A network of substrates of the E3 ubiquitin ligases MDM2 and HUWE1 control apoptosis independently of p53.
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2013-05-07
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In the intrinsic pathway of apoptosis, cell-damaging signals promote the release of cytochrome c from mitochondria, triggering activation of the Apaf-1 and caspase-9 apoptosome. The ubiquitin E3 ligase MDM2 decreases the stability of the proapoptotic factor p53. We show that it also coordinated apoptotic events in a p53-independent manner by ubiquitylating the apoptosome activator CAS and the ubiquitin E3 ligase HUWE1. HUWE1 ubiquitylates the antiapoptotic factor Mcl-1, and we found that HUWE1 also ubiquitylated PP5 (protein phosphatase 5), which indirectly inhibited apoptosome activation. Breast cancers that are positive for the tyrosine receptor kinase HER2 (human epidermal growth factor receptor 2) tend to be highly aggressive. In HER2-positive breast cancer cells treated with the HER2 tyrosine kinase inhibitor lapatinib, MDM2 was degraded and HUWE1 was stabilized. In contrast, in breast cancer cells that acquired resistance to lapatinib, the abundance of MDM2 was not decreased and HUWE1 was degraded, which inhibited apoptosis, regardless of p53 status. MDM2 inhibition overcame lapatinib resistance in cells with either wild-type or mutant p53 and in xenograft models. These findings demonstrate broader, p53-independent roles for MDM2 and HUWE1 in apoptosis and specifically suggest the potential for therapy directed against MDM2 to overcome lapatinib resistance.
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Kurokawa, Manabu, Jiyeon Kim, Joseph Geradts, Kenkyo Matsuura, Liu Liu, Xu Ran, Wenle Xia, Thomas J Ribar, et al. (2013). A network of substrates of the E3 ubiquitin ligases MDM2 and HUWE1 control apoptosis independently of p53. Sci Signal, 6(274). p. ra32. 10.1126/scisignal.2003741 Retrieved from https://hdl.handle.net/10161/8398.
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Scholars@Duke
Joseph Geradts
Dr. Geradts' primary research focus is on the molecular pathology of breast cancer. His laboratory uses genomic profiling strategies to identify novel candidate breast cancer genes. Dr. Geradts is also interested in biomarker development. He directs the Tissue Core of Duke's Breast Cancer SPORE and collaborates on numerous breast cancer related research projects with other investigators at Duke and elsewhere.
Ricardo Henao
Mark Wesley Dewhirst
Mark W. Dewhirst, DVM, PhD is the Gustavo S. Montana Professor of Radiation Oncology and Vice Director for Basic Science in the Duke Cancer Institute. Dr. Dewhirst has research interests in tumor hypoxia, angiogenesis, hyperthermia and drug transport. He has spent 30 years studying causes of tumor hypoxia and the use of hyperthermia to treat cancer. In collaboration with Professor David Needham in the Pratt School of Engineering, he has developed a novel thermally sensitive drug carrying liposome that has been successfully translated to human clinical trials. He has utilized the thermal characteristics of this liposome to develop an MR imageable form that can accurately reflect drug concentrations in tumors, which then is related to the extent of anti-tumor effect in pre-clinical models. This property has been widely used by other investigators, world-wide, particularly in the area of high intensity focused ultrasound, where it would be possible to literally paint drug to a target zone and visualize this process in real time, during heating. For his work in this area, Dr. Dewhirst was named a Fellow in the AAAS. Dr. Dewhirst has well over 500 peer-reviewed publications, book chapters and reviews, with >20,000 citations and an H-index of 73. He has given named lectures at the University of Western Ontario, Thomas Jefferson University and the New Zealand Cancer Society. He was awarded the Failla Medal and Lecture at the Radiation Research Society in 2008, the Eugene Robinson award for excellence hyperthermia research in 1992 and a similar award from the European Society for Hyperthermic Oncology in 2009. He was named a fellow of ASTRO in 2009 and was awarded the prestigious Gold Medal from the same society in 2012. He is a Senior Editor of Cancer Research and Editor-in-Chief of the International Journal of Hyperthermia. He has mentored 24 graduate students, and many postdoctoral fellows, residents, junior faculty and medical students. He has been particularly skillful in assisting those he has mentored to obtain DOD and NIH fellowships, K awards and first R01 grants. His skill in mentoring has been recognized by the Duke Comprehensive Cancer Center, the Medical Physics Graduate Training programs and the School of Medicine, where he has received “Mentor of the Year” awards. In 2011 he was selected to become the first Associate Dean of Faculty Mentoring in the Duke School of Medicine. In this position, he is implementing a comprehensive program to enhance success in obtaining NIH funding. He graduated from the University of Arizona in 1971 with a degree in Chemistry and Colorado State University in 1975 and 1979 with DVM and PhD degrees, respectively.
Sally A. Kornbluth
Our lab studies the regulation of complex cellular processes, including cell cycle progression and programmed cell death (apoptosis). These tightly orchestrated processes are critical for appropriate cell proliferation and cell death, and when they go awry can result in cancer and degenerative disorders. Within these larger fields, we have focused on understanding the cellular mechanisms that prevent the onset of mitosis prior to the completion of DNA replication, the processes that prevent cell division when the mitotic spindle is disrupted, the signaling pathways that prevent apoptotic cell death in cancer cells and the mechanisms that link cell metabolism to cell death and survival.
In our quest to answer these important cell biological and biochemical questions, we are varied in our use of experimental systems. Traditionally, we have used cell-free extracts prepared from eggs of the frog Xenopus laevis which can recapitulate cell cycle events and apoptotic processes in vitro. For the study of cell cycle events, extracts are prepared which can undergo multiple rounds of DNA replication and mitosis in vitro. Progression through the cell cycle can be monitored by microscopic observation of nuclear morphology and by biochemically assaying the activity of serine/threonine kinases which control cell cycle transitions.
For the study of apoptosis, modifications in extract preparation have allowed us to produce extracts which can apoptotically fragment nuclei and can accurately reproduce the biochemical events of apoptosis, including internucleosomal DNA cleavage and activation of apoptotic proteases, the caspases.
More recently, we have focused on studying apoptosis and cell cycle progression in mammalian models, both tissue culture cells and mouse models of cancer. In these studies, we are trying to determine the precise signaling mechanisms used by cancer cells to accelerate proliferation and evade apoptotic cell death mechanisms. We also endeavor to subvert these mechanisms to therapeutic advantage. We are particularly interested in links between metabolism and cell death, as high metabolic rates in cancer cells appear to suppress apoptosis to evade chemotherapy-induced cell death.
Finally, we also have several projects using the facile genetics of Drosophila melanogaster to further understand links between metabolism and cell death and also the ways in which mitochondrial dynamics are linked to apoptotic pathways.
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