Doctor of Philosophy, Loyola University Of Chicago (2010)
B.S., Illinois State University, Chemistry and Biochem/Mol Bio (2004)
Amato Giaccia, Postdoctoral Faculty Sponsor
The p53 tumor suppressor plays a key role in maintaining cellular integrity. In response to diverse stress signals, p53 can trigger apoptosis to eliminate damaged cells or cell-cycle arrest to enable cells to cope with stress and survive. However, the transcriptional networks underlying p53 pro-survival function are incompletely understood. Here, we show that in oncogenic-Ras-expressing cells, p53 promotes oxidative phosphorylation (OXPHOS) and cell survival upon glucose starvation. Analysis of p53 transcriptional activation domain mutants reveals that these responses depend on p53 transactivation function. Using gene expression profiling and ChIP-seq analysis, we identify several p53-inducible fatty acid metabolism-related genes. One such gene, Acad11, encoding a protein involved in fatty acid oxidation, is required for efficient OXPHOS and cell survival upon glucose starvation. This study provides new mechanistic insight into the pro-survival function of p53 and suggests that targeting this pathway may provide a strategy for therapeutic intervention based on metabolic perturbation.
View details for DOI 10.1016/j.celrep.2015.01.043
View details for PubMedID 25704813
Signaling initiated by hypoxia and insulin powerfully alters cellular metabolism. The protein stability of hypoxia-inducible factor-1 alpha (Hif-1α) and Hif-2α is regulated by three prolyl hydroxylase domain-containing protein isoforms (Phd1, Phd2 and Phd3). Insulin receptor substrate-2 (Irs2) is a critical mediator of the anabolic effects of insulin, and its decreased expression contributes to the pathophysiology of insulin resistance and diabetes. Although Hif regulates many metabolic pathways, it is unknown whether the Phd proteins regulate glucose and lipid metabolism in the liver. Here, we show that acute deletion of hepatic Phd3, also known as Egln3, improves insulin sensitivity and ameliorates diabetes by specifically stabilizing Hif-2α, which then increases Irs2 transcription and insulin-stimulated Akt activation. Hif-2α and Irs2 are both necessary for the improved insulin sensitivity, as knockdown of either molecule abrogates the beneficial effects of Phd3 knockout on glucose tolerance and insulin-stimulated Akt phosphorylation. Augmenting levels of Hif-2α through various combinations of Phd gene knockouts did not further improve hepatic metabolism and only added toxicity. Thus, isoform-specific inhibition of Phd3 could be exploited to treat type 2 diabetes without the toxicity that could occur with chronic inhibition of multiple Phd isoforms.
View details for DOI 10.1038/nm.3294
View details for Web of Science ID 000325531700033
View details for PubMedID 24037093
A common genetic mutation found in clear cell renal cell carcinoma (CC-RCC) is the loss of the von Hippel-Lindau (VHL) gene, which results in stabilization of hypoxia-inducible factors (HIFs), and contributes to cancer progression and metastasis. CUB-domain-containing protein 1 (CDCP1) was shown to promote metastasis in scirrhous and lung adenocarcinomas as well as in prostate cancer. In this study, we established a molecular mechanism linking VHL loss to induction of the CDCP1 gene through the HIF-1/2 pathway in renal cancer. Also, we report that Fyn, which forms a complex with CDCP1 and mediates its signaling to PKC?, is a HIF-1 target gene. Mechanistically, we found that CDCP1 specifically regulates phosphorylation of PKC?, but not of focal adhesion kinase or Crk-associated substrate. Signal transduction from CDCP1 to PKC? leads to its activation, increasing migration of CC-RCC. Furthermore, patient survival can be stratified by CDCP1 expression at the cell surface of the tumor. Taken together, our data indicates that CDCP1 protein might serve as a therapeutic target for CC-RCC.
View details for DOI 10.1073/pnas.1011777108
View details for Web of Science ID 000286804700036
View details for PubMedID 21233420
Protein kinase Cdelta (PKCdelta) is an essential component of the intrinsic apoptotic program. Following DNA damage, such as exposure to UV radiation, PKCdelta is cleaved in a caspase-dependent manner, generating a constitutively active catalytic fragment (PKCdelta-cat), which is necessary and sufficient for keratinocyte apoptosis. We found that in addition to inducing apoptosis, expression of PKCdelta-cat caused a pronounced G(2)/M cell cycle arrest in both primary human keratinocytes and immortalized HaCaT cells. Consistent with a G(2)/M arrest, PKCdelta-cat induced phosphorylation of Cdk1 (Tyr(15)), a critical event in the G(2)/M checkpoint. Treatment with the ATM/ATR inhibitor caffeine was unable to prevent PKCdelta-cat-induced G(2)/M arrest, suggesting that PKCdelta-cat is functioning downstream of ATM/ATR in the G(2)/M checkpoint. To better understand the role of PKCdelta and PKCdelta-cat in the cell cycle response to DNA damage, we exposed wild-type and PKCdelta null mouse embryonic fibroblasts (MEFs) to UV radiation. Wild-type MEFs underwent a pronounced G(2)/M arrest, Cdk1 phosphorylation, and induction of apoptosis following UV exposure, whereas PKCdelta null MEFs were resistant to these effects. Expression of PKCdelta-green fluorescent protein, but not caspase-resistant or kinase-inactive PKCdelta, was able to restore G(2)/M checkpoint integrity in PKCdelta null MEFs. The function of PKCdelta in the DNA damage-induced G(2)/M cell cycle checkpoint may be a critical component of its tumor suppressor function.
View details for DOI 10.1074/jbc.M109.055392
View details for Web of Science ID 000273429100034
View details for PubMedID 19917613