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STAT transcription factors signal from the plasma membrane to the nucleus in response to growth factors and cytokines. We have investigated whether plasma membrane "rafts" are involved in cytokine-activated STAT signaling. Cytokine-free human hepatoma Hep3B cells or cells treated with interleukin-6 (IL-6) or orthovanadate (a general activator of STATs) were(More)
In the standard model of cytokine-induced signal transducer and activator of transcription (STAT) protein family signaling to the cell nucleus, it is assumed that STAT3 is recruited to the cytoplasmic side of the cell surface receptor complex from within a cytosolic monomer pool. By using Superose-6 gel-filtration chromatography, we have discovered that(More)
Glucose-regulated protein 58 (GRP58/ER-60/ERp57), best known as a chaperone in the endoplasmic reticulum lumen, was previously identified by us as one of several accessory proteins in the S100 cytosol fraction of human hepatoma Hep3B cells that was differentially coshifted by anti-Stat3 antibody in an antibody-subtracted differential protein display assay.(More)
The 240-kDa proteasome inhibitor has been reported to be an ATP-stabilized component (CF-2) of the 26 S proteasome complex. We now report that this inhibitory factor is indistinguishable from delta-aminolevulinic acid dehydratase (ALAD), the second enzyme in the pathway of heme synthesis, based upon the following observations: 1) common sequence of the(More)
Signal transduction from the plasma membrane to the nucleus by STAT proteins is widely represented as exclusively a soluble cytosolic process. Using cell-fractionation methods, we observed that approximately 5% of cytoplasmic STAT3 was constitutively associated with the purified early endosome (EE) fraction in human Hep3B liver cells. By 15-30 min after(More)
Clenbuterol treatment for several weeks prevented up to one-third of the reduction in mineralization of femurs and tibias caused by sectioning of the sciatic nerve in young rats. The normalizing effect of clenbuterol on bone mineral content was directly proportional to similar alterations in muscle mass, which in turn could be abolished by ablation of the(More)
This article reviews recent studies from our laboratory on protein regulators of the proteasome (multicatalytic proteasome complex) in red blood cells. A 240-kD inhibitory component (CF-2) exists in 26S proteasome complexes in a form which is conjugated to ubiquitin. Interestingly, this factor was shown to be identical to delta-aminolevulinic acid(More)
The cellular physiology of signal transducer and activator of transcription protein family (STAT) transcription factors includes activation by Tyr-phosphorylation (PY) in cytokine and growth factor receptor complexes at the level of plasma membrane rafts, subsequent cytoplasmic transit and nuclear import, and transcriptional regulation of target genes,(More)
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