Xiaodong Wang

http://www.swmed.edu/home_pages/wanglab/





Xiaodong Wang, Ph.D.

Professor of Biochemistry

Assistant Investigator, Howard Hughes Medical Institute



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Biological Chemistry

Integrative Biology

Office: (214) 648-6713

FAX:  (214) 648-5419

Email: xwang@biochem.swmed.edu



The long-term goal of our laboratory is to understand the pathways and biochemical mechanisms controlling the activation and execution of apoptosis in mammalian cells. Apoptosis is a biochemically and morphologically distinct form of programmed cell death. Initiated by a variety of intercellular and intracellular signals, apoptosis is executed through an intrinsic cellular suicide program that results in early DNA fragmentation accompanied by nuclear and cytoplasmic condensation. Apoptosis is believed to play an essential role in development, tissue homeostasis, defense against viral infection, and clearance of damaged cells in multicellular organisms. Inappropriate activation or suppression of apoptosis are associated with the pathogenesis of some of the most devastating human diseases, such as cancer, neurodegenerative disease, auto-immune disease, AIDS, and ischemic stroke.



We have been focusing our research efforts on the dissection of two of the best characterized biochemical events during apoptosis, namely the activation of Caspase 3 protease and fragmentation of DNA into nucleosomal fragments. We have set up in vitro systems that duplicate these two events and fractionated cytosol from large scale cultured HeLa cells to identify and purify the individual protein factors contributing to Caspase 3 activation and the DNA fragmentation reaction. These studies identified protein components that can reconstitute these apoptotic events.
 

Purification of three components elucidated the caspase activation cycle. Apaf-1, the factor responsible for Caspase 3 activation, cause caspase activation of its partner, Caspase 9, through the formation of a multimeric protein complex regulated by cytochrome c binding and dATP hydrolysis. This complex has pointed to the role of cytochrome c release as a key regulatory step for apoptotis.  Nucleosomal DNA fragmentation occurs during apoptosis upon activation of a 40 kD novel protein DNA Fragmentation Factor (DFF40).   This activity is suppressed in normal cells by its inhibitor DFF45 which is removed after caspase cleavage.



Our future research will diverge into two directions: one is to study the biochemical mechanism of Apaf-1 activation and DNA fragmentation using purified recombinant proteins; another is to study the signal transduction pathways that regulate the activity of these factors during apoptosis.



We have set out a variety of techniques involving biochemistry, molecular biology and cell biology in the laboratory. We hope to use the combination of these techniques to uncover the mystery of programmed cell death.



Selected Publications:


 Xu Luo, Imawati Budihardjo, Hua Zou, Clive Slaughter, and Xiaodong Wang (1998). Bid, a Bcl2 Interacting Protein, Mediates Cytochrome c Release from Mitochondria in Response to Activation of Cell Surface Death Receptors. Cell, 94: 481-490.
 

Peng Li, Deepak Nijhawan, Ima Budihardjo, S. M. Srinivasula, M. Ahmad, E. S. Alnemri & Xiaodong Wang (1997). Cytochrome c and dATP-dependent formation of Apaf-1/caspase-9 complex initiates an apoptotic protease cascade. Cell, 91: 479-489



Hua Zou,Willaim J. Henzel, Xuesong Liu, Alexis Lutschg, and Xiaodong Wang (1997). Apaf-1, a human protein homologous to C. elegans CED-4 participates in Cytochrome c-dependent activation of Caspase-3. Cell,90 (3):405-413.



Xuesong Liu, Peng Li, Widlak P, Hua Zou,Xu Luo,William T Garrard,Xiaodong Wang (1998) The 40-kDa subunit of DNA fragmentation factor induces DNA fragmentation and chromatin condensation during apoptosis. Proc Natl Acad Sci U S A 95(15):8461-6.



Xuesong Liu, Hua Zou, Clive Slaughter, Xiaodong Wang (1997). DFF, a heterodimeric protein that functions downstream of caspase-3 to trigger DNA fragmentation during apoptosis.Cell, 89 (2): 175-184.



Jie Yang, Liu Xuesong, Kapil Bhalla, Caryn Naekyung Kim, A.M. Ibrado, J. Cai, T.I. Peng, D.P. Jones, Xiaodong Wang (1997). Prevention of apoptosis by Bcl-2: release of cytochrome c from mitochondria blocked. Science 275(5303): 1129-1132.



Xuesong Liu, Caryn Naekyung Kim, Jan Pohl and Xiaodong Wang (1996). Purification and characterization of an interleukin-1b-converting enzyme family protease that activates cysteine protease P32 (CPP32). J.Biol. Chem. 271, 13371-13376.



Xuesong Liu, Caryn Naekyung Kim, Jie Yang, Ronald Jemmerson, and Xiaodong Wang (1996). Induction of apoptotic program in cell-free extracts: requirement for dATP and cytochrome c. Cell, 86, 147-157.

Publications:



Devrim Acehan, Xuejun Jiang, David Gene Morgan, John E. Heuser, Xiaodong Wang, and Christopher W. Akey (2002). Three-Dimensional Structure of the Apoptosome: Implications for Assembly, Procaspase-9 Binding, and Activation. Mol Cell 9(2): 423-432.  

Xiaodong Wang (2001). The expanding role of mitochondria in apoptosis.Genes Dev 15(22):2922-33.

Piotr Widlak, Lily Y. Li, Xiaodong Wang, and William T. Garrard (2001). Action of recombinant human apoptotic endonuclease G on naked DNA and chromatin substrates: cooperation with exonuclease and DNase I.J Biol Chem 276(51):48404-9.

