Transcription factors in the nuclear factor ?B (NF-?B) family are evolutionarily conserved master regulators of immune and inflammatory responses. They are activated in response to ligation of many receptors including T-cell receptors, B-cell receptors, members of the tumor necrosis factor (TNF) receptor superfamily and the Toll-like receptor/interleukin-1 receptor (TLR/IL-1R) superfamily. The I?B kinase (IKK), comprising IKK? and IKK?, is at the heart of NF-?B activation and mediates two NF-?B activation pathways. The canonical NF-?B pathway is triggered by microbial and viral infections and pro-inflammatory cytokines and is dependent on IKK? phosphorylation and activation. The alternative pathway is triggered by certain members of the TNF cytokine family and selectively activates IKK?. Activated IKK phosphorylates I?Bs, leading to their polyubiquitination and subsequent degradation by the proteasome. The freed NF-?B dimers translocate to the nucleus to mediate transcription. Because of its importance in NF-?B activation, IKK, especially IKK?, has become a potential therapeutic target for many human diseases. The regulatory protein NEMO (also known as IKK? or FIP-3) interacts with IKK? and/or IKK? to form the IKK?, IKK? or IKK?/? holo-complex. The intact IKK? holo-complex is approximately 700-900kD in molecular mass containing multiple copies of IKK? and NEMO. IKK? and IKK? both contain the following conserved recognizable domains: a kinase domain (KD), a leucine zipper domain (LZ), a helix loop helix domain (HLH) and a C-terminal NEMO-binding domain (NBD). NEMO contains an N-terminal kinase-binding domain (KBD), a minimal oligomerization domain (MOD) that is also the ubiquitin binding domain (UBD) and a C-terminal zinc finger domain (ZF). IKK and NF-?B signaling has attracted tremendous attention with more than 30,000 papers published on the subject. Despite the biological importance, not a single successful structure determination has been reported on IKK, an indication on the difficulty of the project. To elucidate the molecular basis of IKK function and to assist the discovery of IKK inhibitors, we propose a series of structural and functional studies on IKK, in particular, IKK? and its regulatory protein NEMO.

Public Health Relevance

The I?B kinase (IKK) is at the heart of NF-?B activation and a potential therapeutic target for many human diseases. The proposal seeks structural studies of IKK, which will enhance our understanding on the molecular basis of IKK function. In addition, the proposed studies will provide a structural basis for discovery and optimization of IKK inhibitors in the treatment of inflammatory diseases and cancer.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
5R01AI079260-04
Application #
8278697
Study Section
Cellular and Molecular Immunology - A Study Section (CMIA)
Program Officer
Mallia, Conrad M
Project Start
2009-06-25
Project End
2012-06-30
Budget Start
2012-06-01
Budget End
2012-06-30
Support Year
4
Fiscal Year
2012
Total Cost
$35,488
Indirect Cost
$14,489
Name
Weill Medical College of Cornell University
Department
Biochemistry
Type
Schools of Medicine
DUNS #
060217502
City
New York
State
NY
Country
United States
Zip Code
10065
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Napetschnig, Johanna; Wu, Hao (2013) Molecular basis of NF-*B signaling. Annu Rev Biophys 42:443-68
Zheng, Chao; Yin, Qian; Wu, Hao (2011) Structural studies of NF-*B signaling. Cell Res 21:183-95
Wu, Hao; Lo, Yu-Chih; Lin, Su-Chang (2010) Recent advances in polyubiquitin chain recognition. F1000 Biol Rep 2:1-5