8-Cl-cAMP induces truncation and down-regulation of the RI alpha subunit and up-regulation of the RII beta subunit of cAMP-dependent protein kinase leading to type II holoenzyme-dependent growth inhibition and differentiation of HL-60 leukemia cells.
8-Cl-cAMP, a site-selective cAMP analog, induces growth inhibition in a variety of cell types of human cancer cell lines. This inhibitory effect of 8-Cl-cAMP was related to its ability to differentially regulate type I versus type II cAMP-dependent protein kinase. In the present study we demonstrated a unique mechanism of action of 8-Cl-cAMP in the regulation of these kinase isozymes in HL-60 human promyelocytic leukemia cells. High-performance liquid chromatography (HPLC) resolved various isoforms of protein kinase present in HL-60 cells. In control cells, type I protein kinase (PKI) comprised more than 90% and type II protein kinase (PKII) less than 10% of the total cAMP-stimulated kinase activity. Treatment with 8-Cl-cAMP (5 microM, 72 h) decreased PKI to a level below 30% of that in untreated control cells and markedly increased PKII composed of three peaks. Photoaffinity labeling/SDS-polyacrylamide gel electrophoresis of column fractions identified the molecular species of regulatory (R) subunits present in protein kinases. Control cells contained high levels of the 48-kDa protein (RI) that composed PKI and low levels of the 50-kDa RII associated with PKII. 8-Cl-cAMP treatment brought about a decrease in the 48-kDa RI along with an increased formation of the truncated 34-kDa RI associated with PKI and an increase in the 50-54-kDa species of RII associated with PKII. A similar protein kinase profile as that shown by 8-Cl-cAMP treatment was observed in cells infected with the human RII beta retroviral vector: the 48-kDa RI of PKI decreased and the 52- and 54-kDa RII associated with PKII increased as compared with uninfected control cells. However, unlike 8-Cl-cAMP treatment, RII beta retroviral vector infection brought about no increase in the 34-kDa-truncated RI but exhibited an increase in the free 48-kDa RI subunit. As the 48-kDa RI and the 50-kDa RII were present in control cells, the enhanced expression of the 52- and 54-kDa RII proteins was due to overexpression of the RII beta gene. We identified the 48-kDa RI as RI alpha, the 50-kDa RII as RII alpha, the 52-kDa RII as RII beta, and the 54-kDa RII as the phosphorylated form of either the RII alpha or RII beta subunit. In vivo labeling experiments using [3H]8-Cl-cAMP demonstrated that 8-Cl-cAMP enters cells and binds to both PKI and PKII.(ABSTRACT TRUNCATED AT 400 WORDS)
Rohlff
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Cellular Biochemistry Section, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892.
Clair
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Cho-Chung
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D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000031:analogs & derivatives* / Q000494:pharmacology; D000970:Antineoplastic Agents / Q000494:pharmacology*; D002454:Cell Differentiation / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D002851:Chromatography, High Pressure Liquid; D015536:Down-Regulation; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism*; D015473:Leukemia, Promyelocytic, Acute; D011494:Protein Kinases / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D014407:Tumor Cells, Cultured; D015854:Up-Regulation
D000970:Antineoplastic Agents; D007527:Isoenzymes; D012333:RNA, Messenger; D015124:8-Bromo Cyclic Adenosine Monophosphate; C044258:8-chloro-cyclic adenosine monophosphate; D011494:Protein Kinases