Caveolae (little caves) are 50 -100 nm invaginations seen on the plasma membrane of most cells. Caveolin-1, the marker protein of caveolae in most tissues, is the structural and functional unit of caveolae.
Previous studies have demonstrated the tumor suppressor capability of caveolin-1. Our lab has already shown that expression of caveolin-1 induces premature senescence in cells, possibly including those with malignant potential. We proposed that this might explain the tumor suppressor function of caveolin-1. We have further shown that oxidative stress induces premature senescence through up regulation of caveolin-1. To further elucidate the molecular mechanisms underlying this process, we used H2O2 as a model to generate stress induced premature senescence (SIPS) and examined the response of caveolin-1 promoter under these conditions.
Constructs with serially truncated segments of the mouse caveolin-1 gene promoter linked to a luciferase reporter gene were made and luciferase assays were carried out. These experiments demonstrated that the critical regions lay in two segments: -222/-372 and -91/-150 of the promoter region. A consensus Sp1 binding sequence was identified within each deleted segment. Gel shift analysis of protein binding from nuclear extracts to these caveolin promoter DNA sequences confirmed that transcription factors were binding to the Sp1 consensus elements as part of the transcriptional response to H2O2 induced senescence. Further deletion mutagenesis of the individual Sp1 consensus sites confirmed the identity of the transcription factor to be Sp1. These findings suggest that Sp1 mediates oxidant induced up regulation of caveolin-1 expression. In subsequent experiments, we examined the effect of inhibitors of p38 Mitogen activated protein kinase pathway on the levels of caveolin-1 expression during SIPS by western blot and luciferase assay. We found that this pathway plays a direct role in the up regulation of caveolin-1 during SIPS, possibly through modification of Sp1 to increase its activity.
Public Health Importance: Cancer is a leading public health concern. Cav-1 has been shown to be a tumor suppressor gene involved in a large number of human tumors. Induction of premature senescence in cells with malignant potential is thought to be a vital tumor suppressor function. Our study aims to define the tumor suppressor capacity of Cav-1 by elucidating the pathway by which it induces premature senescence.
| Identifer | oai:union.ndltd.org:PITT/oai:PITTETD:etd-06092005-234926 |
| Date | 08 July 2005 |
| Creators | Dasari, Arvind |
| Contributors | Dr. Eleanor Feingold, Dr. Robert E Ferrell, Dr. Ferruccio Galbiati |
| Publisher | University of Pittsburgh |
| Source Sets | University of Pittsburgh |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.library.pitt.edu/ETD/available/etd-06092005-234926/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University of Pittsburgh or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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