cAMP induces co-translational modification of proteins in IPC-81 cells.
An elevated cAMP concentration results in growth arrest and protein synthesis-dependent apoptosis in the promyelocytic leukaemia cell line IPC-81. A comparison of two-dimensional gels of extracts from these cells labelled with [(35)S]methionine revealed that five distinct protein spots were induced by cAMP in a protein-synthesis-dependent manner. The spots seemed to result from the acidic shift of a precursor protein. The most abundant spot was phospho-actin. The spots induced by cAMP in intact cells were induced by cAMP-dependent protein kinase (cAPK) during the translation in vitro of mRNA from the leukaemia cells. The effect of cAPK was strictly co-translational, none of the spots being induced when cAPK was added after translation. This suggested that the protein spots arose by co-translational phosphorylation catalysed by cAPK. Two of the protein spots, phospho-actin and a protein with a molecular mass of 30 kDa and an isoelectric point of 4.5, were studied further with respect to expression. They were produced during the whole pre-apoptotic period, had cellular half-lives of several hours and were induced by the same concentrations of cAMP analogue that induced apoptosis. It is suggested that the accumulation of co-translationally modified proteins could be important for long-term cAMP signalling.
Hovland
R
R
Department of Anatomy and Cell Biology, University of Bergen, Arstadveien 19, N-5009 Bergen, Norway.
Døskeland
A P
AP
Eikhom
T S
TS
Robaye
B
B
Døskeland
S O
SO
D000199:Actins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D000818:Animals; D017209:Apoptosis; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D015180:Electrophoresis, Gel, Two-Dimensional; D006207:Half-Life; D007526:Isoelectric Point; D008970:Molecular Weight; D009363:Neoplasm Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D010766:Phosphorylation; D014176:Protein Biosynthesis / Q000187:drug effects*; D051381:Rats; D015398:Signal Transduction; D013873:Thionucleotides / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D000199:Actins; D009363:Neoplasm Proteins; D013873:Thionucleotides; C015929:8-((4-chlorophenyl)thio)cyclic-3',5'-AMP; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases