Topic
MG132
About: MG132 is a research topic. Over the lifetime, 1499 publications have been published within this topic receiving 56589 citations. The topic is also known as: MG132 & Z-Leu-leu-leu-al.
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TL;DR: Investigation of the molecular basis of insulin resistance elicited by FFAs using the human hepatocyte cell line HepG2 revealed that palmitate facilitates ubiquitination of the key insulin signaling molecules, and subsequently elicits their proteasomal degradation.
84 citations
TL;DR: The data support that JSI‐124 is a potentially useful therapeutic agent for ALK+ ALCL and appears to be involved in regulating proteosome degradation for proteins such as JAK3 and NPM‐ALK.
Abstract: JSI-124 (cucurbitacin I) has been recently described as a specific inhibitor of signal transducer and activator of transcription-3 (STAT3). As STAT3 activation is pathogenetically important in anaplastic lymphoma kinase-positive anaplastic large cell lymphoma (ALK+ ALCL), we investigated whether JSI-124 can mediate significant inhibitory effects in this cell type. In two ALK+ ALCL cell lines (Karpas 299 and SU-DHL-1), JSI-124 significantly reduced the number of viable cells to 50% of that of negative controls at a dose of 5-10 micromol/l at 24 h and 1-1.25 micromol/l at 48 h. This decrease in viability was associated with apoptosis, as confirmed by the increase in the subG(0/1) fraction, poly(ADP-ribose)polymerase cleavage and expression of active caspase 3. JSI-124 decreased the phosphorylated-STAT3 and -Janus kinase-3 (JAK3) levels in a dose-dependent fashion, and these changes were coupled with significant decreases in several STAT3 downstream targets, including mcl-1, bcl-2, bcl-xL and cyclin D3. Interestingly, JSI-124 also dramatically decreased the protein levels of JAK3 and nucleophosmin (NPM)-ALK, and these effects were reversible by MG132. Our data support that JSI-124 is a potentially useful therapeutic agent for ALK+ ALCL. In addition to its role as a tyrosine kinase inhibitor, JSI-124 appears to be involved in regulating proteosome degradation for proteins such as JAK3 and NPM-ALK.
83 citations
TL;DR: The findings indicate that proteasome inhibitors do not target caspase-1 directly but instead control an upstream event in LT-treated macrophages leading to caspite-1 activation, which appears to be tightly controlled and differentially regulated by proteasomes depending on the source of casp enzyme induction.
83 citations
TL;DR: Two proteolytic pathways through which the transcriptional regulator can be differentially targeted under different cell growth conditions are illustrated.
83 citations
Journal Article•
TL;DR: It is found that exposure of cultured primary human keratinocytes to UV irradiation substantially reduced RARγ and RXRα mRNA and protein within 8 h, and this indicates that ubiquitin/proteasome-mediated breakdown is an important mechanism regulating the levels of nuclear retinoid receptors.
Abstract: Repeated exposure of human skin to solar UV radiation leads to premature aging (photoaging) and skin cancer. UV-induced skin damage can be ameliorated by all-trans retinoic acid treatment. The actions of retinoic acid in skin keratinocytes are mediated primarily by nuclear retinoic acid receptor gamma (RARgamma) and retinoid X receptor alpha (RXRalpha). We found that exposure of cultured primary human keratinocytes to UV irradiation (30 mJ/cm2) substantially reduced (50-90%) RARgamma and RXRalpha mRNA and protein within 8 h. The rates of disappearance of RARgamma and RXRalpha proteins after UV exposure or treatment with the protein synthesis inhibitor cycloheximide were similar. UV irradiation did not increase the rate of breakdown of RARgamma or RXRalpha but rather reduced their rate of synthesis. The addition of proteasome inhibitors MG132 and LLvL, but not the lysosomal inhibitor E64, prevented loss of RARgamma and RXRalpha proteins after exposure of keratinocytes to either UV radiation or cycloheximide. Soluble extracts from nonirradiated or UV-irradiated keratinocytes possessed similar levels of proteasome activity that degraded RARgamma and RXRalpha proteins in vitro. Furthermore, RARgamma and RXRalpha were polyubiquitinated in intact cells. RXRalpha was found to contain two proline, glutamate/aspartate, serine, and threonine (PEST) motifs, which confer rapid turnover of many short-lived regulatory proteins that are degraded by the ubiquitin/proteasome pathway. However, the PEST motifs in RXRalpha did not function to regulate its stability, because deletion of the PEST motifs individually or together did not alter ubiquitination or proteasome-mediated degradation of RXRalpha. These results demonstrate that loss of RARgamma and RXRalpha proteins after UV irradiation results from degradation via the ubiquitin/proteasome pathway. Taken together, the data here indicate that ubiquitin/proteasome-mediated breakdown is an important mechanism regulating the levels of nuclear retinoid receptors.
82 citations