The v-Ki-Ras oncogene alters cAMP nuclear signaling by regulating the location and the expression of cAMP-dependent protein kinase IIbeta.

The v-Ki-Ras oncoprotein dedifferentiates thyroid cells and inhibits nuclear accumulation of the catalytic subunit of cAMP-dependent protein kinase. After activation of v-Ras or protein kinase C, the regulatory subunit of type II protein kinase A, RIIbeta, translocates from the membranes to the cytosol. RIIbeta mRNA and protein were eventually depleted. These effects were mimicked by expressing AKAP45, a truncated version of the RII anchor protein, AKAP75. Because AKAP45 lacks membrane targeting domains, it induces the translocation of PKAII to the cytoplasm. Expression of AKAP45 markedly decreased thyroglobulin mRNA levels and inhibited accumulation of C-PKA in the nucleus. Our results suggest that: 1) The localization of PKAII influences cAMP signaling to the nucleus; 2) Ras alters the localization and the expression of PKAII; 3) Translocation of PKAII to the cytoplasm reduces nuclear C-PKA accumulation, resulting in decreased expression of cAMP-dependent genes, including RIIbeta, TSH receptor, and thyroglobulin. The loss of RIIbeta permanently down-regulates thyroid-specific gene expression.

The v-erbA oncogene selectively inhibits iodide uptake in rat thyroid cells.

v-erbA is the oncogenic form of the c-erbA proto-oncogene, which encodes the receptor for thyroid hormones. The expression of the v-erbA oncogene in thyroid differentiated cells, PC Cl 3, inhibits iodide uptake and thyrotropin-dependent growth, whereas it has no effect on the expression of the other thyroid specific markers, i.e. thyroglobulin, thyroperoxidase and thyrotropin receptor. The activity of transcription factor AP-1, evaluated by a specific DNA binding assay and by transcription of AP-induced promoter (TRE) is enhanced in PC v-erbA cells. v-erbA mutants in the DNA binding domain do not affect the iodide uptake of thyroid cells nor AP-1 activity. We suggest that this transcriptional activation mediates the selective effects of v-erbA on the expression of thyroid specific markers.

Identification of apolipoproteins A-I and B using high resolution electrophoresis on supported cellulose acetate.

A simple modification of high resolution electrophoresis on supported cellulose acetate is described. This modification is made by adding the surfactant Tween 20 to the buffer and permits the identification of apolipoproteins A-I and B as well as the usually detected serum proteins. The procedure is reproducible using various supported cellulose acetate plates with manual and automated procedures. Furthermore, this improved high resolution electrophoresis allows the semiquantitative evaluation of these apolipoproteins both on freshly collected and on -20 degrees C stored serum samples.

A polymorphism (G-->A transition) in the -78 position of the apolipoprotein A-I promoter increases transcription efficiency.

AG-->A transition at -78 base pairs from the transcription start site of the apolipoprotein A-I (apoA-I) gene has been associated with increased apoA-I serum levels in humans. We report here that this mutation (G-->A) increases significantly (5-7-fold) the expression of a reporter gene fused to the apoA-I promoter in human liver and intestine cells. In addition, the presence of A at -78 base pairs from the transcription start site of the gene significantly decreases the binding affinity of a nuclear factor present in liver and intestine cells. We suggest that the reduced affinity of this factor increases the transcription efficiency of the promoter and explains why individuals carrying the A allele have high serum apoA-I levels.

Early extracoronary atherosclerosis and coronary heart disease risk factors in a sample of civil servants in southern Italy.

One hundred and thirty-eight male subjects working as civil servants in the Catanzaro city hall, aged over 45, underwent Echo-Doppler examination of carotid and femoral arteries. Forty-one subjects (30%) presented evidence of early atherosclerotic lesions in at least 1 of the 10 examined arteries. Age, systolic blood pressure, serum triglycerides and serum glucose were higher in this group when compared with subjects without evidence of extracoronary atherosclerosis (EA), while HDL cholesterol and apolipoprotein A-I were lower. After adjustment for age, only serum triglycerides and apolipoprotein A-I levels remained significantly different. Only 21 subjects had no major coronary heart disease (CHD) risk factors, 46 had one, 47 two and 24 more than two risk factors. The prevalence of lesions was significantly higher in individuals with total cholesterol/HDL cholesterol ratio greater than 5. The presence of smoking and hypertension was almost equally represented in individuals with or without lesions. Serum triglycerides, total cholesterol/HDL cholesterol > 5 and apolipoprotein A-I seem to play a fundamental role in the development of EA, as detected by Duplex examination of carotid and femoral arteries. Age is also closely related to the presence of lesions, probably reflecting the exposure duration to CHD risk factors.