LILY Y. LI, XU LUO & XIAODONG WANG (2001). Endonuclease G is an apoptotic DNase when released from mitochondria. Nature 412(6842):95-9.

JAY PARRISH, LILY LI, KRISTINA KLOTZ, DUNCAN LEDWICH, XIAODONG WANG & DING XUE (2001). Mitochondrial endonuclease G is important for apoptosis in C. elegans. Nature 412(6842):90-4.

Xuejun Jiang and Xiaodong Wang (2000) Cytochrome c Promotes Caspase-9 Activation by Inducing Nucleotide Binding to Apaf-1. J Biol Chem 275(40): 31199-31203.

Michael Lutter, Min Fang, Xu Luo, Masahiro Nishijima, Xiao-song Xie and Xiaodong Wang (2000). Cardiolipin provides specificity for targeting of tBid to mitochondria. Nat Cell Biol 2(10):754-61.

Chunying Du, Min Fang, Yucheng Li, Lily Li, and Xiaodong Wang (2000). Smac, a mitochondrial protein that promotes cytochrome c-dependent caspase activation by eliminating IAP inhibition. Cell 102(1):33-42.

Deepak Nijhawan, Narimon Honarpour, and Xiaodong Wang (2000). Apoptosis in Neural Development and Disease. Annu. Rev. Neurosci. 23:73-87.

Piotr Widlak, Peng Li, Xiaodong Wang, and William T. Garrard (2000). Cleavage Preferences of the Apoptotic Endonuclease DFF40 (Caspase-activated DNase or Nuclease) on Naked DNA and Chromatin Substrates. J Biol Chem 275(11): 8226-8232.

Geng Wu, Jijie Chai, Tomeka L. Suber, Jia-Wei Wu, Chunying Du, Xiaodong Wang & Yigong Shi (2000). Structural basis of IAP recognition by Smac/DIABLO. Nature 408 (6815):1008-12.  

Jijie Chai, Chunying Du, Jia-Wei Wu, Saw Kyin, Xiaodong Wang & Yigong Shi. Structural and biochemical basis of apoptotic activation by Smac/DIABLO. Nature 406(6798):855-62.

Imawati Budihardjo, Holt Oliver, Michael Lutter, Xu Luo, and Xiaodong Wang (1999). BIOCHEMICAL PATHWAYS OF CASPASE ACTIVATION DURING APOPTOSIS. Annu. Rev. Cell Dev. Biol. 15:269-290.

Xuesong Liu, Hua Zou, Piotr Widlak, William Garrard, and Xiaodong Wang (1999). Activation of the Apoptotic Endonuclease DFF40 (Caspase-activated DNase or Nuclease) OLIGOMERIZATION AND DIRECT INTERACTION WITH HISTONE H1. J Biol Chem 274(20): 13836-13840.

Hua Zou, Yuchen Li, Xuesong Liu, and Xiaodong Wang (1999). An APAF-1·Cytochrome c Multimeric Complex Is a Functional Apoptosome That Activates Procaspase-9. J Biol Chem 274(17): 11549-11556.

Xu Luo, Imawati Budihardjo, Hua Zou, Clive Slaughter, and Xiaodong Wang (1998). Bid, a Bcl2 Interacting Protein, Mediates Cytochrome c Release from Mitochondria in Response to Activation of Cell Surface Death Receptors. Cell, 94: 481-490.

Xuesong Liu, Peng Li, Widlak P, Hua Zou,Xu Luo,William T Garrard,Xiaodong Wang (1998) The 40-kDa subunit of DNA fragmentation factor induces DNA fragmentation and chromatin condensation during apoptosis. Proc Natl Acad Sci U S A 95(15):8461-6.

Peng Li, Deepak Nijhawan, Ima Budihardjo, S. M. Srinivasula, M. Ahmad, E. S. Alnemri & Xiaodong Wang (1997). Cytochrome c and dATP-dependent formation of Apaf-1/caspase-9 complex initiates an apoptotic protease cascade. Cell, 91: 479-489

Hua Zou,Willaim J. Henzel, Xuesong Liu, Alexis Lutschg, and Xiaodong Wang (1997). Apaf-1, a human protein homologous to C. elegans CED-4 participates in Cytochrome c-dependent activation of Caspase-3. Cell,90 (3):405-413.

Xuesong Liu, Hua Zou, Clive Slaughter, Xiaodong Wang (1997). DFF, a heterodimeric protein that functions downstream of caspase-3 to trigger DNA fragmentation during apoptosis.Cell, 89 (2): 175-184.

Jie Yang, Liu Xuesong, Kapil Bhalla, Caryn Naekyung Kim, A.M. Ibrado, J. Cai, T.I. Peng, D.P. Jones, Xiaodong Wang (1997). Prevention of apoptosis by Bcl-2: release of cytochrome c from mitochondria blocked. Science 275(5303): 1129-1132.

Xuesong Liu, Caryn Naekyung Kim, Jan Pohl and Xiaodong Wang (1996). Purification and characterization of an interleukin-1b-converting enzyme family protease that activates cysteine protease P32 (CPP32). J.Biol. Chem. 271, 13371-13376.

Xuesong Liu, Caryn Naekyung Kim, Jie Yang, Ronald Jemmerson, and Xiaodong Wang (1996). Induction of apoptotic program in cell-free extracts: requirement for dATP and cytochrome c. Cell, 86, 147-157