pituitary Neoplasms; D011493:Protein Kinase C / Q000378:metabolism*; D011494:Protein Kinases / Q000378:metabolism*; D013379:Substrate Specificity
D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D010750:Phosphoproteins; D011494:Protein Kinases; D011493:Protein Kinase C