ucn-1028-c and Cell-Transformation--Viral

Protein kinase C (PKC) isoforms regulate cell proliferation and apoptosis. Since the PKC isoenzyme complement varies considerably from cell type to cell type, a PKC's responsiveness to an apoptogenic challenge must be defined for both the type of apoptogen and the type of cell. We have already reported that the changes in the distribution and activity of PKC-delta in apoptosing polyomavirus-infected/transformed Fischer rat embryo pyF111 fibroblasts depend on the type of apoptogen. Here, we show that this is also true for PKC-betaI in pyF111 cells treated with the slow DNA-damaging VP-16 (etoposide) or the fast-acting (in the cytoplasm) calphostin C. These apoptogens caused quite different shifts of the PKC-betaI level and activity in the nuclear membrane (NM) and nucleoplasm (NP), but corresponding changes in the cytosol (CS) and cytoplasmic particulate (CP) fractions. The hefty translocation of PKC-betaI onto the CP fraction and its increased activity there suggest the possible triggering of a cytochrome c/caspase-mediated apoptosis-inducing mechanism common to both agents. The present results are a necessary lead-up to functional proteomic analyses aimed at identifying the molecules forming the local PKC-betaI signalling modules under different conditions.

Topics: Animals; Apoptosis; Cell Line; Cell Nucleus; Cell Transformation, Viral; Cytoplasm; Enzyme Inhibitors; Etoposide; Fibroblasts; Isoenzymes; Naphthalenes; Nucleic Acid Synthesis Inhibitors; Polyomavirus; Protein Kinase C; Protein Kinase C beta; Rats; Rats, Inbred F344

The CEF-4/9E3 cytokine gene is expressed aberrantly in chicken embryo fibroblasts (CEF) transformed by the Rous sarcoma virus. The expression of CEF-4 is dependent on both transcriptional and post-transcriptional mechanisms of regulation. The characterization of the promoter region indicated that three distinct regulatory elements corresponding to an AP-1 binding site (or TRE), a PRDII/kappaB domain, and a CAAT box are involved in the activation by pp60(v-)src. In this report we investigate the signaling pathways controlling the expression of the TRE and PRDII domain. The expression of a dominant negative mutant of p21(ras) reduced the activity of both elements. In contrast a similar mutant of c-Raf-1 affected modestly the activation dependent on the TRE but not PRDII. The stress-activated protein kinase (SAPK)/Jun N-terminal kinase (JNK) pathway was important for the activity of PRDII and the TRE but was not markedly stimulated by pp60(v-)src. The addition of calphostin C and the inhibition of protein kinase C (PKC) diminished the accumulation of the CEF-4 mRNA and reduced the activity of a TRE-controlled promoter. Likewise, the depletion of PKC by chronic treatment with phorbol esters inhibited the activation of the TRE. Rous sarcoma virus-transformed CEF treated with calphostin C were also flatter, did not display a high degree of criss-crossing, and appeared morphologically normal. Hence PKC was important for the activation of AP-1 and the morphological transformation of CEF. The constitutive expression of CEF-4 was correlated with transformation only when dependent on the TRE. This was not true for PRDII, which was the only element required for the constitutive activation to the CEF-4 promoter in nontransformed cells treated chronically with phorbol esters.

Topics: Animals; Avian Proteins; Avian Sarcoma Viruses; Blotting, Northern; Cell Transformation, Viral; Chick Embryo; Cytokines; DNA-Binding Proteins; Gene Expression Regulation; Kinetics; Naphthalenes; Nuclear Proteins; Oncogene Protein pp60(v-src); Promoter Regions, Genetic; Protein Kinase C; Protein Serine-Threonine Kinases; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-raf; Proto-Oncogene Proteins p21(ras); Regulatory Factor X Transcription Factors; RNA, Messenger; Signal Transduction; Tetradecanoylphorbol Acetate; Transcription Factor AP-1; Transcription Factors